Stalls and Thoughts

Dudley Henriques wrote in
:

Bob F. wrote:
"Generally"?, "most certainly"?, I'd say "in one case". The other way
around is correct. That is "if you are in the area of reverse command,
you are dragging it in". Notwithstanding that the phrase includes the
notion of approaching and/or landing. The coffin corner is also not on
the back side of the power curve. It is at the asymptote and you can
never get into the back side. That's why it a corner. It is certainly
not referred to as "dragging it in" there. Been there with the best
test pilots in the world in a 747-400 while I was testing the 400. No
one has ever referred to is as that.

You're kidding right?

I believe you are repeating wht I have said. I said that "dragging it
in" generally refers to flying the approach in the area of reverse
command or if you will behind the power curve.

Well, it;s not a tech term, is it? It's slang. This is turning into the
three blind guys and the elephant thing.. I still don't even like doing
stabilised apprlaches in single at all. I see them as tanatmount to
dragging it in and of course, if there;s nowhere to land on the approach,
an engine failure will result in the smae result on either..


Bertie

The term "coffin corner" has the term "critical mach" in the formula. I've
never been at critical mach at such a low altitude. A little to fast for an
approach. So now you're telling me that the term "coffin corner" has been
high jacked to mean something different. Wouldn't be the first time!

--
BobF.
"Dudley Henriques" wrote in message
...
Bob F. wrote:
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.

I'm not confused and neither are you. :-))

The coffin corner YOU are describing can be found in the flight envelope
of the U2 (as well as other airplanes) at high altitude cruise. The coffin
corner I'm describing can be found on a dragged in approach AT LOW
ALTITUDE with the aircraft behind where the flight test community defines
the area of reverse command; that being below the airspeed for maximum
endurance. The corner is reached as you get the airplane low enough on the
approach where the sink rate can't be stopped with power as maximum is
already applied. The ONLY way out of the corner is to reduce angle of
attack. If the proximity between the aircraft and the ground won't allow
that angle of attack reduction, you hve what we call the "coffin corner".

--
Dudley Henriques

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

Bob F. wrote:
The term "coffin corner" has the term "critical mach" in the formula.
I've never been at critical mach at such a low altitude. A little to
fast for an approach. So now you're telling me that the term "coffin
corner" has been high jacked to mean something different. Wouldn't be
the first time!

Yes, that is exactly right. In the engineering sense I as well as you,
have always heard he term used in the sense you are using it.
In the world of high performance singles, especially in the figher
community, terms are often "stolen" or used in conversation so often
that they eventually become generic in the industry.
The term "Coffin Corner" as relates to "dragging it in" has been a
mainstay in our industry since the 50's. The F100 crash at Edwards
in 56 solidified the term to posterity. A young pilot named Barty Brooks
augured in when his nose wheel malfunctioned. He got so far behind the
curve on approach he couldn't lower the nose to recover the sink. The
subsequent crash has been used to demonstrate area of reverse command
issues t both the Naval and Air Force Test Pilot Schools for as long as
I can remember.
Actually, the other use of the term as well had it's origins within the
test community as do most terms like "coffin corner" :-)
Both are correct. I'm sure Bertie will eventually pop in and remind us
both of the blind men feeling the elephant. I agree with him
actually.That one's becoming one of my favorite Usenet analogies :-))

--
Dudley Henriques

Robert Moore wrote:
Dudley Henriques wrote

Coffin corner is the area behind the curve where sink rate
can't be stopped with power but requires reduction in angle of attack.
For a perfect example of an aircraft in coffin corner, see the Edwards
AFB accident involving a young AF pilot who got his F100 so deep into
coffin corner behind the curve he couldn't recover the airplane; not
enough air under him to reduce the angle of attack. He applied full
burner but couldn't fly it out on power alone. Reduction of angle of
attack was what he needed and he didn't have the room. THIS is the
definition of coffin corner and it most certainly IS in the area of
reverse command.

You're kidding, right? Better stick to light plane flight instructing
Dudley. I sure don't see the F-100 pilot anywhere near critical mach
speed. THAT was NOT a case of "coffin corner".

From Wikipedia, the free encyclopedia
Coffin corner (aviation)
The coffin corner or Q-Corner is the altitude at or near which an
aircraft's stall speed is equal to the critical Mach number, at a given
gross weight and G loading. At this altitude the aircraft becomes nearly
impossible to keep in stable flight. Since the stall speed is the
minimum speed required to maintain level flight, any reduction in speed
will cause the airplane to stall and lose altitude. Since the critical
Mach number is maximum speed at which air can travel over the wings
without losing lift to flow separation and shock waves, any increase in
speed will cause the airplane to lose lift, or to pitch heavily nose-
down, and lose altitude. The "corner" refers to the triangular shape at
the top of a flight envelope chart where the stall speed and critical
Mach number lines come together. Some aircraft, such as the Lockheed U-
2, routinely operate in the "coffin corner", which demands great skill
from their pilots.[1]


From Wikipedia, the free encyclopedia
Slow flight
Slow flight is a portion of an airplane's performance envelope above the
speed at which the plane will stall, but below the aircraft's endurance
speed. This part of the performance chart is also known as "the back
side of the power curve" because when flying in this area, more power is
required in order to go slower and still maintain straight and level
flight. A large angle of attack is required in order to maintain the
altitude of the aircraft.

Bob Moore
For God's sake Moore, try actually READING these posts before shooting
off your mouth once in a while. Our mutual dislike for each other is
legendary by now.
As usual, you are beating a dead horse here. Coffin corner is explained
in full in several posts above.
The use of the term is correct in BOTH instances!

--
Dudley Henriques

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

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

"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
:

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


Nope don't think he would have known. He operated in some weird way with
Boeing. Because he did defense stuff he was isolated. I just meant he knows
how all this stuff works.

Do tell, though..


bertie