Littlecub wrote:Limitations of human brain
It may not be possible to prevent all such accidents.
Zane wrote:Approaching coffin corner... for the sake of argument, it may not be as simple as you think to hand fly the aircraft at that altitude in IMC + turbulence from TS + inop airspeed.
OregonMaule wrote: I can do that with just the attitude indicator.
m7flyer wrote:I heard the airbus crew of the future was to be a Pilot and a Dog. The Pilot is there to feed the Dog and the Dog is there to bite the pilot if he tries to touch the controls.
Littlecub wrote:He said/She said.......
Air France doesn't want the pilots to be blamed......
It isn't all sorted out yet......(says AF)
Stol wrote:I flew to the keys a few days ago in a friends CJ-4 Citation Jet.... We cruise at 45 thousand feet and the range between VNE and stall speed is just a few Knots... It is a VERY narrow window to navigate safely......
Ps... The view from up here is tremedous...
porterjet wrote:Mach Tuck: Here is the first paragraph from the wikipedia article;
"Mach tuck is the result of an aerodynamic stall due to an over-speed condition, rather than the more common stalls resulting from boundary layer separation due to insufficient airspeed, increased angle of attack, excessive load factors, or a combination of those causes. As the aircraft's wing approaches its critical Mach number, the aircraft is traveling below Mach 1.0. However, the accelerated airflow over the upper surface of the cambered wing exceeds Mach 1.0 and a shock wave is created at the point on the wing where the accelerated airflow has gone supersonic. While the air ahead of the shock wave is in laminar flow, a boundary layer separation is created aft of the shock wave, and that section of the wing fails to produce lift."
As the indicated Mach number increases beyond critical mach the separation becomes so severe the autopilot and elevators can no longer hold the nose of the aircraft level and a fairly pronounced nose down pitching occurs.
Coffin corner, again from wikipedia;
"The coffin corner (or Q corner) is the altitude at or near which a fast fixed-wing aircraft's stall speed is equal to the critical Mach number, at a given gross weight and G-force loading. At this altitude the airplane becomes nearly impossible to keep in stable flight. Since the stall speed is the minimum speed required to maintain level flight, any reduction in speed will cause the airplane to stall and lose altitude. Since the critical Mach number is the maximum speed at which air can travel over the wings without losing lift due to flow separation and shock waves, any increase in speed will cause the airplane to lose lift, or to pitch heavily nose-down, and lose altitude. The "corner" refers to the triangular shape at the top right of a flight envelope chart where the stall speed and critical Mach number lines come together."
In the case of Air France, IMHO, since they were able to climb to FL 380 before stalling they were nowhere near the coffin corner at FL 350.
It is conceivable that, at night, in turbulence with thunderstorms in close proximity and a sudden loss of reliable airspeed which also kicked off the autothrottles they thought they were in a mach tuck situation rather than a slow speed stall. If you remember the Captain returned to the flight deck and retarded the throttles which is the correct action for mack tuck. Unfortunately they apparently never realized they were in a slow speed stall and not a mach tuck situation.
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