Boeing allegedly Misled FAA on MAX certification.

[Curiousflyer]

Are you insane? It started climbing because they hit the trim switch. It had nothing to do with excess speed.

This entire debate started because you don’t think they should have left the thrust up. They needed the thrust to climb, airplanes don’t climb on pitch trim alone.

It's not just a note - check the header - it is an addition to the FCOM (you do know what that is right?) And it's there to expand on already established procedures as stated...again playing to the lowest denominator.

It is a note providing clarity on the procedure, not the procedure itself. You posted it yourself, it clearly has operating instructions and then a note to provide expanded information. I have no how you can argue this, you posted it.. it says note...

As does the NNC. if you look at the little words in step 2 after disengage autopilot - it says to control airplane pitch attitude manually with control column and main electric trim as needed then use the stab trim cutout switches.
It's basic airmanship 101 to trim out control forces. I think it's one of the first lessons every pilot getting their PPL learns. It's what every pilot does in all flight phases - no matter what they fly.

And they did exactly that, they used the control column and the electric trim as needed. Which they did. They clearly followed the procedure perfectly and believed the procedure would allow them to trim the aircraft manually, which they tried and failed.

Common sense is following a procedure believing that it will allow you to fly the aircraft safely back to the ground. This crew did that and Boeing failed them.

[corethatthermal]

What a wonderful design, flying around at Vmo, take-off thrust and at times in a dive, and 1 friggen broken AOA was running the show! No INS/ IRU no ASI no stall sensing device, no redundancy NOTHING ! and Boeing oversight was not there to see the glaring design faults!
And the sim test pilot was talking about the STS in his emails, nothing to do with the MCAS ! Jail time for the 1st "accident" Murder charges for the second !

[corethatthermal]

If only the pilots knew to go onto the backside of the power curve, no sorry, i meant BACKSIDE, as in roll her and fly inverted to unload the stab, clean her up as she approaches trim speed ( quickly) hit the shut-off and roll her out for a nice landing !

[digits_]

That's not what spraked the discussion. It was your claim that they should have reduced their throttles. With the published boeing document that says to fly closer to the trimmed speed, are you still convinced that reducing throttles would have helped?

Simply put - yes.

There is no way to calculate what the in trim speed for that configuration would be...we are getting into a highly theoretical area in this regard. Flying at VMO is not a very good thing to do at any time, and higher airspeed produces higher forces no matter how you look at it.

It doesn't matter what the exact trimmed for speed was, only that it was higher than what they were initially flying. There is nothing theoretical about that. Planes are flight tested at and above VMO. In the speed range they were flying, performance was documented. And no, flying faster does NOT increase control column forces. If flying level, flying at a higher speed does not increase lift. It increases drag, but that drag is flight tested and does not interfer with the normal operation of flight controls. The higher speeds gets compensated for by a lower AoA of the appropriate aerodynamic surface. That is exactly the reason that the forces on the yoke will get lower if you accelerate towards your trimmed speed.

On the one hand you say the crew should follow what boeing writes down and they should be aware of all the notes and remarks, yet the boeing document that says to accelerate towards the trimmed speed if you can't move the trim manually is suddenly not applicable?

Does a 737 often fly at a speed where you can not manually trim it? Once would assume this only happens at extreme trim settings, which is exactly what this situation is about.

I will state again that reduced thrust to a climb setting would probably not have helped much if at all - I don't know what the reduced forces would be - but I would guess if they were holding say 60 lbs force - 220 or 250 kts may have reduced that to 50 lbs? (just guessing)

I can tell you: there would be no reduction at all if they slowed down. It would have gotten worse.

Anyway, if you don't trust manufacturer's documentation, and you don't agree with the aerodynamic principles, there's really not much else to discuss...

[boeingboy]

And they did exactly that, they used the control column and the electric trim as needed.

LMAO!
If they had done that - then they would not have had to be holding the controls back. It would have ben neutral (or close to it) and they would have been able to use the manual trim afterwards.

[boeingboy]

If flying level, flying at a higher speed does not increase lift.

This was your claim initially...not mine.

It doesn't matter what the exact trimmed for speed was, only that it was higher than what they were initially flying.

On the one hand you say the crew should follow what boeing writes down and they should be aware of all the notes and remarks, yet the boeing document that says to accelerate towards the trimmed speed if you can't move the trim manually is suddenly not applicable?

Does a 737 often fly at a speed where you can not manually trim it? Once would assume this only happens at extreme trim settings, which is exactly what this situation is about.

Your comments lead me to believe you do not understand what in trim speed is. It's true it was much higher than they were flying - but I find it highly unlikely that was what was going through their head at that point. It would have been so fast the airplane would probably come apart before they even got close to it. That is why I said it was theoretical. I never said it was not applicable - just that it was impossible because it was never designed to work at such a gross mis trimmed condition.

Anyway, if you don't trust manufacturer's documentation, and you don't agree with the aerodynamic principles, there's really not much else to discuss...

I agree with you.

[digits_]

it was impossible because it was never designed to work at such a gross mis trimmed condition.

If you are not grossly mistrimmed, is there a realistic scenario where you would not to be able to trim the plane manually due to the high forces on the trim wheel?

[Curiousflyer]

And they did exactly that, they used the control column and the electric trim as needed.

LMAO!
If they had done that - then they would not have had to be holding the controls back. It would have ben neutral (or close to it) and they would have been able to use the manual trim afterwards.

FDR shows the crew pull back on the control column and use the electric trim to get the aircraft out of a descent and climbing. That is the definition of “needed”. Just because it wasn’t trimmed to your liking does not mean they didn’t follow the procedure, they did.

