B-47 coffin corner
George R. Gonzalez
In it they mention the B-47 had a "coffin corner".
No details.
Anybody have any info on this?
Regards,
George
Ed Rasimus
>Reading a fine old book "men of the contrail country".
>In it they mention the B-47 had a "coffin corner".
>No details.
>Anybody have any info on this?
Aircraft stall based on indicated air speed and are structurally
limited sometimes based on mach number. In these sub-sonic airframes,
exceeding the limiting mach can result in a situation in which control
effectiveness is diminished, reversed, or negated. At very high
altitude, the range of allowable airspeed between stall and max
decreases until the envelope is reduced to just a few knots. Turning
flight can result in a stall and descent can result in an out of
control situation due to exceeding the allowable mach number.
The U-2 has exactly this problem.
Ed Rasimus
Fighter Pilot (ret)
***ComputorEdge Magazine
***http://www.computoredge.com
Tarver Engineering
"Ed Rasimus" <thund...@earthlink.net> wrote in message
news:3cd944d0...@news.earthlink.net...
> "George R. Gonzalez" <gr...@flash.net> wrote:
>
> >Reading a fine old book "men of the contrail country".
> >In it they mention the B-47 had a "coffin corner".
> >No details.
> >Anybody have any info on this?
>
> Aircraft stall based on indicated air speed and are structurally
> limited sometimes based on mach number. In these sub-sonic airframes,
> exceeding the limiting mach can result in a situation in which control
> effectiveness is diminished, reversed, or negated.
Airflow seperation from the control surface being the cause.
> At very high
> altitude, the range of allowable airspeed between stall and max
> decreases until the envelope is reduced to just a few knots. Turning
> flight can result in a stall and descent can result in an out of
> control situation due to exceeding the allowable mach number.
>
> The U-2 has exactly this problem.
I didn't know that.
It looks as though they are towing the U2s into Palmdale, with a turboprop
twin.
John
John Kunkel
"Tarver Engineering" <jta...@sierratel.com> wrote in message
news:3cd964f4$1...@news.sierratel.com...
> > altitude, the range of allowable airspeed between stall and max
> > decreases until the envelope is reduced to just a few knots. Turning
> > flight can result in a stall and descent can result in an out of
> > control situation due to exceeding the allowable mach number.
> >
> > The U-2 has exactly this problem.
>
> I didn't know that.
At maximum operating altitude the difference between stall speed and VNE is
reportedly less than 5 knots.
John
Tarver Engineering
"John Kunkel" <kunk...@shorts.attbi.com> wrote in message
news:5GcC8.81664$vX.4645@rwcrnsc53...
The old super critical wing trick. :)
John
Unknown
Don't ALL a/c have this problem Ed?...assuming that they can
climb high enough of course.
--
Gord Beaman
PEI, Canada
"Old age is no place for sissies" -Bette Davis.
Ed Rasimus
>thund...@earthlink.net (Ed Rasimus) wrote:
>>
>>Aircraft stall based on indicated air speed and are structurally
>>limited sometimes based on mach number. In these sub-sonic airframes,
>>exceeding the limiting mach can result in a situation in which control
>>effectiveness is diminished, reversed, or negated. At very high
>>altitude, the range of allowable airspeed between stall and max
>>decreases until the envelope is reduced to just a few knots.
>
>Don't ALL a/c have this problem Ed?...assuming that they can
>climb high enough of course.
There are some corners of the envelope that are hard to reach, and
there are occasionally some factors other than aerodynamics that
govern, such as heat or lack of thrust. The "coffin corner" issue,
however, is one of limiting mach. If you've got an airplane that is
designed to go supersonic, then you don't get the problems.
I suppose if we want to be perfectly accurate, there is probably some
point at which unaccelerated stall can occur at supersonic speed, but
I suspect we run out of atmosphere before that happens. Accelerated
stall, i.e. buffet, occurs with no problem supersonic.
