B-52 Max Altitude

[Kyle Boatright]

Not that it has been relevant for 45 years, but what is the maximum
attainable altitude by a B-52? Googling the subject, I find multiple
references to a 50,000 ft ceiling, but that seems relatively low, since I
know that KC-135's have flown that high. With all of the BUFF's wing area
and the fact that the airplane was designed as a high altitude bomber, my
guess is that it could attain well over 50,000'.

Any takers?

KB

[Nemanja Vukicevic]

Sir,
Service Ceiling of a military airplane is defined as altitude at which
rate of climb reaches 2.5 m/s(8.2 ft/sec). Rate of climb depends on the
difference between available power (Thrust times speed) and power
needed (Drag times speed) which is usually expressed as SEP (Specific
Excess of Power) or through Thrust to Drag ratio (this parameter and
not wing loading or thrust to weight ratio is the most
important when calculating aircraft performance). Both Lift and Drag
are directly proportional to wing
area so it is the Lift to Drag ratio that matters.
According to my data Service Ceiling for B-52 varies between 45 000 ft
and 55 000 ft depending on AUW and between 40 500 ft and 45 000 ft for
C-135 with J-57 and TF-33 engines. B-52 has better ceiling than
C-135 with the same engine type. Re-engined C-135 with F108-CF-100
(CFM-56) have 3000 lb st more per engine and thus improved ceiling.
B-52 can fly higher popping up for a short period, but can not hold the
altitude that is dynamical ceiling.
The problem with data given in books and on the internet is that
weights are rarely specified and drag
polars and thrust charts for the engines are very hard to find, making
exact comparison of performance
betweevery difficult.

Nemanja Vukicevic
aeronautical engineering student

[Seany]

Now that's what I call an answer!!!

Post by Nemanja Vukicevic
Sir,
Service Ceiling of a military airplane is defined as altitude at which
rate of climb reaches 2.5 m/s(8.2 ft/sec). Rate of climb depends on the
difference between available power (Thrust times speed) and power
needed (Drag times speed) which is usually expressed as SEP (Specific
Excess of Power) or through Thrust to Drag ratio (this parameter and
not wing loading or thrust to weight ratio is the most
important when calculating aircraft performance). Both Lift and Drag
are directly proportional to wing
area so it is the Lift to Drag ratio that matters.
According to my data Service Ceiling for B-52 varies between 45 000 ft
and 55 000 ft depending on AUW and between 40 500 ft and 45 000 ft for
C-135 with J-57 and TF-33 engines. B-52 has better ceiling than
C-135 with the same engine type. Re-engined C-135 with F108-CF-100
(CFM-56) have 3000 lb st more per engine and thus improved ceiling.
B-52 can fly higher popping up for a short period, but can not hold the
altitude that is dynamical ceiling.
The problem with data given in books and on the internet is that
weights are rarely specified and drag
polars and thrust charts for the engines are very hard to find, making
exact comparison of performance
betweevery difficult.
Nemanja Vukicevic
aeronautical engineering student

[Rob Arndt]

Hasn't Jane's repeatedly stated with the H-model that the maximum
ceiling is 52,000 ft?

Rob

[Thomas Schoene]

Post by Rob Arndt
Hasn't Jane's repeatedly stated with the H-model that the maximum
ceiling is 52,000 ft?

It may have used that figure somewhere, but that doesn't make it accurate.
The 1978-79 JAWA that I checked claimed a service ceiling (see definition
earlier in the thread) of 55,000 feet for both G and H models. So no, Jane's
hasn't consistently claimed a maximum altitude of 52,000 feet.

[Kyle Boatright]

Post by Thomas Schoene

Post by Rob Arndt
Hasn't Jane's repeatedly stated with the H-model that the maximum
ceiling is 52,000 ft?

It may have used that figure somewhere, but that doesn't make it accurate.
The 1978-79 JAWA that I checked claimed a service ceiling (see definition
earlier in the thread) of 55,000 feet for both G and H models. So no,
Jane's hasn't consistently claimed a maximum altitude of 52,000 feet.
--
Tom Schoene Replace "invalid" with "net" to e-mail
"Our country, right or wrong. When right, to be kept right, when
wrong to be put right." - Senator Carl Schurz, 1872

As a follow up to all of the replies to the thread. There are published
figures for service ceiling, and there are real examples of the altitude the
type could attain. For instance, the US altitude record for an aircraft with
reciprocating engines is slightly under 48 ,000', and is held by a B-29.
That said, the service ceiling of a B-29 is listed as 33,600' in many
publications.

