Do-217P

[Rob Arndt]

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Do-217P:

In September 1941 the design of the P 183 and Do-217 began, and
eventually led to the Do-217P high-altitude bomber. In place of the
highly sophisticated engines, Dornier, like Henschel, settled for a
conventional engine layout consisting of two DB 603S-0 engines and one
DB 605T as power for the central compressor which provided the twp DB
603s with pre-cooled, pre-pressurized inlet air. The first static
tests of these centrally supercharged (HZ) engines began in Stuttgart
in October 1941. From 1942 the fuselage of a Do-217E-2 was used for a
variety of engine tests. A converted aircraft of the same type with
increased wing are (67m squared) was used for vibration and load tests
for the proposed Do-217P series.

From the Do-217E-2 (BK+JR, Wnr 1229), came the first of the initial
three test aircraft of the high-altitude Do-217P. On 6 June 1942 the
Do-217P V1 made its first flight. In mid-August, after a few test
flights reaching an altitude of 11,300m, Dornier fitted wings of
increased area. By 2 April 1943 twenty-three test flights totaling 34
flying hours had taken place, and altitude of 13,000m having been
exceeded on three occasions. The maximum altitude reached was 13,650m.
From the end of August, flights were carried out using the central
supercharger. Up to this time tests had been severely disrupted
because of strong vibrations in the turbocharger and problems with the
propellers. In the meantime, the RLM decided to build a further three
test aircraft, because testing of the Hs-130 had been subject to
severe delays. After various flights with Daimler-Benz engines, which
gave only a small Increase in high-altitude performance, the Do-217P
V1 went to Friedrichshafen in April to have its wing area increased to
71.0m squared. The Do-217P V2 with the earlier air-coolers became
available with Daimler-Benz engines from September 1942. In March 1943
comparative test flights took place, using the V2 with the old cooler
and V3 with the new one.

The Do-217P V2 was lost as a result of an air raid at Cazaux, where it
had been sent for bombing trials. The V4 reached a maximum altitude of
15,200m where it could still climb at 0.25m/s before the test was
ended when stability became too great a problem. The Do-217P V5 and V6
were respectively 95 and 80 percent complete by 1943, but were
scrapped on 11 March 1944. By the end of 1943 the whole high-altitude
program, including turbocharger development, was discontinued because
of the war situation. Work on central turbo charging was stopped in
1944 in favor of the DB 627 design. The Do-217P V1 and V2 were lost
owing to enemy action, together with the Hs-130E-0 on 5 September
1944.

~ “Bombers of the Luftwaffe“, pgs 164-165

Data from “Hitler’s Luftwaffe” pg.148:

Type: Recon and High-Altitude Bomber
Engines: 2x 1860 hp DB 603B supercharged by DB 605T in fuselage
Span: 80’ 4”
Length: 58’ 11”
Height: 16’ 5”
Weight: 35,200 lb
Max Speed: 488 mph
Ceiling: 53,000 ft
Range: 1300 miles
Armament: (bomber version) 3x MG-81Z and 2x 1102 lb bombs on underwing
racks

Rob

[Daryl Hunt]

Post by Rob Arndt
http://rareaircraf1.greyfalcon.us/picturesd/g27.jpg
In September 1941 the design of the P 183 and Do-217 began, and
eventually led to the Do-217P high-altitude bomber. In place of the
highly sophisticated engines, Dornier, like Henschel, settled for a
conventional engine layout consisting of two DB 603S-0 engines and one
DB 605T as power for the central compressor which provided the twp DB
603s with pre-cooled, pre-pressurized inlet air. The first static
tests of these centrally supercharged (HZ) engines began in Stuttgart
in October 1941. From 1942 the fuselage of a Do-217E-2 was used for a
variety of engine tests. A converted aircraft of the same type with
increased wing are (67m squared) was used for vibration and load tests
for the proposed Do-217P series.
From the Do-217E-2 (BK+JR, Wnr 1229), came the first of the initial
three test aircraft of the high-altitude Do-217P. On 6 June 1942 the
Do-217P V1 made its first flight. In mid-August, after a few test
flights reaching an altitude of 11,300m, Dornier fitted wings of
increased area. By 2 April 1943 twenty-three test flights totaling 34
flying hours had taken place, and altitude of 13,000m having been
exceeded on three occasions. The maximum altitude reached was 13,650m.
From the end of August, flights were carried out using the central
supercharger. Up to this time tests had been severely disrupted
because of strong vibrations in the turbocharger and problems with the
propellers. In the meantime, the RLM decided to build a further three
test aircraft, because testing of the Hs-130 had been subject to
severe delays. After various flights with Daimler-Benz engines, which
gave only a small Increase in high-altitude performance, the Do-217P
V1 went to Friedrichshafen in April to have its wing area increased to
71.0m squared. The Do-217P V2 with the earlier air-coolers became
available with Daimler-Benz engines from September 1942. In March 1943
comparative test flights took place, using the V2 with the old cooler
and V3 with the new one.
The Do-217P V2 was lost as a result of an air raid at Cazaux, where it
had been sent for bombing trials. The V4 reached a maximum altitude of
15,200m where it could still climb at 0.25m/s before the test was
ended when stability became too great a problem. The Do-217P V5 and V6
were respectively 95 and 80 percent complete by 1943, but were
scrapped on 11 March 1944. By the end of 1943 the whole high-altitude
program, including turbocharger development, was discontinued because
of the war situation. Work on central turbo charging was stopped in
1944 in favor of the DB 627 design. The Do-217P V1 and V2 were lost
owing to enemy action, together with the Hs-130E-0 on 5 September
1944.
~ “Bombers of the Luftwaffe“, pgs 164-165
Type: Recon and High-Altitude Bomber
Engines: 2x 1860 hp DB 603B supercharged by DB 605T in fuselage
Span: 80’ 4”
Length: 58’ 11”
Height: 16’ 5”
Weight: 35,200 lb
Max Speed: 488 mph
Ceiling: 53,000 ft
Range: 1300 miles
Armament: (bomber version) 3x MG-81Z and 2x 1102 lb bombs on underwing
racks

AS much as I respected the DO-217 over the other bombers that
Germany had, I think the stat of 53k and 488 mph are a bit
lavish. Drop it about 1000 feet and 100 mph and I would not
disagree.

[Rob Arndt]

Post by Daryl Hunt

Post by Rob Arndt
http://rareaircraf1.greyfalcon.us/picturesd/g27.jpg
In September 1941 the design of the P 183 and Do-217 began, and
eventually led to the Do-217P high-altitude bomber. In place of the
highly sophisticated engines, Dornier, like Henschel, settled for a
conventional engine layout consisting of two DB 603S-0 engines and one
DB 605T as power for the central compressor which provided the twp DB
603s with pre-cooled, pre-pressurized inlet air. The first static
tests of these centrally supercharged (HZ) engines began in Stuttgart
in October 1941. From 1942 the fuselage of a Do-217E-2 was used for a
variety of engine tests. A converted aircraft of the same type with
increased wing are (67m squared) was used for vibration and load tests
for the proposed Do-217P series.
 From the Do-217E-2 (BK+JR, Wnr 1229), came the first of the initial
three test aircraft of the high-altitude Do-217P. On 6 June 1942 the
Do-217P V1 made its  first flight. In mid-August, after a few test
flights reaching an altitude of 11,300m, Dornier fitted wings of
increased area. By 2 April 1943 twenty-three test flights totaling 34
flying hours had taken place, and altitude of 13,000m having been
exceeded on three occasions. The maximum altitude reached was 13,650m.
 From the end of August, flights were carried out using the central
supercharger. Up to this time tests had been severely disrupted
because of strong vibrations in the turbocharger and problems with the
propellers. In the meantime, the RLM decided to build a further three
test aircraft, because testing of the Hs-130 had been subject to
severe delays. After various flights with Daimler-Benz engines, which
gave only a small Increase in high-altitude performance, the Do-217P
V1 went to Friedrichshafen in April to have its wing area increased to
71.0m squared. The Do-217P V2 with the earlier air-coolers became
available with Daimler-Benz engines from September 1942. In March 1943
comparative test flights took place, using the V2 with the old cooler
and V3 with the new one.
The Do-217P V2 was lost as a result of an air raid at Cazaux, where it
had been sent for bombing trials. The V4 reached a maximum altitude of
15,200m where it could still climb at 0.25m/s before the test was
ended when stability became too great a problem. The Do-217P V5 and V6
were respectively 95 and 80 percent complete by 1943, but were
scrapped on 11 March 1944. By the end of 1943 the whole high-altitude
program, including turbocharger development, was discontinued because
of the war situation. Work on central turbo charging was stopped in
1944 in favor of the DB 627 design. The Do-217P V1 and V2 were lost
owing to enemy action, together with the Hs-130E-0 on 5 September
1944.
~ Bombers of the Luftwaffe , pgs 164-165
Type: Recon and High-Altitude Bomber
Engines: 2x 1860 hp DB 603B supercharged by DB 605T in fuselage
Span: 80 4
Length: 58 11
Height: 16 5
Weight: 35,200 lb
Max Speed: 488 mph
Ceiling: 53,000 ft
Range: 1300 miles
Armament: (bomber version) 3x MG-81Z and 2x 1102 lb bombs on underwing
racks

AS much as I respected the DO-217 over the other bombers that
Germany had, I think the stat of 53k and 488 mph are a bit
lavish.  Drop it about 1000 feet and 100 mph and I would not
disagree.- Hide quoted text -
- Show quoted text -

Daryl,

The Do-217P was totally unique to the entire series as it was
aerodynamically improved and had the DB 605T inside to supplement the
2x 1860 hp DB 603s. Ceiling and max speed is far above the rest of the
entire series of Do-217s and the appearance is unique.

As for the record, the Do-217P V4 achieved 488 mph @ 9600m (31,500 ft)
while testing.

Note that Capt Eric Brown tested the Do-217M which was nowhere near
the power and aerodynamics of the P and achieved 347 mph in level
flight and 435 mph in a short straight dive (the Do-217s were
multirole and used as dive bomber when suitable as well as
bomber ,nightfighter, anti-shipping, testbed, etc...), so the 488 mph
is not unreasonable. Some think this is 488 km/h (only 303 mph)
instead, but that is not what was reported and would be ridiculous
with the powerplants and aerodynamics.

Pic of Do-217M:
Loading Image...

Rob

[Daryl Hunt]

Post by Rob Arndt

Post by Daryl Hunt

Post by Rob Arndt
http://rareaircraf1.greyfalcon.us/picturesd/g27.jpg
In September 1941 the design of the P 183 and Do-217 began, and
eventually led to the Do-217P high-altitude bomber. In place of the
highly sophisticated engines, Dornier, like Henschel, settled for a
conventional engine layout consisting of two DB 603S-0 engines and one
DB 605T as power for the central compressor which provided the twp DB
603s with pre-cooled, pre-pressurized inlet air. The first static
tests of these centrally supercharged (HZ) engines began in Stuttgart
in October 1941. From 1942 the fuselage of a Do-217E-2 was used for a
variety of engine tests. A converted aircraft of the same type with
increased wing are (67m squared) was used for vibration and load tests
for the proposed Do-217P series.
From the Do-217E-2 (BK+JR, Wnr 1229), came the first of the initial
three test aircraft of the high-altitude Do-217P. On 6 June 1942 the
Do-217P V1 made its first flight. In mid-August, after a few test
flights reaching an altitude of 11,300m, Dornier fitted wings of
increased area. By 2 April 1943 twenty-three test flights totaling 34
flying hours had taken place, and altitude of 13,000m having been
exceeded on three occasions. The maximum altitude reached was 13,650m.
From the end of August, flights were carried out using the central
supercharger. Up to this time tests had been severely disrupted
because of strong vibrations in the turbocharger and problems with the
propellers. In the meantime, the RLM decided to build a further three
test aircraft, because testing of the Hs-130 had been subject to
severe delays. After various flights with Daimler-Benz engines, which
gave only a small Increase in high-altitude performance, the Do-217P
V1 went to Friedrichshafen in April to have its wing area increased to
71.0m squared. The Do-217P V2 with the earlier air-coolers became
available with Daimler-Benz engines from September 1942. In March 1943
comparative test flights took place, using the V2 with the old cooler
and V3 with the new one.
The Do-217P V2 was lost as a result of an air raid at Cazaux, where it
had been sent for bombing trials. The V4 reached a maximum altitude of
15,200m where it could still climb at 0.25m/s before the test was
ended when stability became too great a problem. The Do-217P V5 and V6
were respectively 95 and 80 percent complete by 1943, but were
scrapped on 11 March 1944. By the end of 1943 the whole high-altitude
program, including turbocharger development, was discontinued because
of the war situation. Work on central turbo charging was stopped in
1944 in favor of the DB 627 design. The Do-217P V1 and V2 were lost
owing to enemy action, together with the Hs-130E-0 on 5 September
1944.
~ Bombers of the Luftwaffe , pgs 164-165
Type: Recon and High-Altitude Bomber
Engines: 2x 1860 hp DB 603B supercharged by DB 605T in fuselage
Span: 80 4
Length: 58 11
Height: 16 5
Weight: 35,200 lb
Max Speed: 488 mph
Ceiling: 53,000 ft
Range: 1300 miles
Armament: (bomber version) 3x MG-81Z and 2x 1102 lb bombs on underwing
racks

