More MAX information

[Shuffler]

Which is still inaccurate nomenclature.

Which makes one think journalist, not pilot.

[FLS]

Which makes one think journalist, not pilot.

The report is from the European Union Aviation Safety Agency.

[Shuffler]

The report is from the European Union Aviation Safety Agency.

Which does not necessarily mean it was written by a pilot.

[FLS]

Which does not necessarily mean it was written by a pilot.

Hopefully it rules out journalist. Not that I'd trust the EU bureaucracy with anything.

[Oldman731]

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.

Remember this.

- oldman

[Toad]

There's no excuse for 94% in this situation. None. Pitch + Power = Performance. Argue all you like. If you disagree with that, you are just wrong.

Mr. Bjorn says "And with Stick Shaker and IAS disagree you keep high thrust and fly a slow climb ". Actually, he's almost getting it. You use a KNOWN pitch and power setting that essentially emulates cruise pitch/power. Here's a clue: 94% is WAY too much power. WAY.

BTW, this works for flight with unreliable airspeed as well as a malfunctioning AOA. IIRC the 737-800 was about 2 degrees of pitch and 60% N1 for lower altitudes.

As for not being able to trim the stab manually, yeah, when you have the stick touching your spine, you can't trim manually too well. There's a procedure for that though. I recall Runaway Trim /manual trim demos in the RC-135 (B707-720) simulator. Both pilots pull back hard to get the nose up a bit then release back pressure and trim nose up like a madman using the trim handle (knee knocker). When the nose dropped again, both pull back hard, raise nose a bit, release back pressure, trim up like a madman, rinse, repeat, rinse, repeat. This resulted in a bit of an up and down rodeo but you would be surprised how fast you could get the aircraft back under control. 

I'd bet money all the Boeings with the manual trim wheel/handle work the same way. I think I did this in the 727-200 and 737-200 sims a s well. I don't recall doing it in the -800 though. Too busy playing with the new HUD.

Oh...one other thing.... the pull back, trim madly procedure would not of course work if you left the engines at takeoff power while you rodeoed up and down.

[TyFoo]

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. I'm not suggesting that it is the case but im not surprised if they are going to dig into it.

As part of the Acceptance/ Certification process Aircraft manufacturers address EASA questions and explain their design. EASA will then State their position and approve, disapprove or request further information.

Under the heading "EASA POSITION" on page 15 you inconveniently left off EASA's statement; "The increased safety provided by the Boeing design limits on the thumb switches (for out-of-trim dive characteristics) provides a compensating factor for the inability to use the thumb switches throughout the entire flight envelope". The "Corners" of the flight envelope you mention refer to the operating limitations. e.g Coffin Corner, Operating limits, and or Stall characteristics in different configurations.

The very last line says "The trim systems on the 737Max provide an appropriate level of safety relative to longitudinal trim capability".  (Whether that is true or not today is yet to be seen).

Boeing was asked and they answered and nowhere did EASA make any statements of concern thereafter. EASA only asked why the Trim Switches did not operate thru the entire flight envelope. Boeings answer to EASA was acceptable. Boeing further stated that the FAA initially brought up the same question/ or (concern if you like) for the purpose of certifying the aircraft.

[TyFoo]

One other thing to consider. . . . .

On page 11 of the Preliminary Report issued by Ethiopia it states;

At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working.

8 seconds passed between the time the Captain asked a question, got a reply and then the F.O. asked a question and got a reply and then stated the trim was not working. To talk through those questions takes me 4 seconds. If the F.O. deployed the handle on the trim wheel, and made an attempt to turn the wheel, how many turns could he have possibly made in 4-5 seconds even 8 seconds?

Can anybody definitively say that the trim wheel did not work with the information provided?

[Zimme83]

There's no excuse for 94% in this situation. None. Pitch + Power = Performance. Argue all you like. If you disagree with that, you are just wrong.

Mr. Bjorn says "And with Stick Shaker and IAS disagree you keep high thrust and fly a slow climb ". Actually, he's almost getting it. You use a KNOWN pitch and power setting that essentially emulates cruise pitch/power. Here's a clue: 94% is WAY too much power. WAY.

BTW, this works for flight with unreliable airspeed as well as a malfunctioning AOA. IIRC the 737-800 was about 2 degrees of pitch and 60% N1 for lower altitudes.

As for not being able to trim the stab manually, yeah, when you have the stick touching your spine, you can't trim manually too well. There's a procedure for that though. I recall Runaway Trim /manual trim demos in the RC-135 (B707-720) simulator. Both pilots pull back hard to get the nose up a bit then release back pressure and trim nose up like a madman using the trim handle (knee knocker). When the nose dropped again, both pull back hard, raise nose a bit, release back pressure, trim up like a madman, rinse, repeat, rinse, repeat. This resulted in a bit of an up and down rodeo but you would be surprised how fast you could get the aircraft back under control. 

I'd bet money all the Boeings with the manual trim wheel/handle work the same way. I think I did this in the 727-200 and 737-200 sims a s well. I don't recall doing it in the -800 though. Too busy playing with the new HUD.

Oh...one other thing.... the pull back, trim madly procedure would not of course work if you left the engines at takeoff power while you rodeoed up and down.

That method haven been in the manuals for the 737 for a very long time afaik and isnt anything pilots are trained on today.
10- 15 seconds after take off the normal power setting isnt 60%. You have to remember that they where very low, <1000 ft of the ground with mountains around them. 60% thrust and 2 degree pitch would have killed them even faster...