Same thing with the B-36. That aircraft flew above 50,000' on numerous
occasions, and one got to almost 59,000' while taking photos of an H-bomb
test. However, the service ceiling for the Peacemaker is generally listed in
the low to mid 40,000' range.

In both cases, the altitudes that could be achieved greatly exceeded the
published figures for service ceiling. So, going back to the question I
really want answered (and which I didn't state as clearly as I should have),
how high can a B-52 fly? I'm sure there are B-52 flightcrew in this forum
who have personal knowledge in this area...

Thanks in advance,

KB

[Rob Arndt]

Was the B-52G or H that achieved that height empty or loaded? Makes a
big difference between max. combat altitude and maximum altitude ever
reached- enen then, HOW many B-52s reached 55,000 ft on a regular
basis?
Answer that. I'm sure they bomb well under that altitude so WHY exactly
would they need to climb to 55,000 ft as most fighters, interceptors,
and missiles can easily reach that altitude.
Just curious...

Rob

[Don Harstad]

Post by Rob Arndt
Was the B-52G or H that achieved that height empty or loaded? Makes a
big difference between max. combat altitude and maximum altitude ever
reached- enen then, HOW many B-52s reached 55,000 ft on a regular
basis?
Answer that. I'm sure they bomb well under that altitude so WHY exactly
would they need to climb to 55,000 ft as most fighters, interceptors,
and missiles can easily reach that altitude.
Just curious...
Rob

Now, yes. Back in the late 50's and 60's, when they were SAC's primary
assets, that wasn't the case. For the first several years of service, they
weren't even seriously considered for conventional bombs, and were pure
nuclear strategic machines. You might check into the histories of some US
fighter squadrons regarding attempts to intercept SAC bombers at maximum
altitude. In those days, flying F-86D's, F-89's, and F-94's they pretty
much had to take off with the intention of making a head-on intercept, as
climbing to 55,000 feet in time to meet the bomber took much fuel. If the
bomber made even a small course change the interceptors frequently didn't
have the endurance to chase them after a max effort climb to high altitudes.
Additionally, with their small wing areas, many of the interceptors weren't
very maneuverable at that height,while the large wing span of the B-52 and
even the B-36 gave them an advantage. The main thing that brought the
bombers to low altitude penetrations was the SA-2 installations in the
Soviet Union, not the manned interceptors.

You might also refer to that B-47 over-flight of northern Russia... the
MiG's (17-19) had a very hard time staying with them, and tended to fall
away when they fired their cannon. The chase, as I recall, was from the
Murmansk vicinity down over Finland. Again, you'd have to research that,
but I seem to recall that many, many MiG's tried to shoot them down that
day. The B-47 speed and altitude wasn't all that much different than the
B-52.

Don H.

[Ron Parsons]

Post by Nemanja Vukicevic
According to my data Service Ceiling for B-52 varies between 45 000 ft
and 55 000 ft depending on AUW and between 40 500 ft and 45 000 ft for
C-135 with J-57 and TF-33 engines. B-52 has better ceiling than
C-135 with the same engine type. Re-engined C-135 with F108-CF-100
(CFM-56) have 3000 lb st more per engine and thus improved ceiling.
B-52 can fly higher popping up for a short period, but can not hold the
altitude that is dynamical ceiling.

Might want to challenge your data source. I did quite a few flights in a
KC-135A with the original J-57 engines and many modifications to the
aircraft resulting in an overall performance loss of 13% from the
published data and we routinely returned from being on station at 45,000
for almost 4 hours.

For what it's worth, the performance charts had data up to 55,000 but I
know of no one who had been that high.

[Nemanja Vukicevic]

Post by Ron Parsons
I did quite a few flights in a
KC-135A with the original J-57 engines and many modifications to the
aircraft resulting in an overall performance loss of 13% from the
published data and we routinely returned from being on station at 45,000
for almost 4 hours.
For what it's worth, the performance charts had data up to 55,000 but I
know of no one who had been that high.

Sir,
Thank You for the information. I have neglected the better altitude
performance of turbojets when compared to high bypass ratio turbofans
and indeed older data sources put J-57 engined aircraft service
ceiling at 50 000 ft. It seems that 40 - 45 000 ft refers to turbofan
engined variants chiefly 40 600 ft for TF33-P and 45 000 ft for
F108-CF. The 55 000 ft is most likely absolute (theoretical) ceiling.