AS much as I respected the DO-217 over the other bombers that
Germany had, I think the stat of 53k and 488 mph are a bit
lavish. Drop it about 1000 feet and 100 mph and I would not
disagree.- Hide quoted text -
- Show quoted text -

Daryl,
The Do-217P was totally unique to the entire series as it was
aerodynamically improved and had the DB 605T inside to supplement the
2x 1860 hp DB 603s. Ceiling and max speed is far above the rest of the
entire series of Do-217s and the appearance is unique.
while testing.
Note that Capt Eric Brown tested the Do-217M which was nowhere near
the power and aerodynamics of the P and achieved 347 mph in level
flight and 435 mph in a short straight dive (the Do-217s were
multirole and used as dive bomber when suitable as well as
bomber ,nightfighter, anti-shipping, testbed, etc...), so the 488 mph
is not unreasonable. Some think this is 488 km/h (only 303 mph)
instead, but that is not what was reported and would be ridiculous
with the powerplants and aerodynamics.

I can see you are not aware of what it takes to approach 500 mph
with a Prop. To date, 503 mph is as fast as a piston prop
engined plane has gone. Turboprops have gone faster but only by
about 15mph. It's a limit of the propeller and the power to turn
it.

that being said, those that have gone that fast have either
bulled their way to 475 by sheer power and streamlining or bulled
their way through by going as light as possible with the most
available horsepower.

This means, no extra weight. Case in point, the P-51H did the
475 range but at what cost? They lightened it up quite a bit
from the D/K and increased the power. This caused the P-51H to
never be flown in anger. Even in Korea, the D model was used
because it wasn't quite as light and could withstand the
punishment of just every day operations. No, the D could not
turn with the H nor could it climb with the H, fly as fast and it
certainly could not operate at the extreme altitudes with the H.
But it could do the job without breaking itself every time you
tried to taxi it and take off.

The P-38K could do it but it was just one AC with hotter engines
and the paddle blade props like the P-47D used. It did it with
being slick, real slick and bulling it's way to that kind of speed.

The Ta 152 hit 472 mph. It did by being slick and bulling it's
way to that speed with power.

What do these 3 have in common? They are all slick with lots of
power and nothing except engine, wings, control surfaces and prop
are in the slip stream. No wasted weight. Nothing is wasted.
Unlike the Bomber which waste due to size and fuselage.

Even the B-36J, with all it's massive power, it could only do
maybe 350 mph with props alone and only 414 with the 4 jets
burning. It takes Jets to push a heavy bomber to 475. Sometime
before that speed is reached, you have reached the absolute
limits of the Prop on something that isn't a single engine or a
very over power twin fighter. And it appears that the absolute
limit for a usable heavy bomber is below 400 mph.

In order to use the 3800 hp X 6 it took something the size of the
B-36. You are trying to use 6 x 2800 hp hybrids. Your bird
won't be as big as the B-36 but it's certainly going to have to
larger by far than a B-29 which was huge until the B-36 came
along and change the B-29 from a heavy to a medium bomber.

What made the B-29 work? Massive power with a very slick
fuselage and nacelles. And even then, it could only do a 357 mph
top speed. The B-36 with all it's massive power could do about
the same without the jets.

there were only 3 DO-217P made and they were preproduction. It's
calculated speed was 481 mph. Physics come into play here. It
wasn't slick at all. It had extended wings to high altitude
Recon duties. it wasn't even a bomber anymore. It was a Recce.
No guns, no racks, no bombs, stripped with extra gas. But the
bulbous nose definately made it less than optimal for slickness.
The M model had a top speed of 348mph at 1750 hp X 2. The P
model had 1860 X 2. There is no way that that extra 200 hp can
push it 130 mph faster than the M. Someone is being very
creative in those estimates.

To be fair, the DO-317 was pretty much a cleaned up DO-217. But
it was not produced because it didn't show any appreciative
advantage to the DO-217P. It's performance was a bit better but
not enough to warrant the expenditure. And it topped out at high
altitude at 411 mph. And it used the DB610 at 2800 hp for
engines and topped out at just over 35,000 feet.

the DO-217 is my pick for the best Luftwaffe bomber of them all
but some of these people are really stretching stats, let alone,
physics a bit far.

Post by Rob Arndt
http://2.bp.blogspot.com/_fhZZ63PRjhQ/TEC2mxUQD3I/AAAAAAAABJw/VKQvWtuAam4/s1600/do217.jpg
Rob

[Rob Arndt]

There were more than 3 Do-217Ps- six Versuchs V1-V6, all accounted
for.

As for the engines and internal DB 605T supercharger driving the DB
603s with 4-blade props and aerodynamic refinement... I'll wait for
Euno to go into further detail.

Here are the other Do-217 models with engines and max speeds:

E-2/J-2: 2x 1580 hp BMW 801A or 801M
K-2: 2X 1700 hp BMW 801D
M-1/N-2: 2x 1750 hp DB 603A
P-1: 2X 1860 hp DB 603B supercharged by internal 1475 hp DB 605T

Max speeds:

E-2: 320 mph
K-2: 333 mph
M-1: 348 mph
J and N: 311 mph
P-1: 488 mph

~ "Hitler's Luftwaffe"

Rob

[Daryl Hunt]

Post by Rob Arndt
There were more than 3 Do-217Ps- six Versuchs V1-V6, all accounted
for.
As for the engines and internal DB 605T supercharger driving the DB
603s with 4-blade props and aerodynamic refinement... I'll wait for
Euno to go into further detail.
E-2/J-2: 2x 1580 hp BMW 801A or 801M
K-2: 2X 1700 hp BMW 801D
M-1/N-2: 2x 1750 hp DB 603A
P-1: 2X 1860 hp DB 603B supercharged by internal 1475 hp DB 605T
E-2: 320 mph
K-2: 333 mph
M-1: 348 mph
J and N: 311 mph
P-1: 488 mph
~ "Hitler's Luftwaffe"
Rob

Already covered this. There is no way in hell that the P-1 could
have reached 488 short of a dive.

[Eunometic]

Post by Daryl Hunt
I can see you are not aware of what it takes to approach 500 mph
with a Prop.  To date, 503 mph is as fast as a piston prop
engined plane has gone.  Turboprops have gone faster but only by
about 15mph.  It's a limit of the propeller and the power to turn
it.

If I might just add here:

There would be very significant Jet thrust on this aircraft.

The DB605T installed in the Belly of the Do 217P, is a 35L turbo
superhcarged engine, would still be producing nearly its full power of
1420hp at 31500ft and not much less at 40,000ft. It would be feeding
compressed air to the two 44.66L DB603 engines in the wings. This air
would I imagine be at about 1 atmosphere pressure, perhaps more. The
air would be cooled by a rather large intecooler in the belly of the
Dornier Do 217P. The main engines effectively would experience sea
level conditions however the exahust backpressure would only be 0.3
atmospheres.

The DB603B engines would have their own superchaagers, generally
capable of maintaining one atmosphere to about 5700m (could be 7200m
as in the DB603AA). It is likely that the DB603 superchargers would
be running at a manifold pressure of around 1.3-1.42 ata.

At 31500ft the atmopshere is only 0.3 of one at sea level. The
aircraft would just about fly without props.

The jet thrust would be tremenous maybe even more than the prop power.

[Daryl Hunt]

Post by Eunometic

Post by Daryl Hunt
I can see you are not aware of what it takes to approach 500 mph
with a Prop. To date, 503 mph is as fast as a piston prop
engined plane has gone. Turboprops have gone faster but only by
about 15mph. It's a limit of the propeller and the power to turn
it.

There would be very significant Jet thrust on this aircraft.

Not 100 mph worth.

Post by Eunometic
The DB605T installed in the Belly of the Do 217P, is a 35L turbo
superhcarged engine, would still be producing nearly its full power of
1420hp at 31500ft and not much less at 40,000ft. It would be feeding
compressed air to the two 44.66L DB603 engines in the wings. This air
would I imagine be at about 1 atmosphere pressure, perhaps more. The
air would be cooled by a rather large intecooler in the belly of the
Dornier Do 217P. The main engines effectively would experience sea
level conditions however the exahust backpressure would only be 0.3
atmospheres.
The DB603B engines would have their own superchaagers, generally
capable of maintaining one atmosphere to about 5700m (could be 7200m
as in the DB603AA). It is likely that the DB603 superchargers would
be running at a manifold pressure of around 1.3-1.42 ata.
At 31500ft the atmopshere is only 0.3 of one at sea level. The
aircraft would just about fly without props.
The jet thrust would be tremenous maybe even more than the prop power.

Wrong. You still can't justify the over 100 mph over the M model
which was the fastest except for the P. Physics is not your best
subject.

[Eunometic]

Post by Daryl Hunt

Post by Eunometic

Post by Daryl Hunt
I can see you are not aware of what it takes to approach 500 mph
with a Prop.  To date, 503 mph is as fast as a piston prop
engined plane has gone.  Turboprops have gone faster but only by
about 15mph.  It's a limit of the propeller and the power to turn
it.

There would be very significant Jet thrust on this aircraft.

Not 100 mph worth.

Post by Eunometic
The DB605T installed in the Belly of the Do 217P, is a 35L turbo
superhcarged engine, would still be producing nearly its full power of
1420hp at 31500ft and not much less at 40,000ft.   It would be feeding
compressed air to the two 44.66L DB603 engines in the wings.  This air
would I imagine be at about 1 atmosphere pressure, perhaps more.  The
air would be cooled by a rather large intecooler in the belly of the
Dornier Do 217P.  The main engines effectively would experience sea
level conditions however the exahust backpressure would only be 0.3
atmospheres.
The DB603B engines would have their own superchaagers, generally
capable of maintaining one atmosphere to about 5700m (could be 7200m
as in the DB603AA).  It is likely that the DB603 superchargers would
be running at a manifold pressure of around 1.3-1.42 ata.
At 31500ft the atmopshere is only 0.3 of one at sea level.  The
aircraft would just about fly without props.
The jet thrust would be tremenous maybe even more than the prop power.

Wrong.  You still can't justify the over 100 mph over the M model
which was the fastest except for the P.  Physics is not your best
subject.- Hide quoted text -
- Show quoted text -

Do 217M1 speed 347mph (about 20,000ft) engine power at sea level
1750hp, assume 1500hp at 20,000ft.

Relative Air Density at 20,000ft = 0.5

Now flying at 31500ft reduces air density to 0.3. There is thus a 40%
reduction in parasitic drag to 60% of that at 20kfeet.. Induced drag
is a negligable component.

I will compare the speed increase of going from 20,000ft to 31500ft as
power goes from 1500hp to 1850hp.

Using a cube law the increase in speed due to having only 60% as much
drag will be 18%

P = V1^3 = 0.6.V2^3

cuberoot(V1^3/0.6) = V2 = 408mph

So I am claiming 18% for the thiner air.

There will also be a 22% increase in power from 1500hp to about 1850hp
equal to a 7% increase in speed from 408 to 437mph.

Jet thrust of two stage Merlin 66 was 300lbs (130kg) and that of the
two sage Jumo 213E was 200kg. I assume the DB603 at 20,000ft produced
only 100kg. However the preboosted DB603bBinto only 0.3 ata assume
250kp = 150kP extra thrust.

From the equaltion P = F X v. At 440mph (200ms) this is worth 200m/
s x 1500N = 300kW power about 400hp = 500hp at the shaft assuming 80%
prop efficiency

We thus have another 27% increase in power, again using a cube law we
have 9% increase in speed 437mph -> 476mph.

In fact for jets the increase in speed follows only a sqare law not a
cube one but a square so we get 13% should go to 493.

to sumarise
1 18% increase in speed due to thinner air at high altitude
2 addition 7% increase in speed due to higher power
4 additional 9% increase in speed due to jet thurst doubling (probably
more like 13%)

If you compound 1.18 x 1.07 x 1.13 = 45% increase in speed.

Admitedly no comressabillity correction but we are only at Mach 0.73.

[Daryl Hunt]

Post by Eunometic

Post by Daryl Hunt

Post by Eunometic

Post by Daryl Hunt
I can see you are not aware of what it takes to approach 500 mph
with a Prop. To date, 503 mph is as fast as a piston prop
engined plane has gone. Turboprops have gone faster but only by
about 15mph. It's a limit of the propeller and the power to turn
it.

There would be very significant Jet thrust on this aircraft.

Not 100 mph worth.

Post by Eunometic
The DB605T installed in the Belly of the Do 217P, is a 35L turbo
superhcarged engine, would still be producing nearly its full power of
1420hp at 31500ft and not much less at 40,000ft. It would be feeding
compressed air to the two 44.66L DB603 engines in the wings. This air
would I imagine be at about 1 atmosphere pressure, perhaps more. The
air would be cooled by a rather large intecooler in the belly of the
Dornier Do 217P. The main engines effectively would experience sea
level conditions however the exahust backpressure would only be 0.3
atmospheres.
The DB603B engines would have their own superchaagers, generally
capable of maintaining one atmosphere to about 5700m (could be 7200m
as in the DB603AA). It is likely that the DB603 superchargers would
be running at a manifold pressure of around 1.3-1.42 ata.
At 31500ft the atmopshere is only 0.3 of one at sea level. The
aircraft would just about fly without props.
The jet thrust would be tremenous maybe even more than the prop power.

Wrong. You still can't justify the over 100 mph over the M model
which was the fastest except for the P. Physics is not your best
subject.- Hide quoted text -
- Show quoted text -

Do 217M1 speed 347mph (about 20,000ft) engine power at sea level
1750hp, assume 1500hp at 20,000ft.
Relative Air Density at 20,000ft = 0.5
Now flying at 31500ft reduces air density to 0.3. There is thus a 40%
reduction in parasitic drag to 60% of that at 20kfeet.. Induced drag
is a negligable component.

You can stop anytime. No one else is buying your outlandish claim.

[Keith Willshaw]

H is >>

Post by Daryl Hunt

Post by Eunometic
Now flying at 31500ft reduces air density to 0.3. There is thus a 40%
reduction in parasitic drag to 60% of that at 20kfeet.. Induced drag
is a negligable component.

You can stop anytime. No one else is buying your outlandish claim.

He is completely off his trolley.

Keith

[Daryl Hunt]

H is>>

Post by Daryl Hunt

Post by Eunometic
Now flying at 31500ft reduces air density to 0.3. There is thus a 40%
reduction in parasitic drag to 60% of that at 20kfeet.. Induced drag
is a negligable component.

You can stop anytime. No one else is buying your outlandish claim.

He is completely off his trolley.
Keith

He's now trying to claim birth rights to the Scandanavian
countries for the Germans. Didn't work out so good the last
time, did it.

[bbrought]

I seem to recall the Do-217P claim was discussed here before, but
since some people like Rob seem to believe the equations and numbers
presented by Euno without question, I thought I'd respond for the sake
of those who don't have the background to critically evaluate Euno's
version of flight physics. Of course, I have no illusions that I'll
change Euno's mind, because he has a bit of a history of believing his
own woulda/coulda/shoulda claims regardless of overwhelming evidence
to the contrary. By the way, Euno, your high altitude range
calculations in the other thread are also messed up, but I think I'll
take this one thread at a time.

Do 217M1 speed 347mph  (about 20,000ft) engine power at sea level
1750hp, assume 1500hp at 20,000ft.
Relative Air Density at 20,000ft = 0.5
Now flying at 31500ft reduces air density to 0.3.  There is thus a 40%
reduction in parasitic drag to 60% of that at 20kfeet..  Induced drag
is a negligable component.

347 mph @ 20000ft, approx M=0.49
488 mph @ 31500ft, approx M=0.72

Now look at a picture of a Do-217 - just about nothing on that
airframe is designed for transonic speed. Most of the components, and
in particular that nose, would hit their critical Mach number
somewhere between 0.6 and 0.7. The root airfoil, in particular, is
very thick - close to 18%. If it was a NACA 2218, as used on previous
Dornier designs, it would also have a critical Mach number close to
Mach 0.6, depending on what the lift coefficient at that speed is. By
the time this aircraft got to 488 mph, if it was able to get there,
drag would probably have more than doubled.

It is surprising (or maybe not) that you neglected one of the most
significant drag components at that speed.

Then there is of course the fact that a large proportion of those
propeller blades would be transonic, resulting in a huge hit in
propeller efficiency.

If you still don't get it, the Tu-114, which holds the speed record
for a propeller driven aircraft, will do about Mach 0.78 maximum, but
that is with very powerful turboprops and a design that from the
beginning intended it to fly at that speed. The propellers are highly
optimised for transonic flight, and so is the entire airframe, which
includes swept wings and a very slender fuselage. Even then, it
doesn't cruise at Mach 0.78, but closer to Mach 0.7, as it is much
more efficient at that Mach number. Now, go have a look at some
pictures of a Tu-114 and compare to the layout of the Do-217P. Surely,
even you must see how ridiculous this 0.72M claim is?

On the other hand, the fastest piston engined aircraft is the Rare
Bear, which only achieved about Mach 0.69 during its record setting
flight of 528 mph. Reno racers in general use different propeller and
gearbox combinations than their production counterparts specifically
to reduce the propeller tip Mach number. As you can see, even they hit
a limit at around Mach 0.7. I'll get back to these two aircraft at the
end of the post.

I will compare the speed increase of going from 20,000ft to 31500ft as
power goes from 1500hp to 1850hp.
Using a cube law the increase in speed due to having only 60% as much
drag will be 18%

40% reduction in drag if you forget you are now entering the transonic
regime. Even that is not strictly correct. If you change altitude but
keep the speed (TAS) the same, as you did here, you must increase the
lift coefficient as your lift force must stay constant, which would
change induced drag. What would have made a lot more sense, would be
to work out what speed gives you the same drag at the higher altitude,
and then how much power you need to accelerate from that speed to your
new claimed top speed.

For example (assuming ISA):
@20,000 ft, 347 mph TAS = 257 mph CAS
@31,500 ft, 418 mph TAS = 257 mph CAS

By keeping CAS and therefore dynamics pressure the same, you stay at
the same place on the L/D graph (once again, ignoring
compressibility), and since L = constant, you know D = constant. Of
course, prop efficiency is taking a hit, but I'll get to that later.

Now, you can work out how much more power is needed to go from 418 mph
to 488 mph:
P_required = (constant)*V^3 (approximately)
thus P2/P1 = V2^3/V1^3
P2/P1 = 488^3/418^3 = 1.59

So, at an absolute minimum, you need 59% more power. This cube law
assumes constant CD, which ignores compressibility which is very
definitely not negligible, so it is still an extremely optimistic
figure, but lets stick with it for now. Following your own
calculations, you gained 350 hp for each engine and effectively 500 hp
from that third engine. That gives you 1200 hp over the original 3000
hp, or 40% more power. So, in an absolute ideal world, with no
compressibility and no reduction in propeller efficiency, you don't
even come close to having enough power to get to that speed. In fact,
assuming you are getting the 2x350hp extra from the two main engines,
you would still need 1070 hp effective output form the third one - in
other words, power that add directly to thrust after all losses have
been taken into account. Alternatively, you need just over 400 kg or
880 lbs additional direct thrust. And once again, we have totally
ignored compressibility or propeller efficiency.

P = V1^3 = 0.6.V2^3
cuberoot(V1^3/0.6) = V2 = 408mph

Assuming you still get the same propeller efficiency than before, but
now with the tips going supersonic. However, see my notes above - you
started from the wrong place anyway.

Jet thrust of  two stage Merlin 66 was 300lbs (130kg) and that of the
two sage Jumo 213E was 200kg.  I assume the DB603 at 20,000ft produced
only 100kg.  However the preboosted DB603bBinto only 0.3 ata assume
250kp = 150kP extra thrust.

Probably still a bit optimistic, but I'll give that to you. Yet, look
above at what you would need as an absolute minimum in ideal
circumstances.

From the equaltion P = F X v.    At 440mph (200ms) this is worth 200m/
s x 1500N = 300kW power about 400hp = 500hp at the shaft assuming 80%
prop efficiency

80% prop efficiency, at that speed? With a WWII technology prop?
Ironically, it doesn't matter, because jet thrust counters drag
directly and your conversion back to an equivalent power is
nonsensical. Just like in the case of turboprop analysis, you have to
do a dual calculation - one for power converted to thrust via the prop
and one for direct thrust. So, you didn't have to make the propeller
efficiency correction here at all - the 500 hp still doesn't help you
enough, though.

to sumarise
1 18% increase in speed due to thinner air at high altitude
2 addition 7% increase in speed due to higher power
4 additional 9% increase in speed due to jet thurst doubling (probably
more like 13%)
If you compound 1.18 x 1.07 x 1.13 = 45% increase in speed.
Admitedly no comressabillity correction but we are only at Mach 0.73.

ONLY Mach 0.73 :-)

I have done a lot of aircraft performance calculations in my lifetime.
And the first thing I usually do is take a few historical figures to
get an idea of what to expect - it helps as a "sanity check" when you
get to the more detailed analysis. So, you have an aircraft here that
you claim will reach M=0.72 with two piston engines and a third that
is only used to pressurise the other two. Let's see what history tells
us we need to achieve that speed in level flight:

Tu-114, cruise M=0.7, but will do around M=0.78
Loaded weight: 289,000 lbs
Empty weight: 92,000 lbs
Installed power: 59,200 hp
Power/weight (empty): 0.643 hp/lb
Power/weight (loaded): 0.205 hp/lb
Highly optimised airframe and propellers for cruise at low transonic
Mach numbers.

Rare Bear, will do about M=0.69
Weight (minimal fuel): 8500 lb
Installed power: 4000 hp
Power/weight: 0.471 hp/lb
Not initially designed for transonic flight, but highly cleaned up
airframe, modified power system

Do-217P
Claimed max speed at M=0.72
Empty weight: 22,817 lb
Max T/O weight: 34,921 lb
Installed power (including third engine): 5140 hp
Power/weight (empty): 0.225 hp/lb
Power/weight (all up): 0.127 hp/lb

So, of the three, you are expecting the one with the dirtiest airframe
by an order of magnitude, and by far the lowest power-to-weight ratio,
to achieve the same Mach number as the other two - and that even after
I included the third engine as if it is directly adding to the power
like the other two.

Of course, none of this will prevent either you or Rob and probably
dozens of other Luft-46 types to continue repeating this claim which
most likely started as a misprint in some document. You will dig for
more "jet thrust", magic area ruling that only you can see, or some
secret Nazi thrust technology until you can justify that ridiculous
claim.

[Rob Arndt]

Post by bbrought
I seem to recall the Do-217P claim was discussed here before, but
since some people like Rob seem to believe the equations and numbers
presented by Euno without question, I thought I'd respond for the sake
of those who don't have the background to critically evaluate Euno's
version of flight physics. Of course, I have no illusions that I'll
change Euno's mind, because he has a bit of a history of believing his
own woulda/coulda/shoulda claims regardless of overwhelming evidence
to the contrary. By the way, Euno, your high altitude range
calculations in the other thread are also messed up, but I think I'll
take this one thread at a time.

Do 217M1 speed 347mph  (about 20,000ft) engine power at sea level
1750hp, assume 1500hp at 20,000ft.
Relative Air Density at 20,000ft = 0.5
Now flying at 31500ft reduces air density to 0.3.  There is thus a 40%
reduction in parasitic drag to 60% of that at 20kfeet..  Induced drag
is a negligable component.

