henra, grity, jd_ee,
Thanks for the additional comments on your previous posts.
I am looking forward for the next BEA report, and see how more it will contribute to the theoretical side of the accident understanding and interpretations.
Dutch M,
Originally Posted by Dutch M;6592778;Post #636
....Initially, I also thought the PF
screwed up. Though following the discussion .... I more or less changed
my mind.
Interestingly, I am among those that went through the same reaction, from an initial, simplistic, trivial "pilots fault" to understanding better and better the complexity of a rare intersection and confluence of multiple causes, that have a much wider span, and involve so many more players. Consequently, I believe, the AF 447 is one of those cases - the allocated resources were a big help as well - which will contribute to improving multiple aspects of the safety of commercial air transport.
post #636
1. Usage of TAS to calculate Kinetic Energie exchange for height.
====================================
...
Since the Kinetic Energy is the SQR of the speed, the Kinetic
Energy of different perpendicular axis are independent.
I think the spacial 3D/3axle character of the Kinetic Energy requires a consideration in its conversion to Potential Energy, regardless of it being linear or non-linear in terms of a mathematical function. However - if I understand correctly your sentence - I could not consider each of the 3 axle components "independent" of each other, by virtue of them all depending on the same spacial element, of which they are a component of.
post #636
- For general exchange of speed into another direction or height
(Potential Energy), the actual inertial speed has to be used,
so at least the ground speed and not TAS. I would even say, groundspeed
corrected with the earths' rotational speed (roughly 1800 m/s). This can be understood from the following thought-experiments:
= Assume the windspeed suddenly becomes zero. Will the effective
Kinetic Energy of the airplane change ? Nop.
(The airplane will show reactions after the change, though that's because
the force-field does change).
I have struggled with the use of airspeeds, including TAS, for the Kinetic to Potential Energy conversion/conservation, and I came to the same conclusion that the speed relative to the ground is the one that is relevant. Two elements are relevant, IMO, in this very order: (i)the height is relative to the ground, and therefore, that's the reference system, and (ii) air can transition from adding, diminishing, or being a null factor in the A/C speed relative to the ground, and thus Kinetic Energy, which is conserved from one (air) transition to the next, and relative to the ground.
I would not go that far though, as to using the ground rotational speed.
Post #636
... 4. The correlation between Stall (-warning) and AoA
=====================================
This item has been raised, including the statement, a stall (-warning)
is only a function of AoA. On first glance, this is true. However,
there are more aspects very important for this AF447 situation.
....the airplane can be stalled, without the
stall warning being triggered.
Based on the info that we have so far - this may change, once we have the next BEA report, and more info about the state of awareness in the cockpit - the Stall Warning or the lack of it is, IMO, a very, very important contributor to the accident. It was the lack of a Stall Warning while in the middle of the "stall" and the presence of a Stall Warning, when the A/C was close to "exit" from the "stall"..
Post #636
5. Icing type, super cooled water vs huge "clouds" of ice-xtals.
=======================================
...it's pretty likely the pitots did
absorb a lot of ice-xtals and not super cooled water freezing up
in the pitots.
One or another, is ultimately less relevant as the fact, that in adverse weather condition, all fail the same way, reducing this part of the system's "redundancy" to zero. This is an industry wide element, not only Airbus. The redundancy built in may work for individual electrical or mechanical failure, but such events are arguably less frequent than adverse weather conditions, and thus a weak point in passenger A/C design industry wide.
Post #636
6. Effect of ice-xtal on wing stall.
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The first approximation of ice-xtal polluted air, would be to consider
this type of air as "thick" air. And thicker air gives more lift, so
an increase of lift.
Interesting....
I appreciate your post
