PPRuNe Forums - View Single Post - MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures Mk II
Old 17th Dec 2019, 18:03
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PEI_3721
 
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Checklist - delay

The reported of poor performance in checklist action during simulator tests might identify further problems.
Assuming that MCAS 2.0 is sufficiently protected from AoA input failure - MCAS trim is inhibited, then why should checklist items be of great concern.

Considering the MAX as an extension of the NG, the baseline alerts with AoA failure are the Air Data disagree alerts (speed, altitude), Feel Diff Pressure - higher stick force, together with AP disengagement and continuous Stick Shake. Also, there will be changes in the EFIS display of speed and altitude and the low speed awareness symbology, and AoA display if shown.
The addition of AoA (mis compare) alert might not be a significant burden; it is available for the NG.

We might confidently assume that there will be an MCAS ‘OFF’ (fail /inhibit) alert, but the consequences of this on flight restriction is not known.
Why should there be discussion about additional checks; would this involve further layer of trim inhibit - manual switching.
If so why; MCAS inhibit should be sufficiently robust so that pilots do not have to disable electric trim (assume no AP/FD due to Air Data Issues).

Why was there reference to a reset procedure; why should MCAS be reset. It might be expected that the aircraft can be flown safely - away from the edges of the flight envelope, and thus for landing similar to any other system malfunction. If not … what is the nature of the residual problem - stability, manual handling, stick force (higher forces due to Feel Diff).

If the problem has its roots in the combination of many alerts, then the after takeoff situation might be most limiting, irrespective of the accident crews performance. There is no need to inhibit MCAS (trim system) immediately if the flap inhibit works, but if it is inhibited, then it may be overly difficult to manage the flight and several drills without electric trim. The NG would be similar except for inhibiting the trim; which could strengthen any argument that pilot trimming is a high workload task in combination checklist actions.

Also see discussion on trim issues in Flydubai crash at RVI final report out
Would the trim characteristics add problems with manual trim wheel operation and stick centering/feel, particularly when resolving stick shake and unreliable airspeed issues with higher stick forces ?
Would higher stick force (feel diff) change the feel - the ease of operating the trim wheel ?
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