Weather and Aerodynamics
Some questions:
1. Would the A330’s engines continue to run in the event of a Flat Spin, considering the intake angle to relative wind would be upwards of 60° and as much as 90°? Even though Relative Wind in severe convective activity with tops in excess of 50,000 feet, with potential for both vertical and horizontal air currents, may be a little hard to define… I would suggest that although the potential of ice may be a contributing factor, it is not required to lose the engines.
2. If the engines did fail, would the ACARS system still have the power necessary to transmit and receive and would data still be available for download to the ACARS system? I suspect not.
3. Given the size and condition of some of the recovered bits and pieces, with particular reference to the Galley, what logical solution is there apart from the Flat Spin that will bring the aircraft from where it was, to where it ended up, with just the right momentum to break its back, yet not destroy its contents beyond what we see? I suspect that in practical terms there is none.
4. Does tracking the transmitted 10 minute position reports and the last position transmitted take the aircraft through the convective activity displayed on the satellite graphics as submitted by Tim Vazquez, as it appears it does, and if so, what activity would you expect within such weather, especially as it seems to have been building at the time? Moderate or Extreme turbulence? Vertical air currents? Horizontal air currents? I would suggest all of the above
5. I understand, from reading this thread, that AF447 likely had limited rudder authority. Can it then be assumed that there was no rudder, or not enough rudder, to keep the wings level during the flight complexity of CB penetration, especially considering the effects of adverse yaw, should aileron be used at unintentionally high angles of attack? In other words is limited rudder authority, necessary in cruise, a detriment that might even contribute to an accident in this case?
6. Is it reasonable to suppose that given entry into the convective activity, apparently present in the area, as would appear likely to most, the crew would be faced with an impossible situation with an aircraft dancing around at the mercy of the storm (for want of a better description) small room for error with VS on one hand, VD on the other and apparent loss of rather important information (airspeed)? Not that it would make that much difference as it would likely be impossible to read the tape anyway, nor is it too likely that they could keep the aircraft level either in pitch or roll as nature played with it; you just cannot underestimate the power unleashed in these things and you simply cannot predict what will happen next.
7. Which pilot, hand on heart, would ever think of turning in a CB, let alone turning back to go through it again once it has caused difficulty? Nobody I know!!
8. Why is it so difficult to believe that loss of control due to weather assisted by pitot ice resulting in a spin is the most likely outcome?
9. You can be fairly certain that a Flat Spin does not degrade into a “full” Steep Spin, or a Spiral Dive, which might be considered a part of a recovery (getting the nose down) – if you are fortunate enough to do so, which is doubtful unless the weather that got you there also influences a recovery assist. With the wrong (or right, depending on your point of view) control inputs a Steep Spin will turn into a Flat Spin, even without the effect of turbulence which is quite likely to do the job for you.
10. I say again, do not underestimate the forces at work in a building 50,000+ foot convective build-up, I am sure most pilots respect and avoid them, so to suggest a crew, any crew, would turn back into the weather is frankly unbelievable – in fact even attempting a turn in the condition one can suspect they had on their hands would be frankly foolhardy and does not allow the crew the credit they deserve.
11. Although subject to considerable yaw force, it should not be assumed that a flat spin will cause the Vertical Stabilizer to part company, (it might actually be blanked out by the wing) or that such a departure is required to establish a flat spin which has a rotational rate that is less than a Full Spin and a rate of descent that is also about 50% less than a Full Spin all of which makes it the more logical manoeuvre for getting from A to B given the apparent arrival impact. I suspect it is far more likely that the Vertical Stabilizer failed as a result of the forces in play at impact, but would not insist on it.
12. Center of Gravity in a flat spin will really only dictate the relative position of the nose to the horizon – which need not be constant initially. It is easier to Flat Spin an aircraft with an aft (less stable) C of G and if cruise policy is to operate this way, it only adds to the Flat Spin suspicion. An aircraft with a more forward C of G will simply not look as flat.
13. I asked before if anyone could recognize a spin on instruments – no one seems to have that confidence. When I was in a Flat Spin I was VFR and could see the horizon going round, and round and round. I wonder how electronic instruments would depict this, would they become non-functional as the old steam driven instruments did. I don’t expect you could tell what was going on unless you had been there before, in the not too distant past
14. What was the sea state at impact? Anything but smooth, I suspect, yet the talk is as if the aircraft arrived out of the overcast in a glide, or at worst in a spiral and didn’t quite manage to pull out. This sort of thing typically ends up with what was an aircraft wrapped into a ball of wreckage by the forces of impact and sinking in tiny pieces. The dead stick landing in the river recently was impressive because of the unusually minimal damage caused. All the indications we have seem to refute this sort of scenario. But the sea and changing winds under the convective skies must surely have played a part that “normal” can't explain.
15. I have never flown trans-oceanic without guarding (listening to) 121.5. In fact I seldom fly anywhere without having it quietly selected. Other aircraft in the sky that night were doing just that – of course they were, they were diverting off course and announcing their intentions, as a courtesy, no doubt – yet none heard a word from AF447, no courtesy advice of a diversion, no mayday, nothing. That, and the fact that life vests do not seem to have been deployed, or should I say the cabin prepared, implies sudden onset of something totally unexpected that, simply took over.
In the end, it doesn’t really matter how the aircraft descended. I think one of the few things agreed is that it did, and no one can turn back the clock; it’s all history now. What matters is; what happened to cause the series of events that defeated the aircraft and its crew? There are not that many candidates and I would suggest pitot ice alone would not be one. From many of the things stated on this thread, there would appear to be some dark corners in airliner cockpits where light needs to shine and lessons be learned, other than the more obvious avoidance of weather.