Originally Posted by tubby linton
Imagine the folowing scenario- pitots ice up generating an overspeed. The aircraft pitches up and the athr retards the power to idle,add in a powerful upcurrent as a cb is penetrated adding to the pitch up. The aircraft has a lot of energy and due to the big wing a lot of manouvrability at altitude Whilst the crew is reacting to the autopilot dropping out and the aircraft fbw law degrading the aircraft stalls. If the aircraft has been cruising at 15-20kt above VLS and assuming a rapid decelleration the crew may have had only ten seconds or less to counter the stall but having penetrated a cb they are still in an updraft. The aircraft continues to climb. The crew pitch down to counteract the stall but the speedtape is still showing an overspeed. VLS is now overlaying the Barbers pole and the crew struggle to interpret what what has happened.Their computerised FBW protected aircraft had turned against them.
The cockpit is full of warning chimes and the ecam is full of failure messages due to the icing up of the ADR. The aircraft exits the CB core and is still in a
stalled condition but now is in the downdraft of the CB and it rapidly descends towards the sea and to their demise
I'm feeling that we are now back to the early discussions we had two years back, right after the crash.
If one really want to have his "FBW upset" fitting into those five minutes flight while covering less than five Nautic Miles, one would have to make a big distortion of everything in order to fit well into his thesis.
Here are the main ingredients for your catastrophe dish:
* First, you'll need an incompetent crew (the one flying blindly straight into a giant storm);
* Second, you'll need a bunch of incompetent designers (for all those unreliable flight envelope protection systems);
* Third, you'll need a good deal of very bad luck convenientely applied with the right timming (updraft here, downdraft there, and bits of ice scattered over the whole dish).
As a matter of fact, pitots icing at FL350 would not instantaneously switch the airspeed from Mach 0.82 to Mach 0.87, triggering a pull up to 60,000 feet (due to rogue C-3PO in command), then declare all the pitots frozen, then quit, handling over the whole situation with zero speed left (but displaying mach 1 and 90 degrees AoA) to the poor doomed crew which will try to figure out what to do next into the storm until contact with the ocean surface, flying backward, tail first, as per Bearfoil's analysis.
S~
Olivier