Boeing Systemic Problems Continue

[pianokeys]

Are they perfect? Are they infallible? Not at all but show me any other device that is as complex that does not have its challenges? Samsung cellphones with exploding batteries, vehicles with mandatory recalls etc.

Last I checked rushing a phone to market only caused tech envy and not mass fatalities.

Yup. One of these is not like the other! One can wipe out 180 plus people in one go, the other one is just annoying.

[goingnowherefast]

Transport category aircraft require redundancy in almost every part of the design. MCAS somehow escaped this despite a second sensor being installed, but not included. The AOA display and AOA disagree being integral to a flight control system, but being options for cost points at money being more important than safety.

It is one layer in the swiss cheese, but it's a pretty big hole in that slice.

[Inverted2]

Ralph Nader's viewpoint:-

https://www.commondreams.org/views/2019 ... muilenburg

I agree - this Virtue Signalling CEO Dennis Muilenburg has to go.

At least a Ralph didn’t call it the Corvair.

[L39Guy]

There's a reason they don't give you multiple compounding failures in the sim. It can be very confusing. Why put pilots in that situation in the first place due to a simple AOA sensor error? Why no comparator system? Why make even an AOA DISAGREE light an optional extra? Why not tell pilots about the MCAS system at all other than what it stands for? It's getting pretty obvious that the answer is money which is why people are upset with Boeing.

If you study the preliminary reports as I have done (and not based one's understanding from the New York Times or Wall Street Journal), one quickly discovers that neither of the accident aircraft crews did the Unreliable Airspeed Checklist (UAS) yet the crew of the Lion Air incident aircraft the day before did. The airspeed was unreliable the moment that aircraft lifted off - stick shaker, IAS Disagree, etc., yet neither of the accident crews executed a pretty simple recall (memory) procedure (autopilot off, autothrottle off, set 10 degrees pitch and 80% power). This was long before MCAS kicked in when the flaps were raised (raising the flaps with the apparent intention of proceeding to destination with UAS is questionable airmanship). It is also interesting to note that in the Ethiopian case, the Captain tried to engage the autopilot at 400 ft ("Command"), a definite no-no with UAS or, alternatively, if he thought he was stalling - one does not recover from a stall with the autopilot.

The incident aircraft crew did perform the UAS checklist and they were able to control the aircraft even after MCAS reared its ugly head. Why were they able to control the aircraft? Because they were not racing around at Vmo (about 340 kts) like the others trying to manually trim the aircraft with the trim wheel - the forces to turn that trim wheel at that speed are impossible for even the fittest pilot. The fact that the incident aircraft crew did not know the Stab Trim Runaway checklist and relied upon a B737 jump-seater from another airline to tell them to turn off the stab trim is another story. So is the fact that they continued to destination (1 1/2 hour flight) and not land immediately with both UAS and a Stab Trim Runaway is another (airmanship) issue.

So while multiple unrelated failures are not provided in sim training, the crews of the accident aircraft did not even do the UAS procedure from the moment they lifted off to when the retracted the flaps. Up until flap retraction, this was a single failure event not a multiple, unrelated failure.

[L39Guy]

Transport category aircraft require redundancy in almost every part of the design. MCAS somehow escaped this despite a second sensor being installed, but not included. The AOA display and AOA disagree being integral to a flight control system, but being options for cost points at money being more important than safety.

It is one layer in the swiss cheese, but it's a pretty big hole in that slice.

Not quite true - in the case of the B737, the electrical stab trim system is a single point of failure (single trim motor, etc), and that is why there is a Stab Trim Runaway checklist and a manual procedure to fly the aircraft thereafter. An engine failure is a single point of failure (for whatever reason) that requires pilot intervention - that is why we do V1 cuts, etc. Same thing with the outflow valves for the pressurization system.

I agree, however, that MCAS needs some redesign however to tone it down a bit. There will never be three AOA sensors on the B737 so there will be no means to do democracy of AOA (vote the erroneous one out).

The Turkish accident at Schipol was the result of a single radar altimeter input into the autothrottle; when the single source thought it was at zero feet it retarded the thrust levers, the speed decayed and the aircraft stalled, despite three pilots being in the flight deck. Boeing then modified the system to take two inputs.

[L39Guy]

[/quote]

All excellent examples of the same corporate mandate to push products to consumers without due diligence. Just because others are just as negligent does not justify the practice!
Last I checked rushing a phone to market only caused tech envy and not mass fatalities.

It's all fucking bullshirt if you ask me.
[/quote]

Boeing's big mistake was assuming that professional, B737 type rated pilots could handle an MCAS runaway, which is identical in characteristics to the stab trim runaway that has been part of the B737 for the past 50 years. Boeing, every other aircraft manufacturer, every airline, every CAA and every pilot association is going to have to have a rethink of the assumption that pilots can actually hand fly an aircraft without the automation saving their skins.

