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Boeing ..., Part 2

  • Jan Kulísek
  • 4/7/2019, 14:17:51

I am sure that I am not the only one, who's is surprised how the Boeing 737 MAX story changes requiring a Part 2 of the original article.

In my previous note Boeing, We Have a Problem i put most of the blame on the pilots according to the information that was available at the time. Now we know more and things are more complicated, but the new info is not exonerating the pilots and the airline. As per mainstream media, the Ethiopian Air flight crashed despite that the crew executed recommended procedure for MCAS failure. That is false. At first, it looks like the memory item of unreliable speed indication that occurred before MCAS malfunction was not executed and neither was the MCAS recommended procedure.

And yes, I am aware that there may be some poor engineering practices at Boeing and questions on the aircraft certification by FAA. The media beat this dead horse many times over and I am not going there since it was done before.

The preliminary report of the Ethiopian Air crash has been released and is available here: Aircraft Accident Investigation Bureau Preliminary Report.

One must like and admire the professionalism of Mentour Pilot to inform public on many aviation topics. Here is his take on the accident after the release of the preliminary report:

Let's have an updated opinion considering the new information:

The first malfunction occurred at 05:38:44 immediately after takeoff. It included mismatched reading from the left and right AoA sensors (see what is AoA here: Angle of Attack) and also the airspeed, altitude and flight director pitch bar values from the left side deviating from the corresponding right side values. Then MCAS first activated as soon as flaps were retracted, which was at approx. 1000 feet above ground. The pilots corrected manually by electrical trim and aircraft started gaining altitude a little. When MCAS engaged for the second time, the Second Officer switched off the electrical power to stabilizer via cutoff switches.

Up to this point the crew was compliant with the recommended procedure for MCAS malfunction, but the Preliminary Report doesn't mention if the crew addressed the unreliable airspeed malfunction, which has its own memory item and checklist. However, the crew could not comply fully with the MCAS directive because of excessive speed and low elevation, which created too high aerodynamic forces for manual trim adjustments.

With the cutoff switches in off position Second Officer was instructed to move the stabilizer manually, but that was not possible due to the aerodynamic forces being too great. The crew then opted to switch the cutoff switches back on and then attempted to re-trim the aircraft to desired climbing pitch. This action had at first some partial success and the aircraft climbed a little again. However, after a few seconds MCAS re-activated and sent the aircraft to its final and deadly plunge at 40 degree angle of the last 30 seconds of the six minutes flight.

Was there anything that the pilots could do to save the flight? It is hard to tell. The most important question is why the Unreliable Airspeed Non Normal Checklist was not executed right after 05:38:44, because in no place this checklist directs the crew to raise the flaps. MCAS doesn't turn on with flaps down. This is per entries by Bob Strahm, John and Mark in Bjorn’s Corner in comments section.

Another issue to be considered is the Ethiopian Air flight 409 crash in 2010 that killed all crew and passengers aboard. The crash was caused by the crew's lack of competence, but the Ethiopian government owned airline is still denying this fact. Anyone for a bet that the Ethiopians' behavior is not changed?

The EA 302 flight was most likely doomed right at the very moment when the wheels were off the tarmac since the pilots made wrong choice of tasks to approach the first emergencies and that's why the crew's training is one of the most important issues to be investigated. We will find out, but my guess is that it will be later rather than sooner.


Updates after 04/20/2019

An exhaustive analysis by Simon Hradecky in Aviation Herald: Crash: Ethiopian B38M near Bishoftu on Mar 10th 2019, impacted terrain after departure

Juan Brown brilliant and informative as always:

The latest from Mentour Pilot as of 04/20/2019: