4 ms·

That is true. But please keep in mind that the whole MCAS fiasco was precipitated by a dubious cost-cutting initiative related to an engine placed more in front

by sn41 7y ago

That is true. But please keep in mind that the whole MCAS fiasco was precipitated by a dubious cost-cutting initiative related to an engine placed more in front than would be aerodynamically stable. The game was lost in the first quarter. The whole point is that civilian aircraft, unlike fighter jets, have to be aerodynamically stable without the need for such software, whether developed by holistic engineers, or compartmentalised subcontractors.

_ph_ 7y ago
The 737 MAX is aerodynamically stable. MCAS isn't even active while any flap is extended. MCAS should be active only at angle of attacks, which wouldn't be reached at extreme angle of attacks. The sole purpose of MCAS is to emulate the exact reactions of the older 737 machines in this domain, as this was required for maintaining the same type rating. That is also the reason, the pilots are supposed to deactivate MCAS via the runaway stabilizer checklist. This software isn't required for stable operations of the airplane - Lion air had a MCAS malfunction the day before the crash, but disengaging the electric stabilizers solved the problem and they were able to finish their flight without incidents.
- salawat 7y ago
  Incorrect. The aircraft is not aerodynamically stable in pitch unaided by software, thereby failing the demonstration of positive pitch stability as written in FAR 25.173. The non-compliance is of the form of a slackening of control stick response force at high AoA due to extra lift generation ahead of the center of gravity caused by the forward mounted engine nacelles. In regulatory parlance, this specifically means the airframe (the specific physical assembly of parts that collectively determine the flight characteristics of the object in question) possesses an "instability" that disqualifies it from being certified airworthy as a Civil Transport Aircraft unless the FAA amends or reinterprets the requirement. The penultimate Lion Air flight only recovered thanks to The intervention of a third pilot; a luxury not universal to every cockpit. >MCAS should be active only at angle of attacks, which wouldn't be reached at extreme angle of attacks. The potential for MCAS subroutine activation is active during all phases of manually controlled (Autopilot off), flaps up flight,and is gated only by readings from an AoA sensor; which can fail in flight to catastrophic effect. >The sole purpose of MCAS is to emulate the exact reactions of the older 737 machines in this domain, as this was required for maintaining the same type rating. Incorrect. The sole purpose of MCAS is to induce an intentional "mistrim" during certain points of the flight envelope to counter the extra lift generated by the repositioned engines, with the end goal of smoothing out the non-compliant stick force response curve. Note, jury is still out whether this should even be allowed. I've gotten wildly different responses based on who I've talked to. Pilots seem to express horror or extreme discomfort. Aerodynamicsts are disconcertingly quiet, but tend toward hard reconfiguration to obviate the need for a software based solution. Also, MCAS specifically deviates from oldaircraft behavior in that it removes an override of auto-trim commands activated by heavy back pressure on the yoke. There were also specific reconfiguration of the stabilizer trim cutout switches that removed any capability of locking out the MCAS system's ability to actuate the trim motor, while leaving pilot's thrim switches active. https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/ https://www.seattletimes.com/seattle-news/times-watchdog/the... https://www.seattletimes.com/business/boeing-aerospace/boeing-altered-key-switches-in-737-max-cockpit-limiting-ability-to-shut-off-mcas/?amp=1 https://www.seattletimes.com/business/boeing-aerospace/boein... Make no mistake: Boeing screwed the pooch. Big Time.

by sn41 7y ago

_ph_ 7y ago

The 737 MAX is aerodynamically stable. MCAS isn't even active while any flap is extended. MCAS should be active only at angle of attacks, which wouldn't be reached at extreme angle of attacks. The sole purpose of MCAS is to emulate the exact reactions of the older 737 machines in this domain, as this was required for maintaining the same type rating. That is also the reason, the pilots are supposed to deactivate MCAS via the runaway stabilizer checklist. This software isn't required for stable operations of the airplane - Lion air had a MCAS malfunction the day before the crash, but disengaging the electric stabilizers solved the problem and they were able to finish their flight without incidents.

salawat 7y ago
Incorrect. The aircraft is not aerodynamically stable in pitch unaided by software, thereby failing the demonstration of positive pitch stability as written in FAR 25.173. The non-compliance is of the form of a slackening of control stick response force at high AoA due to extra lift generation ahead of the center of gravity caused by the forward mounted engine nacelles. In regulatory parlance, this specifically means the airframe (the specific physical assembly of parts that collectively determine the flight characteristics of the object in question) possesses an "instability" that disqualifies it from being certified airworthy as a Civil Transport Aircraft unless the FAA amends or reinterprets the requirement. The penultimate Lion Air flight only recovered thanks to The intervention of a third pilot; a luxury not universal to every cockpit. >MCAS should be active only at angle of attacks, which wouldn't be reached at extreme angle of attacks. The potential for MCAS subroutine activation is active during all phases of manually controlled (Autopilot off), flaps up flight,and is gated only by readings from an AoA sensor; which can fail in flight to catastrophic effect. >The sole purpose of MCAS is to emulate the exact reactions of the older 737 machines in this domain, as this was required for maintaining the same type rating. Incorrect. The sole purpose of MCAS is to induce an intentional "mistrim" during certain points of the flight envelope to counter the extra lift generated by the repositioned engines, with the end goal of smoothing out the non-compliant stick force response curve. Note, jury is still out whether this should even be allowed. I've gotten wildly different responses based on who I've talked to. Pilots seem to express horror or extreme discomfort. Aerodynamicsts are disconcertingly quiet, but tend toward hard reconfiguration to obviate the need for a software based solution. Also, MCAS specifically deviates from oldaircraft behavior in that it removes an override of auto-trim commands activated by heavy back pressure on the yoke. There were also specific reconfiguration of the stabilizer trim cutout switches that removed any capability of locking out the MCAS system's ability to actuate the trim motor, while leaving pilot's thrim switches active. https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/ https://www.seattletimes.com/seattle-news/times-watchdog/the... https://www.seattletimes.com/business/boeing-aerospace/boeing-altered-key-switches-in-737-max-cockpit-limiting-ability-to-shut-off-mcas/?amp=1 https://www.seattletimes.com/business/boeing-aerospace/boein... Make no mistake: Boeing screwed the pooch. Big Time.