3 ms·

From https://en.wikipedia.org/wiki/Maneuvering_Characteristics_Augmentation_System#Operation https://en.wikipedia.org/wiki/Maneuvering_Characteristics_Au... >

by avar 7y ago

From https://en.wikipedia.org/wiki/Maneuvering_Characteristics_Augmentation_System#Operation https://en.wikipedia.org/wiki/Maneuvering_Characteristics_Au... > "The system is explicitly designed to override pilot action and prevent them from regaining control authority, in order to avoid an inadvertent stall." If it's not an anti-stall system what would you characterize it as?

danharaj 7y ago
The purpose of a system is what it does, not what it was designed to do.
FabHK 7y ago
Good question. Not sure the "flight envelope protection" description in the Wikipedia article is good. If I'm not mistaken, MCAS was put in to fulfil certification requirements stipulated in 14 CFR § 25.173 - Static longitudinal stability, and § 25.175 Demonstration of static longitudinal stability, which states that "The stick force curve must have a stable slope". The MAX has a curved slope in some regions of the flight envelope, due to the fact that the nacelles generate lift in front of the centre of gravity. (It is not clear to me whether the slope of the stick force at high AoA in a MAX without MCAS goes negative, or just decreases (while staying positive)). Note the Wikipedia article you quote also says: > It is thus distinct from an anti-stall device, such as stick pusher which physically moves the pilot's control column forward when the airplane is approaching a stall.[5] See also here [1]: > Numerous reports have incorrectly said that MCAS is a stall prevention, or stall recovery, system. It is a Maneuvering Characteristics Augmentation System and would not be expected to activate during any normal flight conditions. Or here: >> It does seem MCAS is closely related to protecting the plane from entering a stall scenario. > Only in the sense that it is giving the pilots the feedback, through the stick force, about how close the plane is to a stall, that the pilots are used to from previous 737 models. The point of MCAS is that without it, the stick force feedback as a function of angle of attack would be different from what the pilots were used to, so they might misjudge how close to a stall they were. [1] https://www.pilotsofamerica.com/community/threads/engineers-take-on-the-737-max-design.118273/ https://www.pilotsofamerica.com/community/threads/engineers-... [2] https://www.physicsforums.com/threads/boeing-737-max-mcas-system.967958/page-3 https://www.physicsforums.com/threads/boeing-737-max-mcas-sy...

by avar 7y ago

danharaj 7y ago

The purpose of a system is what it does, not what it was designed to do.

FabHK 7y ago

Good question. Not sure the "flight envelope protection" description in the Wikipedia article is good. If I'm not mistaken, MCAS was put in to fulfil certification requirements stipulated in 14 CFR § 25.173 - Static longitudinal stability, and § 25.175 Demonstration of static longitudinal stability, which states that "The stick force curve must have a stable slope". The MAX has a curved slope in some regions of the flight envelope, due to the fact that the nacelles generate lift in front of the centre of gravity. (It is not clear to me whether the slope of the stick force at high AoA in a MAX without MCAS goes negative, or just decreases (while staying positive)). Note the Wikipedia article you quote also says: > It is thus distinct from an anti-stall device, such as stick pusher which physically moves the pilot's control column forward when the airplane is approaching a stall.[5] See also here [1]: > Numerous reports have incorrectly said that MCAS is a stall prevention, or stall recovery, system. It is a Maneuvering Characteristics Augmentation System and would not be expected to activate during any normal flight conditions. Or here: >> It does seem MCAS is closely related to protecting the plane from entering a stall scenario. > Only in the sense that it is giving the pilots the feedback, through the stick force, about how close the plane is to a stall, that the pilots are used to from previous 737 models. The point of MCAS is that without it, the stick force feedback as a function of angle of attack would be different from what the pilots were used to, so they might misjudge how close to a stall they were. [1] https://www.pilotsofamerica.com/community/threads/engineers-take-on-the-737-max-design.118273/ https://www.pilotsofamerica.com/community/threads/engineers-... [2] https://www.physicsforums.com/threads/boeing-737-max-mcas-system.967958/page-3 https://www.physicsforums.com/threads/boeing-737-max-mcas-sy...