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Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

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Re: Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

#281

Post by mlyle »

x0x0 wrote: post #279
mlyle wrote: post #274

Earlier quoted context omitted.

I disagree that deciding to stretch the 737 is fundamentally bad engineering. Yes, it realistically requires some control augmentation (and maybe earlier 737's should really have had something like MCAS, too). Yes, bigger engines and heavier 737's have the problem worse, but it isn't unreasonable to fix this with systems. I think there were failures across the board. The fundamental analysis of MCAS was flawed: it wa…

Just for clarity, I have no qualms about stretching the plane. It's building in a new control system and not telling the pilots about it that seems crazy to me. Thanks so much for your thoughts!

Yup, I agree completely. There's some people who say that because the longer 737 is less stable in pitch it should have never been built, and I think that's over the top.

Thank you for the discussion and questions!

Re: Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

#282

Post by mantap »

losvedir wrote: post #262
jakeogh wrote: post #229

Earlier quoted context omitted.

Not stalling on takeoff is pilot 101. If an aircraft is prone to it I personally do not want layers of software hiding the issue. It's practically a law of nature that software is full of bugs.

> Not stalling on takeoff is pilot 101 So is trimming the stabilizer. Boeing was proven wrong by the two crashes but it's not a priori obvious that pilots wouldn't know to manually trim the stabilizer and then pull the cutout after MCAS kept kicking in.

They were following Boeing's advice! Boeing said if MCAS misbehaves then pull the cutout. They did that but then they couldn't move the manual trim wheel because of the forces on the stabilizer. So they reenabled the electric trim, at which point MCAS jumped in again and everybody died.

Re: Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

#283

Post by salawat »

mlyle wrote: post #251
joe_the_user wrote: post #234

Earlier quoted context omitted.

Specifically it's the argument in the article that large disasters often have multiple causes. "Perrow says, Murphy's Law is wrong—what can go wrong usually goes right. But then one day a few of the bad little choices come together, and circumstances take an airplane down. Who, then, is really to blame?" But that's exactly what's disingenuous about the GP's claim. Many disasters do indeed involve a sequence of mistak…

> The situation with 737 max was one terribly system and the pilot's complete inability to stop this - inability that could have been anticipated and which was the product of the original bad design. You accuse me of being disingenuous and immediately follow it with a false claim. This is untrue. Stabilator trim can be turned off. Indeed, before Lion Air 610 the previous flight had experienced the problem and had dea…

>This is untrue. Stabilator trim can be turned off. Indeed, before Lion Air 610 the previous flight had experienced the problem and had dealt with it correctly.

In the Lion Air penultimate flight, the situation was handled thanks to a third pilot in the cockpit with no other responsibilities contributing extra attention and reasoning. This is not available on every flight, and should not be considered a proof of safe operability. The mental model of a pilot unconcerned with the immediacy of flying the plane is more accommodating to unconventional occurrences due to being removed from the majority of learned perspective.

>Also, re-trimming using the trim switch disables MCAS for some number of seconds.

It also resets the activation cycle, and increments the amount by which the trim is activated. Both these details were unknown to all pilots at the time.

>In the case of ET302, they turned the system off, but allowed the aircraft to overspeed

And did nothing wrong. Given the stage of flight the problem occurred, they left the throttle in exactly the position they should have. Addis Ababa is also a "hot & high" airport, meaning the engines were already in the uppermost range of their operating envelope anyway. Furthermore, when the AoA sensor went bonkers, that leads to an airspeed unreliable checklist due to bad AoA figures throwing off the airspeed indicators which are dependent on AoA being correct for calibration. The airspeed unreliable checklist requires advancing throttles to the appropriate setting for the current stage of the flight regime, which was climb out.

>...and were, as a result, unable to retrim manually. Still, they had a positive rate of climb. It is only when they turned it back on in violation of training/checklist and inexplicably did not use it to retrim nose up that they were doomed.

They turned it back on in the hopes that the electronic trim could overpower the aerodynamic load where they could not, they did not realize that closing the circuit would give at most five seconds before MCAS dove again. Also, by this point, they were out of checklist.

It is almost as if I've heard these arguments before. (I have. We discussed it long ago when most things were conjecture.)

Sibling poster is correct. We've worked through this, and the pilots really couldn't have done any better considering the amount of information there was out at the time.

Also, later on, Boeing also notified airlines that only the MAX 10 I believe should be used in hot and high airports. The MAX 8 could take off due to Addis Ababa's extra long runway, but it just goes to ram home how uncomfortable a margin the Engineering firm was with safety margins afterwards.

Re: Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

#284

Post by dahart »

bdamm wrote: post #271
dahart wrote: post #177

Earlier quoted context omitted.

You're right. Boeing did not make an outlandish leap of logic, or any leap of logic at all in this context, because it was fully their intent to get away with no training. They worked their butts off to minimize the training, to minimize even the very idea that training was needed, and to prevent the Max from having to be re-certified by the FAA.

