Originally Posted by
Chiefttp
FDR,
Any blame accorded to the Ethiopian pilot who left the throttles, ooops I mean Thrust Levers at max power the whole time? Isn’t that the reason why the manual trim system was ineffective due to the excessive speed and high loads on it?
CTP, a good point.
The pilots are humans, and they got airborne and encountered an array of warnings, failures and handling difficulties, a number of those indicative of low speed. Some pilots will have the bandwidth to their cognitive capacity to check the many other cues to indicate the speed of the plane, but under stress that is not all pilots.
The plane did accelerate to a high speed, but the speed was not the factor with the stabiliser other than the higher the speed the rate of change of the MCAS trim which gave a high rate of trim change at all speeds would have exacerbated the out of trim case. The plane was however out of trim at the point that the crew finally hit the stab trims to cutoff between 05:40:45 and 05:40:55 (there was still an MCAS signal, and no subsequent AND trim command until much later). At that point the aircraft had all the bells and whistles going and all the mess on the PFD. Just before 005:43:10, the trim system was reactivated by the crew for a couple of short ANU inputs, and then immediately after, the final AND input occurred. After this AND input by MCAS, for a period the erroneous output of the LH AOA ceased, returned partially and then ceased again. At this point the aircraft had gone to a negative g dive, and that increased towards a recorded negative 2 g pitch rate, which is going to cause major issues in the cockpit.
The pilot has a decision to make in the confusion in the cockpit as to what is done with the thrust. The training programs that the authorities require to be trained and which is reinforced by the airlines FOQA programs teaches the crews to be afraid of stalls. Airlines don't normally provide opportunity for the crews to go fly aircraft that they can actually fly instead of manage, so a reticence in closing the taps is not surprising. There have been numerous events where the crews given a surprise leave the taps where they are. I recall one impressive deal I investigated that the crew got to 435KIAS in a B747-400, which was only just a new data point for the manufacturer, except that the autopilot was still engaged, and the blenders were on full noise. That was at 3000' heading towards mountains, and the subsequent pullup was most impressive.
Crew have a reasonable expectation that they should be able to have control of the aircraft, taps open or not. It is unfortunate that the speed wasn't kept at a lower speed, but that is quite in line with other events that have occurred, the crew were not outliers.
Should crew be able to cope with this sort of event? Would hope so, but it won't happen under the system of training, selection and qualification requirements that we have in place now or in the foreseeable future. Our training and also quality processes actively ensure that the crews remain underprepared for abnormals that are dynamic or complex.
The B744 noted above, had a fast jet captain as the driver and PF, a fast jet examiner in the back seat, and another one in the RHS. they still got startled by a pretty simple trigger event. The amazing thing is that no damage occurred to the aircraft, including with retracting the LE devices at 60 kts over their limit speed. Gotta love Joe Sutters conservative engineering.
I apologize if anyone thinks this commentary stems from a "High Horse" opinion, it is not intended to be, over my safety, accident and flight test career I have had the opportunity to explore into some interesting places and do things like take Part 25 aircraft out to Mdive, and to investigate what may seem like a staggering number of serious events and accidents, but which were mainly repeats of lessons lost. An exceptional crew can achieve remarkable solutions, many crew will do exactly what the checklist calls for in the simulator, and then the serious event analysis shows they don't do it in the real world, for reasons that remain fascinating. The crew prior to the lion air accident coped with the issue without difficulty, another crew on the next leg, with essentially the same training and standardisation did not. ET302 did follow the guidance material, and then at some point got to the place where they re established the stab trim, and it killed them. My point on the certification is that the manual trim should have been able to be applied to the aircraft for the 3 minutes in between, but there was negligible change in the trim, and some point thereafter the crew reversed the cut-out, and the system put them in a big-time dive. -2g at the sensor which by memory was located around the forward CG MAC is a much more intense experience in the cockpit.