Based upon the timeline not sure the crew even had time to save the aircraft in Ethiopia.
I strongly disagree. The pilots violated the 3 basic rules for any aircraft emergency
1. Maintain Aircraft Control
2. Analyze the Situation, Take Proper Action
3. Land as soon as practicable
IMHO, the pilots' biggest mistake is they left the power levers (throttles) at close to takeoff power. Step 6 of the Runaway Stabilizer Checklist is Stabilizer...Trim manually. The pilots should have known that trimming manually is impossible when airspeed is above 250 KIAS. If they had slowed down below 250 KIAS and left the stab trim cut out switches at Cut Out, they could have trimmed the aircraft manually, and landed safely.
The pilots were unable to trim manually and elected to re-engage the stab trim switches to enable the yoke trim switches. Unfortunately, this re-engaged MCAS which overrode the yoke trim switches, putting the aircraft in a dive which the pilots did not recover from.
Basic airmanship...the pilots did not perform a high speed dive recovery procedure. Throttles-idle, roll wings level, pull maximum G allowable.
WhoisAlanGreenspan?
The outrage is the Ethiopian pilots followed Boeing's MCAS sensor failure procedure by exercising a runaway stabilizer trim recovery, but it didn't work.
I don't disagree with this statement, however, there are contributing factors:
Boeing disabled the AOA disagree warning...therefore, the pilots were unable to determine the aircraft malfunction. Boeing also made AOA gauge displays as an option. If the AOA gages were displayed, and the pilots got the AOA disagree warning, and Boeing had published checklist procedures for this malfunction, the pilots should have been able to safely land the aircraft.
The runaway stabilizer trim recovery procedure did not work because the airspeed was too high for the pilots to manually trim the stabilier. Basic airmanship would dictate the pilots should have slowed down. The checklist should have instructed the pilots to fly at 250 KIAS or slower.
Note 1: Boeing has made significant changes to the MCAS software and are currently flight testing the upgrades. IMHO, these changes would have prevented both 737 MAX accidents.
Note 2: I have referenced 250 KIAS as the maximum speed that pilots can manually trim the aircraft. I am not type rated in the 737 and don't know the exact airspeed where manual trim is achievable. If anyone knows the actual airspeed, please post...thanks.
You make some very good points in your post.
However, when the stab trim switches are placed in the manual position the trim wheel controls the position of the stabilizer trim... it does this regardless of the airspeed of the 737. I looked at the link you provided and there is nothing at that location to indicate that the plane has to be slowed down to use the manual trim wheel.
The two “stab trim” cutout switches have separate purposes. The one on the left labeled “MAIN ELECT” cuts all of the power to the system, the switch on the right labeled “AUTO PILOT” disconnects the automatic trim from the autopilot and allows the trim jack to be moved up and down manually with the electric motor assisting.
There is no speed limit at which the manual trim can be used, but if there were excessive aerodynamic forces on the trim jack, it would be much easier to use the manual trim with the assistance of the electric motor
If you can find any information that disputes this I would love to hear it so I can correct my brother and neighbors who are long time Captains on 737 aircraft and the primary sources of my information.
Every aircraft accident has more than one cause (it seems). I agree that the crew violated some very basic principles of aircraft control and I am just a guy with a single engine ticket. One thing I know from my business (not related to flying), which has complex control systems, is that once an operator becomes confused or disoriented the recovery/action time is significantly longer than “normal”. If this flight crew wound up fighting each other then all bets are off.
I am waiting for the input from a family friend who has a long career flying 737’s in the US. He is very conservative in his comments and is very concerned about these incidents. His last comment to me was “What else is Boeing not telling us?”
As a side I watched the Air Disasters show last night on the 777 crash at SFO. The upshot was the guy flying the plane had a few thousand hours on a 320 and had NEVER made a non-instrument landing in a 777. Two senior captains managed to confuse the 777 control system to where it disabled the auto-throttle feature.
The AOA feeds the calculated airspeed which (along with the autopilot) were sounding alarms.
The faulty airspeed alarm checklist requires reducing power to 75%.