So, my answer (remember, I'm a political scientist by education, not
an aero engineer), is that, no, all aircraft don't have a
stall/limiting mach convergence.
Mac
snip
Great post, superbly explained as usual, you missed your teaching
vocation :).
Interesting post on pprune a while ago [Ed you should visit, your
presence would be much appreciated I'm sure] an RAF pilot who talked of
the halcyon days when we {brits] had a few aircraft that could do things
that would impress. He talked of piloting his Vulcan at 55k and lazily
turning at 30 degree AoB and laughing at the Phantoms as they fell out
of the sky trying to catch him.
--
Mac.
Ed Rasimus
>Ed Rasimus wrote:
>
>snip
>
>Great post, superbly explained as usual, you missed your teaching
>vocation :).
Thanks for the kind words. Actually, a career in the military almost
inevitably leads to considerable time teaching. I've done the normal
bits as a flight IP, but also logged several years as a classroom
instructor in USAF undergrad pilot training, plus a couple of years
teaching IPs how to IP.
Now, I fill my spare time teaching political science classes in the
local community college.
>Interesting post on pprune
"pprune"???
>a while ago [Ed you should visit, your
>presence would be much appreciated I'm sure] an RAF pilot who talked of
>the halcyon days when we {brits] had a few aircraft that could do things
>that would impress. He talked of piloting his Vulcan at 55k and lazily
>turning at 30 degree AoB and laughing at the Phantoms as they fell out
>of the sky trying to catch him.
I can imagine it. The F-4 was no performer when it came to altitude. I
remember the occasional tasking as B-52 escort. They liked the FL
370-410 regime and an A/A loaded F-4 (3 tanks, 3 Sparrows, 4
Sidewinders, 1 ECM pod) liked the low twenties. Compound the problem
by SAC preferring to fly at night, and B-52 EWOs not liking to be
touched by radar and you've got a real handfull trying to keep
somewhere in the vicinity.
I also recall buddying with a KC-135 out of Torrejon enroute to
Incirlik. Cruising on the wing at FL 310 and getting intercepted by a
Spanish Mirage 3. He joined up on the wing, waved at us then did a
level 360 turn back to the wing position. Starting at 325 IAS, that
took an incredible wing and lots of power to show off.
I can only imagine the kind of lift that Vulcan could deliver.
Tarver Engineering
"Mac" <mac...@ntlworldTAKEOUT.com> wrote in message
news:3CD994...@ntlworldTAKEOUT.com...
> Ed Rasimus wrote:
>
> snip
>
> Great post, superbly explained as usual, you missed your teaching
> vocation :).
What a loser, out doing, instead of teaching. :)
John
Guy Alcala
> On Wed, 08 May 2002 22:10:37 +0100, you wrote:
>
> >Interesting post on pprune
>
> "pprune"???
the "Professional Pilots Rumor NEtwork," but really just so they can use an
acronym that memorializes the cartoon Pilot Officer Prune of WW2 RAF training
fame (equivalent perhaps to the navy's Dilbert). Lots of great people to
read/converse with. Just go to the the "military aircrew" forum, or any of
the others that interest you. Lightly moderated after the fact, and only
when someone's been very rude, although you can always edit your own posts.
Guy
Ron Parsons
"Gord Beaman" (ve...@rac.ca) wrote:
B-47 didn't have spoilers or speed brakes, so once in the corner, it had
no way down.
At some point, they added the ability to lower the aft landing gear for
drag.
In addition, the wing was so flexible that the ailerons became flying
tabs and flexed the wing resulting in a bank opposite of control input.
Both B-52 and KC-135 had combination spoilers/speed brakes as a result
of the B-47's problems. Plus you will note that the KC-135 and 707 had
inboard ailerons placed in stiff part of the wing for high speed use and
the outboard ailerons were locked out.
And you probably know that the B-52H has no ailerons, only spoilers.
