Quote:
Originally Posted by biker1
The MCAS system controls the trim. As I understand the system, the pilots can disable the automatic trim control. I believe that is what they should have done but failed to do. I will, of course, defer to any pilots who can expand on that, not “google experts”.
|
.
.
not really>>>
The JATR said,
"MCAS used the stabilizer to change the column force feel, not trim the aircraft. This is a case of using the control surface in a new way that the regulations never accounted for and should have required an issue paper for further analysis by the FAA. If the FAA technical staff had been fully aware of the details of the MCAS function, the JATR team believes the agency likely would have required an issue paper for using the stabilizer in a way that it had not previously been used; this [might have] identified the potential for the stabilizer to overpower the elevator
The Maneuvering Characteristics Augmentation System (MCAS) is an automated flight control developed by Boeing which became notorious for its role in two fatal accidents of the Boeing 737 MAX before the aircraft was grounded worldwide. First deployed on the Boeing KC-46 Air Force tanker, the MCAS software flight control law
adjusts the horizontal stabilizer to push the nose down when the aircraft is operating in manual flight with flaps up at an elevated angle of attack (AoA), so the pilot will not inadvertently pull the airplane up too steeply, potentially causing a stall.
In both crashes, MCAS was activated by an erroneous indication from an AoA sensor on the exterior of the airplane. (that single point of failure - stupidly intergrated into the MCAS system software).
During certification of the MAX, Boeing removed a description of MCAS from the flight manuals, leaving pilots unaware of the system when the airplane entered service. On November 10, 2018, twelve days after the first crash, Lion Air Flight 610, Boeing publicly revealed MCAS in a discussion with airline operators and other aviation interests. A recovery procedure highlighted by Boeing and the U.S. Federal Aviation Administration (FAA) after the Lion Air accident failed to prevent the crash of Ethiopian Airlines Flight 302, which led to the global grounding of all 737 MAX aircraft pending investigations and software fixes.
In April 2019, Boeing admitted that the MCAS played a role in both accidents and asserted that MCAS is not an anti-stall system. On the Boeing 737 MAX, MCAS was intended to mimic pitching behavior similar to aircraft in the previous generation of the series, the Boeing 737 NG. The investigations identified numerous defects with associated systems, including a non-functioning AoA disagree message that could have alerted pilots to a problem. The Wall Street Journal reported that Boeing had failed to share information about that issue for "about a year" before the Lion Air crash. The Maneuvering Characteristics Augmentation System (MCAS) flight control law was implemented on the 737 MAX to mitigate the aircraft's tendency to pitch up because of the aerodynamic effect of its larger, heavier, and more powerful CFM LEAP-1B engines and nacelles. The stated goal of MCAS, according to Boeing, was to provide consistent aircraft handling characteristics at elevated angles of attack in certain unusual flight conditions only and hence make the 737 MAX perform similarly to its immediate predecessor, the 737NG. (Thus Boeing's attempt to NOT include MCAS in any MAX operational documention for airlines and pilots , fast-track the FAA approvals, and not requiring airlines to invest $$$$ in additional pilot training for the MAX.)
.
.