Now look at a picture of a Do-217 - just about nothing on that
airframe is designed for transonic speed. Most of the components, and
in particular that nose, would hit their critical Mach number
somewhere between 0.6 and 0.7. The root airfoil, in particular, is
very thick - close to 18%. If it was a NACA 2218, as used on previous
Dornier designs, it would also have a critical Mach number close to
Mach 0.6, depending on what the lift coefficient at that speed is. By
the time this aircraft got to 488 mph, if it was able to get there,
drag would probably have more than doubled.
It is surprising (or maybe not) that you neglected one of the most
significant drag components at that speed.
Then there is of course the fact that a large proportion of those
propeller blades would be transonic, resulting in a huge hit in
propeller efficiency.
If you still don't get it, the Tu-114, which holds the speed record
for a propeller driven aircraft, will do about Mach 0.78 maximum, but
that is with very powerful turboprops and a design that from the
beginning intended it to fly at that speed. The propellers are highly
optimised for transonic flight, and so is the entire airframe, which
includes swept wings and a very slender fuselage. Even then, it
doesn't cruise at Mach 0.78, but closer to Mach 0.7, as it is much
more efficient at that Mach number. Now, go have a look at some
pictures of a Tu-114 and compare to the layout of the Do-217P. Surely,
even you must see how ridiculous this 0.72M claim is?
On the other hand, the fastest piston engined aircraft is the Rare
Bear, which only achieved about Mach 0.69 during its record setting
flight of 528 mph. Reno racers in general use different propeller and
gearbox combinations than their production counterparts specifically
to reduce the propeller tip Mach number. As you can see, even they hit
a limit at around Mach 0.7. I'll get back to these two aircraft at the
end of the post.

I will compare the speed increase of going from 20,000ft to 31500ft as
power goes from 1500hp to 1850hp.
Using a cube law the increase in speed due to having only 60% as much
drag will be 18%

40% reduction in drag if you forget you are now entering the transonic
regime. Even that is not strictly correct. If you change altitude but
keep the speed (TAS) the same, as you did here, you must increase the
lift coefficient as your lift force must stay constant, which would
change induced drag. What would have made a lot more sense, would be
to work out what speed gives you the same drag at the higher altitude,
and then how much power you need to accelerate from that speed to your
new claimed top speed.
@20,000 ft, 347 mph TAS = 257 mph CAS
@31,500 ft, 418 mph TAS = 257 mph CAS
By keeping CAS and therefore dynamics pressure the same, you stay at
the same place on the L/D graph (once again, ignoring
compressibility), and since L = constant, you know D = constant. Of
course, prop efficiency is taking a hit, but I'll get to that later.
Now, you can work out how much more power is needed to go from 418 mph
P_required = (constant)*V^3 (approximately)
thus P2/P1 = V2^3/V1^3
P2/P1 = 488^3/418^3 = 1.59
So, at an absolute minimum, you need 59% more power. This cube law
assumes constant CD, which ignores compressibility which is very
definitely not negligible, so it is still an extremely optimistic
figure, but lets stick with it for now. Following your own
calculations, you gained 350 hp for each engine and effectively 500 hp
from that third engine. That gives you 1200 hp over the original 3000
hp, or 40% more power. So, in an absolute ideal world, with no
compressibility and no reduction in propeller efficiency, you don't
even come close to having enough power to get to that speed. In fact,
assuming you are getting the 2x350hp extra from the two main engines,
you would still need 1070 hp effective output form the third one - in
other words, power that add directly to thrust after all losses have
been taken into account. Alternatively, you need just over 400 kg or
880 lbs additional direct thrust. And once again, we have totally
ignored compressibility or propeller efficiency.

P = V1^3 = 0.6.V2^3
cuberoot(V1^3/0.6) = V2 = 408mph

Assuming you still get the same propeller efficiency than before, but
now with the tips going supersonic. However, see my notes above - you
started from the wrong place anyway.

Jet thrust of  two stage Merlin 66 was 300lbs (130kg) and that of the
two sage Jumo 213E was 200kg.  I assume the DB603 at 20,000ft produced
only 100kg.  However the preboosted DB603bBinto only 0.3 ata assume
250kp = 150kP extra thrust.

Probably still a bit optimistic, but I'll give that to you. Yet, look
above at what you would need as an absolute minimum in ideal
circumstances.

From the equaltion P = F X v.    At 440mph (200ms) this is worth 200m/
s x 1500N = 300kW power about 400hp = 500hp at the shaft assuming 80%
prop efficiency

80% prop efficiency, at that speed? With a WWII technology prop?
Ironically, it doesn't matter, because jet thrust counters drag
directly and your conversion back to an equivalent power is
nonsensical. Just like in the case of turboprop analysis, you have to
do a dual calculation - one for power converted to thrust via the prop
and one for direct thrust. So, you didn't have to make the propeller
efficiency correction here at all - the 500 hp still doesn't help you
enough, though.

to sumarise
1 18% increase in speed due to thinner air at high altitude
2 addition 7% increase in speed due to higher power
4 additional 9% increase in speed due to jet thurst doubling (probably
more like 13%)
If you compound 1.18 x 1.07 x 1.13 = 45% increase in speed.
Admitedly no comressabillity correction but we are only at Mach 0.73.

ONLY Mach 0.73 :-)
I have done a lot of aircraft performance calculations in my lifetime.
And the first thing I usually do is take a few historical figures to
get an idea of what to expect - it helps as a "sanity check" when you
get to the more detailed analysis. So, you have an aircraft here that
you claim will reach M=0.72 with two piston engines and a third that
is only used to pressurise the other two. Let's see what history tells
Tu-114, cruise M=0.7, but will do around M=0.78
Loaded weight: 289,000 lbs
Empty weight: 92,000 lbs
Installed power: 59,200 hp
Power/weight (empty): 0.643 hp/lb
Power/weight (loaded): 0.205 hp/lb
Highly optimised airframe and propellers for cruise at low transonic
Mach numbers.
Rare Bear, will do about M=0.69
Weight (minimal fuel): 8500 lb
Installed power: 4000 hp
Power/weight: 0.471 hp/lb
Not initially designed for transonic flight, but highly cleaned up
airframe, modified power system
Do-217P
Claimed max speed at M=0.72
Empty weight: 22,817 lb
Max T/O weight: 34,921 lb
Installed power (including third engine): 5140 hp
Power/weight (empty): 0.225 hp/lb
Power/weight (all up): 0.127 hp/lb
So, of the three, you are expecting the one with the dirtiest airframe
by an order of magnitude, and by far the lowest power-to-weight ratio,
to achieve the same Mach number as the other two - and that even after
I included the third engine as if it is directly adding to the power
like the other two.
Of course, none of this will prevent either you or Rob and probably
dozens of other Luft-46 types to continue repeating this claim which
most likely started as a misprint in some document. You will dig for
more "jet thrust", magic area ruling that only you can see, or some
secret Nazi thrust technology until you can justify that ridiculous
claim.

Pardon me, but these are not my claims nor Euno's for that matter. I
think it started with Green and "Warplanes of the Third Reich" which
is the old source for LW a/c and yet is still there at 488 mph with
latter sources like "Hitler's Luftwaffe" (a widely used ref that is
very credible, 1990 edition) to "Bombers of the Luftwaffe" (1994) and
so on...

But at least now we know what a/c that speed is claimed for- the
Do-217P V4 @ 31,500 ft. That was a test machine and it could have been
attained in a dive; however, the altitude is very specific at 31,500
ft giving the firm impression of level flight.

My point is that you need to argue with the makers of that claim vs me
and Euno- we have the refs. The Do-217P also looks NOTHING like any
other of the Do-217 series- fact and only it carried the 1475 hp DB
605T internally.

OK?

Your argument is with William Green, , Tony Wood, Bill Gunston,
Joachim Dressel, and Manfried Griehl, etc...

Capt Eric Brown only evaluated the Do-217M which is different from a
Do-217N, P, E, or K…

Rob

[Daryl Hunt]

Post by Rob Arndt

Post by bbrought
I seem to recall the Do-217P claim was discussed here before, but
since some people like Rob seem to believe the equations and numbers
presented by Euno without question, I thought I'd respond for the sake
of those who don't have the background to critically evaluate Euno's
version of flight physics. Of course, I have no illusions that I'll
change Euno's mind, because he has a bit of a history of believing his
own woulda/coulda/shoulda claims regardless of overwhelming evidence
to the contrary. By the way, Euno, your high altitude range
calculations in the other thread are also messed up, but I think I'll
take this one thread at a time.

Post by Eunometic
Do 217M1 speed 347mph (about 20,000ft) engine power at sea level
1750hp, assume 1500hp at 20,000ft.
Relative Air Density at 20,000ft = 0.5
Now flying at 31500ft reduces air density to 0.3. There is thus a 40%
reduction in parasitic drag to 60% of that at 20kfeet.. Induced drag
is a negligable component.

Now look at a picture of a Do-217 - just about nothing on that
airframe is designed for transonic speed. Most of the components, and
in particular that nose, would hit their critical Mach number
somewhere between 0.6 and 0.7. The root airfoil, in particular, is
very thick - close to 18%. If it was a NACA 2218, as used on previous
Dornier designs, it would also have a critical Mach number close to
Mach 0.6, depending on what the lift coefficient at that speed is. By
the time this aircraft got to 488 mph, if it was able to get there,
drag would probably have more than doubled.
It is surprising (or maybe not) that you neglected one of the most
significant drag components at that speed.
Then there is of course the fact that a large proportion of those
propeller blades would be transonic, resulting in a huge hit in
propeller efficiency.
If you still don't get it, the Tu-114, which holds the speed record
for a propeller driven aircraft, will do about Mach 0.78 maximum, but
that is with very powerful turboprops and a design that from the
beginning intended it to fly at that speed. The propellers are highly
optimised for transonic flight, and so is the entire airframe, which
includes swept wings and a very slender fuselage. Even then, it
doesn't cruise at Mach 0.78, but closer to Mach 0.7, as it is much
more efficient at that Mach number. Now, go have a look at some
pictures of a Tu-114 and compare to the layout of the Do-217P. Surely,
even you must see how ridiculous this 0.72M claim is?
On the other hand, the fastest piston engined aircraft is the Rare
Bear, which only achieved about Mach 0.69 during its record setting
flight of 528 mph. Reno racers in general use different propeller and
gearbox combinations than their production counterparts specifically
to reduce the propeller tip Mach number. As you can see, even they hit
a limit at around Mach 0.7. I'll get back to these two aircraft at the
end of the post.

Post by Eunometic
I will compare the speed increase of going from 20,000ft to 31500ft as
power goes from 1500hp to 1850hp.
Using a cube law the increase in speed due to having only 60% as much
drag will be 18%

40% reduction in drag if you forget you are now entering the transonic
regime. Even that is not strictly correct. If you change altitude but
keep the speed (TAS) the same, as you did here, you must increase the
lift coefficient as your lift force must stay constant, which would
change induced drag. What would have made a lot more sense, would be
to work out what speed gives you the same drag at the higher altitude,
and then how much power you need to accelerate from that speed to your
new claimed top speed.
@20,000 ft, 347 mph TAS = 257 mph CAS
@31,500 ft, 418 mph TAS = 257 mph CAS
By keeping CAS and therefore dynamics pressure the same, you stay at
the same place on the L/D graph (once again, ignoring
compressibility), and since L = constant, you know D = constant. Of
course, prop efficiency is taking a hit, but I'll get to that later.
Now, you can work out how much more power is needed to go from 418 mph
P_required = (constant)*V^3 (approximately)
thus P2/P1 = V2^3/V1^3
P2/P1 = 488^3/418^3 = 1.59
So, at an absolute minimum, you need 59% more power. This cube law
assumes constant CD, which ignores compressibility which is very
definitely not negligible, so it is still an extremely optimistic
figure, but lets stick with it for now. Following your own
calculations, you gained 350 hp for each engine and effectively 500 hp
from that third engine. That gives you 1200 hp over the original 3000
hp, or 40% more power. So, in an absolute ideal world, with no
compressibility and no reduction in propeller efficiency, you don't
even come close to having enough power to get to that speed. In fact,
assuming you are getting the 2x350hp extra from the two main engines,
you would still need 1070 hp effective output form the third one - in
other words, power that add directly to thrust after all losses have
been taken into account. Alternatively, you need just over 400 kg or
880 lbs additional direct thrust. And once again, we have totally
ignored compressibility or propeller efficiency.

Post by Eunometic
P = V1^3 = 0.6.V2^3
cuberoot(V1^3/0.6) = V2 = 408mph

Assuming you still get the same propeller efficiency than before, but
now with the tips going supersonic. However, see my notes above - you
started from the wrong place anyway.

Post by Eunometic
Jet thrust of two stage Merlin 66 was 300lbs (130kg) and that of the
two sage Jumo 213E was 200kg. I assume the DB603 at 20,000ft produced
only 100kg. However the preboosted DB603bBinto only 0.3 ata assume
250kp = 150kP extra thrust.

Probably still a bit optimistic, but I'll give that to you. Yet, look
above at what you would need as an absolute minimum in ideal
circumstances.

Post by Eunometic
From the equaltion P = F X v. At 440mph (200ms) this is worth 200m/
s x 1500N = 300kW power about 400hp = 500hp at the shaft assuming 80%
prop efficiency

80% prop efficiency, at that speed? With a WWII technology prop?
Ironically, it doesn't matter, because jet thrust counters drag
directly and your conversion back to an equivalent power is
nonsensical. Just like in the case of turboprop analysis, you have to
do a dual calculation - one for power converted to thrust via the prop
and one for direct thrust. So, you didn't have to make the propeller
efficiency correction here at all - the 500 hp still doesn't help you
enough, though.

Post by Eunometic
to sumarise
1 18% increase in speed due to thinner air at high altitude
2 addition 7% increase in speed due to higher power
4 additional 9% increase in speed due to jet thurst doubling (probably
more like 13%)
If you compound 1.18 x 1.07 x 1.13 = 45% increase in speed.
Admitedly no comressabillity correction but we are only at Mach 0.73.

ONLY Mach 0.73 :-)
I have done a lot of aircraft performance calculations in my lifetime.
And the first thing I usually do is take a few historical figures to
get an idea of what to expect - it helps as a "sanity check" when you
get to the more detailed analysis. So, you have an aircraft here that
you claim will reach M=0.72 with two piston engines and a third that
is only used to pressurise the other two. Let's see what history tells
Tu-114, cruise M=0.7, but will do around M=0.78
Loaded weight: 289,000 lbs
Empty weight: 92,000 lbs
Installed power: 59,200 hp
Power/weight (empty): 0.643 hp/lb
Power/weight (loaded): 0.205 hp/lb
Highly optimised airframe and propellers for cruise at low transonic
Mach numbers.
Rare Bear, will do about M=0.69
Weight (minimal fuel): 8500 lb
Installed power: 4000 hp
Power/weight: 0.471 hp/lb
Not initially designed for transonic flight, but highly cleaned up
airframe, modified power system
Do-217P
Claimed max speed at M=0.72
Empty weight: 22,817 lb
Max T/O weight: 34,921 lb
Installed power (including third engine): 5140 hp
Power/weight (empty): 0.225 hp/lb
Power/weight (all up): 0.127 hp/lb
So, of the three, you are expecting the one with the dirtiest airframe
by an order of magnitude, and by far the lowest power-to-weight ratio,
to achieve the same Mach number as the other two - and that even after
I included the third engine as if it is directly adding to the power
like the other two.
Of course, none of this will prevent either you or Rob and probably
dozens of other Luft-46 types to continue repeating this claim which
most likely started as a misprint in some document. You will dig for
more "jet thrust", magic area ruling that only you can see, or some
secret Nazi thrust technology until you can justify that ridiculous
claim.

Pardon me, but these are not my claims nor Euno's for that matter. I
think it started with Green and "Warplanes of the Third Reich" which
is the old source for LW a/c and yet is still there at 488 mph with
latter sources like "Hitler's Luftwaffe" (a widely used ref that is
very credible, 1990 edition) to "Bombers of the Luftwaffe" (1994) and
so on...

Errors like this is why I question the sources. No matter how
hard one tries, 488 cannot be explained except as a typo.

Post by Rob Arndt
But at least now we know what a/c that speed is claimed for- the
attained in a dive; however, the altitude is very specific at 31,500
ft giving the firm impression of level flight.
My point is that you need to argue with the makers of that claim vs me
and Euno- we have the refs. The Do-217P also looks NOTHING like any
other of the Do-217 series- fact and only it carried the 1475 hp DB
605T internally.
OK?
Your argument is with William Green, , Tony Wood, Bill Gunston,
Joachim Dressel, and Manfried Griehl, etc...
Capt Eric Brown only evaluated the Do-217M which is different from a
Do-217N, P, E, or K…

No, you should be experienced enough to know that 488 in such a
vehicle is physically impossible short of a dive.

[bbrought]

Post by Rob Arndt
My point is that you need to argue with the makers of that claim vs me
and Euno- we have the refs. The Do-217P also looks NOTHING like any
other of the Do-217 series- fact and only it ...

I am not arguing at all with what you have seen in your refs - I
believe you that it says 488mph as that number is repeated all over
the internet. I am arguing (a) about how realistic that number is and
(b) about the validity and accuracy of Eunometric's analysis.

Are any of your references first hand, such as a copy of the
performance plot made during the actual test flight with the
accompanying calculations? These would have measured an indicated
airspeed, which was then converted to calibrated airspeed, temperature
and ambient pressure would have been taken into account and finally
the CAS would have been converted to TAS. The test pilot report would
have included all these calculations. All other references are second
and third hand, and it is very easy for a typo to slip in and then be
repeated from one source to the next.

[Jim Wilkins]

Post by Rob Arndt
...>
Pardon me, but these are not my claims nor Euno's for that matter. I
think it started with Green and "Warplanes of the Third Reich" which
is the old source for LW a/c and yet is still there at 488 mph with
latter sources like "Hitler's Luftwaffe" (a widely used ref that is
very credible, 1990 edition) to "Bombers of the Luftwaffe" (1994) and
so on...
...

My 1986 printing of 'The Warplanes of the Third Reich' gives Do 217P-0
maximum speed (at 29,250 lb) 363 mph at 46,000 feet.
Bottom of p.154.

jsw

[bbrought]

Post by Jim Wilkins

Post by Rob Arndt
...>
Pardon me, but these are not my claims nor Euno's for that matter. I
think it started with Green and "Warplanes of the Third Reich" which
is the old source for LW a/c and yet is still there at 488 mph with
latter sources like "Hitler's Luftwaffe" (a widely used ref that is
very credible, 1990 edition) to "Bombers of the Luftwaffe" (1994) and
so on...
...

My 1986 printing of 'The Warplanes of the Third Reich' gives Do 217P-0
maximum speed (at 29,250 lb) 363 mph at 46,000 feet.
Bottom of p.154.
jsw

Thanks for that - very interesting. So it seems there is even more
evidence that the other number is simply a misprint.

[Rob Arndt]

Post by bbrought

Post by Jim Wilkins

Post by Rob Arndt
...>
Pardon me, but these are not my claims nor Euno's for that matter. I
think it started with Green and "Warplanes of the Third Reich" which
is the old source for LW a/c and yet is still there at 488 mph with
latter sources like "Hitler's Luftwaffe" (a widely used ref that is
very credible, 1990 edition) to "Bombers of the Luftwaffe" (1994) and
so on...
...

My 1986 printing of 'The Warplanes of the Third Reich' gives Do 217P-0
maximum speed (at 29,250 lb) 363 mph at 46,000 feet.
Bottom of p.154.
jsw

Thanks for that - very interesting. So it seems there is even more
evidence that the other number is simply a misprint.- Hide quoted text -
- Show quoted text -

Yes, seems reasonable except that one states 363 mph at 46,000 ft vs
488 mph at 31,500 ft.

That would be more than a simple discrepancy or maybe the a/c was max.
speed in dive... but unlikely with high weight.

Rob

[Daryl Hunt]

Post by Rob Arndt

Post by bbrought

Post by Jim Wilkins

Post by Rob Arndt
...>
Pardon me, but these are not my claims nor Euno's for that matter. I
think it started with Green and "Warplanes of the Third Reich" which
is the old source for LW a/c and yet is still there at 488 mph with
latter sources like "Hitler's Luftwaffe" (a widely used ref that is
very credible, 1990 edition) to "Bombers of the Luftwaffe" (1994) and
so on...
...

My 1986 printing of 'The Warplanes of the Third Reich' gives Do 217P-0
maximum speed (at 29,250 lb) 363 mph at 46,000 feet.
Bottom of p.154.
jsw

Thanks for that - very interesting. So it seems there is even more
evidence that the other number is simply a misprint.- Hide quoted text -
- Show quoted text -

Yes, seems reasonable except that one states 363 mph at 46,000 ft vs
488 mph at 31,500 ft.
That would be more than a simple discrepancy or maybe the a/c was max.
speed in dive... but unlikely with high weight.
Rob

I already point out that it might have been a dive speed. And
larger AC like that have a lower dive speed than the fighters
lest things go flying off into the night in small pieces.

[Eunometic]

Post by Jim Wilkins

Post by Rob Arndt
...>
Pardon me, but these are not my claims nor Euno's for that matter. I
think it started with Green and "Warplanes of the Third Reich" which
is the old source for LW a/c and yet is still there at 488 mph with
latter sources like "Hitler's Luftwaffe" (a widely used ref that is
very credible, 1990 edition) to "Bombers of the Luftwaffe" (1994) and
so on...
...

My 1986 printing of 'The Warplanes of the Third Reich' gives Do 217P-0
maximum speed (at 29,250 lb) 363 mph at 46,000 feet.
Bottom of p.154.
jsw

This is possibly not the overall maximum speed but the maximum speed
at the opperational or combat ceiling.

The service ceiling is where climb drops to 100ft/minute, while the
combat/opperational ceiling is where it drops to 500ft/min. This is
where a reasonable pilot can be expected to opperate the aircraft and
the speed there is of tactical importance. It is however not the
maximum speed which may occur at other optimal altitudes.

[Eunometic]

Post by bbrought
I seem to recall the Do-217P claim was discussed here before, but
since some people like Rob seem to believe the equations and numbers
presented by Euno without question, I thought I'd respond for the sake
of those who don't have the background to critically evaluate Euno's
version of flight physics. Of course, I have no illusions that I'll
change Euno's mind, because he has a bit of a history of believing his
own woulda/coulda/shoulda claims regardless of overwhelming evidence
to the contrary. By the way, Euno, your high altitude range
calculations in the other thread are also messed up, but I think I'll
take this one thread at a time.

Do 217M1 speed 347mph  (about 20,000ft) engine power at sea level
1750hp, assume 1500hp at 20,000ft.
Relative Air Density at 20,000ft = 0.5
Now flying at 31500ft reduces air density to 0.3.  There is thus a 40%
reduction in parasitic drag to 60% of that at 20kfeet..  Induced drag
is a negligable component.

Now look at a picture of a Do-217 - just about nothing on that
airframe is designed for transonic speed. Most of the components, and
in particular that nose, would hit their critical Mach number
somewhere between 0.6 and 0.7. The root airfoil, in particular, is
very thick - close to 18%. If it was a NACA 2218, as used on previous
Dornier designs, it would also have a critical Mach number close to
Mach 0.6, depending on what the lift coefficient at that speed is. By
the time this aircraft got to 488 mph, if it was able to get there,
drag would probably have more than doubled.
It is surprising (or maybe not) that you neglected one of the most
significant drag components at that speed.
Then there is of course the fact that a large proportion of those
propeller blades would be transonic, resulting in a huge hit in
propeller efficiency.
If you still don't get it, the Tu-114, which holds the speed record
for a propeller driven aircraft, will do about Mach 0.78 maximum, but
that is with very powerful turboprops and a design that from the
beginning intended it to fly at that speed. The propellers are highly
optimised for transonic flight, and so is the entire airframe, which
includes swept wings and a very slender fuselage. Even then, it
doesn't cruise at Mach 0.78, but closer to Mach 0.7, as it is much
more efficient at that Mach number. Now, go have a look at some
pictures of a Tu-114 and compare to the layout of the Do-217P. Surely,
even you must see how ridiculous this 0.72M claim is?
On the other hand, the fastest piston engined aircraft is the Rare
Bear, which only achieved about Mach 0.69 during its record setting
flight of 528 mph. Reno racers in general use different propeller and
gearbox combinations than their production counterparts specifically
to reduce the propeller tip Mach number. As you can see, even they hit
a limit at around Mach 0.7. I'll get back to these two aircraft at the
end of the post.

