Mentour Forum

Similarities between STS of 737 Classic and MCAS of 737 Max?  


Terry Wilson
Joined: 2 weeks ago
Posts: 6
13/01/2020 9:21 am  

Just after watching Peter's latest, I happened upon Wikipedia's notes on the Speed Trim System for the 737 Classic, the first versions of the 737 to switch to the CFM56 series engines.  The STS and Maneuvering Characteristics Augmentation System (MCAS) are identical at the one-line-description level: hand flying trim helpers to deal with engine acceleration pitch moments because of new bigger, higher bypass, reduced disk-loading engines.  I'm not all that familiar with either system, but there must be some pretty drastic differences under the hood because STS has never made the news while the MCAS has crashed two planes and grounded the type for months.  I'd love to get more insight into the differences between these systems, especially in how they were certified.


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