Of course, we can just as easily blame the FAA. If it's so hard to establish a differential training program then maybe the re-certification program the FAA requires (to certify a pilot to fly a slightly different aircraft) is too onerous. It's easy for the government to require too much work and seize up innovation, and I think we see that at work here. If the re-certification program wasn't so onerous, we could hav…

The FAA definitely bears some responsibility, but not because the regulation is too stringent, it’s because they looked the other way. Recertification is onerous for a reason; it’s safety we’re talking about, and the result of not being careful enough is exactly what happened, hundreds of deaths. The FAA’s process in this case is already a product of regulatory capture; Boeing is already practically certifying themselves. Lots of reporting on this already; it’s easy to find more info.

Re: Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

#285

Post by mlyle »

mantap wrote: post #282
losvedir wrote: post #262

Earlier quoted context omitted.

> Not stalling on takeoff is pilot 101 So is trimming the stabilizer. Boeing was proven wrong by the two crashes but it's not a priori obvious that pilots wouldn't know to manually trim the stabilizer and then pull the cutout after MCAS kept kicking in.

They were following Boeing's advice! Boeing said if MCAS misbehaves then pull the cutout. They did that but then they couldn't move the manual trim wheel because of the forces on the stabilizer. So they reenabled the electric trim, at which point MCAS jumped in again and everybody died.

They couldn't move the manual trim wheel because the plane had been allowed to overspeed.

It was climbing at Vmo; they could have pulled back the power to not let the plane overspeed, rather than exceeding Vmo.

Hopefully at Vmo they could move the trim wheel, but if not, they could wait until they had a few thousand feet more height, aerodynamically unloaded and trimmed.

> So they reenabled the electric trim, at which point MCAS jumped in again and everybody died.

They re-enabled the electric trim, and touched the electric trim switch a couple of times but left the plane far out of trim. I can't figure this out-- there's even an indicator that makes it obvious you're out of trim. Why re-enable electric trim and not really use it?

Then after a timeout after they pushed the trim switch, MCAS jumped in again and everyone died.

Re: Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

#286

Post by mlyle »

alexis_fr wrote: post #199
dahart wrote: post #73

Earlier quoted context omitted.

I love those articles, and the lesson learned from them. But there is no automatic parallel in this situation, in fact the opposite here. The NTSB isn’t suggesting that Boeing model a single “average” pilot. They’re suggesting that Boeing test using many pilots who are not highly trained in test procedures. The “flaw of averages” problem is one of combining averages in multiple dimensions and assuming the result is s…

I like the idea that they pick pilots at random: - Either it’s Boeing’s fault for improper UX, - Either it’s Boeing’s fault for pilot certifications not being stringent enough. In either case, the aircraft manufacturer must improve. I think of it as an “integration test”, “let’s see how the pilot+plane integrate together”. Not necessarily Boeing, btw. It could be Airbus. It could even be a move from the US regulator…

It's always fun to look at the performance figures in aircraft manuals.

Somewhere, a skilled test pilot got those numbers in a pristine plane.

But mere humans in a real-world plane will typically not obtain them.

Re: Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

#287

Post by mlyle »

salawat wrote: post #283
mlyle wrote: post #251

Earlier quoted context omitted.

> The situation with 737 max was one terribly system and the pilot's complete inability to stop this - inability that could have been anticipated and which was the product of the original bad design. You accuse me of being disingenuous and immediately follow it with a false claim. This is untrue. Stabilator trim can be turned off. Indeed, before Lion Air 610 the previous flight had experienced the problem and had dea…

>This is untrue. Stabilator trim can be turned off. Indeed, before Lion Air 610 the previous flight had experienced the problem and had dealt with it correctly. In the Lion Air penultimate flight, the situation was handled thanks to a third pilot in the cockpit with no other responsibilities contributing extra attention and reasoning. This is not available on every flight, and should not be considered a proof of safe…

> The airspeed unreliable checklist requires advancing throttles to the appropriate setting for the current stage of the flight regime, which was climb out.

It's basic airmanship to know that if you are not in climb attitude, that high power is going to overspeed in anything slick. Combine that with "overspeed" alerts and you should maybe realize it's time to pull the power back.

> They turned it back on in the hopes that the electronic trim could overpower the aerodynamic load where they could not, they did not realize that closing the circuit would give at most five seconds before MCAS dove again. Also, by this point, they were out of checklist.

They turned it back on, clicked the trim switch briefly, and then left it alone, despite knowing they were way out of trim. Can you explain why this makes sense? Why turn it on and not get back to nominal trim?

Also, they were still climbing at Vmmo (or overspeed). It would have always been an option to climb a bit...

Re: Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

#288

Post by salawat »

mlyle wrote: post #254
joe_the_user wrote: post #253

Earlier quoted context omitted.

I believe my position is that of the strong consensus of the long debates that have gone on in detail here and in numerous mainstream and technical publications. I can't summarize all the arguments there and I won't try but the conclusion has been Boeing is to blame (period). In this day and age, I'm suspicious and annoyed even small effort to improperly spread blame when that spreading serves powerful interests.