[boeingboy]

If you are not grossly mistrimmed, is there a realistic scenario where you would not to be able to trim the plane manually due to the high forces on the trim wheel?

There is - it doesn't happen very often. 9 times out of 10 it's a non-issue (being able to manually trim), sometimes it happens that the crews can recover it using more force than normal, and the least likely is having to unload the airplane. There are different failure scenarios that can pop up such as a "Stab out of trim" light or a speed trim failure. Again - it all depends how close they are to the in speed trim setting that will determine if the stab can be moved normally or not.

Below is just one example. While in this example It did not need to be unloaded - they needed much more force to get it to work:

From Avherald:

A Mango Airlines Boeing 737-800, registration ZS-SJD performing flight JE-129 from Johannesburg to Cape Town (South Africa) with 141 passengers and 6 crew, was climbing out of Johannesburg. Just prior to reaching the cruise level FL360 the crew received a "STAB OUT OF TRIM" indication. While working the checklists the crew disengaged the autopilot, which resulted in a significant nose down pitch moment suggesting to the crew that a signficant out of trim situation developed. The crew counteracted, however, the electrical trim was inoperative. The crew subsequently attempted to manually trim off the control forces, however, the trim wheel always jumped back to the original position. The crew followed the relevant checklists override the horizontal stabilizer electrical trim clutch by applying more force to the trim wheel, which succeeded and restore the manual stabilizer trim. The crew subsequently advised ATC that their autopilot had failed, they were no longer compliant with reduced vertical separation minima (RVSM) airspace requirements, ATC cleared the flight to descend to FL280. The crew determined that at FL280 the fuel quantity, computed for FL360, would be insufficient and decided to return to Johannesburg. Due to the flight control problems encountered the flaps were limited to 15 degrees, the crew therefore requested emergency services on stand by. The aircraft landed safely on Johannesburg's runway 03L about 55 minutes after departure.

The South African Civil Aviation Authority (SACAA) reported the captain (43, ATPL, 12,345 hours total, 3,696 hours on type) was assisted by a first officer (29, ATPL, 2,592 hours total, 1,888 hours on type). The aircraft had undergone various maintenance activities between May 22nd 2019 and Jul 26th 2019 due to a flight crew report the aircraft had started oscillating in flight. On Aug 5th 2019 the electrical trim motor was removed from the airframe and used on another airframe. On Aug 7th 2019 another trim motor, the service history of which so far could not be determined, was installed on the airframe.

On Oct 22nd 2019 the SACAA issued a statement reading (editorial note: it remains unclear whether this is related to the trim motor without determined service history mentioned above or not, a number of South African Media had speculated about fake parts being discovered prompting a statement released by South African Airways Technical on Oct 10th 2019 that no fake parts had been used):

[boeingboy]

FDR shows the crew pull back on the control column and use the electric trim to get the aircraft out of a descent and climbing. That is the definition of “needed”. Just because it wasn’t trimmed to your liking does not mean they didn’t follow the procedure, they did.

Sigh....

[digits_]

it all depends how close they are to the in speed trim setting that will determine if the stab can be moved normally or not.

Regardless of what caused it, that's exactly the situation the crew of the mcas incident encountered. Out of trim, too far away from the trimmed speed to move it manually. Solution? Accelerate (or decelerate if requried) towards the trimmed speed.

[photofly]

Your comments lead me to believe you do not understand what in trim speed is. It's true it was much higher than they were flying - but I find it highly unlikely that was what was going through their head at that point. It would have been so fast the airplane would probably come apart before they even got close to it.

I'm curious as to why you think Boeing would design a trim system where full nose down trim would result in a speed so fast the airplane would come apart.

There wouldn't be much point in doing that, would there?

In fact if you read 14 CFR 25.655 along with 14 CFR 25.161, the trim speed limit for a moving stabilizer should be no faster than VMO/MMO.

[sportingrifle]

Photofly....the great authority of the stab tim is not to cater to the speed range, but to the large C of G range the airplane is designed for. This is why with almost all transport category aircraft, the stab trim is usually far more powerful than the elevators. Which is also why using the stab as a stability aid or stall prevention device was so stupid. Cheap, quick, but stupid. The airplane should have used elevator force to provide artificial stability....but then it would have been a different airplane. And there wasn't enough "Jedi Mind Tricking " available for that to work.

[photofly]

So you're saying that if full nose down trim was limited to VMO/MMO with most adverse cg (per 14CFR25.655) - I guess that would be with the cg at the rear limit - then with normal cg the trim speed would significantly have exceeded VMO/MMO. I guess that makes sense.

This is why with almost all transport category aircraft, the stab trim is usually far more powerful than the elevators. Which is also why using the stab as a stability aid or stall prevention device was so stupid. Cheap, quick, but stupid.

That's the most compelling two line argument I've read.

[iflyforpie]

Isn’t that the reason why Mach Trim is with the elevator and not the stab?

[valleyboy]

https://www.cbc.ca/news/business/lion-a ... -1.5334769

[boeingboy]

I'm curious as to why you think Boeing would design a trim system where full nose down trim would result in a speed so fast the airplane would come apart.

Sportingrifle gave a very good explanation. I don't even know if the trim speed could be calculated as it was never designed to fly around so grossly mis-trimmed - hence and earlier reference to it being theoretical.

Second - in the configuration they were in (92% N1 and full nose down trim) they would easily get close to the speed of sound in a dive in short order last FDR data showed 500 kts. Don't forget = they were already climbing and had hit VMO (350 kts)