Stalls and Thoughts

"Bob F." wrote in
:

WrongO againO. The "coffin corner" is an altitude (point on a chart
where the stall speed and Mach come together) with a max power
setting. If you go faster, you get mach buffet. If you go to slow,
you stall. If you reduce power setting, you stall. If you nose over
to recover, you mach buffet. With your example I can see why you're
confused.


Acctually, the low side buffet isn't strictly a stall. The proof of this is
it happens at a much higher indicated and much lower alpha than a stall at
low altitudes. The wing doe lose lift, so in the broadest definition of a a
stall the wing stals, but what's actualy happening is that the increased
angle of attack you neccesarily have as you reduce speed increases the
speed of the air over the wing so that there are localised areas of
supersonic flow with an accompanying buffet. So what coffin corner actually
is is an onset of mach buffet caused by any combination of speed and alpha.


Bertie

That's exactly right Bertie. I never ran into anyone who knew that except
for a few engineers at Boeing. I'd love to meet you sometime. I was
fortunate enough to be able to take all the aero engineering courses they
offered. It was great. Most of the instructors were old 707 engineers. I
had great respect for them. They had all kinds of rules of thumb that I
never hear about. I have a note book full of them. I don't even see
reference to them in the the my bible, the NAVWEPS.

--
BobF.
"Bertie the Bunyip" wrote in message
...
"Bob F." wrote in
:

WrongO againO. The "coffin corner" is an altitude (point on a chart
where the stall speed and Mach come together) with a max power
setting. If you go faster, you get mach buffet. If you go to slow,
you stall. If you reduce power setting, you stall. If you nose over
to recover, you mach buffet. With your example I can see why you're
confused.


Acctually, the low side buffet isn't strictly a stall. The proof of this
is
it happens at a much higher indicated and much lower alpha than a stall at
low altitudes. The wing doe lose lift, so in the broadest definition of a
a
stall the wing stals, but what's actualy happening is that the increased
angle of attack you neccesarily have as you reduce speed increases the
speed of the air over the wing so that there are localised areas of
supersonic flow with an accompanying buffet. So what coffin corner
actually
is is an onset of mach buffet caused by any combination of speed and
alpha.


Bertie

"Bob F." wrote in
:

That's exactly right Bertie. I never ran into anyone who knew that
except for a few engineers at Boeing. I'd love to meet you sometime.
I was fortunate enough to be able to take all the aero engineering
courses they offered. It was great. Most of the instructors were old
707 engineers. I had great respect for them. They had all kinds of
rules of thumb that I never hear about. I have a note book full of
them. I don't even see reference to them in the the my bible, the
NAVWEPS.


I got a mole at Boeing. A rocket scientist, in fact. Meganerd. We grew up
together. This guy built a Piet in his basement starting at the age of 14.
( I helped) The things he found to do with Estes rockets and various
explosives as a teen were numerous and exciting! Especially to the local
cops.
He's just left Boeing to work for some millionaire on a commercial space
flight project. In texas I think.
I can't understand why they don't teach this in a bit more detail, though.
There are very few airline pilots who understand this nowadays. There's an
OK-ish FAA circular on it, but causes and recoveries ae not gone into in
any great detail. They seem to be happy to let the FMC look after it.

BTW, ever get a yaw damper failure in the 707? I've doen them in the sim in
the 727 and they were pretty exciting.
I've been told the 707 was worse.

Bertie

Yes, you learn a lot about Dutch rolls real quick. ...and I did experience
a elevator hydraulic cylinder stall once in a 707. That was an experience.

--
BobF.
"Bertie the Bunyip" wrote in message
...
"Bob F." wrote in
:

That's exactly right Bertie. I never ran into anyone who knew that
except for a few engineers at Boeing. I'd love to meet you sometime.
I was fortunate enough to be able to take all the aero engineering
courses they offered. It was great. Most of the instructors were old
707 engineers. I had great respect for them. They had all kinds of
rules of thumb that I never hear about. I have a note book full of
them. I don't even see reference to them in the the my bible, the
NAVWEPS.