Basically all of aviation safety is about the spreading of blame and plugging up holes. Either approach is wrong: just pointing to the pilot and saying "hah-hah error" without considering what led to the error is what aviation did for decades. "Crash less!" we said to pilots, and were surprised when things didn't improve much. But you can't ignore crew performance, either. The crews that crashed did not do great. But…

>The crews that crashed did not do great.

Not necessarily fair since one didn't even know what they were up against, and the other was trusting a Boeing checklist that wasn't guaranteed to work, and only stood a realistic chance at working if the failure did not occur at a critical stage of the flight, where a currently undocumented maneuver could be performed. (The 'roller coaster' by which the pilot allows the plane to dive to unload the stabilizer so it can be trimmed)

>And MCAS is more easily improved than the rest: we can more easily reduce the frequency and severity of that "testing" than we can improve all flight crews. But we shouldn't ignore the problems in crew decision-making, and the related training choices (e.g. not requiring crews to demonstrate handling of runaway trim in some jurisdictions).

This is just poppycock, if you ask me.

MCAS was a desperate attempt to satisfy a prescriptive behavior requirement (FAR 25.173, demonstration of longitudinal stability) during which the plane should not experience slackening control forces all the way to the stall in a wind up turn, which non-compliance with would disqualify the airframe from certification under the grandfathered 737 type certificate and as a Civil Transport Airplane.

There would have been no need to consider the skill of the pilots if due diligence and proper redundancy concomitant to the actual hazards of the design had been done, which weren't due to management's pressure to get this damn plane flying on time at any cost.

Re: Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

#289

Post by mlyle »

salawat wrote: post #288
mlyle wrote: post #254

Earlier quoted context omitted.

Basically all of aviation safety is about the spreading of blame and plugging up holes. Either approach is wrong: just pointing to the pilot and saying "hah-hah error" without considering what led to the error is what aviation did for decades. "Crash less!" we said to pilots, and were surprised when things didn't improve much. But you can't ignore crew performance, either. The crews that crashed did not do great. But…

>The crews that crashed did not do great. Not necessarily fair since one didn't even know what they were up against, and the other was trusting a Boeing checklist that wasn't guaranteed to work, and only stood a realistic chance at working if the failure did not occur at a critical stage of the flight, where a currently undocumented maneuver could be performed. (The 'roller coaster' by which the pilot allows the plan…

> Not necessarily fair since one didn't even know what they were up against, and the other was trusting a Boeing checklist that wasn't guaranteed to work, and only stood a realistic chance at working if the failure did not occur at a critical stage of the flight

Well, it did get them back to positive rate climb, didn't it? :P Just, dubious subsequent actions gave that back.

> This is just poppycock, if not straight up, grade A bullshit; no personal disrespect intended to you, fine sir.

Well, it is absolutely personal disrespect, and adding qualifiers amplifies rather than undoes it. A decent person should do better.

> There would have been no need to consider the skill of the pilots if due diligence and proper redundancy concomitant to the actual hazards of the design had been done, which weren't due to management's pressure to get this damn plane flying on time at any cost.

I already said MCAS is awful, kthx? At the same time, it's exposed that many air crews in developing countries don't know how to deal with trim runaway. And trim runaway happens: switches get stuck. So the other links in the failure chain should be dealt with, so that they don't conspire to bring down aircraft under other conditions.

Re: Plane Tests Must Use Average Pilots, NTSB Says After 737 Max Crashes

#290

Post by salawat »

mlyle wrote: post #285
mantap wrote: post #282

Earlier quoted context omitted.

They were following Boeing's advice! Boeing said if MCAS misbehaves then pull the cutout. They did that but then they couldn't move the manual trim wheel because of the forces on the stabilizer. So they reenabled the electric trim, at which point MCAS jumped in again and everybody died.

They couldn't move the manual trim wheel because the plane had been allowed to overspeed. It was climbing at Vmo; they could have pulled back the power to not let the plane overspeed, rather than exceeding Vmo. Hopefully at Vmo they could move the trim wheel, but if not, they could wait until they had a few thousand feet more height, aerodynamically unloaded and trimmed. > So they reenabled the electric trim, at whic…

That's what you would do, you weren't there though, they were. Confronting a system whose implementation details were not well known, already two potential memory item checklists into the flight to the ground.

It's easy now to point the finger and say "Airmanship" when you know the innards of the damn thing. They had one airworthyness directive, and maybe a grand total of five paragraphs in the entire manual, plus a memory item checklist that didn't accurately reflect the detail of an MCAS failure. An MCAS failure is not continuous uncommanded trim. It's discrete pulses,

I appreciate the detail and effort, and you certainly speak as an experienced member of the industry; but pushing this off to the pilot's when there is so much that had to happen before the plane left the factory for them to be in that position is a bit much.

There is whistleblower testimony that the decision to not implement a multi-sensor MCAS was intentional to avoid the financial consequences of having to have pilots put in simulator time.

You can't sit here and say the pilots weren't good enough when the manufacturer went out of their way to make sure they could skulk a plane by regulators with the least amount of training humanly possible, safety be damned. To do so is not just mad, it's unconscionable. It's the very thing of insanity. A Catch-22 if I've ever heard one.

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