PPRuNe Forums - View Single Post - MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures Mk II
Old 21st Dec 2019, 15:07
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PEI_3721
 
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jimtx, #74 ‘just use the AP’.
This is similar to the calls for FBW; unfortunately the AP argument is flawed.

The Air Data Computers use AoA for corrections. The output of the two ADCs is used by the AP (Flight Guidance Computer) which compares values. If the values of speed / alt disagree ‘by xx’, AoA input error, then the AP will disengage - ‘invalid data’, and the relevant Disagree alerts given.
For Speed and Alt the crew can crosscheck the StBy systems: a checklist item. There is no third AoA, thus the consequential and distracting alerting remains on; no AP available: abnormal conditions #17 (https://www.pprune.org/rumours-news/628134-max-s-return-delayed-faa-reevaluation-737-safety-procedures-mk-ii.html#post10643705).

The ‘don’t pull too hard’ quip might represent residual problems relating to the design of the trim system and subsequent use without MCAS - see below.
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