[Busher]

That method haven been in the manuals for the 737 for a very long time afaik and isnt anything pilots are trained on today.
10- 15 seconds after take off the normal power setting isnt 60%. You have to remember that they where very low, <1000 ft of the ground with mountains around them. 60% thrust and 2 degree pitch would have killed them even faster...

I have no idea what you are saying in the first sentence.
But allowing the airplane to get to 340KIAS certainly did kill them faster.

[Zimme83]

I have no idea what you are saying in the first sentence.
But allowing the airplane to get to 340KIAS certainly did kill them faster.

I was answering to this:

As for not being able to trim the stab manually, yeah, when you have the stick touching your spine, you can't trim manually too well. There's a procedure for that though. I recall Runaway Trim /manual trim demos in the RC-135 (B707-720) simulator. Both pilots pull back hard to get the nose up a bit then release back pressure and trim nose up like a madman using the trim handle (knee knocker). When the nose dropped again, both pull back hard, raise nose a bit, release back pressure, trim up like a madman, rinse, repeat, rinse, repeat. This resulted in a bit of an up and down rodeo but you would be surprised how fast you could get the aircraft back under control.

I'd bet money all the Boeings with the manual trim wheel/handle work the same way. I think I did this in the 727-200 and 737-200 sims a s well. I don't recall doing it in the -800 though. Too busy playing with the new HUD.

[Puma44]

......and isnt anything pilots are trained on today.

You know this how?

[Zimme83]

Havent seen anything about it in newer manuals and it have been mentioned by a lot of people, for ex here.
https://www.satcom.guru/2019/03/aoa-vane-must-have-failed-boeing-fix.html

    Extract from the Boeing 737-200 Pilot Training Manual February 1982 page 04.80.31. Edited for brevity. Runaway and Manual Stabiliser - Recovery from Severe Out-of-Trim

    "In an extreme nose-up out-of-trim condition, requiring almost full forward control column, decelerate, extend the flaps and/or reduce thrust to a minimum practical setting consistent with flight conditions until elevator control is established. Do not decrease airspeed below the minimum maneuvering speed for the flap configuration. A bank of 30 degrees or more will relieve some force on the control column. This, combined with flap extension and reduced speed should permit easier manual trimming.

    If other methods fail to relieve the elevator load and control column force, use the "roller coaster" technique. If nose-up trim is required, raise the nose well above the horizon with elevator control. Then slowly relax the control column pressure and manually trim nose-up. Allow the nose to drop below the horizon while trimming. Repeat this sequence until the airplane is trim.

 

But this seems to have been cut out sometimes in the 80s.

from the NG manual:

    Manual Stabilizer Trim
If manual stabilizer trim is necessary, ensure both stabilizer trim cutout switches are in CUTOUT prior to extending the manual trim wheel handles.Excessive airloads on the stabilizer may require effort by both pilots to correct the mis-trim. In extreme cases it may be necessary to aerodynamically relieve the airloads to allow manual trimming. Accelerate or decelerate towards the in-trim speed while attempting to trim manually.Anticipate the trim changes required for the approach. Configure the airplane early in the approach. When reaching the landing configuration, maintain as constant a trim setting as possible. If a go-around is required, anticipate the trim changes as airspeed increases.

This is obviously not helpful in the case of ET302

[Puma44]

One other thing to consider. . . . .

On page 11 of the Preliminary Report issued by Ethiopia it states;

At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try. At 05:41:54, the First-Officer replied that it is not working.

8 seconds passed between the time the Captain asked a question, got a reply and then the F.O. asked a question and got a reply and then stated the trim was not working. To talk through those questions takes me 4 seconds. If the F.O. deployed the handle on the trim wheel, and made an attempt to turn the wheel, how many turns could he have possibly made in 4-5 seconds even 8 seconds?

Can anybody definitively say that the trim wheel did not work with the information provided?

Not knowing how they are supposed to do pre-start checklists and flows, it’s hard to say exactly what the Captain was actually getting at.  In my 737 experience, the Captain was responsible for doing a trim check involving the stab trim cutout switches as part of his/her pre start setup flow.  The stabilizer trim handles were not extended as a part of this check.  As an FO, I never had a Captain ask if the trim was functional.

Assuming the Captain was flying at the time, it would have been more than obvious if the trim was not functional.  Why would he ask the FO?  If the FO was flying, why didn’t the Captain take command of the aircraft?  So many questions and so few answers.

So, this begs questions.  Did the Captain see something in the aircraft logbook that motivated his question?  In their airline, who is procedurally responsible for the trim check?  Is the trim check part of the airline pre start checklist procedure? Did the FO know how to do the trim check?  We’re the stab trim cutout switches properly checked by either pilot during preflight?

[Zimme83]

Not knowing how they are supposed to do pre-start checklists and flows, it’s hard to say exactly what the Captain was actually getting at.  In my 737 experience, the Captain did a trim check involving the stab trim cutout switches as part of his/her pre start setup flow.  The stabilizer trim handles were not extended as a part of this check.  As an FO, I never had a Captain ask if the trim was functional.

So, this begs questions.  Did the Captain see something in the aircraft logbook that motivated his question?  In their airline, who is procedural responsible for the trim check?  Is the trim check part of the airline pre start checklist procedure? Did the FO know how to do the trim check?

Without the full transcript its hard to tell, But at he at this point where looking in the logbook is highly unlikely as he is pulling a shaking yoke. My best guess is that he either wanted to make sure that the electric trim was indeed off or that he wanted to know if the electric trim was working despite having the switches cut. But thats only a guess.