I got a mole at Boeing. A rocket scientist, in fact. Meganerd. We grew up
together. This guy built a Piet in his basement starting at the age of
14.
( I helped) The things he found to do with Estes rockets and various
explosives as a teen were numerous and exciting! Especially to the local
cops.
He's just left Boeing to work for some millionaire on a commercial space
flight project. In texas I think.
I can't understand why they don't teach this in a bit more detail, though.
There are very few airline pilots who understand this nowadays. There's an
OK-ish FAA circular on it, but causes and recoveries ae not gone into in
any great detail. They seem to be happy to let the FMC look after it.

BTW, ever get a yaw damper failure in the 707? I've doen them in the sim
in
the 727 and they were pretty exciting.
I've been told the 707 was worse.

Bertie

"Bob F." wrote in
news
Yes, you learn a lot about Dutch rolls real quick. ...and I did
experience a elevator hydraulic cylinder stall once in a 707. That
was an experience.


Ouch. I didn't know they had hydraulics on the elevator. I thought the 707
was all tab control except the rudder.
I had a pitch problem in an A300 at about FL190 once. That was pretty
exciting, but since it was the automatics that caused it we were able to
disconnnect and get it all back under control. Scared the crap out of us.
We thought we had something on the airframe come loose and cause the pitch
problems. Nothing else made sense until we got down and maintenence
diagnosed the problem. We got a mach buffet recovering (2.5 G) but of
course that part of it wasnt too dramatic because of the relatively low
altitude. It would have been a different story at 330 ( the 'Bus was not
good at altitude)


Bertie

Right, right...it is actually controlled by tabs, my slip. Boy, not many
know that either, I'll bet. Anyway, if you pull too hard, they stall, that
is won't move, So you have to relax the back pressure almost completely and
then pull not so hard the next time. Weird feeling when you are descending,
trying to check altitude quickly, and don't know what's happening.
--
BobF.
"Bertie the Bunyip" wrote in message
...
"Bob F." wrote in
news
Yes, you learn a lot about Dutch rolls real quick. ...and I did
experience a elevator hydraulic cylinder stall once in a 707. That
was an experience.


Ouch. I didn't know they had hydraulics on the elevator. I thought the 707
was all tab control except the rudder.
I had a pitch problem in an A300 at about FL190 once. That was pretty
exciting, but since it was the automatics that caused it we were able to
disconnnect and get it all back under control. Scared the crap out of us.
We thought we had something on the airframe come loose and cause the pitch
problems. Nothing else made sense until we got down and maintenence
diagnosed the problem. We got a mach buffet recovering (2.5 G) but of
course that part of it wasnt too dramatic because of the relatively low
altitude. It would have been a different story at 330 ( the 'Bus was not
good at altitude)


Bertie

"Bob F." wrote in
:

Right, right...it is actually controlled by tabs, my slip. Boy, not
many know that either, I'll bet. Anyway, if you pull too hard, they
stall, that is won't move, So you have to relax the back pressure
almost completely and then pull not so hard the next time. Weird
feeling when you are descending, trying to check altitude quickly, and
don't know what's happening.

i retrained a lot of 707 guys on the 727 and the 'Bus and they had the
weirdest way of flying! They'd start to interecept an altitude with
thousands of feet to go sometime. They also used to just about have a heart
attack if you used the speedbrake.

Bertie

On Mar 15, 7:57*pm, Bertie the Bunyip wrote:
"Bob F." wrote innews
Yes, you learn a lot about Dutch rolls real quick. *...and I did
experience a elevator hydraulic cylinder stall once in a 707. *That
was an experience.

Ouch. I didn't know they had hydraulics on the elevator. I thought the 707 *
was all tab control except the rudder.
I had a pitch problem in an A300 at about FL190 once. That was pretty
exciting, but since it was the automatics that caused it we were able to
disconnnect and get it all back under control. Scared the crap out of us.
We thought we had something on the airframe come loose and cause the pitch
problems. Nothing else made sense until we got down and maintenence
diagnosed the problem. We got a mach buffet recovering (2.5 G) but of
course that part of it wasnt too dramatic because of the relatively low
altitude. It would have been a different story at 330 ( the 'Bus was not
good at altitude)

Bertie

2.5 G ... that would be something new in the passenger cabin. Get any
screams or spilt coke?

Speaking of g and jets, what kind of g loads can airliners like 707,
727, 737, and then the really big ones take?

wrote in
:

On Mar 15, 7:57*pm, Bertie the Bunyip wrote:
"Bob F." wrote
innewsradndOZJqc580HanZ2dnUVZ_qOk
:

Yes, you learn a lot about Dutch rolls real quick. *...and I did
experience a elevator hydraulic cylinder stall once in a 707. *That
was an experience.