--
Ron
Peter Stickney
The margin is small enough, and the U-2's span is wide enough, that at
altitude, it is possible, in a turn, to have one wingtip in the
pre-stall buffet zone, and the other in the Mach buffet zone.
--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
Peter Stickney
thund...@earthlink.net (Ed Rasimus) writes:
> "George R. Gonzalez" <gr...@flash.net> wrote:
>
>>Reading a fine old book "men of the contrail country".
>>In it they mention the B-47 had a "coffin corner".
>>No details.
>>Anybody have any info on this?
>
> Aircraft stall based on indicated air speed and are structurally
> limited sometimes based on mach number. In these sub-sonic airframes,
> exceeding the limiting mach can result in a situation in which control
> effectiveness is diminished, reversed, or negated. At very high
> altitude, the range of allowable airspeed between stall and max
> decreases until the envelope is reduced to just a few knots. Turning
> flight can result in a stall and descent can result in an out of
> control situation due to exceeding the allowable mach number.
In the case of the B-47, it wasn't helped any by the fact that the -47
had no airbrakes, and a very low-drag shape. Stick the nose down a
little bit, and it speed up but fast! Descents had to be very
carefully planned and monitored. Oh, yeah, as if that wasn't enough,
there was also an IAS/EAS linit of 425 kts. The ailerons would twist
the flexible wing as IAS increased, reducung and eventually reversing
roll control. In its own way, the B-47 was teh SR-71 or Space Shuttle
of its day. It took large aircraft performance to an entirely
different level, and had many potentially fatal quirks. Refuelling
them from KC-97s was a delicate and dangerous process, with the B-47
at the very left edge of its performance envelope (The slow side) and
the C-97 way over at the right edge ot its envelope. (The fast side)
BUFDRVR
So does nearly every sub-sonic aircraft. Flying at B-52H at FL 500 (only did it
once) is a nightmare, not only for the reasons you described, and the effort
required to get there, but getting down is a real pain. Can't pull the
throttles back too far or you'll get slow and stall, can't put the nose down
too far or you'll overspeed the jet.
BUFDRVR
"Stay on the bomb run boys, I'm gonna get those bomb doors open if it harelips
everyone on Bear Creek"
Cub Driver
>altitude, the range of allowable airspeed between stall and max
>decreases until the envelope is reduced to just a few knots. Turning
>flight can result in a stall and descent can result in an out of
>control situation due to exceeding the allowable mach number.
>
>The U-2 has exactly this problem.
So, as I recall, did the Spirit of St Louis, at least at the gas load
it was carrying early in the flight.
Still, the B-47 did better than fighters of the time. There's a grand
story by the pilot of an RB-47 who was intercepted by MiG 17s over
Archangle (whatever). The MiGs were still chasing him over Finland,
whose newspapers reported the cannon fire. (The report was in the New
York Times next day.)
He said that the MiGs could get up to his altitude all right, but
whenever they maneuvered to get him in sight, they fell away. However,
one of them got close enough that he had a fist-sized hole in the skin
of his plane. A ground crewman in England cut the piece out and framed
it for him; he was still carrying it around when I heard him speak
about it.
all the best -- Dan Ford (email: webm...@danford.net)
see the Warbird's Forum at http://www.danford.net
Vietnam | Flying Tigers | Pacific War | Brewster Buffalo | Piper Cub
Ron Parsons
Cub Driver <lo...@my.sig.file> wrote:
>Still, the B-47 did better than fighters of the time. There's a grand
>story by the pilot of an RB-47 who was intercepted by MiG 17s over
>Archangle (whatever). The MiGs were still chasing him over Finland,
>whose newspapers reported the cannon fire. (The report was in the New
>York Times next day.)
Out of Offutt we used to tank the guys from the 55th fairly regularly.
Never knew if the RB was different or it was those particular fliers,
but they were head and shoulders above the rest of the B-47 drivers when
it came to sticking on the boom.
