PPRuNe Forums - View Single Post - MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
Old 11th Jun 2019, 12:19
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PEI_3721
 
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petit plateau, AoA.
Perhaps a slip, but it’s the parameter ‘AoA’, opposed to an indicator which is important in MCAS.

The certification issue appears to involve stability margin, often simplified to stick force vs speed, providing a cue of speed change at constant trim via change of stick force. Minor discrepancies can be adjusted by non pilot trim change according to speed, creating a false stick force, but maintaining a sufficient cue according to requirement.

However, if the problem involves manoeuvre, ‘g’, at constant speed, i.e. stick force reduction when entering a turn without changing speed, then AoA is an alternative input to command trim which induces stick force (AoA would increase in a level turn). Perhaps used together with Mach for additional non linear high speed induced variation.

A major feedback cue for manoeuvre in manual flight is stick force, but an attitude instrument is required without visual cues. Attempting to fly on an AoA indicator could induce even greater instability, “Attempting to follow AOA or speed indications too closely without stabilizing the airplane in pitch can lead to an oscillatory flight path” (Boeing Aero 10).



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