MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

[Pilot DAR]

Hello posters,

I've had to delete some posts which were a bit more passionate than informative. This is a difficult topic, with factors somewhat new to our industry. We are all here because we want to be. May we please focus the discussion on the topic, rather than each other? Moderators are unwilling to tolerate what could appear to be attacks on other posters. It's lots of work reading through all the posts, looking for unwelcome statements. Would you please save us moderators some of this work, and post with courtesy? This request is uniform to all posters, there is no intent to support or single out any poster, so let it go, okay?

Please play the ball, not the player...

Thanks, Pilot DAR

[Bend alot]

Originally Posted by Pilot DAR

Hello posters,

I've had to delete some posts which were a bit more passionate than informative. This is a difficult topic, with factors somewhat new to our industry. We are all here because we want to be. May we please focus the discussion on the topic, rather than each other? Moderators are unwilling to tolerate what could appear to be attacks on other posters. It's lots of work reading through all the posts, looking for unwelcome statements. Would you please save us moderators some of this work, and post with courtesy? This request is uniform to all posters, there is no intent to support or single out any poster, so let it go, okay?

Please play the ball, not the player...

Thanks, Pilot DAR

Passionate on many levels and even outside aviation now code is very relevant - thanks to the Mod's for keeping it (this thread) open & thanks for the work.

Just this week we have EASA concerns including the trim wheel and autopilot disconnect & the FAA Non Disclosure requests, so a thread should be open.

Play the ball and return serve, not a tangent.

[Lake1952]

Add me to those who believe that yoko1 has added much to this discussion. I believe that what he is saying is that any solution that brings the MAX back into service will have to address the pilot training and capability issues that have contributed in no small way to the two accidents. He has not attacked "foreign" or "third world" specifically except to say that is where you can find a 300 hour FO in a cockpit. I would think it helpful if yoko1 would offer a concise review of what his position has been on this board, but I believe that he is on record as accepting the software design flaws of Boeing multiple times over. But the title of this thread is about "safety procedures" and clearly training of pilots falls under that title.

I hold a single engine land/sea instrument license since the 1970s, and have owned and flown a Lake LA-4-200 for for over 30 years.

[bill fly]

Which means that the electric breaks must be electric disengaged to be able to move the mechanical trim wheel. How is this done?

Can't be done EDLB. If it could be done it might one day help somebody. As a matter of fact it could be done on the MD-80 - one control was the brake and one the motor.

Tried it. Basically, once you get it so fast the nose can't be held up with the Yoke on the back stop. Closing the throttles, causes a nose drop and the rate is sufficient that you will not lose any speed to regain control. We froze the sim with 9,500fpm showing...... Done at about 15,000ft.
Quite sobering.

Thanks for the info RVF. Buy you a beer one day!!

[infrequentflyer789]

Originally Posted by GXER

There are several indicators that to me represent clear signs that air travel is ‘incorrectly’ priced: it ought not be (but generally is) cheaper to fly from (say) London to Edinburgh than take a train; it ought not be (but I believe it is) cheaper to employ a fully certified FO for passenger transport than it is to employ a train driver (overground or tube).

Off topic, but: there are other factors at play in that particular comparison, notably that the East Coast mainline is operating at max capacity already - they are actively trying to price pax off that railway and have been for years. The trains cannot be lengthened or double-decked as the infrastructure won't support it and they cannot run any more often because the signalling won't allow it. More specifically, they are pricing pax off the trains that are running full, hence the any-time/open ticket prices are utterly ridiculous, but book in advance for a specific train and travel off-peak and you can get London to Edinburgh for 26 quid or so, allegedly.

The capacity issue isn't unique to that train line either, or trains in general - much of the UK road network also runs at or over capacity (at certain times). Pricing people off the roads onto the rails only works if there is train capacity to switch to, and often there isn't. Our ability to build new road or rail infrastructure is itself constrained (mostly by existing land use, but also quite possibly by utter incompetence, looking at you CrossRail). Aviation has a significant advantage in that it needs essentially zero infrastructure except at the ends, there is not a significant constraint there (excepting particular localities), if there was I submit that the A380 would not have been cancelled...

[Bend alot]

Originally Posted by Lake1952

Add me to those who believe that yoko1 has added much to this discussion. I believe that what he is saying is that any solution that brings the MAX back into service will have to address the pilot training and capability issues that have contributed in no small way to the two accidents. He has not attacked "foreign" or "third world" specifically except to say that is where you can find a 300 hour FO in a cockpit. I would think it helpful if yoko1 would offer a concise review of what his position has been on this board, but I believe that he is on record as accepting the software design flaws of Boeing multiple times over. But the title of this thread is about "safety procedures" and clearly training of pilots falls under that title.

I hold a single engine land/sea instrument license since the 1970s, and have owned and flown a Lake LA-4-200 for for over 30 years.

From what I hear many 300 hr FO pilots exist in Europe and certainly here in my country, and hold a better safety record than the USA over the past decade.