Nemanja vukicevic
aeronautical engineering student

[Nemanja Vukicevic]

Post by Ron Parsons
I did quite a few flights in a
KC-135A with the original J-57 engines and many modifications to the
aircraft resulting in an overall performance loss of 13% from the
published data and we routinely returned from being on station at 45,000
for almost 4 hours.
For what it's worth, the performance charts had data up to 55,000 but I
know of no one who had been that high.

Sir,
Thank You for the information. I have neglected the better altitude
performance of turbojets when compared to high bypass ratio turbofans
and indeed older data sources put J-57 engined aircraft service
ceiling at 50 000 ft. It seems that 40 - 45 000 ft refers to turbofan
engined variants chiefly 40 600 ft for TF33-P and 45 000 ft for
F108-CF. The 55 000 ft is most likely absolute (theoretical) ceiling.

Nemanja Vukicevic
aeronautical engineering student

[Ron Parsons]

Post by Nemanja Vukicevic

Post by Ron Parsons
I did quite a few flights in a
KC-135A with the original J-57 engines and many modifications to the
aircraft resulting in an overall performance loss of 13% from the
published data and we routinely returned from being on station at 45,000
for almost 4 hours.
For what it's worth, the performance charts had data up to 55,000 but I
know of no one who had been that high.

Sir,
Thank You for the information. I have neglected the better altitude
performance of turbojets when compared to high bypass ratio turbofans
and indeed older data sources put J-57 engined aircraft service
ceiling at 50 000 ft. It seems that 40 - 45 000 ft refers to turbofan
engined variants chiefly 40 600 ft for TF33-P and 45 000 ft for
F108-CF. The 55 000 ft is most likely absolute (theoretical) ceiling.
Nemanja Vukicevic
aeronautical engineering student

You are correct, the efficiencies of the fan engines are at moderate
altitudes and speeds.

[Paul Hirose]

Post by Kyle Boatright
Not that it has been relevant for 45 years, but what is the maximum
attainable altitude by a B-52?

Have you looked in the Google archives of this newsgroup? Within the
past few years (definitely 2000 or later) I remember a posting by a
B-52 pilot on G vs. H model altitude capability. I think he used the
name BUFDRVR (maybe 2 F's). Haven't seen him around lately.

[t***@msn.com]

Post by Paul Hirose

Post by Kyle Boatright
Not that it has been relevant for 45 years, but what is the maximum
attainable altitude by a B-52?

Have you looked in the Google archives of this newsgroup? Within the
past few years (definitely 2000 or later) I remember a posting by a
B-52 pilot on G vs. H model altitude capability. I think he used the
name BUFDRVR (maybe 2 F's). Haven't seen him around lately.
--
To reply by email remove INVALID

I have over 800 hours in B-47s and nearly 6,000 hours in B-52s of all
models. I don't know the answer to the original question, but I have
never flown either aircraft over 42,000 feet. In B-47s back in the
late 60s we would have to slow down and descend in order to log fighter
attacks from F-86Ds. All the bombing I did in Vietnam and Cambodia was
around 35,000 to 38,000 ft.
Gene Myers

[Bob Matthews]

Post by t***@msn.com

Post by Paul Hirose

Post by Kyle Boatright
Not that it has been relevant for 45 years, but what is the maximum
attainable altitude by a B-52?

Have you looked in the Google archives of this newsgroup? Within the
past few years (definitely 2000 or later) I remember a posting by a
B-52 pilot on G vs. H model altitude capability. I think he used the
name BUFDRVR (maybe 2 F's). Haven't seen him around lately.
--
To reply by email remove INVALID

I have over 800 hours in B-47s and nearly 6,000 hours in B-52s of all
models. I don't know the answer to the original question, but I have
never flown either aircraft over 42,000 feet. In B-47s back in the
late 60s we would have to slow down and descend in order to log fighter
attacks from F-86Ds.

How late were F-86Ds used by the USAF? Or, are you talking NG units?

==bob

All the bombing I did in Vietnam and Cambodia was

Post by t***@msn.com
around 35,000 to 38,000 ft.
Gene Myers

[t***@msn.com]

I should have said the "late 50s". My mistake. The fighters were
stationed at Clinton Sherman, TX.
Gene Myers