I will compare the speed increase of going from 20,000ft to 31500ft as
power goes from 1500hp to 1850hp.
Using a cube law the increase in speed due to having only 60% as much
drag will be 18%

40% reduction in drag if you forget you are now entering the transonic
regime. Even that is not strictly correct. If you change altitude but
keep the speed (TAS) the same, as you did here, you must increase the
lift coefficient as your lift force must stay constant, which would
change induced drag. What would have made a lot more sense, would be
to work out what speed gives you the same drag at the higher altitude,
and then how much power you need to accelerate from that speed to your
new claimed top speed.
@20,000 ft, 347 mph TAS = 257 mph CAS
@31,500 ft, 418 mph TAS = 257 mph CAS
By keeping CAS and therefore dynamics pressure the same, you stay at
the same place on the L/D graph (once again, ignoring
compressibility), and since L = constant, you know D = constant. Of
course, prop efficiency is taking a hit, but I'll get to that later.
Now, you can work out how much more power is needed to go from 418 mph
P_required = (constant)*V^3 (approximately)
thus P2/P1 = V2^3/V1^3
P2/P1 = 488^3/418^3 = 1.59
So, at an absolute minimum, you need 59% more power. This cube law
assumes constant CD, which ignores compressibility which is very
definitely not negligible, so it is still an extremely optimistic
figure, but lets stick with it for now. Following your own
calculations, you gained 350 hp for each engine and effectively 500 hp
from that third engine. That gives you 1200 hp over the original 3000
hp, or 40% more power. So, in an absolute ideal world, with no
compressibility and no reduction in propeller efficiency, you don't
even come close to having enough power to get to that speed. In fact,
assuming you are getting the 2x350hp extra from the two main engines,
you would still need 1070 hp effective output form the third one - in
other words, power that add directly to thrust after all losses have
been taken into account. Alternatively, you need just over 400 kg or
880 lbs additional direct thrust. And once again, we have totally
ignored compressibility or propeller efficiency.

P = V1^3 = 0.6.V2^3
cuberoot(V1^3/0.6) = V2 = 408mph

Assuming you still get the same propeller efficiency than before, but
now with the tips going supersonic. However, see my notes above - you
started from the wrong place anyway.

Jet thrust of  two stage Merlin 66 was 300lbs (130kg) and that of the
two sage Jumo 213E was 200kg.  I assume the DB603 at 20,000ft produced
only 100kg.  However the preboosted DB603bBinto only 0.3 ata assume
250kp = 150kP extra thrust.

Probably still a bit optimistic, but I'll give that to you. Yet, look
above at what you would need as an absolute minimum in ideal
circumstances.

From the equaltion P = F X v.    At 440mph (200ms) this is worth 200m/
s x 1500N = 300kW power about 400hp = 500hp at the shaft assuming 80%
prop efficiency

80% prop efficiency, at that speed? With a WWII technology prop?
Ironically, it doesn't matter, because jet thrust counters drag
directly and your conversion back to an equivalent power is
nonsensical. Just like in the case of turboprop analysis, you have to
do a dual calculation - one for power converted to thrust via the prop
and one for direct thrust. So, you didn't have to make the propeller
efficiency correction here at all - the 500 hp still doesn't help you
enough, though.

to sumarise
1 18% increase in speed due to thinner air at high altitude
2 addition 7% increase in speed due to higher power
4 additional 9% increase in speed due to jet thurst doubling (probably
more like 13%)
If you compound 1.18 x 1.07 x 1.13 = 45% increase in speed.
Admitedly no comressabillity correction but we are only at Mach 0.73.

ONLY Mach 0.73 :-)
I have done a lot of aircraft performance calculations in my lifetime.
And the first thing I usually do is take a few historical figures to
get an idea of what to expect - it helps as a "sanity check" when you
get to the more detailed analysis. So, you have an aircraft here that
you claim will reach M=0.72 with two piston engines and a third that
is only used to pressurise the other two. Let's see what history tells
Tu-114, cruise M=0.7, but will do around M=0.78
Loaded weight: 289,000 lbs
Empty weight: 92,000 lbs
Installed power: 59,200 hp
Power/weight (empty): 0.643 hp/lb
Power/weight (loaded): 0.205 hp/lb
Highly optimised airframe and propellers for cruise at low transonic
Mach numbers.
Rare Bear, will do about M=0.69
Weight (minimal fuel): 8500 lb
Installed power: 4000 hp
Power/weight: 0.471 hp/lb
Not initially designed for transonic flight, but highly cleaned up
airframe, modified power system
Do-217P
Claimed max speed at M=0.72
Empty weight: 22,817 lb
Max T/O weight: 34,921 lb
Installed power (including third engine): 5140 hp
Power/weight (empty): 0.225 hp/lb
Power/weight (all up): 0.127 hp/lb
So, of the three, you are expecting the one with the dirtiest airframe
by an order of magnitude, and by far the lowest power-to-weight ratio,
to achieve the same Mach number as the other two - and that even after
I included the third engine as if it is directly adding to the power
like the other two.
Of course, none of this will prevent either you or Rob and probably
dozens of other Luft-46 types to continue repeating this claim which
most likely started as a misprint in some document. You will dig for
more "jet thrust", magic area ruling that only you can see, or some
secret Nazi thrust technology until you can justify that ridiculous
claim.

First of all let me say that I DID say there was no compressibillity
correction, I did the calculation to test the plausibillity of the
782kmh /485mph. Some web sites claim only 660kmh/409mph.

Now as to your criticsims:

1 Propellor efficiency:

a/ Photographs of the the Do 217P show a 4 baded propeller of somewhat
broader chord than the 4 bladed propellor on the DB603 engined Do
217M. The BMW 801 engined version used a 3 bladed propellor. It
seems a special high altitude propellor was provided.
b/ In converting an estimated increase in jet thrust of 150kP to ehp
(equivalent horsepower) at the shaft at 440mph/200meters/sec I assumed
a prop efficiency of 80%. In fact if I was more pessimistic and
assumed 60% efficiency the ehp refered to the shaft actually RISES.
So assuming a high prop efficiency actually is pessimistic and
conservative on my part

2 Comparisons to turbo-props.
a/ turboprops are limited in power by the turbine inlet temperature.
Fly in air that is 0.5 the density then you must reduce fuel flow to
0.5 maintain the same fuel/air dilution and turbine temperature.
The exception is engines that have been deliberatly derated for stress/
mechanical reasons and use this reserve to compensate for altitude or
high ambient temperatures at takeoff

b/ In contrast the pre-supercharged Do 217P is not going to loose
power with altitude, unlike most turboprops, at least untill it gets
to close to 30,000ft when the DB605T will no longer be able to
maintain sea level conditions at the intakes of the main engine.

So the comparison is not valid: the Do 217P will have MORE power at
high altitude than turbo-props.

3 Comparisons with "Rare Bear" Bearcat and other aircrafts speed and
Mach rating.

You have NOT quoted altitudes, this is quite sloppy. Mach 1 is 750mph
at sea level, perhaps a little more in the high temperatures in the
dessert where rare Bear races. Mach 1 is 660mph at 36000ft and about
700 at 30,0000ft where the Do 217P supposedly flew at 485mph. Mach is
temperature related.

At 31500ft the Do 217P is experiencing an air density of 0.3 which is
3.33 x less drag than at the low altitudes rare bear races.

4 Do 217P "Jet thrust" due to the Pre-supercharger the Jet thrust will
be very valuable.

5 Comparisons with the power to weight ratings of other aircraft.

The Do 217P will have virtually its entire power rating available at
very high altitudes where the drag is low but other aircraft have lost
much of their power and jet thrust.

6 Critical Mach. The standard Do 217 possibly had NACA 2218 at the
wing roots and 2209 at the wing tips however this is derived from the
Do 217 on the incomplete airfoils usage sight so may be a guess. For
comparison the Spitifre had 2213 at the roots and 2207.7 at rib 21
where the detachable tip was and 2209.4 at the outer alierlon hinge.
Considering the often cropped spitfire tips the Do 217P wing had about
the same form from just outside of the engine nacells.

Most of the Mc mach issues will come from inboard section, (where the
P-38 also dereived its problems due to the large fuel tankage there.)

There are correction factors eg Prandle Glauert but if we assume the
following
For Mc of 0.60 x 700mph = 420mph.
For Mc of 0.66 x 700mph = 462mph

It's fairly clear this aircraft is going to plausibly get to 420-462
before serious compressibillity issues crop up.

[bbrought]

Post by Eunometic
First of all let me say that I DID say there was no compressibillity
correction, I did the calculation to test the plausibillity of the
782kmh /485mph.

Yes, but with your highly optimistic approach you still just made it
to the claimed number. How can it then be plausible if you know you
left out a significant contributor to drag and overestimated prop-
efficiency for that Mach number? You will note I did not argue with
your numbers on engine performance - not even on your number for jet
thrust. But at the same time I also showed you needed a lot more power
to get there even if you ignored both compressibility and a reduction
in propeller efficiency.

Post by Eunometic
b/ In converting an estimated increase in jet thrust of 150kP to ehp
(equivalent horsepower) at the shaft at 440mph/200meters/sec I assumed
a prop efficiency of 80%.

Read my post again - for the jet thrust you didn't have to take prop
efficiency into account as the thrust directly counters drag - I was
giving you the full benefit of your estimated thrust number. It was
still far short of what you required even when ignoring
compressibility.

Post by Eunometic
It's fairly clear this aircraft is going to plausibly get to 420-462
before serious compressibillity issues crop up.

1) The lower end of this range, possibly, as I also admitted.
2) The upper end of this range: plausible to you maybe, but for the
altitude where these speeds are claimed, the aerodynamic configuration
of the aircraft and the propeller technology of that time, very few
aerodynamicists would agree with you.
3) Even your upper estimate is still well short of the 488 mph claim.
4) You are, as I predicted at the end of my post, still wildly
optimistic on prop efficiency at that speed, engine performance at
that altitude and total drag at that Mach number. Not to mention that
even when optimistic with these numbers the total installed power
still don't get you to the 488 mph number.

The obvious answer is still that the number is simply a misprint.

[Eunometic]

Post by bbrought

Post by Eunometic
First of all let me say that I DID say there was no compressibillity
correction, I did the calculation to test the plausibillity of the
782kmh /485mph.

Yes, but with your highly optimistic approach you still just made it
to the claimed number. How can it then be plausible if you know you
left out a significant contributor to drag and overestimated prop-
efficiency for that Mach number?

It was a first order approximation to check plausibillity, from there
more complicated effects can be estimated in.

Now about the propellor efficiency, for which I assumed 80% for the
purposes of estimating ehp. This was indeed an excellent choice.

Note the Propellor efficiency curves for a P-39 on Figure 6a and 6b on
page 14:
http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA800745
NACA TECHNICAL NOTE No. 1414

You will note an efficiency of over 90% at Mach 0.6 (420 mph), which
declines very little till Mach 0.65 (455mph) and does not decline
seriously till Mach 0.7 (490mph) when efficiency is down to 80%. Prop
efficiencies do exede 90% and are at their optimimum up to Mach 0.65.

So prop efficiency decline can be neglected since it does not effect
the aircraft untill Mach 0.65 (455mph).

If the Do 217 V4 (P prototype) is restricted to below say Mach 0.65
(455 mph) then it is not due to propellor efficiency decline at high
Mach.

This would have to be attributed entirely to aerodynamic issues. The
Do 217 is listed as having a profile of NACA 2218? at the roots and
NACA 2209? tip on the "incomplete guide to airfoil usage". The
question mark is clearly there because these numbers are simply
assumed from the Do 17 and Do 215 which are two completely different
much smaller aircraft. Furthermore from prototype V4 the wing span
was increased by 5m.

I will agree that airfoils of between NACA 2218 to NACA 2212 (the last
2 digits indicate thickness/chord ratio) will be entering
compressibility from Mach 0.5 onwards at the 18% end and about Mach
0.6 at the 13% end onwards. Furthermore there are the effects of the
very large intercoolers beneath the inner wings, which I assume might
be neglected in that they would be well engineered for ram effect
recovery (ie merdedith effect) and the large belly installation of
the DB605T.