A 737 Max seems"now" very different to a NG. Sort of like comparing your Lake LA-4-200 to my AN2.

[OldnGrounded]

Originally Posted by Persdawg

[. . .] I want someone in the front that can recover from practically ANYTHING.

"If wishes were horses . . ."

Sorry, Yeager and Sully aren't available any longer, and everyone else is merely human. We should probably focus on hardware and software that will help the mere humans fly safely.

[programmerPax]

Originally Posted by OldnGrounded

"If wishes were horses . . ."

Sorry, Yeager and Sully aren't available any longer, and everyone else is merely human. We should probably focus on hardware and software that will help the mere humans fly safely.

You should also mention Robert Pearson - of the Gimli Glider fame.

[walkon19]

jackscrew

Originally Posted by bill fly

Hi Walkon,

As I understand you, the stab mechanical parts, forgetting the motor for now, thanks to the recirculating ball nut can not get so frictionally overloaded that they won’t run, even at high aerodynamic loads.
It could even be forced to run in reverse, if no brake is preventing this due to the efficiency of the ball bearings within the nut. Is that right?

Because if this is so, the cause of stabiliser mechanism stalling which may require yo-yo technique could only be an overloaded motor in the electrical case, or lack of trim wheel moment in the mechanical case. .
The principle could even be used, if so designed, to allow an out of position stab to “freewheel” to a near unloaded position if the brake alone could be disengaged.

I have learned something, thanks.
B

Yes- most- but not all ball screw mechanisms can be back driven absent some sort of brake

I'll try to post a jpeg of the boeing 737 NG system and several items to search on which will result in more than most want to know.

The first should get you to a utube video of a jackscrew in operation- note that as it reaches full leading edge up, it sounds like the molor is struggling- and this is with NO airload.

Boeing 737NG horizontal stabilizer jackscrew cycle

boeing_737_ng_horizontal_stabilizer_trim_actuator try search on this term

recirculating ball jackscrew

Ball screw
Roller screw
Cannot post url so try search

[sadtraveller]

Originally Posted by bill fly

Well at least that’s one theory which can be tried out in the sim - any NG will do

Why would any NG do? The repositioned, larger, more powerful (and faster responding?) engines on the MAX completely change her aerodynamics under this scenario.

[bill fly]

Originally Posted by sadtraveller

Why would any NG do? The repositioned, larger, more powerful (and faster responding?) engines on the MAX completely change her aerodynamics under this scenario.

Well it’s to prove the principle of power pitch couple at high speeds Sad, not much to do with the nacelle lift problem at high AoA.

[infrequentflyer789]

Originally Posted by RVF750

Tried it. Basically, once you get it so fast the nose can't be held up with the Yoke on the back stop. Closing the throttles, causes a nose drop and the rate is sufficient that you will not lose any speed to regain control. We froze the sim with 9,500fpm showing...... Done at about 15,000ft.

Quite sobering.

Quite fascinating, and indeed sobering, thanks. Would this be on NG sim or MAX (guessing the former)? - MAX will likely have less pitch-power couple and possibly less nose-down effect, as the thrust line is closer to the wing as the engines are mounted higher, but how much difference that will make I don't know, they are also further forward... I don't suppose the MAX differences course has any info on a difference in pitch-power couple(?) - if not, then surely we have to expect the pilots to be very reluctant to reduce thrust to avoid further nose-down based on their NG experience, especially when GPWS is going off?

[bill fly]

Good info from the sim.

Next exercise is once again flat out with trim so far fwd that it can just be held but this time crack the speed brakes and see how pitch reacts.

Again a beer for the poster...

[hans brinker]

Originally Posted by Eclectic

A low wing with underslung engines.
Open the throttles and the nose goes up. Close the throttles and the nose goes down.
Simple physics.
So when out of control aircraft systems were forcing the nose down at low altitude it would have taken balls of steel by the pilot to throttle back.
Keeping the throttle open was about the only tool open to him to fight to save his aircraft.

Not disagreeing with the physics. Having said that, the lack of pilot trim inputs after MCAS input, leading to the out of trim situation doesn't make me conclude that they kept the power where it was a decision, but more likely an oversight.
I am not sure if I would have done better, because of all the alarms going off it would have been a very difficult situation, and all the people here that say "power, pitch, attitude" have probably never been in there.

[Tomaski]

Mostly a lurker, but I saw some discussion about the lack of detail to the write-ups by the Lion Air crew (the first one that didn’t crash), and I thought I would add my 2 cents as someone who has been there. It might have been very helpful and possibly saved all those lives if more information was included, but maybe not. I don’t know how Lion Air does it, but there are times when I talk to a mechanic about what I saw and then make an entry and there are times that I make the entry, leave the logbook in the aircraft, and go on to my next flight. This kind of malfunction strikes me as the types where a whole team of mechanics would have met the aircraft and the pilots would have thoroughly debriefed what they saw. In that case, they may have not actually written every detail down in the logbook because that just told the guy who is going to work on the plane. Been there done that. On a more concerning side, sometimes I’ve been told that if you write it up like this, then we have to do X, but if you write it up like this other way, then we have to do Y, where X is a whole lot more work. Not saying that’s the case here, but it happens. Regardless, it looks like the maintenance did all the things that one would expect they should do given that the problem was a bad AOA vane in the first place. Very odd that there were 2 back to back AOA failures.

