A33Zab,
I've created this graph that could be used to illustrate your references in a perhaps easier fashion.
The graph is indicating the separation between Normal (Phase 1 in BEA Report) and Alternate Law (Phase 2 and 3 in BEA Report). It further separate the Alternate Law section in two, first corresponding to the Climb (Phase 2 in BEA Report) and second corresponding to the Stall and Stall Recovery (Phase 3 in the BEA Report)
Also the graphs illustrate well a number of observations, of which at least one were a surprise (to me):
1. During a large part of the climb - marked area 1 (blue rectangular area)
there is a continuation of a strong Normal Accelaration variation - perhaps the strongest in the graph, indicating the strong (est) Turbulence - that started during Normal Law.
2. The Elevators (resultant) move during this area (1) seems (if any) to be ND (the graph is slightly above -3 degree line). This seems to be in spite of the Pitch Commands mostly NU. -
surprise Elevators don't move NU with Pitch Command NU Is this a consequence of a strong Updraft?
It coincides with Normal Acceleration above 1g - confirms A33Zab observation.
A more accurate, or higher granularity (DPI) graph may show this a lot better.
3. The Elevators started to move NU more significantly only in the last 2/3rd of the Climb period - marked area (2) on the graph. This comes later than the Pitch NU commands, and coincides at the beginning with the slowing of the Vertical Speed, all the way, until the Vertical Speed becomes Zero, soon after which the Stall state is entered - same surprise - why the delay in significant Elevator move?
4. The most significant Elevators NU move occurs during the beginning of the Stall, particularly during the Section Marked 4. The move It is followed by THS NU from -3 to -13 degrees. This coincides with a strong Pitch NU command, while the Vertical Speed (falling) goes from 5000 to 10000ft/min. - Normal acceleration is at approx constant level, of approx 1g.
Originally Posted by
A33Zab
For SS (pitch) relaxed:
If you follow the Nz (Normal Acceleration) traces for every Nz above 1g
the elevator would have been deflected ND.
Indeed.
For Nz below 1g the elevator would have been NU to achive the 1g.
The graph does not have the granularity to show this clearly.
So it depends at which time the SS (pitch) was relaxed and you have to
keep in mind that after that the Nz trace would have been very different.
IMHO if altitude did permit this A/C (SS relaxed) would have
been stabilized finaly to normal flight.
A larger and sustained SS ND command (initiating THS to drive to normal value)
would have helped a lot!
Limiting the THS NU when Stall Started, would have helped with the THS never getting to max NU. as it has been discussed recently a couple of pages back.
