Boeing Boeing - part the third

Well, some recent reporting that bears reading. Supports the increased likelihood of The Worst Case Scenario.

[A]fter intense lobbying by industry, [FAA] adopted new rules in 2005 that would give manufacturers like Boeing even more control.

Are you surprised that this was during a 'Business Friendly' Republican president? Didn't think so.

The salient fact of the crashes is that MCAS was not intended or designed to deal with the phase of flight when the crashes occurred. It's one thing to blame the AoA sensor, but it has to be recognized that MCAS is designed to compensate for dangerous aerodynamics, due to engine position, in level flight phase.

The review described a system that would activate only in rare situations, when a plane was making a sharp turn at high speeds.

One might say, when the Max was flying like an F-15! Or, perhaps, the Grumman X-29; given that it was controlled by 80s computers, it might perform using today's components. But, even so, should a passenger aircraft need so much compute just to keep it flying? Not to assert that the Max is as troublesome as the backward wing X-29, but how close is too close? IOW, some more, automation to accomplish otherwise tedious pilot input is one thing, using unbidden automation just to stay in flight is quite another.

Which brings us to the lede, appropriately buried near the end of the article:

The overhauled version would move the stabilizer by as much as 2.5 degrees each time it triggered, significantly pushing down the nose of the plane. The earlier version move the stabilizer by 0.6 degrees.

Yes, that's a bunch different. For those only vaguely familiar with how aircraft wings work, the rear wing, aka horizontal stabilizer in standard wing designs, has two moveable parts. One is the elevator, which is the trailing edge hinged, just as the main wing aileron and is managed by the pilot's control, the yoke. It provides fine control over the nose angle in flight. On larger aircraft (and some small private aircraft), such as the 737, the whole tail wing can be rotated. Setting the stabilizer is normally done to balance the aircraft in level flight. Such rotation, being the entire wing, produces very large force. This is what MCAS moves around. I can't find any numbers on the relative max force of elevator deflection and stabilizer rotation, but given the very large difference in area of the two and the fact that rotating the stabilizer also changes the AoA of said stabilizer, it's no surprise that pilots couldn't counteract the MCAS generated stabilizer rotation by moving the yoke/elevator.

The Worst Case Scenario remains in play.