While I’m here, I’d like to say that like a few other posters I was really bothered by how some people were ganging up on Yoko1. Yes, he came across as a bit strident at times but he seemed to know his stuff and had access to information and history that I haven’t seen anywhere else. I saw a number of folks trying to label him as a racist for the mere fact that the accident pilots weren’t “western” whatever that means. Ive heard it said that you can’t choose your family and likewise you cant’ chose in advance whose day it is to be handed a broken jet. He’s right that pilot training isn’t what it used to be and maybe that will change and maybe it won’t. The 737 came of age when there was a different mentality toward what was expected of a pilot and while that philosophy is still baked into the design, the world has changed around it. Yoko hasn’t posted for a couple of days, so maybe he’s gone. I would count that as a loss.

[MurphyWasRight]

Originally Posted by Tomaski

Mostly a lurker, but I saw some discussion about the lack of detail to the write-ups by the Lion Air crew (the first one that didn’t crash), and I thought I would add my 2 cents as someone who has been there. It might have been very helpful and possibly saved all those lives if more information was included, but maybe not. I don’t know how Lion Air does it, but there are times when I talk to a mechanic about what I saw and then make an entry and there are times that I make the entry, leave the logbook in the aircraft, and go on to my next flight. This kind of malfunction strikes me as the types where a whole team of mechanics would have met the aircraft and the pilots would have thoroughly debriefed what they saw. In that case, they may have not actually written every detail down in the logbook because that just told the guy who is going to work on the plane. Been there done that. On a more concerning side, sometimes I’ve been told that if you write it up like this, then we have to do X, but if you write it up like this other way, then we have to do Y, where X is a whole lot more work. Not saying that’s the case here, but it happens. Regardless, it looks like the maintenance did all the things that one would expect they should do given that the problem was a bad AOA vane in the first place. Very odd that there were 2 back to back AOA failures.
..
.

To be clear there was the same AoA fault on the last 2 flights; the recorded values disagreed by a mostly constant 22 degrees.
The AoA system was not touched before the accident flight.
The AoA sensor had been replaced prior to the last 2 flights, as an apparent troubleshooting step.

The concern is that the penultimate flight crew did not log use of stab trim cutouts or the continuous stick shaker either of which might have led maintenance to check the AoA systems.
At the moment there is no record of "a whole team of mechanics would have met the aircraft". Hopefully the final report will include a detailed debrief of the penultimate crew.

Your comment on different work levels depending on exact write up is interesting, seems to suggest a somewhat rigid procedure based methodology, rather than a look at all the symptoms and prove things have been resolved.

BTW 22 degrees disagree is from memory, it was somewhere in that range. I also carefully state AoA system rather than AoA vane to avoid stirring up the discussion on possible causes.

[GXER]

Originally Posted by hans brinker

Not disagreeing with the physics. Having said that, the lack of pilot trim inputs after MCAS input, leading to the out of trim situation doesn't make me conclude that they kept the power where it was a decision, but more likely an oversight.
I am not sure if I would have done better, because of all the alarms going off it would have been a very difficult situation, and all the people here that say "power, pitch, attitude" have probably never been in there.

Who are those people, exactly?

[walkon19]

Trim or else ...

back on 18 march post 2027 on Thread Ethopian airliner down africa 102




Mick GO105 posted the following


Quote:

Originally Posted by JT8D-17

How many turns of the wheel are required to change trim by one unit?

10 rotations for one unit of trim.

(Source: Boeing FCOM Bulletin FLR-6(FR) dated August 10, 2012. Subject: Runaway Stabilizer Procedure. From Background '.. the stabilizer trim wheel coasted up to 40 turns (four units of trim).')



++++

So IF MCAS or other fubar system runs AND for.5 degrees/units (?) in ?? seconds- twice as fast as trim switch- and then one reverts to manual - how long and how hard to wind wheel at least 5 turns- and how long to turn 40 turns ... while being lifted by negative G and ground approaching and now one is supposed to cut throttles to avoid overspeed - try this in the sim at say 5000 AGL ! With a sSm that at least requires force as a function of airspeed... plus feel force and override of clutch or break.

[hans brinker]

Originally Posted by GXER

Who are those people, exactly?

I have read every post on every MCAS related thread ( including all the closed ones) so forgive me if I don't remember the posters names. I am absolutely positively sure there were several that said exactly that.

[SteinarN]

Originally Posted by hans brinker

I have read every post on every MCAS related thread ( including all the closed ones) so forgive me if I don't remember the posters names. I am absolutely positively sure there were several that said exactly that.

737 driver to name one was very assertive about just that. He made it sound so easy, too easy in my view.