5 ms·
Same thing, surely? Altering the trim means that pulling a certain amount on the stick doesn't make the plane pitch up as much as it would otherwise, hence you
by joosters 8y ago
Same thing, surely? Altering the trim means that pulling a certain amount on the stick doesn't make the plane pitch up as much as it would otherwise, hence you need to pull more on the stick (than a plane without MCAS). So the (intended) end effect is the same, right?
- sokoloff 8y agoYes. Stick force curve certification compliance is a primary reason for MCAS to exist.
- inferiorhuman 8y agoNo, because what changes is how far you move the yoke not necessarily how hard you have to pull (on the penultimate Lion Air flight the elevator feel system was non-op which meant that the yokes were probably extremely light for the whole flight). There will also come a point where you cannot overcome the stabilizer with the elevator.
- jacquesm 8y agoThe bit you put between brackets '(intended)' is the key here. What they intended was one thing, what they got was an entirely different thing. The stabilizer being as large as it is and the degree of authority afforded the MCAS system could cause the tail plane to deflect to a degree that the stick could not overcome it at all, the elevators are simply not large enough to counteract a tailplane that is trimmed purposefully the wrong way to the maximum deflection, in part because trimming the tailplane wrong also limits elevator effectiveness.