Piers,
When one flies routinely with the help of modern automated control systems,
it is easy to become complacent. When that world collapses on a dark night
in weather, it is difficult to say what would have helped. If the AoA
display had been available before the upset, perhaps they would have
realized how close to the flight boundaries they were operating, and that
could have given them a clue about the problem they faced. After the fact,
I'm sure they had both a lack of critical information from the airspeed
system, and an overload of unusual presentations that they were not equipped
to resolve.
Jim Nichols
Tullahoma, TN USA
----- Original Message -----
From: "Piers Hemy" <piers@xxxxxxxx>
To: "'Olympus Camera Discussion'" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Friday, August 26, 2011 5:19 AM
Subject: Re: [OM] Titanic, was More from the Airport
> 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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