Bad Week for Airbus

On Nov 24, 2:07 pm, Bertie the Bunyip wrote:

No, you really can;'t abruptly do anything in an Airbus in the flight mode
he would have been in at cruise.


The computer won't let you? What if you need to maneuver abruptly to
avoid a collision?


Or would people pass out so quickly that they fell and

injured themselves?

Probably not that either. You're only slumping to the floor like you would
naywhere else.

It doesn't say what the altitude is, but I would

have thought that people would stay conscious long enough to get to a
seat and use the oxygen mask.

Mebbe, mebbe not.

An explosive decompression can do a lot of damage to the body. Sinuses,
ears lungs..

Amazing. I never would have guessed that you could get a spinal
injury from the decompression itself.


Makes you fart too.

Now that I would have guessed.

Phil

Phil wrote in
:

On Nov 24, 2:07 pm, Bertie the Bunyip wrote:

No, you really can;'t abruptly do anything in an Airbus in the flight
mode he would have been in at cruise.


The computer won't let you? What if you need to maneuver abruptly to
avoid a collision?


That's right. It won't let you manuever more thna a given acceleration for
the flight mode you are in,particulaly at high alt due to mahc manuevering
considerations. Can't give you numbers because I'm not flying one at the
moment.


Or would people pass out so quickly that they fell and

injured themselves?

Probably not that either. You're only slumping to the floor like you
would naywhere else.

It doesn't say what the altitude is, but I would

have thought that people would stay conscious long enough to get to
a seat and use the oxygen mask.

Mebbe, mebbe not.

An explosive decompression can do a lot of damage to the body.
Sinuses, ears lungs..

Amazing. I never would have guessed that you could get a spinal
injury from the decompression itself.


Didn't know about that one either. Could be just misreported or it may be
so. We get training in the physiological aspects of a blowout and some are
pretty nasty (an aneurism on the brain in several cases) but this is a new
one on me. It's not really something we need be to concerned about, it'll
either happen or it won't. Hopefully won't..




Makes you fart too.

Now that I would have guessed.

Phil

"Bertie the Bunyip" wrote in message
.. .
Phil wrote in
:

On Nov 24, 2:07 pm, Bertie the Bunyip wrote:

No, you really can;'t abruptly do anything in an Airbus in the flight
mode he would have been in at cruise.


The computer won't let you? What if you need to maneuver abruptly to
avoid a collision?


That's right. It won't let you manuever more thna a given acceleration for
the flight mode you are in,particulaly at high alt due to mahc manuevering
considerations. Can't give you numbers because I'm not flying one at the
moment.


I know basically zero about high altitude flying, what are the
considerations? Does it have a lot to due with being close to the envelope
between flying and stalling in the thin air?

"Darkwing" theducksmailATyahoo.com wrote in
:


"Bertie the Bunyip" wrote in message
.. .
Phil wrote in
news:dc605aa6-d47d-4121-bcdd-

:

On Nov 24, 2:07 pm, Bertie the Bunyip wrote:

No, you really can;'t abruptly do anything in an Airbus in the
flight mode he would have been in at cruise.


The computer won't let you? What if you need to maneuver abruptly
to avoid a collision?


That's right. It won't let you manuever more thna a given
acceleration for the flight mode you are in,particulaly at high alt
due to mahc manuevering considerations. Can't give you numbers
because I'm not flying one at the moment.


I know basically zero about high altitude flying, what are the
considerations? Does it have a lot to due with being close to the
envelope between flying and stalling in the thin air?



Not exactly. Indicated stall speed remains constant with altitude. What
does come into play is mach buffet. On the high end of the speed
envelope , obviously, you have the air accelerating around the airplane
and over the top of the wing and that gives you a buffet which destroys
lift. But if you slow the airplane down you have to increase alpha to
maintain your line of flight and the increased alpha will accelerate the
air over the top of the wing to supersonic even though the airplane is
going slower than it was in cruise.
Anything that increases the angle of attack, such as putting more weight
in the airplane will bring the minimum and maximum speed closer to your
cruise speed reducing yuor buffet margins. This means higher weights
bring the max altitude down. Loading the wing up with G either by
manuevering or an encounter with turbulence and even a forward CG will
bring the buffet on sooner, which is why some airplanes pump fuel into
the tail after takeoff once the autopilot is engaged. .
The one that comes into play here is the G consideration. They were
light, so they actually had quite a lot of G available to manuever, but
still, if you screw up at either end of the envelope, you have a big
problem. By the way, some airplanes operate with a margin of as little
as 1.25G. To give this some perspective, a thirty deg bank is 1.15 G.
These would be mostly medium long haul operators doing it to save fuel.
The margins depend on type.. most are more like 1.4 G.
If the airplane falls over, there's a good chance you'll end up through
the high end of envelope (too fast) and if that happens three things
happen to conspire to screw you. One, the center of pressure shifts back
on the wing bringing the nose down, which tends to increase speed, which
exacerbates the problem. Two, the center section of the wing is affected
more because of Area rule. the fuselage has already accelerated the air
when it meets the wing, so the center of the wing is affected more thsan
the tips, and since the center of the wing is mostly ahead of the CG the
loss of lift there brings the nose down and increases sped which
exacerbates the problem. This is mach tuck and though it isn't directly
caused by pulling excessive G it is the likely end result of an upset at
altitude.
The third factor in mach tuck is the stab. As you try pulling the nose
up as it's coming down, the increased camber of the stab (wrong way
round, f course) will accelerate the air to supersonic levels and buffet
the stab. Presto, no elevator control and you're dead.
Whatever it was that started that Egyptair airplane down over the
Atlantic, what finished them off was Mach tuck. If it develops past a
certain point there is almost nothing you can do.
So, Airbus have, for better or worse, decided to allow the airplane
itself to monitor these inflight parameters and not to allow it to do
anything too funky G wise. In reality, it hasn't worked so well. They
seem to have just as many upsets as any other aircraft.


BTW, a Cessna 172 would have these same problems if you were to get it
high enough! There are some high performance homebuilts with blowers
that need mach meters, but if you get any airplane up high enough you
have mach issues. The airplane they're planning on sending to Mars fits
into this category. It's going to be cruising at the equivelant of
somthing like a 150,000 even though it's near the surface. I thing
they're planning on a 250 knot TAS for it and that will be very tight at
those sorts of pressures.

Or maybe we should ask Anthony to check it out on his new version of
X-plane!
Version 9 is out now Anthony! Better get your order in! I'm sure the
outpouring of wisdom will wash us away like the great flood.






Bertie

On Sun, 25 Nov 2007 07:55:05 +0000 (UTC), Bertie the Bunyip
wrote:

"Darkwing" theducksmailATyahoo.com wrote in
m:


"Bertie the Bunyip" wrote in message
.. .
Phil wrote in
news:dc605aa6-d47d-4121-bcdd-

:

On Nov 24, 2:07 pm, Bertie the Bunyip wrote:

No, you really can;'t abruptly do anything in an Airbus in the
flight mode he would have been in at cruise.


The computer won't let you? What if you need to maneuver abruptly
to avoid a collision?


That's right. It won't let you manuever more thna a given
acceleration for the flight mode you are in,particulaly at high alt
due to mahc manuevering considerations. Can't give you numbers
because I'm not flying one at the moment.


I know basically zero about high altitude flying, what are the
considerations? Does it have a lot to due with being close to the
envelope between flying and stalling in the thin air?



Not exactly. Indicated stall speed remains constant with altitude. What
does come into play is mach buffet. On the high end of the speed
envelope , obviously, you have the air accelerating around the airplane
and over the top of the wing and that gives you a buffet which destroys
lift. But if you slow the airplane down you have to increase alpha to
maintain your line of flight and the increased alpha will accelerate the
air over the top of the wing to supersonic even though the airplane is
going slower than it was in cruise.
Anything that increases the angle of attack, such as putting more weight
in the airplane will bring the minimum and maximum speed closer to your
cruise speed reducing yuor buffet margins. This means higher weights
bring the max altitude down. Loading the wing up with G either by
manuevering or an encounter with turbulence and even a forward CG will
bring the buffet on sooner, which is why some airplanes pump fuel into
the tail after takeoff once the autopilot is engaged. .
The one that comes into play here is the G consideration. They were
light, so they actually had quite a lot of G available to manuever, but
still, if you screw up at either end of the envelope, you have a big
problem. By the way, some airplanes operate with a margin of as little
as 1.25G. To give this some perspective, a thirty deg bank is 1.15 G.
These would be mostly medium long haul operators doing it to save fuel.
The margins depend on type.. most are more like 1.4 G.
If the airplane falls over, there's a good chance you'll end up through
the high end of envelope (too fast) and if that happens three things
happen to conspire to screw you. One, the center of pressure shifts back
on the wing bringing the nose down, which tends to increase speed, which
exacerbates the problem. Two, the center section of the wing is affected
more because of Area rule. the fuselage has already accelerated the air
when it meets the wing, so the center of the wing is affected more thsan
the tips, and since the center of the wing is mostly ahead of the CG the
loss of lift there brings the nose down and increases sped which
exacerbates the problem. This is mach tuck and though it isn't directly
caused by pulling excessive G it is the likely end result of an upset at
altitude.
The third factor in mach tuck is the stab. As you try pulling the nose
up as it's coming down, the increased camber of the stab (wrong way
round, f course) will accelerate the air to supersonic levels and buffet
the stab. Presto, no elevator control and you're dead.
Whatever it was that started that Egyptair airplane down over the
Atlantic, what finished them off was Mach tuck. If it develops past a
certain point there is almost nothing you can do.
So, Airbus have, for better or worse, decided to allow the airplane
itself to monitor these inflight parameters and not to allow it to do
anything too funky G wise. In reality, it hasn't worked so well. They
seem to have just as many upsets as any other aircraft.