They also taught us a trick which helped all the B-47's and that was to
pull back the inboards a bit and increase the outboards. Somehow that
altered the airflow greatly in their favor.
--
Ron
John R Weiss
will ever actually be able to fly in a narrow "coffin corner." If there is
enough airframe drag that critical Mach is not attainable, or insufficient
thrust such that the altitude at which critical Mach and stall speed converge is
not attainable, a pilot may never operate in the regime. The airplane might
stall at best climb speed (max attainable altitude), but not be near critical
Mach.
For example, the A-6 had such high drag at high Mach that .96 was the highest
attainable in any condition. The A-4 with the J52-P6A engine could get to about
45,000' at best climb speed around .7 Mach when light and relatively clean, but
was not near critical mach at max operating altitude.
OTOH, the Boeing 747-400 with the CF6-80C2B5F engines has a _lot_ of excess
thrust (248,400 lb total) at "light" weights (<200,000 Kg [440,000 lb]). The
Mmo is relatively high (0.92), but the Vmo is lower (365 KIAS) than a subsonic
fighter with similar Mach capability. The depicted Mach buffet and stall buffet
limit indicators on the PFD (primary Flight Display) start to converge at
43,000', but there is plenty of thrust available to climb higher. The airplane
is only certified to 45,100', but it certainly could climb higher at light
weights, and I suspect one could find its "coffin corner" somewhat above that
altitude.
OTOOH, relatively few aircraft routinely operate in the regime. The U-2 is
apparently among them.
"BUFDRVR" <buf...@aol.com> wrote...
buf3
I have been in the "coffin corner" in an RB-47 and have experienced
"aileron reversal" at speeds above 425 IAS so I can confirm the
phenomenon. I also have over 5,000 hours in various models of the B-52
and never had a reason to fly above 42,000 feet. We hated to fly that
high because of the oxygen discipline required by the regs. I would
rather fly around 35,000 feet. In the "good old days" before civilian
jet passenger aircraft we (the military) were the only ones flying
around "VFR on top" and had the skys to ourselves.
Gene Myers
BUFDRVR
>and never had a reason to fly above 42,000 feet.
USAF Weapons School sortie. We were testing the -1-1. We computed combat
ceiling then tested it in flight, then computed absolute ceiling and tested
that. Current oxygen requirements in 11-2B-52 Volume III state if cabin
pressure exceeds 10,000' all crew members must be on oxygen. It all depends on
the jet, but most go above 10,000' in 7.45 around 43,000'. So yes, we were all
up O2.
Darrell
(mach tuck) speed. We flew the B-47 before there was positive
control airspace up high. We flew mostly "VFR on top". During
the afternoon the cumulous clouds would begin to build and rise
higher and higher. We'd continue to climb to stay "on top".
When you'd get above optimum altitude, low speed stall was just a
couple knots slower than your current speed and MMO with Mach
tuck or buzz was just a couple knots faster that your current
speed. You were in "coffin corner", especially if you had to
make a simulated bomb run using a combat breakaway manuever.
And, during the breakaway, because of the highly swept wings, the
beginning stall would start from the wingtip and work towards the
fuselage. This caused a strong nose up reaction. I remember
doing breakaways above optimum altitude and having to use full
forward elevator to keep the nose from rising further into the
incipient stall.
"George R. Gonzalez" wrote:
--
Darrell R. Schmidt
dsch...@cox.net
B-58 Hustler History: http://members.cox.net/dschmidt1/
My email address is wrong to stop SPAM.
To respond remove the "stop" from it.
Bob McKellar
Darrell wrote:
> Safe flight is accomplished above stall speed but below maximum
> (mach tuck) speed. We flew the B-47 before there was positive
> control airspace up high. We flew mostly "VFR on top". During
> the afternoon the cumulous clouds would begin to build and rise
> higher and higher. We'd continue to climb to stay "on top".
