Another 737 down

[Busher]

It’s wearying but my audience isn’t the closed-minded drum-banging trolls, it is my fellow aviators like you (because I can still learn something) and the open-minded lurkers...   Also folks like Bustr who are using logic and reasoning to try and reach a proper conclusion.   

The speculation has made me crazy, but since the lemmings want to speculate and blame the jet we might as well speculate ourselves from an informed, professional perspective with the hope someone will find it edifying. 

 

I appreciate what you are saying but unfortunately I think the opportunity to "learn" from this accident has passed.

As you well know, the foundation for the NTSB's huge budget is to educate airlines, pilots, mechanics, manufacturers and even the FAA so that any of the factors contributing to a crash of an airline do not happen again.

I for one, do not believe that the details of all elements contributing to these accidents will ever be published in a credible report.

[Puma44]

I for one, do not believe that the details of all elements contributing to these accidents will ever be published in a credible report.

Couldn’t agree more.  By now, most major accidents have some sort of info either released or leaked.  For both of these, nothing but crickets.  More than likely, saving face on a national level is the number one priority. 

[FLS]

I'm optimistic. Boeing made the appropriate noises and the people who matter know they build good airplanes.  The flying public hasn't abandoned Toyotas, which had actual problems.

The software fix of slowing the rate of trim for the MCAS seems like it will make it less effective when it's actually needed.

[Toad]

I for one, do not believe that the details of all elements contributing to these accidents will ever be published in a credible report.

Agreed. They can't publish all of the factors after having pushed the MCAS KILLS! narrative.

Imagine what would happen if the truth came out. Imagine the investigating agencies said - well, there was a relatively simple AOA problem and both crews totally mis-handled it.  So, the story line will not change no matter where the facts actually lead.

As for why Vraciu and I keep responding, I guess I we feel someone has to shine the light of truth into the dark corners of political correctness.

When I tell the truth, it is not for the sake of convincing those who do not know it, but for the sake of defending those that do.    William Blake

[deSelys]

Sorry if I'm annoying, and don't feel forced to answer if you don't want to, but I have some extra questions:

1) re single sensor stall protection: from what I could find, warnings like stick shakers are indeed in most cases avtivated as soon as one sensor triggers, also for 'mild' actions like inhibition of 'pull up terrain' alerts or airbrakes retraction. More drastic systems like stick shakers otoh, are often interlinked to many different sensors (see description of the system on the Q400 in the Colgan Air accident report). I've read that there is no stick pusher on the Falcon 900, is this correct? Is there a similar system installed?

2) On the principle of 1 sensor is better than 2 because less chances of failure: the probabilities of failure are indeed lower but this gives much less options to have a 'graceful degradation' of the system. This is were I have a really hard time to understand your point of view.
In the case of MCAS, an 'AOA disagree' alert could deactivate the system smoothly while informing the pilots that they now have to be more careful with the engine throttle (which they have to be anyway if they follow the trim runaway procedure...) without having to go through the 'roller coaster' event beforehand.
I found yesterday a safety report about activation of stick shakers and stick pushers over a period of time by airliners and, if I remember correctly, there had been not one legit stick pusher activation reported (a couple due to malfunctions). I'll post it next week as it is in my browsing history at work, if I'm wrong I'll have my asbestos undies ready
So MCAS (originally implemented) is maybe a solution more hazardous than the risk it addresses.

3) About the 3rd pilot in cockpit the day before the Lion Air crash: maybe he hadn't extra knowledge but, free of having to repeatedly wrestle the controls and positioned further back allowing him to see the trim wheel spinning, he was much more able to correctly troubleshoot the event. So damn unacceptable that the info wasn't passed to the techs and the other pilots

4) about the page of the manual posted by Vraciu: I suggested that maybe it was a manual for technicians. Can somebody confirm this?

Thanks

[pembquist]

deSelys MCAS isn't a stall prevention system except obliquely. It is meant to change the feel of the aircraft so that when it is in a very small part of the flight envelope the pressure the pilot puts on the control column to pitch up is consistent with other flight regimes. Without it if the airplane is flown into that small part of the envelope the presumption is that the pilot could inadvertently allow a pitch up to stall as he would have to actively hold pitch down to remain at a consistent angle of attack after pitching up which is the reverse of what one would expect. MCAS is supposed to add pitch down trim so that the 'feel' of the airplane is consistent. This is why, as described in the snippet from the manual provided by V, the switch in the control column that would ordinarily interrupt the action of the trim motors if the column was pulled back is effectively disabled as it would defeat the purpose of MCAS.

It is more akin to adding a bob weight than it is to a stick shaker or stall horn.

Clearly MCAS was a factor in the two fatal crashes so in a sense it would have to save a lot of lives before the equation you posit would balance. On the other hand there seems to be a very strong argument that the compounding of the failure of MCAS by the maladroitness of the aircrews reduces the relevance of MCAS to that of a spilling hot coffee in a pilots lap. Personally I think aircrews should be trained to a very high standard and have a lot of experience before they tote around 200 people. Realistically this isn't the case, how is this going to be fixed.

