More MAX information

[Busher]

Here is, again, a pretty good analysis:
https://leehamnews.com/2019/04/05/bjorns-corner-et302-crash-report-the-first-analysis/

I don't disagree. They key comments in Bjorn's analysis are

The throttles are left at 94% thrust for the whole flight. This is higher than normal but this is a high takeoff. At 7,600ft it is a full 2,200ft higher than Denver, which is the US Benchmark for high takeoffs. And with Stick Shaker and IAS disagree you keep high thrust and fly a slow climb (the IAS disagree is present in the traces but not mentioned in the report specifically. We don’t have all the Crew callouts and discussions present in the report is my conclusion).

The high speed of 340kts indicated airspeed and the trim at 2.3 units causes the Stabilator manual trim to jam, one can’t move it by hand. The crew is busy trying to hand trim the next two minutes but no trim change is achieved.
 
It presents more questions than it answers:
1: The IAS disagree suggests as I mentioned in a previous post that there was more to this accident than MCAS. The snag list I mentioned showed no resolution to apparently recurring pitot-static issues.

2: It leads me to question how well the crew were trained to use the standby airspeed indicator to determine whether the Captain's or the FO's indicator was faulty.

3: Why there was no attempt to reduce thrust. I appreciate that a pilot who thinks he maybe stalling wants power but 340kias is extreme and as Bjorn suggested, trim adjustments at that speed need to be "gentle".

4: I am not endorsed on 737's but he suggests that the manual trim wheel jams at high speed and I have to question that. Could our 737 pilot please chime in. It functioned at any speed in the 727.

[Puma44]

4: I am not endorsed on 737's but he suggests that the manual trim wheel jams at high speed and I have to question that. Could our 737 pilot please chime in. It functioned at any speed in the 727.

Same in the 737.  Maybe the relatively inexperienced crew found it difficult to turn the manual trim wheel at that high speed and assumed it was jammed.  Curious as to whether either trim handle (knee knocker) was extended.  Without one or both of the handles extended, it may have been much more difficult to get the desired trim response rolling the trim wheel by hand at high airspeed.

With regard to the stab trim cutout switches, as I remember, there’s no valid reason to re-engage the switches once they’ve been turned off per a non normal checklist procedure.  So, if the switches were re-engaged, the crew may have just compounded their emergency situation.

Additionally, is Bjorne a pilot? An air transport pilot? Or, is he a journalist with aviation “expertise”?

[Zimme83]

I don't disagree. They key comments in Bjorn's analysis are

The throttles are left at 94% thrust for the whole flight. This is higher than normal but this is a high takeoff. At 7,600ft it is a full 2,200ft higher than Denver, which is the US Benchmark for high takeoffs. And with Stick Shaker and IAS disagree you keep high thrust and fly a slow climb (the IAS disagree is present in the traces but not mentioned in the report specifically. We don’t have all the Crew callouts and discussions present in the report is my conclusion).

The high speed of 340kts indicated airspeed and the trim at 2.3 units causes the Stabilator manual trim to jam, one can’t move it by hand. The crew is busy trying to hand trim the next two minutes but no trim change is achieved.
 
It presents more questions than it answers:
1: The IAS disagree suggests as I mentioned in a previous post that there was more to this accident than MCAS. The snag list I mentioned showed no resolution to apparently recurring pitot-static issues.

2: It leads me to question how well the crew were trained to use the standby airspeed indicator to determine whether the Captain's or the FO's indicator was faulty.

3: Why there was no attempt to reduce thrust. I appreciate that a pilot who thinks he maybe stalling wants power but 340kias is extreme and as Bjorn suggested, trim adjustments at that speed need to be "gentle".

4: I am not endorsed on 737's but he suggests that the manual trim wheel jams at high speed and I have to question that. Could our 737 pilot please chime in. It functioned at any speed in the 727.

They tested it a simulator in a now deleted video and has also been backed by a 737 instructor so imo there is pretty much substance behind it. When the plane is out of trim at higher speeds and the pilots are pulling (or pushing) on the yoke  the aerodynamic load on the control surfaces creates a force that are very hard for the crew to overcome with the trim wheel. 