For those of us who earned our chops hand flying aircraft this might seem ridiculous however when one considers that in many parts of the world there is no bush operation or corporate operation or any other operation where hand flying is mandatory. Airline pilots get minimal training (the Ethiopian had 351 hours total time of which 207 was B737) then start flying an airliner and are taught from day one to engage the autopilot at 400 ft and keep it on autopilot until just prior to touchdown so they have no manual flying skills or, if they did, they quickly atrophy.

As we have tragically seen with the MCAS issue and other, avoidable accidents, the lack of basic flying skills is becoming a significant factor in accidents now.

[Eric Janson]

The Turkish accident at Schipol was the result of a single radar altimeter input into the autothrottle; when the single source thought it was at zero feet it retarded the thrust levers, the speed decayed and the aircraft stalled, despite three pilots being in the flight deck. Boeing then modified the system to take two inputs.

I used to instruct on the 737 - this failure case was not addressed in the manuals or in training. I didn't know about this.

Of course back then it was "Manual Flight - Manual Thrust" - this would never have happened in normal operations. The autothrottle was only used for Cat II/III approaches and you paid close attention to what was going on.

On the airbus we have a bulletin in the QRH about this (same system design).

[Rezy]

Boeing's big mistake was assuming that professional, B737 type rated pilots could handle an MCAS runaway, which is identical in characteristics to the stab trim runaway that has been part of the B737 for the past 50 years. Boeing, every other aircraft manufacturer, every airline, every CAA and every pilot association is going to have to have a rethink of the assumption that pilots can actually hand fly an aircraft without the automation saving their skins.

For those of us who earned our chops hand flying aircraft this might seem ridiculous however when one considers that in many parts of the world there is no bush operation or corporate operation or any other operation where hand flying is mandatory. Airline pilots get minimal training (the Ethiopian had 351 hours total time of which 207 was B737) then start flying an airliner and are taught from day one to engage the autopilot at 400 ft and keep it on autopilot until just prior to touchdown so they have no manual flying skills or, if they did, they quickly atrophy.

As we have tragically seen with the MCAS issue and other, avoidable accidents, the lack of basic flying skills is becoming a significant factor in accidents now.

That’s really understating the problem I think. The MCAS problem is a combination of unreliable airspeed, a false stall warning, and a stab trim runaway all at the same time. It takes time to diagnose a problem, US Airways 1549 proved that, and unfortunately it doesn’t look like the Ethiopian crew was able to do that soon enough.
What basic flying skill would have helped them?
-Turn off the Autopilot? They did that.
-Turn off the Electric Trim? They did that.

[L39Guy]

That’s really understating the problem I think. The MCAS problem is a combination of unreliable airspeed, a false stall warning, and a stab trim runaway all at the same time. It takes time to diagnose a problem, US Airways 1549 proved that, and unfortunately it doesn’t look like the Ethiopian crew was able to do that soon enough.
What basic flying skill would have helped them?
-Turn off the Autopilot? They did that.
-Turn off the Electric Trim? They did that.
[/quote]

It all started with an Unreliable Airspeed (which includes the false warning) then, once the flaps were up and in manual flight, the Stab Trim Runaway. Two emergencies, both with recognized procedures.

The additional flying skills that would have helped would have been:

• autothrottle - off
  set 10 degrees pitch
  set 80% power
  (these are part of the NNC
  with or without doing the NNC, someone should have been flying the airplane, and this includes
  manage the speed, instead the speed got up to max velocity of 340 Kts, which made manual trimming nearly impossible
  trim the aircraft, to maintain an in trim condition, with large bursts of trim, not timid, little tickles of the trim switch

There are other airmanship issues that I think we can all learn lessons about too:

• with either problem, you are not going anywhere. Land the aircraft immediately
  if the problem stops, stay in that configuration and don't change configuration back to one that causes the issue to reappear
  know your emergencies

[Rezy]

I’m agree there are many things they could have done. I just disagree with the assessment that those responses are ‘basic flying skills’. And even your treating it like 2 simple emergencies, well that’s a total understatement because the preliminary report shows there was a lot more going on in the flight deck. Master Caution, stick shaker (that lasted the entire flight), “Don’t Sink” calls because of the descent after takeoff, and ATC interruptions. All while flying on faulty instruments with a runway trim. It’s not a simple emergency, which is why 2 crews failed to solve the problem.
Reduce thrust with a stick shaker going off? That’s not basic flying skills. that’s the only point I’m trying to make here.

[L39Guy]

I agree that there were lots of bells and whistles as there often are when something malfunctions...engine fire with lights flashing, horns blaring, confusion, startle factor, etc. But one has to fight through all of that and focus on the problem. That's why simulators are so good at practising that.