This aircraft is going to get to Mach 0.6 before any serious 2nd order
effects accumulate

Post by bbrought
You will note I did not argue with
your numbers on engine performance - not even on your number for jet
thrust. But at the same time I also showed you needed a lot more power
to get there even if you ignored both compressibility and a reduction
in propeller efficiency.

Post by Eunometic
b/ In converting an estimated increase in jet thrust of 150kP to ehp
(equivalent horsepower) at the shaft at 440mph/200meters/sec I assumed
a prop efficiency of 80%.

Read my post again - for the jet thrust you didn't have to take prop
efficiency into account as the thrust directly counters drag - I was
giving you the full benefit of your estimated thrust number. It was
still far short of what you required even when ignoring
compressibility.

Post by Eunometic
It's fairly clear this aircraft is going to plausibly get to 420-462
before serious compressibillity issues crop up.

1) The lower end of this range, possibly, as I also admitted.

Many web sites state a top speed of 660kph which is 410mph however
note that there were two wing spans used on the Do 217P prototypes
that would effect matters.

Post by bbrought
2) The upper end of this range: plausible to you maybe, but for the
altitude where these speeds are claimed, the aerodynamic configuration
of the aircraft and the propeller technology of that time, very few
aerodynamicists would agree with you.

An ordinary armed Do 217M achieved 348mph in combat trim at 18700ft
one would expect that an Do 217P with more power at 31500ft would be
much faster apart form the agglomorations of intercoolers.

Post by bbrought
3) Even your upper estimate is still well short of the 488 mph claim.

My upper estimate ignoring any compressibillity was actually 493.

Post by bbrought
4) You are, as I predicted at the end of my post, still wildly
optimistic on prop efficiency at that speed, engine performance at
that altitude and total drag at that Mach number. Not to mention that
even when optimistic with these numbers the total installed power
still don't get you to the 488 mph number.
The obvious answer is still that the number is simply a misprint.

Possibly, in my experience when there are what appears to be
extravagent claims for German project aircraft is is from muddling up
specifications from advanced versions. For instance noting the Mach
limitation of the Do 217P the engineers may have suggested a laminar
profile wing (as they installed on the BV 155 and were planning for
the do 335) and estimated the performance for that. In fact the
Germans were testing scimitar props for the Me 109 that should have
driven speed up from 440mph to 462mph alone. Along comes someone
writing books for the mass market possibly with poor engineering or
language skills and takes the estimated value for that.

[bbrought]

Post by Eunometic
It was a first order approximation to check plausibillity, from there
more complicated effects can be estimated in.

All the complicated effects reduce performance. If it just get there
when you ignore them, you have clearly proved it is not plausible.
Every single estimate you included was for the best or ideal
conditions.

Post by Eunometic
Now about the propellor efficiency, for which I assumed 80% for the
purposes of estimating ehp.   This was indeed an excellent choice.
Note the Propellor efficiency curves for a P-39 on Figure 6a and 6b on
page 14:http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=...
NACA TECHNICAL NOTE No. 1414

Did you even read the NACA report you quoted? How many blades did this
propeller have? You do realise that fewer blades increase propeller
efficiency, yes? What does the line from which you read the 90%
efficiency represent? You clearly missed the most obvious hint: The
title of the report. The purpose of those tests were to determine what
the shank losses on a typical propeller were and to look at ways to
reduce them. They were not attempting to characterise a representative
P-39 propeller for installed, in-flight performance. Let me quote from
the report: "Measured propeller efficiencies (corrected for slipstream
losses) for the two test power coefficients are presented in figure 6.
Also given are the propeller efficiencies with the shank losses
neglected." The purpose of this research was to try and quantify the
shank losses. They corrected all the losses not directly related to
the blade performance itself out so that they were only left with
propeller blade efficiency, which they could then use as a theoretical
ideal to compare with. If you read a little further, you would also
have noticed that they never claim the shank losses could be
eliminated entirely. Nowhere in the report do they plot the actual
measured efficiency including all the real losses, and it is still for
a non-representative two-blade prop. The test rpm and power
coefficients were also for economic cruise conditions and not maximum
power, maximum speed conditions.

Instead, here is a report where they actually tried to quantify
propeller efficiency for a representative engine/propeller/aircraft
combination:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030063991_2003072763.pdf
The report above is for the YP-47M. They only went to a free-stream
Mach number of 0.5. The highest efficiency they got was around 0.82 at
the ideal Cp for the propeller, which is not the Cp you get at the
aircraft's maximum speed (Figures 5 and 6). That was at Mach 0.4. At
Mach 0.5 the best efficiency had dropped to around 0.76 (Figures 10
and 11). What do you think it will be by the time you get to Mach 0.7?

[Snipped a bunch of stuff derived from the misinterpreted report].

[snipped a discussion that come to the same conclusion I did]

Post by Eunometic
This aircraft is going to get to Mach 0.6 before any serious 2nd order
effects accumulate

Which is what I said. Once components on the aircraft start hitting
their critical Mach numbers, however, drag starts to skyrocket.

Post by Eunometic
Many web sites state a top speed of 660kph which is 410mph however
note that there were two wing spans used on the Do 217P prototypes
that would effect matters.

I now said several times I don't have a problem with the 410 mph
number. Are you suggesting a wing span change would reduce the
transonic drag rise - suddenly letting you get to 488 mph?

Post by Eunometic
An ordinary armed Do 217M achieved 348mph in combat trim at 18700ft
one would expect that an Do 217P with more power at 31500ft would be
much faster apart form the agglomorations of intercoolers.

And 410 mph is much faster. 488 mph is a Eunometric fantasy.

Post by Eunometic

Post by bbrought
3) Even your upper estimate is still well short of the 488 mph claim.

My upper estimate ignoring any compressibillity was actually 493.

That analysis was wrong. I showed you in my first post that the
correct numbers and calculations for exactly the same assumptions you
made do not get you even close to that number. You also snipped the

Post by Eunometic

Post by bbrought
It's fairly clear this aircraft is going to plausibly get to 420-462
before serious compressibillity issues crop up.
The obvious answer is still that the number is simply a misprint.

Possibly, in my experience when there are what appears to be
extravagent claims for German project aircraft is is from muddling up
specifications from advanced versions.

Or it is simply a misprint.

[Keith Willshaw]

Post by bbrought
I seem to recall the Do-217P claim was discussed here before, but
claim.
First of all let me say that I DID say there was no compressibillity
correction, I did the calculation to test the plausibillity of the
782kmh /485mph. Some web sites claim only 660kmh/409mph.
a/ Photographs of the the Do 217P show a 4 baded propeller of somewhat
broader chord than the 4 bladed propellor on the DB603 engined Do
217M. The BMW 801 engined version used a 3 bladed propellor. It
seems a special high altitude propellor was provided.
In converting an estimated increase in jet thrust of 150kP to ehp
(equivalent horsepower) at the shaft at 440mph/200meters/sec I assumed
a prop efficiency of 80%. In fact if I was more pessimistic and
assumed 60% efficiency the ehp refered to the shaft actually RISES.
So assuming a high prop efficiency actually is pessimistic and
conservative on my part

So in Euno world low propeller efficiency is good - on German engines only
of course


<more equally delusional stuff snipped>

Keith

[Ken S. Tucker]

Post by Keith Willshaw

Post by bbrought
I seem to recall the Do-217P claim was discussed here before, but
claim.
First of all let me say that I DID say there was no compressibillity
correction, I did the calculation to test the plausibillity of the
782kmh /485mph. Some web sites claim only 660kmh/409mph.
a/ Photographs of the the Do 217P show a 4 baded propeller of somewhat
broader chord than the 4 bladed propellor on the DB603 engined Do
217M. The BMW 801 engined version used a 3 bladed propellor. It
seems a special high altitude propellor was provided.
In converting an estimated increase in jet thrust of 150kP to ehp
(equivalent horsepower) at the shaft at 440mph/200meters/sec I assumed
a prop efficiency of 80%. In fact if I was more pessimistic and
assumed 60% efficiency the ehp refered to the shaft actually RISES.
So assuming a high prop efficiency actually is pessimistic and
conservative on my part

So in Euno world low propeller efficiency is good - on German engines only
of course
<more equally delusional stuff snipped>
Keith

One can run the Do217p against vastly superior a/c such as the DH
Musky
or Hughes XF11,

http://en.wikipedia.org/wiki/Hughes_XF-11

the Do217p looks like a pig with wings.
Normally Nazi's grossly overestimated German engineering and
industrial
capability, wasting a lot of money on junk. The allies seem to have
stayed
on 'the cutting edge', knowledgeable that average guys got to build
and
use them.
Ken

[Daryl Hunt]

Post by Ken S. Tucker

Post by Keith Willshaw

Post by bbrought
I seem to recall the Do-217P claim was discussed here before, but
claim.
First of all let me say that I DID say there was no compressibillity
correction, I did the calculation to test the plausibillity of the
782kmh /485mph. Some web sites claim only 660kmh/409mph.
a/ Photographs of the the Do 217P show a 4 baded propeller of somewhat
broader chord than the 4 bladed propellor on the DB603 engined Do
217M. The BMW 801 engined version used a 3 bladed propellor. It
seems a special high altitude propellor was provided.
In converting an estimated increase in jet thrust of 150kP to ehp
(equivalent horsepower) at the shaft at 440mph/200meters/sec I assumed
a prop efficiency of 80%. In fact if I was more pessimistic and
assumed 60% efficiency the ehp refered to the shaft actually RISES.
So assuming a high prop efficiency actually is pessimistic and
conservative on my part

So in Euno world low propeller efficiency is good - on German engines only
of course
<more equally delusional stuff snipped>
Keith

One can run the Do217p against vastly superior a/c such as the DH
Musky
or Hughes XF11,
http://en.wikipedia.org/wiki/Hughes_XF-11
the Do217p looks like a pig with wings.
Normally Nazi's grossly overestimated German engineering and
industrial
capability, wasting a lot of money on junk. The allies seem to have
stayed
on 'the cutting edge', knowledgeable that average guys got to build
and
use them.
Ken

The following AC was what the Germans would have built if they
didn't build such pugugly things that were about as aerodynamic
as a brick wall. The Performance that the two goose steppers
claim was realized but not by the Germans but by the US. And
that AC was cancelled as the jet age was already coming online as
early as 1943. The B-45 was already on the drawing board.

http://en.wikipedia.org/wiki/Republic_XF-12

[Keith Willshaw]

Post by Ken S. Tucker

Post by Keith Willshaw

Post by bbrought
I seem to recall the Do-217P claim was discussed here before, but
claim.
First of all let me say that I DID say there was no compressibillity
correction, I did the calculation to test the plausibillity of the
782kmh /485mph. Some web sites claim only 660kmh/409mph.
a/ Photographs of the the Do 217P show a 4 baded propeller of somewhat
broader chord than the 4 bladed propellor on the DB603 engined Do
217M. The BMW 801 engined version used a 3 bladed propellor. It
seems a special high altitude propellor was provided.
In converting an estimated increase in jet thrust of 150kP to ehp
(equivalent horsepower) at the shaft at 440mph/200meters/sec I assumed
a prop efficiency of 80%. In fact if I was more pessimistic and
assumed 60% efficiency the ehp refered to the shaft actually RISES.
So assuming a high prop efficiency actually is pessimistic and
conservative on my part

So in Euno world low propeller efficiency is good - on German engines only
of course
<more equally delusional stuff snipped>
Keith

One can run the Do217p against vastly superior a/c such as the DH
Musky
or Hughes XF11,
http://en.wikipedia.org/wiki/Hughes_XF-11
the Do217p looks like a pig with wings.
Normally Nazi's grossly overestimated German engineering and
industrial
capability, wasting a lot of money on junk. The allies seem to have
stayed
on 'the cutting edge', knowledgeable that average guys got to build
and
use them.
Ken

The following AC was what the Germans would have built if they didn't
build such pugugly things that were about as aerodynamic as a brick wall.
The Performance that the two goose steppers claim was realized but not by
the Germans but by the US. And that AC was cancelled as the jet age was
already coming online as early as 1943. The B-45 was already on the
drawing board.
http://en.wikipedia.org/wiki/Republic_XF-12

An impressive aircraft indeed but note that even such a
clean design with very powerful engines didnt
have the performance claimed for the Do-217 P

Keith

[Eunometic]

Post by Ken S. Tucker

Post by Keith Willshaw

Post by bbrought
I seem to recall the Do-217P claim was discussed here before, but
claim.
First of all let me say that I DID say there was no compressibillity
correction, I did the calculation to test the plausibillity of the
782kmh /485mph.  Some web sites claim only 660kmh/409mph.
a/ Photographs of the the Do 217P show a 4 baded propeller of somewhat
broader chord than the 4 bladed propellor on the DB603 engined Do
217M.  The BMW 801 engined version used a 3 bladed propellor.  It
seems a special high altitude propellor was provided.
 In converting an estimated increase in jet thrust of 150kP to ehp
(equivalent horsepower) at the shaft at 440mph/200meters/sec I assumed
a prop efficiency of 80%.  In fact if I was more pessimistic and
assumed 60% efficiency the ehp refered to the shaft actually RISES.
So assuming a high prop efficiency actually is pessimistic and
conservative on my part

So in Euno world low propeller efficiency is good - on German engines only
of course
<more equally delusional stuff snipped>
Keith

One can run the Do217p against vastly superior a/c such as the DH
Musky
or Hughes XF11,
http://en.wikipedia.org/wiki/Hughes_XF-11

Well Ken I would take the 1943 Do 217P against the Hughes XF_11
anyday.