[Zimme83]

There are btw a risk  that the MAX might be in even bigger trouble. EASA have had concerns regarding the authority of the electrical trim in certain corners of the flight envelope.

https://www.easa.europa.eu/sites/default/files/dfu/IM.A.120%20Boeing737%20TCDS%20APPENDIX%20ISS%2010.pdf (page 15)

STATEMENT OF ISSUE
The aisle stand trim switches can be used to trim the airplane throughout the flight envelope and fully complies with the reference regulation Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts.
In those cases, longitudinal trim is achieved by using the manual stabilizer trim wheel to position the stabilizer. The trim wheel can be used to trim the airplane throughout the entire flight envelope.
In addition, the autopilot has the authority to trim the airplane in these conditions.
The reference regulation and policy do not specify the method of trim, nor do they state that when multiple pilot trim control paths exist that they must each independently be able to trim the airplane throughout the flight envelope.
Boeing did not initially consider this to be a compliance issue because trim could always be achieved, even during the conditions where use of the aisle stand trim switch was required.
Subsequent to flight testing, the FAA-TAD expressed concern with compliance to the reference regulation based on an interpretation of the intent behind “trim”. The main issue being that longitudinal trim cannot be achieved throughout the flight envelope using thumb switch trim only.

  (you can read the rest in the document)

So basically the crew have to rely on the trim wheels when in those areas of the envelope. But if turns out that the trim wheel cannot be used either then the MAX probably wont fly for quite some time. Im not suggesting that it is the case but im not surprised if they are going to dig into it.

[ACE]

There are btw a risk  that the MAX might be in even bigger trouble. EASA have had concerns regarding the authority of the electrical trim in certain corners of the flight envelope.

https://www.easa.europa.eu/sites/default/files/dfu/IM.A.120%20Boeing737%20TCDS%20APPENDIX%20ISS%2010.pdf (page 15)
  (you can read the rest in the document)

So basically the crew have to rely on the trim wheels when in those areas of the envelope. But if turns out that the trim wheel cannot be used either then the MAX probably wont fly for quite some time. Im not suggesting that it is the case but im not surprised if they are going to dig into it.

Another good read. Wow it’s almost like the plane has issues making it ground worthy.

[FLS]

There are btw a risk  that the MAX might be in even bigger trouble. EASA have had concerns regarding the authority of the electrical trim in certain corners of the flight envelope.

https://www.easa.europa.eu/sites/default/files/dfu/IM.A.120%20Boeing737%20TCDS%20APPENDIX%20ISS%2010.pdf (page 15)
  (you can read the rest in the document)

So basically the crew have to rely on the trim wheels when in those areas of the envelope. But if turns out that the trim wheel cannot be used either then the MAX probably wont fly for quite some time. Im not suggesting that it is the case but im not surprised if they are going to dig into it.

You should read that again. Your quote says "The aisle stand trim switches can be used to trim the airplane throughout the flight envelope and fully complies with the reference regulation."  The yoke trim is the problem. That's why it looks like pilot error.

Another good read. Wow it’s almost like the plane has issues making it ground worthy.

You read it and still got it wrong?

[Zimme83]

I don't disagree. They key comments in Bjorn's analysis are

The throttles are left at 94% thrust for the whole flight. This is higher than normal but this is a high takeoff. At 7,600ft it is a full 2,200ft higher than Denver, which is the US Benchmark for high takeoffs. And with Stick Shaker and IAS disagree you keep high thrust and fly a slow climb (the IAS disagree is present in the traces but not mentioned in the report specifically. We don’t have all the Crew callouts and discussions present in the report is my conclusion).

The high speed of 340kts indicated airspeed and the trim at 2.3 units causes the Stabilator manual trim to jam, one can’t move it by hand. The crew is busy trying to hand trim the next two minutes but no trim change is achieved.
 
It presents more questions than it answers:
1: The IAS disagree suggests as I mentioned in a previous post that there was more to this accident than MCAS. The snag list I mentioned showed no resolution to apparently recurring pitot-static issues.

2: It leads me to question how well the crew were trained to use the standby airspeed indicator to determine whether the Captain's or the FO's indicator was faulty.

3: Why there was no attempt to reduce thrust. I appreciate that a pilot who thinks he maybe stalling wants power but 340kias is extreme and as Bjorn suggested, trim adjustments at that speed need to be "gentle".