> When you'd get above optimum altitude, low speed stall was just a
> couple knots slower than your current speed and MMO with Mach
> tuck or buzz was just a couple knots faster that your current
> speed. You were in "coffin corner", especially if you had to
> make a simulated bomb run using a combat breakaway manuever.
>
> And, during the breakaway, because of the highly swept wings, the
> beginning stall would start from the wingtip and work towards the
> fuselage. This caused a strong nose up reaction. I remember
> doing breakaways above optimum altitude and having to use full
> forward elevator to keep the nose from rising further into the
> incipient stall.
I don't think they paid you guys enough.
Bob McKellar
Walt BJ
the mission altitude was precomped according to the weather forecast.
Now if the density altitude/temp changed the U2 pilot could find
himself flying level according to his altimeter yet drive right into
'coffin corner'. This from an old friend and colleague who was a U2
forecaster. In the same vein, there have been several Learjet
accidents due to coffin corner - stall, drop the nose, and end up
riding critical mach.
Walt BJ
buf3
> I don't think they paid you guys enough.
>
> Bob McKellar
I wondered about that myself when I was on alert at RAF Fairford,
England with an H bomb that filled the bomb bay and was so heavy we
had to use full nose down trim and 30 ATO bottles for takeoff and our
target was Moscow and we didn't quiet have enough range to reach our
post strike base. If it hadn't been for the trips down to London
.....
Gene Myers
Darrell
Perhaps not but... I retired at age 38. I'm now 68. I plan to live
forever to make it cost 'em!!!! :)
(and I retired from American Airlines at age 60, and now work for
Flight Safety Boeing.. Retire early and often, that's my motto).
MLenoch
>forever to make it cost 'em!!!! :)
>(and I retired from American Airlines at age 60, and now work for
>Flight Safety Boeing.. Retire early and often, that's my motto).
>
Do you know Terry Chamberlain?
V. Lenoch
ex- Lazy B Ranch
Keith Kissane
buf3 wrote:
> Bob McKellar <b...@coastcomp.com> wrote in message news:<3CDB2EA1...@coastcomp.com>...
>
> > I don't think they paid you guys enough.
> >
> > Bob McKellar
>
> I wondered about that myself when I was on alert at RAF Fairford,
> England with an H bomb that filled the bomb bay and was so heavy we
> had to use full nose down trim and 30 ATO bottles for takeoff and our
> target was Moscow and we didn't quiet have enough range to reach our
> post strike base.
Your post strike base probably would have been a glowing crater by the time you could have
gotten there, anyway.
Unknown
Y'know, someday, in the far distant misty future, man will look
back at these archived posts, shudder and say, "My God!...did our
ancestors really come that close to exterminating the human
race"?.
At least I hope there'll be humans available to say that.
Not a bunch of cockroaches chirping and screwing and gathering at
Horten's for double double bugjuices. :)
Darrell
Doesn't ring a bell but I'm becoming a little forgetful Where would I
know him from?
Mac
>
> Ed Rasimus wrote:
>
> > On Wed, 08 May 2002 22:10:37 +0100, you wrote:
> >
> > >Interesting post on pprune
> >
> > "pprune"???
>
> www.pprune.org
Thats the one, sorry. Worth reading if only for the 'NL - no more
questions' thread on Rotorheads, funniest thing I've read in ages:)
--
Mac.
Unknown
>MLenoch wrote:
>
>> > I'm now 68. I plan to live
>> >forever to make it cost 'em!!!! :)
>> >(and I retired from American Airlines at age 60, and now work for
>> >Flight Safety Boeing.. Retire early and often, that's my motto).
>> >
>>
>> Do you know Terry Chamberlain?
>> V. Lenoch
>> ex- Lazy B Ranch
>
>Doesn't ring a bell but I'm becoming a little forgetful Where would I
>know him from?
>--
>Darrell R. Schmidt
I'm the same age Darrell, and I know what you mean about...