The unarmed xf 11 exhibited the service ceiling of the Mustang from
1942 onwards, it would have been signifcantly slower than Mustangs
with the Merlin 100 (Packard V-1650-9) and had less service ceiling
than Mustangs or Spitifre VIII optimised for High Flying.

The Ta 152H with a speed of 472mph at 41,000ft and a service ceiling
of 48500ft with a glorious armament of 4 x 2mm and 1 x 30mm would have
had it for breakfast. Aircraft such as the P-47N could intercept is
as could Spitifre 22.

It is not wonder it was cancelled. The Do 217P with an opperational
ceiling of over 46,000 and a service ceiling of 51,000ft would have at
least stayed out of celing range of the early jets.

Post by Ken S. Tucker
the Do217p looks like a pig with wings.

I adore the intercoolers, they are very sexy.

Post by Ken S. Tucker
Normally Nazi's grossly overestimated German engineering and
industrial
capability, wasting a lot of money on junk.

Actually the Nazis estimated their industrial capacity correctly,
which is why they cancelled a lot programs that would not be completed
in time to effect the course of the war and instead refocused energy
on the ones that could.



The allies seem to have

Post by Ken S. Tucker
stayed
on 'the cutting edge', knowledgeable that average guys got to build
and
use them.
Ken- Hide quoted text -

The XF 11 was not cutting edge. It was a White elephant, along with
the B-36 that the USAF could afford becaiuse the USAF is a resource
rich, large country far from a war.. By the time they entered
service they would have been so inefficient compared to alternatives
such as in flight refueling that they would be a contribution to the
enemy. A 28 cylinder engine is nuts. No airline used the things.

[Ken S. Tucker]

Post by Eunometic

Post by Ken S. Tucker

Post by Keith Willshaw

Post by bbrought
I seem to recall the Do-217P claim was discussed here before, but
claim.
First of all let me say that I DID say there was no compressibillity
correction, I did the calculation to test the plausibillity of the
782kmh /485mph. Some web sites claim only 660kmh/409mph.
a/ Photographs of the the Do 217P show a 4 baded propeller of somewhat
broader chord than the 4 bladed propellor on the DB603 engined Do
217M. The BMW 801 engined version used a 3 bladed propellor. It
seems a special high altitude propellor was provided.
In converting an estimated increase in jet thrust of 150kP to ehp
(equivalent horsepower) at the shaft at 440mph/200meters/sec I assumed
a prop efficiency of 80%. In fact if I was more pessimistic and
assumed 60% efficiency the ehp refered to the shaft actually RISES.
So assuming a high prop efficiency actually is pessimistic and
conservative on my part

So in Euno world low propeller efficiency is good - on German engines only
of course
<more equally delusional stuff snipped>
Keith

One can run the Do217p against vastly superior a/c such as the DH
Musky
or Hughes XF11,
http://en.wikipedia.org/wiki/Hughes_XF-11

Well Ken I would take the 1943 Do 217P against the Hughes XF_11
anyday.
The unarmed xf 11 exhibited the service ceiling of the Mustang from
1942 onwards, it would have been signifcantly slower than Mustangs
with the Merlin 100 (Packard V-1650-9) and had less service ceiling
than Mustangs or Spitifre VIII optimised for High Flying.
The Ta 152H with a speed of 472mph at 41,000ft and a service ceiling
of 48500ft with a glorious armament of 4 x 2mm and 1 x 30mm would have
had it for breakfast. Aircraft such as the P-47N could intercept is
as could Spitifre 22.
It is not wonder it was cancelled. The Do 217P with an opperational
ceiling of over 46,000 and a service ceiling of 51,000ft would have at
least stayed out of celing range of the early jets.

Post by Ken S. Tucker
the Do217p looks like a pig with wings.

I adore the intercoolers, they are very sexy.

Post by Ken S. Tucker
Normally Nazi's grossly overestimated German engineering and
industrial
capability, wasting a lot of money on junk.

Actually the Nazis estimated their industrial capacity correctly,
which is why they cancelled a lot programs that would not be completed
in time to effect the course of the war and instead refocused energy
on the ones that could.

Stalin won, "quantity is quality", you need to understand that.
WW2 was an attrition, I suppose so was Nam, and maybe Afghan,
the hard thing about the Afghans, is they can't retreat or surrender.

Post by Eunometic
The allies seem to have

Post by Ken S. Tucker
stayed
on 'the cutting edge', knowledgeable that average guys got to build
and
use them.
Ken- Hide quoted text -

The XF 11 was not cutting edge. It was a White elephant, along with
the B-36 that the USAF could afford becaiuse the USAF is a resource
rich, large country far from a war.. By the time they entered
service they would have been so inefficient compared to alternatives
such as in flight refueling that they would be a contribution to the
enemy. A 28 cylinder engine is nuts. No airline used the things.

The problem with DO217p is it had a severely faceted windscreen,
blunting the nose, causing vicous turbulence and lots of drag.
But you want to compare realistic figures of the best twins the allies
built with the DOP, Nazi extravagance aside, which is mostly BS.
(Daryl posted about a slippery 4 engine job).
Ken

[Rob Arndt]

Post by Daryl Hunt
I can see you are not aware of what it takes to approach 500 mph
with a Prop.  To date, 503 mph is as fast as a piston prop
engined plane has gone.  Turboprops have gone faster but only by
about 15mph.  It's a limit of the propeller and the power to turn
it.

Nope. The Supermarine Spiteful Mk.XVI was capable of 494 mph (pretty
close to 500 mph) and one hit 504 mph on a test run in May 1945. This
was most likely the Griffon 101 engined machine with 3-speed
supercharger and 5-blade prop.

As I have stated repeatedly, this is my favorite WW2 fighter. Seafang
was slower at 475 mph and naval, but still likeable IMHO.

Rob

[bbrought]

Post by Rob Arndt

Post by Daryl Hunt
I can see you are not aware of what it takes to approach 500 mph
with a Prop.  To date, 503 mph is as fast as a piston prop
engined plane has gone.  Turboprops have gone faster but only by
about 15mph.  It's a limit of the propeller and the power to turn
it.

Nope. The Supermarine Spiteful Mk.XVI was capable of 494 mph (pretty
close to 500 mph) and one hit 504 mph on a test run in May 1945. This
was most likely the Griffon 101 engined machine with 3-speed
supercharger and 5-blade prop.

At a lower altitude (around 21,000 ft), so that the Mach number was
around 0.69 and it had a much better power-to-weight ratio than the
Do-217P.

Spiteful empty: 0.328 hp/lb
Max T/O: 0.238 hp/lb

Not to mention that it was aerodynamically extremely clean and had an
airfoil that was ideal for the lower end of the subsonic regime.

[bbrought]

Post by bbrought
Not to mention that it was aerodynamically extremely clean and had an
airfoil that was ideal for the lower end of the subsonic regime.

Should be: "lower end of transonic regime".

[Jim Wilkins]

...

E-2: 320 mph
K-2: 333 mph
M-1: 348 mph
J and N: 311 mph
P-1: 488 mph

Do the numbers make sense if "488" was a typo for "388"?

jsw

[bbrought]

Post by Rob Arndt

...

E-2: 320 mph
K-2: 333 mph
M-1: 348 mph
J and N: 311 mph
P-1: 488 mph
Do the numbers make sense if "488" was a typo for "388"?
jsw

Certainly. However, due to the higher operating altitude, I suspect
even 418 mph would have been quite believable.

[Daryl Hunt]

Post by Rob Arndt

...

E-2: 320 mph
K-2: 333 mph
M-1: 348 mph
J and N: 311 mph
P-1: 488 mph
Do the numbers make sense if "488" was a typo for "388"?
jsw

yes, they do.

[Rob Arndt]

Post by Daryl Hunt

Post by Rob Arndt

...

E-2: 320 mph
K-2: 333 mph
M-1: 348 mph
J and N: 311 mph
P-1: 488 mph
Do the numbers make sense if "488" was a typo for "388"?
jsw

yes, they do.

I might be inclined to believe that too... but that is pure
specualtion. Multiple good refs list 488 mph @ 31,500 ft. I searched
the "Luftwaffe Secret Projects' book on bombers but the Do-217P was
not a secret project. They did list the Do-317 due to the projected
Jumo 222 version and max speed est was 372 mph over 348 mph with BMW
801s. But that is a different a/c as well, so that gets us nowhere...

Rob

[Eunometic]

Post by bbrought
At a lower altitude (around 21,000 ft), so that the Mach number was
around 0.69 and it had a much better power-to-weight ratio than the
Do-217P.
Spiteful empty: 0.328 hp/lb
Max T/O: 0.238 hp/lb

These calcualtions need to be done with respect to the power at at the
correct altitude. Quoting low alttiude relative WEP power does not
provide an incidcation of power at optimal max speed alttidue.

[Daryl Hunt]

Post by Rob Arndt

Post by Daryl Hunt
I can see you are not aware of what it takes to approach 500 mph
with a Prop. To date, 503 mph is as fast as a piston prop
engined plane has gone. Turboprops have gone faster but only by
about 15mph. It's a limit of the propeller and the power to turn
it.

Nope. The Supermarine Spiteful Mk.XVI was capable of 494 mph (pretty
close to 500 mph) and one hit 504 mph on a test run in May 1945. This
was most likely the Griffon 101 engined machine with 3-speed
supercharger and 5-blade prop.

Thank you for verifying the wall. In order to get that fast, you
are going to be running a stipped down specially prepared ship.
Saying that all F-15s have the performance demonstrated by the
Steak Eagle is just silly. At least the records held by the
Naval F-4 was real since they used a fully operational bird.
Like our Tankers that still hold 5 world time to climb records
set in the 80s, we used the next bird on the line to do it. AC
3520 wasn't even one of our good ones. But using what amounts to
a Streak Eagle to set records is nice but has little bearing on
reality.

Post by Rob Arndt
As I have stated repeatedly, this is my favorite WW2 fighter. Seafang
was slower at 475 mph and naval, but still likeable IMHO.

Like all the ones that ran that fast, they had no impact on
anything other than speed records. While they were setting prop
records, the Jets were coming on line fast.

[Keith Willshaw]

Post by Rob Arndt

Post by Daryl Hunt
I can see you are not aware of what it takes to approach 500 mph
with a Prop. To date, 503 mph is as fast as a piston prop
engined plane has gone. Turboprops have gone faster but only by
about 15mph. It's a limit of the propeller and the power to turn
it.

Nope. The Supermarine Spiteful Mk.XVI was capable of 494 mph (pretty
close to 500 mph) and one hit 504 mph on a test run in May 1945. This
was most likely the Griffon 101 engined machine with 3-speed
supercharger and 5-blade prop.

According to aerospace.web the record is held by a modified Bearcat

<Quote>
The record for the fastest single-engined piston plane is held by a modified
Grumman F8F Bearcat, the Rare Bear, with a speed of 850.24 km/h (528.31 mph)
on 21 August 1989 at Las Vegas, Nevada, United States of America
</Quote>


The point is valid though, VERY few piston engined aircraft have beaten the
500 mph
barrier and for sur noned of them were medium bombers.

Keith