Thread: Ethiopian air lines flight goes down all killed

The other factor rarely mentioned about this crash is that it is a long way above sea level - Addis Ababa is higher than anywhere in Australia (2355m, 7726ft). This means that for the same IAS, you are actually moving a lot faster. I noticed this when I was living in PNG - after six months flying out of Mendi (5,680ft) I flew down to Wewak (19ft) for a weekend, and was struck by the fact that, approaching for a landing at the usual IAS, I seemed to be nearly stopped.

This would have meant that things happened a lot faster in this case than they would have at sea level - most importantly, for the same nose down angle and IAS, the ground is approaching faster.

Yeah, it's not the fall,it's that sudden stop at the bottom.

Six Minutes To Disaster: How Ethiopian Air Pilots Battled Boeing Max

"One of the "angle-of-attack" gauges read 15.3 degrees, likely an accurate reading for a plane taking off. The other erroneously read 74.5 degrees -- which would suggest a plane pointing almost straight skyward."

I don’t think things would have happened any faster at the higher elevation. The aeroplane only knows IAS. The pilots fly IAS, except when dealing with an unreliable airspeed situation (setting a known thrust/attitude combination as part of finding the correct indicating airspeed indicator). But this appears to be a faulty L alpha vane data to flight control computer #1, to the MCAS. I say ‘appears’ because it’s still speculation.
Reports that the crew “switched off” the MCAS are typical media stupidity. It cannot be switched off. The Stab Trim system that the MCAS drives however, CAN be switched off. This is what the Stabilizer (sic) Trim Runaway checklist directs the crew to do. NOWHERE in the checklist does it direct the crew to switch it back on. Switching it back on when effectively the problem is solved puts you into test pilot territory. That’s somewhere you DON’T want to be close to the ground. Sure, operating the Stab Trim manually is physical, and needs to be well coordinated between the crew, but you would be mad to knowingly re-introduce the problem by reapplying power to the system.
Reading the FDR transcript, this appears to be what the crew did towards the end of the flight.

Below is the Stabilizer Trim Runaway checklist.


Below is an amplification of the procedure. My highlighting on the position of the Stab Trim Cutout switches.

Originally Posted by Hugh Jars

I don’t think things would have happened any faster at the higher elevation. The aeroplane only knows IAS. The pilots fly IAS.......

Of course. My point was that for a given aircraft attitude (other than level flight) and IAS the higher the density altitude, the greater the rate of climb or, what matters close to the ground, descent. This reduces the time available to fix the issues before the ground intervenes.

The aircrew in this case, being local, would have been very familiar with this, but many of those who are talking about the crash would not be. Some, for example US pilots who regularly fly into Denver would have an idea, but I suspect Addis Ababa regularly gets a lot higher density altitude than Denver - its 2,000 feet higher and 30 degrees closer to the equator.

The one time I flew into Margarima in PNG, which has an altitude of 7800ft from memory, the density altitude was over 12,000ft.

Out of interest......how easy to it to navigate the manual, find the pages, read and do the action when in a major situation??

I imagine it would be a challenge.

Originally Posted by weeds

Out of interest......how easy to it to navigate the manual, find the pages, read and do the action when in a major situation??

I imagine it would be a challenge.

Hi Weeds,
If you look at the checklist above, everything above the dotted line are what’s called ‘memory items’. They must be performed from memory by the crew without reference to the QRH. There are quite a few of these checklists on the 737. Checklists that must be done from memory are that way because they are flight safety critical and need to be completed in a timely manner. The ‘Engine Fire or Engine Severe Damage or Separation’ checklist is another.

Once the memory items are done (and any other necessary tasks completed) we go back and do the whole checklist from the beginning for 2 reasons: 1. To confirm all the memory items are complete, and 2. to complete the reference items below the dotted line, which contain info of a less urgent nature, such as performance effects of the failure, and effects on the remainder of the flight, such as other systems degraded by the malfunction, and other relevant data. In this case, you stay in this checklist until landing. In other checklists, you might finish it and go back to the normal checklists for the remainder of the flight. It just depends on what the failure is.

Below is an example of running 2 checklists in the B777. The crew deal with an engine fire (all from memory). They only do the memory items of the first checklist as they are unable to extinguish the fire (more important to get the folks off than running through the reference items, which have no effect).
They then run the Evacuation Checklist (read and do - no memory items).

The scenario is similar on all Boeing jets.
YouTube

Boeing finds second software problem , not associated with the first.

Additional software problem detected in Boeing 737 Max flight control system, officials say