Thanks for the clear exposition, Jim. In the same way that an unfortunate
car driver might "run out of road", maybe the pilot can just "run out of
air" in which to maintain flight? And your point about lack of experience
among crew of fly-by-wire aircraft is well taken. The BEA interim report
makes it clear that at high altitude the range of permissible AoA and
airspeed is significantly reduced (pages 17 and 18).
Regarding AoA, recommendation 4.2 of the BEA interim report:
"Angle of Attack Measurement
The crew never formally identified the stall situation. Information on angle
of attack is not directly accessible to pilots. The angle of attack in
cruise is close to the stall warning trigger angle of attack in a law other
than normal law. Under these conditions, manual handling can bring the
airplane to high angles of attack such as those encountered during the
event. It is essential in order to ensure flight safety to reduce the angle
of attack when a stall is imminent. Only a direct readout of the angle of
attack could enable crews to rapidly identify the aerodynamic situation of
the airplane and take the actions that may be required.
Consequently, the BEA recommends:
* that EASA and the FAA evaluate the relevance of requiring the presence of
an angle of attack indicator directly accessible to pilots on board
airplanes."
But, back to human factors, I wonder whether the [dis]information overload
the crew clearly suffered would have made an AoA indication superfluous? If
it is clear (after the event) to a layman what was going wrong, there must
be other factors at play to have hidden the reality from experienced
aviators (even though insufficiently experienced in the prevailing
conditions).
Piers
-----Original Message-----
From: Jim Nichols [mailto:jhnichols@xxxxxxxxxxxxx]
Sent: 26 August 2011 06:24
To: Olympus Camera Discussion
Subject: Re: [OM] Titanic, was More from the Airport
Chris,
I trying to recall something I read a number of years ago. In an upper
corner of the flight envelope, the cruise AoA can approach the stall AoA.
Think of it this way: The aircraft weight does not change, except for the
fuel that is burned off. As you climb to jet cruising altitudes, the air
density falls rapidly, so the dynamic pressure, or "q", falls off as well.
This means that, in order to support the weight, the wing requires higher
and higher angles of attack. When the flight AoA approaches the stall AoA
for the flight Mach number, it takes very little stick force to get into
trouble. For crews flying fly by wire systems with computers in the loop,
they very seldom experience the subtleties of hand flying in this regime.
Loss of pitot pressure on a dark night under such conditions is a worst-case
scenario.
I've heard the term "departure" used to describe the loss of flying ability
in such cases. I think I first heard of it in reference to the early Lear
jets.
Jim Nichols
Tullahoma, TN USA
----- Original Message -----
From: "Chris Barker" <ftog@xxxxxxxxxxxxxx>
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Thursday, August 25, 2011 11:43 PM
Subject: Re: [OM] Titanic, was More from the Airport
> Jim
>
> It would be bad if there were no indication of AoA, but I don't know for
> certain what they have.
>
> Chris
>
> On Thursday, 25 August 2011, Jim Nichols <jhnichols@xxxxxxxxxxxxx> wrote:
>> Piers,
>>
>> Thanks for the link. As an aeronautical engineer with a career in wind
>> tunnel testing, and as a civilian pilot, that was interesting reading.
>>
>> I noted that the Company's actions did not make reference to the
>> recommendation of an AOA indication in the cockpit in view of the pilots.
>> Some other articles I have read recently have considered this to be a
>> worthwhile addition in many aircraft. I have seen sensors on several
>> business jets, but have no idea how the data are used or displayed.
>>
> --
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>
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