Ouch. I didn't know they had hydraulics on the elevator. I thought
the 707
*
was all tab control except the rudder.
I had a pitch problem in an A300 at about FL190 once. That was pretty
exciting, but since it was the automatics that caused it we were able
to disconnnect and get it all back under control. Scared the crap out
of us. We thought we had something on the airframe come loose and
cause the pitch

problems. Nothing else made sense until we got down and maintenence
diagnosed the problem. We got a mach buffet recovering (2.5 G) but of
course that part of it wasnt too dramatic because of the relatively
low altitude. It would have been a different story at 330 ( the 'Bus
was not good at altitude)

Bertie

2.5 G ... that would be something new in the passenger cabin. Get any
screams or spilt coke?


Nope, no pax on that flight.

the airplane had just come off a heavy check. A 'D' Check which is nigh
on a complete rebuild. It was a cluster**** of certification, paperwork
and miscomunication that caused the problems. For one thing the airplane
had had a complete refit of all it's control surface bearings, and i had
known that which is what made me think we had airframe damage. The guy
who had tested it after the rebuild had discovered that the stal warning
system and alpha floor protection ( automatics that engage the
autothrottles and apply power regardless of what you want) was firing
off too early.
All this hapened to us on this flight and then some. The power came on
and the nose pitched up fairly quickly ( because of the underslung
engines) the pitch trim failed simultaneously which allowed the nose to
come up even more. The FO was flying but I took it and disconnected the
autoflight and put the nose down. Out intercept alt of FL 190 was coming
up quick so I pulled ( doing over 260 indicated) and the nose came up
very quickly due to the stab trim being wildly out for the speed. That's
when we got the buffet. Analysis of the FDR after determined the G and
flight profile. Airbus tried to blame me but actually caught hell for
inadequate flight testing both during certifiaction and failure to
rectify reported faults from the D check flight test.

Speaking of g and jets, what kind of g loads can airliners like 707,
727, 737, and then the really big ones take?

Certified limits are +2.5 , -1.0 clean and +2.0 and 0.0 with flaps out.
I believe it's the smae for all jet transoprts. They'll come apart after
that. Scary, eh?
The airplane needed to be checked for damage after this exposure, but
there was none.


Bertie

Bertie,
Did your mole ever tell you the story about Jack Waddell when he took the
maiden 747-100 flight to Farnborough?

--
BobF.
"Bertie the Bunyip" wrote in message
...
"Bob F." wrote in
:

That's exactly right Bertie. I never ran into anyone who knew that
except for a few engineers at Boeing. I'd love to meet you sometime.
I was fortunate enough to be able to take all the aero engineering
courses they offered. It was great. Most of the instructors were old
707 engineers. I had great respect for them. They had all kinds of
rules of thumb that I never hear about. I have a note book full of
them. I don't even see reference to them in the the my bible, the
NAVWEPS.


I got a mole at Boeing. A rocket scientist, in fact. Meganerd. We grew up
together. This guy built a Piet in his basement starting at the age of
14.
( I helped) The things he found to do with Estes rockets and various
explosives as a teen were numerous and exciting! Especially to the local
cops.
He's just left Boeing to work for some millionaire on a commercial space
flight project. In texas I think.
I can't understand why they don't teach this in a bit more detail, though.
There are very few airline pilots who understand this nowadays. There's an
OK-ish FAA circular on it, but causes and recoveries ae not gone into in
any great detail. They seem to be happy to let the FMC look after it.

BTW, ever get a yaw damper failure in the 707? I've doen them in the sim
in
the 727 and they were pretty exciting.
I've been told the 707 was worse.

Bertie