Stalls and Thoughts

"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.

--
BobF.
"Dudley Henriques" wrote in message
...
Bob F. wrote:
"Dragging it in" does not necessarily mean "in in the area of reverse
command". It just means that you have added power instead of reducing
drag by retracting flaps or gear, etc. "The area of reverse command" is
an exteme example.

The coffin corner of the back side of the power curve is the extreme. You
can add power flaps or no flaps and still be well on the front side of the
power curve.
Generally speaking, if you are "dragging it in, you are most certainly in
the area of reverse command

--
Dudley Henriques

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. This is absolutely
correct. 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.

--
Dudley Henriques

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.

--
BobF.
"Dudley Henriques" wrote in message
...
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. This is absolutely correct. 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.

--
Dudley Henriques

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

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

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

Well, the bit of the envelope you're talking about is the low end of the
speed envelope fro every airplane. The coffin corner really only applies to
high alt/high speed transonic airplanes. When you climb up above transition
and reach th ealtitude where the airplane is mach limited the rules
changed.
I've attached a diagram of a typical flight envelope showing the constant
indicated max/min speeds up to transition where they taper in. The point in
dashded lines at the top is the point Bob was talking about where both
happen at the same time. To maintain a margin a max altitude dictated by a
G is determined. Going to fast or sow or pulling too much G at or near max
will result in a buffet and loss of lift, just for starters.





I've just reposted this because I've gotten some e-mail complaining that
the attachment didn't come through. I'll repost that in
alt.binaries.pictures.aviation


Bertie

Bertie the Bunyip wrote:
Well, the bit of the envelope you're talking about is the low end of the
speed envelope fro every airplane. The coffin corner really only applies to
high alt/high speed transonic airplanes. When you climb up above transition
and reach th ealtitude where the airplane is mach limited the rules
changed.
I've attached a diagram of a typical flight envelope showing the constant
indicated max/min speeds up to transition where they taper in. The point in
dashded lines at the top is the point Bob was talking about where both
happen at the same time. To maintain a margin a max altitude dictated by a
G is determined. Going to fast or sow or pulling too much G at or near max
will result in a buffet and loss of lift, just for starters.





I've just reposted this because I've gotten some e-mail complaining that
the attachment didn't come through. I'll repost that in
alt.binaries.pictures.aviation


Bertie
If you read my post first mentioning "coffin corner", you will notice I
used it as an adjective to describe a "condition" found t the extreme
end of the back side of the power curve; this being the "condition"
where low altitude and no more power available necessitate a reduction
in angle of attack to stop a developing sink rate; a very dangerous
situation on any approach.
It should be obvious that I never meant to convey that the term "coffin
corner" didn't refer to it's classic definition for high altitude
critical mach vs stall condition.
I will not get into a shouting match with Usenet advasiaries who wish to
convey I have no idea what coffin corner is as defined in the
aeronautical engineering sense.
Good God, I've even heard coffin corner used to define
the warnings block on an approach plate!

--
Dudley Henriques

"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