As far as the first emergency is concerned (unreliable airspeed), the Boeing drill is simple - autopilot off, autothrust off, 10 degrees pitch/80% power (it is a similar drill in all Boeing airplanes). That simple drill, even with all of the noise and confusion, was not done and it was clear that something was wrong with the airspeed system.

If it was a stall, then the nose should be lowered and power carefully added; it was not. Autopilot on at 400 ft. is a no-no in either case of a stall or an unreliable airspeed. There are three independent airspeed indicators in the B737 so the erroneous one can be easily identified and control passed to the pilot with the good airspeed indicator.

None of these basis things were not done in the ET case (and Lion Air too). Identifying the erroneous airspeed indicator, following the drill and maintain the proper speed is all basic stuff expected of a professional pilot. And this was long before the flaps were raised and the MCAS pitched the nose down.

[Rezy]

I agree that there were lots of bells and whistles as there often are when something malfunctions...engine fire with lights flashing, horns blaring, confusion, startle factor, etc. But one has to fight through all of that and focus on the problem. That's why simulators are so good at practising that.

As far as the first emergency is concerned (unreliable airspeed), the Boeing drill is simple - autopilot off, autothrust off, 10 degrees pitch/80% power (it is a similar drill in all Boeing airplanes). That simple drill, even with all of the noise and confusion, was not done and it was clear that something was wrong with the airspeed system.

If it was a stall, then the nose should be lowered and power carefully added; it was not. Autopilot on at 400 ft. is a no-no in either case of a stall or an unreliable airspeed. There are three independent airspeed indicators in the B737 so the erroneous one can be easily identified and control passed to the pilot with the good airspeed indicator.

None of these basis things were not done in the ET case (and Lion Air too). Identifying the erroneous airspeed indicator, following the drill and maintain the proper speed is all basic stuff expected of a professional pilot. And this was long before the flaps were raised and the MCAS pitched the nose down.

What clue did both crews have to run the unreliable airspeed drill?

[L39Guy]

The main clue was an otherwise normal take-off followed by stick shaker, depute normal power on both engines. The other indications listed in the reports also adds to the UAS diagnosis.

It is important to note that the Lion Air incident flight diagnosed UAS immediately, controlled the aircraft (including speed) and managed to land the aircraft (after flying it an hour and a half to the original destination).

[ahramin]

In any jet I have flown including the B737 a stall warning at liftoff is not an indication of unreliable speed. Stall warning combined with overspeed warning is, but stall on its own is not. This was not an unreliable speed indication and the airspeed indications were normal and correct all the way to the ground on both accidents.

[L39Guy]

In any jet I have flown including the B737 a stall warning at liftoff is not an indication of unreliable speed. Stall warning combined with overspeed warning is, but stall on its own is not. This was not an unreliable speed indication and the airspeed indications were normal and correct all the way to the ground on both accidents.

All three events had stick shaker, the ET accident report PDF page 11 states that there was a 20-25 knot airspeed disagreement, the CVR from the Lion Air incident states that there was an IAS DISAGREE annunciation.

If you look at the computed speed traces for all three flights in the two reports they show the same split therefore one can assume that all three had a 20-25 knot airspeed disagreement. I think it is probably a good assumption that the other two flights had an IAS DISAGREE annunciation too. Finally, the captain of the incident flight called for the UAS checklist.

I would suggest that this all points to an unreliable airspeed event.

[ahramin]

Interesting. So it looks like the entire Air Data computer was messed up? Not just a bad AOA vane? Or does a bad AOA vane mess up the Air Data computer?

the stick shaker activated and remained active until near the end of the flight.
 After autopilot engagement, there were small amplitude roll oscillations accompanied by
lateral acceleration, rudder oscillations and slight heading changes; these oscillations also
continued after the autopilot disengaged.
 After the autopilot disengaged, the DFDR recorded an automatic aircraft nose down (AND)
trim command four times without pilot’s input.

That's a lot of stuff to go wrong all at once. I'd say if they noticed the airspeed deviations it warrants the Airspeed Disagree Checklist, but in hindsight we can see that it wouldn't have fixed the problem anyway. I'm not sure I would have noticed a 20 kt difference while trying to deal with an apparent flight control problem.

[Eric Janson]

I would also suggest the possibility that the sound of the continuously operating stick shaker may have masked the sound of the trim wheel moving.

[plhought]

On the Max the AOA information is used by the ADIRS as part of the 'position error' correction for calculating KCAS/IAS...

Hence once you have a bung AoA vanes you get the unreliable airspeed flag.

Don't ask me why Boeing decided that - just another head scratcher.

[Daniel Cooper]

Why would they design a manual trim wheel that doesn't have enough mechanical advantage to retrim the aircraft after a significant runaway?

[L39Guy]

Why would they design a manual trim wheel that doesn't have enough mechanical advantage to retrim the aircraft after a significant runaway?

You mean being able to manually trim while flying around at Vne (340 kits+)? I don’t think that any aircraft can be manually trimmed at those types of speeds.