[Dowly]

I know I'm going to regret this, but someone has to add a pinch of realism to this rambling.

Originally Posted by Rockin Robbins

MCAS is not just in the 737 and it is not a new system. It also appears and has been used with a perfect safety record in US Military KC-46 tankers. It is NOT a bandaid put in place to save an unflyable airplane.

KC-46 is a 767 and the need for MCAS is for different reason (changing fuel load). The KC-46 also includes various safety systems that the MAX doesn't, for example the pilot can cancel out MCAS by moving the yoke. Apples and oranges.

Moreover, while the MAX 8 MCAS will reset and come back on automatically, the KC-46’s system is “disengaged if the pilot makes a stick input,” according to the Air Force. “The KC-46 has protections that ensure pilot manual inputs have override priority.”

From: http://www.airforcemag.com/Features/...AS-System.aspx

When the plane nosed down slightly on the first MCAS control, the sensor outside the plane didn't move at all. MCAS thought the plane was still stalling. After a short delay, programmed into the system, MCAS applied more authorative down trim. The plane had been either level or slightly nose down this entire time so far since the first MCAS "adjustment."

However the pilot and copilot forgot to fly the plane. Their throttles were still set at the 94% full climb position. The plane was accelerating like a dragster and they never touched the throttles throughout the flight, all the way to impact. That's fatal mistake #1.

They were fighting the nose down at this point and were still at low altitude. Reducing throttle *might* have made the nose down worse and as they were climbing, I see no reason to not get at a safer altitude.

After MCAS provided the larger down trim in its second attempt, the co-pilot, a low time guy with less than 100 hours in type, remembered that memory procedure for a trim overrun (exactly what an MCAS malfunction causes) and recommended engaging the elevator trim cutout switch on the console of the aircraft, yes the same elevator trim cutout switch that has been on every 737 of any type built since 1967 for three generations of pilots, and the procedure for using it is required to be memorized by every pilot of the 737 series.

Earlier 737s required flipping one switch to stop autotrim, leaving the electrical trim still operational. The MAX, however, required turning off also the electrical trim leaving the crew with only manual trim. This is what they did.

With the 737NG cutout switches, MCAS runaway is stopped by just throwing the autopilot cutout switch, leaving electric trim fully operable.

With the 737MAX cutout switches, MCAS runaway is stopped by throwing both switches, losing electric trim altogether. In this case, the flight crew must rely on manual trim via turning the trim wheel/crank. As discussed above, the manual crank can bind up, making flying much more difficult.

From: https://www.satcom.guru/2019/04/stab...and-range.html

In fact, after it was disconnected, the Preliminary Accident Report clearly says that MCAS commanded many additional clicks of down elevator trim which were unable to be carried out because the elevator trim cutout switch was activated. The plane was flying level. It accelerated past the maximum operating speed of the airframe and the crew didn't touch the throttle.

It flew *somewhat* level for about 30 seconds and only because both pilots were fighting the nose down.

They then attempted to manually trim the elevator up. That's mistake #2. First fly the plane! Proper procedure would be for both of them to ignore other problems, since they now had control of the airplane. They should have realized that they were unable to trim the elevator because their over 400 knot airspeed was putting aerodynamic loads that were too great for them to overcome manually and if they didn't get their act straight (overspeed warnings were screaming in their ears from the point they exceeded 360 knots and throughout the remainder of the flight), they would shortly have no yoke authority either.

They were trying to fly the plane, both of them. Problem that requires both pilots to pull back on the controls to keep the plane from nosing down is not something they can just ignore. The plane reached 400kts when it was going down, not earlier than that. Its speed hoovered around VMO before until the final dive.

The immediate need was to reduce airspeed. The throttle should have been retarded to level cruise setting. After the plane slowed down they STILL should have ignored the out of trim condition, and achieved a climb to a safe altitude, using the yoke alone, ignoring trim. They would adjust throttle to achieve that climb, of course.

I would imagine that reducing airspeed and leveling out would make the AND condition even worse. Definitely not something that they could just ignore. Again, the both the pilots at this time are fighting the plane.

They simply forgot to fly the airplane! They were still in level flight at takeoff 94% throttle, accelerating to past maximum operating speed of the 737. That was fatal mistake #2

The plane was not in level flight. Both pilots were fighting to keep it level with varying success.

Both their efforts on the manual trim wheels were unsuccessful at moving the trim.

Indeed. A problem that would not have occurred had there been a way to disable MCAS without affecting electrical trim.

By impact, it was still at 94% power, traveling over 500 knots, an almost impossible speed for that plane to achieve at that low altitude.

Umm... yeah... the plane was in a steep -40deg dive when it reached 500kts.

It is as if a terrorist had seized control of the plane, diving it to its doom. But the pilot and copilot overpowered the terrorist, resuming control of the plane. And then they decided that perhaps the terrorist was better able to handle the situation than they, and they voluntarily put the terrorist back at the controls, allowing him to crash them.

Who crashed the plane? The proximate cause was the terrorist, but the ultimate cause was the fatal decision to put the terrorist, who they knew was intent on turning a perfectly good airplane into an ugly crater in the ground, back in control of the aircraft.

So.. the MCAS was intent on crashing the plane then? Great safety system!


Here's portion of the trace from page 26 of the report. Does that look like the had control of the plane and were at level flight?