??
...what was that again?...
Darrell
> Darrell <dschmi...@cox.net> wrote:
>
> >MLenoch wrote:
> >
> >> > I'm now 68. I plan to live
> >> >forever to make it cost 'em!!!! :)
> >> >(and I retired from American Airlines at age 60, and now work for
> >> >Flight Safety Boeing.. Retire early and often, that's my motto).
> >> >
> >>
> >> Do you know Terry Chamberlain?
> >> V. Lenoch
> >> ex- Lazy B Ranch
> >
> >Doesn't ring a bell but I'm becoming a little forgetful Where would I
> >know him from?
> >--
> >Darrell R. Schmidt
>
> I'm the same age Darrell, and I know what you mean about...
> ??
> ...what was that again?...
Yeah. After I retired from AA I taught the 737 and MD80 at FSI. Finally
had to drop the 737. Hard enough to remember just the MD80, now with FSB,
what with MD80 with steam gauges and PMS, MD88 with EFIS and FMS. Generic
pilots... specific airline procedures. JETSGO, KAL, VANGUARD, US MARSHALS,
FAA, etc. What's a mother to do?
Bill Horne
were low-level using single-engine just to have enough fuel to make the
target. I never heard any talk about going somewhere afterwards.
Bill Horne
P.S. This is all hearsay for me. I only flew then later when all we did
was in-flight re-fueling and ECM.
C.D.Damron
"Bill Horne" <wfh...@swbell.net> wrote in message
news:3CE04B8...@swbell.net...
Ron Parsons
"Gord Beaman" (ve...@rac.ca) wrote:
>Keith Kissane <kk...@earthlink.net> wrote:
>
>>
>>
>>buf3 wrote:
>>
>>> Bob McKellar <b...@coastcomp.com> wrote in message
>>> news:<3CDB2EA1...@coastcomp.com>...
>>>
>>> > I don't think they paid you guys enough.
>>> >
>>> > Bob McKellar
>>>
>>> I wondered about that myself when I was on alert at RAF Fairford,
>>> England with an H bomb that filled the bomb bay and was so heavy we
>>> had to use full nose down trim and 30 ATO bottles for takeoff and our
>>> target was Moscow and we didn't quiet have enough range to reach our
>>> post strike base.
>>
>>Your post strike base probably would have been a glowing crater by the time
>>you could have
>>gotten there, anyway.
>>
>
>Y'know, someday, in the far distant misty future, man will look
>back at these archived posts, shudder and say, "My God!...did our
>ancestors really come that close to exterminating the human
>race"?.
Gord, we not only came that close, we teetered at that age for 20 years.
--
Ron
Bill Horne
Bill Horne
Deep Avali
>>>> > I don't think they paid you guys enough.
>>>> >
>>>> > Bob McKellar
>>>>
>>>> I wondered about that myself when I was on alert at RAF Fairford,
>>>> England with an H bomb that filled the bomb bay and was so heavy we
>>>> had to use full nose down trim and 30 ATO bottles for takeoff and our
>>>> target was Moscow and we didn't quiet have enough range to reach our
>>>> post strike base.
>>>
>>>Your post strike base probably would have been a glowing crater by the time
>>>you could have
>>>gotten there, anyway.
>>>
>>
>>Y'know, someday, in the far distant misty future, man will look
>>back at these archived posts, shudder and say, "My God!...did our
>>ancestors really come that close to exterminating the human
>>race"?.
>
>Gord, we not only came that close, we teetered at that age for 20 years.
>
Kind of offtopic, and from a different era, but I was reading this the
other day and it's talking about this very subject.
Richard Brooks
"Ron Parsons" <jr...@gte.net> wrote in message
news:jrp59-59A227....@news.bellatlantic.net...
At least they helped me get to sleep, watching them doing "circuits and
bumps through the night at RAF/USAF Brize Norton.
Richard.
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