4: I am not endorsed on 737's but he suggests that the manual trim wheel jams at high speed and I have to question that. Could our 737 pilot please chime in. It functioned at any speed in the 727.

Regarding the rest:
 Everything is probably related. The stick shaker and unreliable airspeed occured when the AOA sensor failed. But yes- they where having some issues to handle even before MCAS kicked in. Most of the excessive speed buildup happened when the MCAS was active.
It started less than 15 seconds after rotation and MCAS kicked in at 1000ft and also caused some GPWS alarms so its understandable that reducing the throttles wasnt their main concern at the time. It is also quite possible that they in the stressful and confusion situation had too much to do and simply failed to keep an eye on the instruments. This is something often seen in stressful situations, the brain becomes saturated and cannot deal with new inputs.

And reducing the speed with no trim can be a problem since the plane becomes more nose heavy when it slows down.


But if I should speculate my guess is that the combination of a very stressful situation and a strong desire to get away from the ground caused them to leave the throttles.

[Busher]

Regarding the rest:
 Everything is probably related. The stick shaker and unreliable airspeed occured when the AOA sensor failed. But yes- they where having some issues to handle even before MCAS kicked in. Most of the excessive speed buildup happened when the MCAS was active.
It started less than 15 seconds after rotation and MCAS kicked in at 1000ft and also caused some GPWS alarms so its understandable that reducing the throttles wasnt their main concern at the time. It is also quite possible that they in the stressful and confusion situation had too much to do and simply failed to keep an eye on the instruments. This is something often seen in stressful situations, the brain becomes saturated and cannot deal with new inputs.

And reducing the speed with no trim can be a problem since the plane becomes more nose heavy when it slows down.

Well Sir, with respect, this brings us back to one of the original discussions of experience in the cockpit.
Terms you used such as "confusion" "failed to keep an eye on" "saturated" etc just don't happen with experienced airline pilots. Any experienced airline pilot knows if he flies a known body angle at a known thrust value, that his airplane might feel like crap but it will fly. 94% N1 all the way to a crash is unconscionable.
Furthermore an experienced 737 pilot has confirmed as I suspected, that manual trim is available though the full flight envelope... it has to be fail safe.. it is the only backup for a critical flight control.
While I believe this airplane like the Lion Air 737 had uncorrected mechanical issues that should have grounded it, I still believe that experienced professional pilots would have prevented a catastrophic result.

[ACE]

You should read that again. Your quote says "The aisle stand trim switches can be used to trim the airplane throughout the flight envelope and fully complies with the reference regulation."  The yoke trim is the problem. That's why it looks like pilot error.

You read it and still got it wrong?

No I think you should.

[FLS]

No I think you should.

Explain the error.

[Puma44]

Is “The aisle stand trim switches” referring to the center console stab trim cutout switches?  If so, it would be helpful to use the correct nomenclature to avoid confusion.

[Mister Fork]

(cough) back to the subject at hand... why didn't they just follow the elevator/stab malfunction checklist? Problem is, we don't know what the pilots were saying to one another...what their thought process was. What systems did they turn off? Why did they cycle a malfunctioning system? Exactly what kind of emergency systems training did they have?

So many questions. I just hope that it all comes out eventually and ends all this debate.

[Busher]

I am sorry. This statement should not have been within the body of your quote when I posted it.

"Well Sir, with respect, this brings us back to one of the original discussions of experience in the cockpit.
Terms you used such as "confusion" "failed to keep an eye on" "saturated" etc just don't happen with experienced airline pilots. Any experienced airline pilot knows if he flies a known body angle at a known thrust value, that his airplane might feel like crap but it will fly. 94% N1 all the way to a crash is unconscionable.
Furthermore an experienced 737 pilot has confirmed as I suspected, that manual trim is available though the full flight envelope... it has to be fail safe.. it is the only backup for a critical flight control.
While I believe this airplane like the Lion Air 737 had uncorrected mechanical issues that should have grounded it, I still believe that experienced professional pilots would have prevented a catastrophic result.

[FLS]

Is “The aisle stand trim switches” referring to the center console stab trim cutout switches?  If so, it would be helpful to use the correct nomenclature to avoid confusion.

That's quoted from the report Zimme83 posted a link to.

[Puma44]

That's quoted from the report Zimme83 posted a link to.

Which is still inaccurate nomenclature.