Boeing, yes no problems , but a 737 MAX8 no way, Lucky there are none with Australian carriersQuote:
Originally Posted by Eevo
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Boeing, yes no problems , but a 737 MAX8 no way, Lucky there are none with Australian carriersQuote:
Originally Posted by Eevo
This is how the MCAS works:
•either FCC commands nose down stabilizer to enhance pitch characteristics during steep turns with elevated load factors and at airspeeds approaching stall
•activated without pilot input and only operates in manual, flaps up flight
-the yoke trim switch or STAB TRIM cutout switches will override MCAS input
-the control column cutout switches do no stop electric trimming
•stabilizer incremental commands are limited to 2.5 °; uses A/P trim (0.27 units/sec)
-the function is reset once AOA falls below the AOA threshold or if a yoke trim switch is activated
•if the elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command
•in the event of erroneous AOA data, the pitch trim sys. can trim the stabilizer nose down in increments lasting up to 10 sec, but are limited to a 2.5° commanded change per run
Now, the 737 also has a speed trim system, which works automatically during manual flight. For those of us that fly the 737, it looks a little unusual to see the trim spinning after takeoff (without pilot input), but it’s there to make our job a little easier. We see this most during takeoff, climb, or go-around. Typically with high thrust.
I have never seen this in any aeroplane I’ve flown. Usually the pilot actuates the stab trim. Having said that, hearing and seeing the trim wheels spinning after takeoff and during climb to a 737 pilot is normal.
However, the MCAS operates in a similar manner and during periods of high workload (takeoff), perhaps the pilots didn’t recognise it was the MCAS and not the speed tim? Maybe they recognised and trimmed it back out, without realising that if the condition still exists the MCAS will activate again after 5 seconds, and they’re back to square one? This doesn’t assume they were getting erroneous indications on their PFD’s wit one or more faulty alpha vanes.
Both actions can be stopped (momentarily) by operating the stab trim switches on the control yoke. Both can be stopped permanently by operating the stab trim cutout switches (as per the Runaway Stabilizer checklist in the QRH.
Even if the crew disabled the system as described above, I do not believe they could have stalled the aeroplane just because of that. The Max still has the same stall warning system as the other NG’s, that being an aural low speed warning, followed by a stick shaker.
I was chatting to one of our engineers today. He’s rated on the Max.
He showed me data from that aircraft, and for the majority of the time it was below 1000’ AGL. The MCAS does not function with flap extended. And, as far as I know, the Max always uses some flap for takeoff. At 1000’ AGL, the aircraft should still have takeoff flap extended and, assuming there are no obstacles, it would have commenced acceleration around this altitude THEN commenced the flap retraction schedule.
So another question is - was the active FCC getting invalid flap position data, causing the MCAS activate at such a low level?
All I can say is I’m glad I wasn’t there...
Interesting question - unless I am mistaken, this flight departed Addis Ababa airport, which is over 7600ft ASL, and only nine degrees off the equator, so this was taking off in very different circumstances to the Lion Air flight. To put this into a local perspective, it would have been similar conditions to, for example, Mt Hagen - (relatively) hot and high, guessing a density altitude of about 10,000ft.
Presumably the crew was very familiar with these conditions (and so should Boeing be - think Denver), but it does suggest that rather than the MCAS system that is the immediate suspect, anything that degraded performance, especially an engine issue, could easily have narrowed the margin between climbout and stall.
Pilot training questioned.
Concerns over pilot training raised after deadly Ethiopian plane crash
We don't even know whether the MCAS was a factor. In any instance, it presents with similar characteristics of a runaway stabiliser, which has a memory item checklist to disable the stabiliser trim.
Regarding the possibility of a stall (as an alternative), there are other aural and visual warnings that, when activated, requite immediate recovery action by the crew.
It's not rocker science...
Friends who used to live in Africa said Ethopian Air had the best reputation of any airline on the continent. They used to choose it. So it seems unlikely the airline is at fault. I see Boeing has now grounded the aircraft worldwide.
Humans are involved therefore bit early to be saying the airline isn’t at fault.Quote:
Originally Posted by DiscoMick
In the last three days I’ve done a round trip to China.....five flights, the 737-800, A350 and A320 and pilots performed as they should.......except for the baggage handlers as my bag is still in transit.
Seems the finger is pointing towards an auto-pilot software problem.
Mick, the thing is the MCAS (the alleged culprit) is only enabled when the pilots are manually flying the aeroplane. The software problem (if there is one) would be with the flight control computers (FCC's).Quote:
Originally Posted by DiscoMick