Stalls and Thoughts

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

Where did you come to the conclusion it was correct in both cases? I just
said I am not surprised the term got "high jacked. and it wouldn't be the
first time" Meaning, incorrectly. I've just never heard it being used
associated with the back of the power curve in 50 years of aviation that's
all. Could have missed it. Love to see some real documentation.

--
BobF.
"Dudley Henriques" wrote in message
...
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

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

Well, I'll tell you right here and now.

Seems Jack, who already had lots of test hours in the 100 and made a flight
to NY already, was preparing for a flight to the air show in England. Bill
Allen (president) came on board just before he was about to depart and said.
"You know Jack, if you don't want to make a maiden cross Atlantic flight
now, it's ok, we don't have to take this plane there." Jack said "It's ok
Bill, I don't see any problem in doing so". Bill nodded and walked off the
plane but came back a few minutes later and said "Jack, I'm serious, if you
feel any reason why you don't want to make the flight, it's ok", Jack looked
a little puzzled but said "It's ok Bill, I have no bad feelings at all
about it and I feel completely confident it'll be ok" Bill looked at Jack
for a few seconds, said nothing and walked of the plane but returned almost
immediately and said "Jack, I know you'll do the right thing, but when you
get to the air show, please don't roll this airplane !"

--
BobF.
"Bertie the Bunyip" wrote in message
...
"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

On Mar 15, 7:10 pm, Dudley Henriques wrote:
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

Wouldn't a more exact definition be that the "region of reversed
command" is that condition where induced drag is at its greatest,
pitch only controls airspeed, and power only controls altitude?

One can "drag in" and airplane and not meet all the aforementioned
conditions.

The usefulness of this condition is apparent in short field landings.

Dan Mc

Well I only have a few 707 hours like 200, but in the first model there was
a hydraulic system between the elevator and tab. I thought it was on all
models. That's all I know about it. This was the model without the
Yahoodi.
--
BobF.
"Robert Moore" wrote in message
46.128...
"Bob F." wrote
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.

Tell us more about that "elevator hydraulic cylinder". I have flown
just about every model B-707/720 made and they all had elevators
operated by control tabs which were moved by the yoke. No hydraulics
what-so-ever, the elevators actually free-floated until the aircraft
was moving at a fair speed.

The only hydraulic flight controls on the B-707 were the rudder and
the flaps and the spoilers.

Bob Moore
ATP B-707, B-727
PanAm (retired)

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
:

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

"Bob F." wrote in
:

Well, I'll tell you right here and now.

Seems Jack, who already had lots of test hours in the 100 and made a
flight to NY already, was preparing for a flight to the air show in
England. Bill Allen (president) came on board just before he was
about to depart and said. "You know Jack, if you don't want to make a
maiden cross Atlantic flight now, it's ok, we don't have to take this
plane there." Jack said "It's ok Bill, I don't see any problem in
doing so". Bill nodded and walked off the plane but came back a few
minutes later and said "Jack, I'm serious, if you feel any reason why
you don't want to make the flight, it's ok", Jack looked a little
puzzled but said "It's ok Bill, I have no bad feelings at all about
it and I feel completely confident it'll be ok" Bill looked at Jack
for a few seconds, said nothing and walked of the plane but returned
almost immediately and said "Jack, I know you'll do the right thing,
but when you get to the air show, please don't roll this airplane !"


Heh heh. I wonder if anyone has. I know someone who claims to have rolled a
Convair 880 9 the FAA's own flying lab) and some Lufty guys tried to roll
a 707 and pulled two engines off it ( so the story goes, anyway) The 757
would be a piece of cake to roll if you were so inclined. The sim does some
fine aerobatics anyway.


Bertie

Dan wrote in news:a7bc480e-2c0d-44ee-b560-e8d7aaa866a5
@p73g2000hsd.googlegroups.com:

On Mar 15, 7:10 pm, Dudley Henriques wrote:
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

Wouldn't a more exact definition be that the "region of reversed
command" is that condition where induced drag is at its greatest,
pitch only controls airspeed, and power only controls altitude?

One can "drag in" and airplane and not meet all the aforementioned
conditions.

The usefulness of this condition is apparent in short field landings.


Wel, I don't do it and I bet you ten bucks I can pull off the runway
shorter than you.

Bertie