[Vraciu]

To answer the question above, the Falcon does not have a pusher except for British-certified airplanes.  It's their thing I guess.   

I am an EMBRAER guy all the way.   To me they do things, at least on the 145-series, that make the most sense of anyone out there (with very few exceptions).  The Legacy 600/650 manual explains the stall protection system and gives some parameters that will disable it.   Had some of these been in place the Lion Air crash would have been avoided.   (This does not absolve the crew for its decision making which turned a bad situation into a fatal one.)

 
CREW AWARENESS
AIRPLANE OPERATIONS MANUAL (EMB-135BJ)
2-04-25
Page 2
Code 01
SEPTEMBER 30, 2002

SYSTEM INHIBITION

The stick pusher does not actuate in the following conditions:

−On the ground (except during test).
−Below 0.5 g.
−If the quick disconnect button is pressed (except for JAA certification).
−Below 200 ft AGL. If radio altimeter has failed, this condition reverts to a 10-second delay after takeoff.
−If any cutout buttons are released.
−Above 200 KIAS.
−If at least one channel is inoperative.


As for the jumpseater observing the trim wheels rather than the crew...   They’re right by the knees of the pilots themselves.    There’s no mistaking that thing once it starts churning butter.  It’s loud and is right there.    I find it impossible to believe they didn’t hear it.     

[Vraciu]

I appreciate what you are saying but unfortunately I think the opportunity to "learn" from this accident has passed.

As you well know, the foundation for the NTSB's huge budget is to educate airlines, pilots, mechanics, manufacturers and even the FAA so that any of the factors contributing to a crash of an airline do not happen again.

I for one, do not believe that the details of all elements contributing to these accidents will ever be published in a credible report.

I learn from the comments all you pros make.   

[deSelys]

Thanks for the info gents   

[Toad]

In the case of MCAS, an 'AOA disagree' alert could deactivate the system smoothly

In the aircraft I deal with, an AOA disagreement is signaled to the crew by a Crew Alerting System (CAS) message that displays in Amber and simply says "AOA Miscompare". When the crew looks up the CAS message in the QRH (Quick Reaction Handbook) it just says "Determine correct AOA indication". It assumes, therefore, crew situational awareness and competency. To your point, this AOA Miscompare DOES NOT disable any stick shaker or stall barrier function. Were either of those systems to actually trigger, there are different CAS messages and procedures.

3) About the 3rd pilot in cockpit the day before the Lion Air crash: maybe he hadn't extra knowledge but, free of having to repeatedly wrestle the controls and positioned further back allowing him to see the trim wheel spinning, he was much more able to correctly troubleshoot the event.

As Vraciu mentioned, it's pretty hard to miss the trim wheels spinning on either side of the center pedestal. They are right next to your inboard leg. I know in the earlier Boeings by design they made a "clank" sound as they spun; don't know about the MAX.

Secondly, when you earn your ATP part of the test is to see if you have the judgement and situational awareness to keep your wits about you and troubleshoot problems when things are going to excrement. The PIC and SIC in the Lion Air jumpseat situation should have realized they had an AOA/trim problem and dealt with it. Same with the Ethiopian crew.

As for stall warning events, there is a 2018 Annual C-FOQA Centerline Statistical Summary Report. FOQA stands for Flight Operational Quality Assurance. A lot (most?) modern aircraft now have tattle-tale Flight Data Recorders. When a limitation is exceeded or a serious flight event occurs, the systems report. These events go into the FOQA summary.

I have access to the 2018 report through mygulfstream.com. I could not find the report published on the open internet. Maybe someone else can.

Anyway, the 2018 summary shows the rate of stall warning events at about .05 per 100 flights, so 5 events per 100 flights.

This data was collected from 424,000 flights of 815 different aircraft of 22 different models, from Boeings, Bombardier, Cessna, Dassault, Embraer and Gulfstream.

So, think about that. in 2018, 5 out of 100 flights in this data set had a stall warning event. That does not speak well for pilot competency IMO. That's just too frequent.

[Busher]

So, think about that. in 2018, 5 out of 100 flights in this data set had a stall warning event. That does not speak well for pilot competency IMO. That's just too frequent.

Toad, "too frequent" is a gross understatement. Stall events in commercial airliners should never happen.... I certainly never had one nor did any of the pilots I knew and worked with. I am shocked.

[FLS]

Isn't  .05 in 100 = 1 in 2000? Still high though.

[Toad]

FLS, you are correct.

It's 1 stall warning in 2000 flights. My mistake.

In any event...still too high.

[Busher]

FLS, you are correct.

It's 1 stall warning in 2000 flights. My mistake.

In any event...still too high.

Almost 90000 commercial flights everyday in the USA. By that math 45 have a stall warning incident?

[Toad]

About 3-4 years ago Busher there was a FOQA report of 360 in a year in just the large cabin Gulfstream fleet. All models from the GI up to the G650. So about one a day.

Scary, huh?