TurbineD;
Turbulence penetration speed is 260kts at FL350, M0.78 higher, which would normally be selected on the FCU [Flight Control Unit on the glareshield]. Manual thrust is often selected to avoid large thrust changes with airspeed variation. The A330/A340 ALT mode is a "soft" hold which permits about a 50' altitude variation above/below the target altitude. This is primarily for fuel conservation purposes but permitting minor variations in turbulence also works. seem to recall that the books say that maintaining attitude and allowing altitude variations in severe conditions is preferred. Sounds easy, doesn't it?
On the VS...
I'm a bit surprised that the present discussion regarding the VS is taking on the dimensions of the MLG-extended discussion. It has been discussed at length in the past. I think it can be assumed that both will be resolved in the next few months.
That said, for those who argued two years ago and continue to do so today that the VS came off in flight, the question remains regarding the relatively pristine condition of most of the cabin interior parts, and, as we know now, the undersea wreckage.
We know from past accidents that a
complete loss of the VS, as in this case, will, without fail in a swept-wing aircraft, result in a loss-of-control, almost certainly, but not inevitably, followed by a high-speed impact.
Notwithstanding that qualification, there isn't a single case of a transport category aircraft surviving the loss of the
entire vertical stabilizer.*
We now know that the wreckage is concentrated indicating an intact aircraft at impact, but by the few photographs seen in public, large sections of the aircraft have survived relatively intact meaning a low-forward-speed impact. Contrast this with the condition of the Swissair 111 MD11 remains, even after a LOC from between 5000 and 2000ft, (
TSB Report, Sec 1.18.9.3, pg.196)**
The wreckage found on the surface, and now onsite, does not bear the earmarks of a high-forward-speed impact. I think a more reasonable conclusion is that the VS broke off at impact, ostensibly as
mm43 describes above, (8th Apr 2011 16:38).
*I am fully aware of the photograph and survival of the Vietnam B52, which has been used to counter this example before. But some of the VS remains, enough, obviously to provide the lateral stability needed to make it home - I would be interested in an engineer's POV on this; the JapanAir B747 bulkhead accident remained aloft through extremely competent airmanship providing deft handling of power, but was eventually lost - the circumstances under which AF447 was operating would almost certainly preclude such a response.
**The TSB Report on SR111 is interesting reading for a number of reasons, some of which may possibly relate to a few aspects of AF447. Not thinking of a fire-on-board as a possibility but of comments regarding crew confusion from multiple warnings and system failures, and other aspects such as wreckage recovery, and investigation processes. Impact was 300kts, as explained in the report. The China Airlines B747-200 in-flight disintegration is also an interesting report to read in the light of both what is known and what may some expectations may be.