BTW, a Cessna 172 would have these same problems if you were to get it
high enough! There are some high performance homebuilts with blowers
that need mach meters, but if you get any airplane up high enough you
have mach issues. The airplane they're planning on sending to Mars fits
into this category. It's going to be cruising at the equivelant of
somthing like a 150,000 even though it's near the surface. I thing
they're planning on a 250 knot TAS for it and that will be very tight at
those sorts of pressures.

Or maybe we should ask Anthony to check it out on his new version of
X-plane!
Version 9 is out now Anthony! Better get your order in! I'm sure the
outpouring of wisdom will wash us away like the great flood.






Bertie


Bertie and all

To add some to your data.

The B-47 had what was called the "coffen corner". At high altitude the
airspeed was just above the stall and if you increased your airspeed
you were into Mach. This required very close attention by B-47
drivers.

Big John

Big John wrote in
:



The B-47 had what was called the "coffen corner". At high altitude the
airspeed was just above the stall and if you increased your airspeed
you were into Mach. This required very close attention by B-47
drivers.



Yeah, it's petty much the same with any transonic aircraft. Technically,
though, what you had at the low end wasn't a stall, though it's commonly
referred to as such. The end result was the same (plummeting to earth) but
the biggest difference was that it happened well above indicated stall
speed and well below crit Alpha.
But even the FAA call it a stall in their advisory material.

http://rgl.faa.gov/Regulatory_and_Gu...Circular.nsf/0
/e04e9b9732ba93fd86256caa005ca97e/$FILE/AC61-107A.pdf

You probably flew looser margins than we do, in fact. I've flown with about
ten knots either direction to buffet, but it's a non-event with us in
coffin corner because of the more sophisticated autopilots and
autothrottles.

In the U2 they flew with a +/- 2 knot margin! The autopiot did th ework and
they let the altitude do what it wanted in deference to speedkeeping.


Bertie

Phil schrieb:

The computer won't let you? What if you need to maneuver abruptly to
avoid a collision?

The computer prevents you to rip off the wings. But you can always
disengage this functionality, if you really want to do something stupid.

Amazing. I never would have guessed that you could get a spinal
injury from the decompression itself.

If a bubble forms and blocks a vessel, it can do so anywhere.

Stefan wrote in news:6e9ce$4748a8da$54487377
:

Phil schrieb:

The computer won't let you? What if you need to maneuver abruptly to
avoid a collision?

The computer prevents you to rip off the wings. But you can always
disengage this functionality, if you really want to do something stupid.


You can't do it quickly. It's a fairly intricate procedure, in fact..

And the computer does a lot more that protecting the airframe..






Bertie

Phil writes:

Amazing. I never would have guessed that you could get a spinal
injury from the decompression itself.

Bubbles in the CNS after sudden decompression can cause serious neurological
symptoms and persistent sequelae, but it's a very rare complication.

"Mxsmanic" wrote in message
news
Phil writes:

Amazing. I never would have guessed that you could get a spinal
injury from the decompression itself.

Bubbles in the CNS after sudden decompression can cause serious
neurological
symptoms and persistent sequelae, but it's a very rare complication.

Is there anything you aren't an expert on??