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Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

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Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#131

Post by CamperBob2 »

js2 wrote: post #119
Someone1234 wrote: post #116

Earlier quoted context omitted.

US pilots say they didn't either. The training wasn't out there.

The runaway stabilizer trim procedure is how it was expected to be handled: https://www.flightglobal.com/news/articles/faa-order-tells-h... https://www.youtube.com/watch?v=3pPRuFHR1co The specifics of MCAS weren't out there because Boeing expected the pre-existing procedure to have been sufficient. That procedure wasn't sufficient, or the Lion and Ethiopian Air pilots were somehow not aware of it, or they forgot thei…

One thing I've been wondering: somehow the pilots were able to bring the nose back up... it was only (apparently) after multiple nose downs that they eventually failed to recover the plane. What was going on there? It's as if they understood how to correct the stabilizer trim, but weren't aware of the cut-off switches.

My understanding is that every time the MCAS activated, its effect was incremental. It could command only a limited deflection of the relevant control surface each time -- less than 1 degree? -- but the cumulative effect of multiple activations would eventually exceed the ability of the manual controls to override it.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#132

Post by ibejoeb »

rvolkan wrote: post #100
kunkurus wrote: post #86

Earlier quoted context omitted.

If Boeing knowingly exposed the passengers to the risk of injury it's criminal negligence and usually the punishment is imprisonment: https://en.wikipedia.org/wiki/Criminal_negligence

Exactly my point. Imprisonment should come into play when the accidents are proven to be caused by Boeing's negligence.

Is it negligence or just a bad design? Who decides? The thing is starting to look like Boeing thought that MCAS failure was similar to and corrected by the same procedure as runaway trim. Time will tell if that is the case, but if it does, should the pilots be posthumously tried for negligence?

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#133

Post by inferiorhuman »

6nf wrote: post #129
inferiorhuman wrote: post #123

Earlier quoted context omitted.

In many aircraft hard elevation will overpower even a faulty horizontal stabilizer In the 737 you can get into situations where the elevator has insufficient authority to overcome a stabilizer. Excessive pitch up (leading to a potential stall) that you can't counter by pushing on the yoke is exactly what MCAS is designed to prevent. There was a mechanical failure, the AoA sensor. A fixed offset from reality is an int…

The left alpha vane was being interpreted as almost exactly twenty degrees higher than the right. Is that because the plane was in a banking maneuver at the time maybe? I dont know anything about planes but I heard that when you're turning the two sensors will disagree by some amount

Is that because the plane was in a banking maneuver at the time maybe? I dont know anything about planes but I heard that when you're turning the two sensors will disagree by some amount

The difference in angle of attack was consistent throughout the entire flight (well up until the crash where the values began to converge). The threshold for the optional 'angle-of-attack disagree' warning is, I think, ten degrees. It seems very unlikely that the plane had a twenty degree bank angle for two entire flights.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#134

Post by jki275 »

mikeash wrote: post #90
jki275 wrote: post #84

Earlier quoted context omitted.

Honestly, those top positions in almost any organization are often political appointments that have little to do with day to day operations. The current "actings" are generally the ones who "advise" the political appointees on how to handle things. Obviously there are some exceptions, but most bureaucracies tend to run that way. Not to comment specifically on this as FAA isn't my area, but if the secdef doesn't come…

Amusing example, considering the Secretary of Defense has been vacant since January.

Well, Shanahan is acting and will be confirmed when the senate gets around to it... that's kind of the point though. DOD is still running and will continue to run, exactly as it has, with only minor political differences from the top. They have a lot of theoretical power, but little ability to actually change day to day operations of anything.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#135

Post by cryptonector »

zaphirplane wrote: post #106
Someone1234 wrote: post #91

Earlier quoted context omitted.

It didn't need to be included in the preliminary report since it is contextual/background information. They did include in the report that on a previous flight the same sensor error occurred and the pilots resolved it by disabling auto-trim. The fact there was a third pilot there is definitely interesting, but they didn't make anyone less safe by not including it in the report. There's no bombshell here. Previous pro…

This is very important, as it shows the ratio of pilots aware of the mitigation is low, and/or the stress of fighting with the the computer makes you forget you training amendments Edited to add it’s a training amendment

It also shows that pilot awareness (and therefore training) should have been sufficient. The key deficiency here was Boeing's. The agency not disclosing this detail is a problem too.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#136

Post by sandworm101 »

js2 wrote: post #125
Someone1234 wrote: post #124

Earlier quoted context omitted.

Runaway stabilizer feels nothing like MCAS. They likely didn't associate the training they received with the problem at hand.

Can you explain how they are different? Both cause the stabilizer to tilt. Both cause the stabilizer wheels next to the pilot/co-pilot to turn. If the plane is pitching down, and you pull back the yoke and that still doesn't recover, don't you at some point check the stabilizer angle? If it's wrong, you use the stabilizer trim switch on the yoke under your thumb to correct it. Won't you see the stabilizer wheel turn…

A runaway stabilizer is a single motion. The control surface moves, you react by shutting down the motor or fighting it by hand, and the situation should calm down. A malfunctioning MCAS will feel like multiple different runaways, in various directions. Once you react to the first, the system could be start pulling things the other way. Rather than a steady pull one way or another, you get into a back-and-forth fight.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#137

Post by comex »

RandomTisk wrote: post #120
chrisseaton wrote: post #64

Earlier quoted context omitted.

> You can't have them all be redundant. Why not?

Redundant wings? Fuselage? Just 2 obvious examples, back to my armchair.

True, there are some parts which are both safety critical and fundamentally unable to be made redundant, at least not without drastically compromising the overall design. But that doesn’t justify leaving out redundancy in parts which are able.

In any case, the actual regulations in play here would have required redundancy if the consequences of failure had been properly categorized:

> [I]n normal flight, an activation of MCAS to the maximum assumed authority of 0.6 degrees was classified as only a “major failure,” meaning that it could cause physical distress to people on the plane, but not death.

[..]

> He said virtually all equipment on any commercial airplane, including the various sensors, is reliable enough to meet the “major failure” requirement, which is that the probability of a failure must be less than one in 100,000. Such systems are therefore typically allowed to rely on a single input sensor.

> But when the consequences are assessed to be more severe, with a “hazardous failure” requirement demanding a more stringent probability of one in 10 million, then a system typically must have at least two separate input channels in case one goes wrong.

https://www.seattletimes.com/business/boeing-aerospace/faile...

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#138

Post by cryptonector »

Someone1234 wrote: post #94
sterlind wrote: post #89

Earlier quoted context omitted.

Seems like pilots are overburdened by so much automation, as alluded to by the famous "Children of the Magenta" video[0]. I don't get why the plane doesn't just say what it's doing, and why it's doing it, and have a big red button to put the plane into a safe-mode alternate law. 737s already say warnings like "BANK ANGLE", couldn't it just say "DANGEROUS CLIMB DETECTED, TRIMMING NOSE DOWN. PRESS RED BUTTON TO CANCEL.…

Boeing offered that, but it was a paid extra that few airlines purchased. https://theaircurrent.com/aviation-safety/southwest-airlines...

Yeah, maybe it shouldn't be an extra.

Re: Pilot Who Hitched a Ride Saved Lion Air 737 on the Day Before Deadly Crash

#139

Post by euyyn »

inferiorhuman wrote: post #70
dsfyu404ed wrote: post #57

Earlier quoted context omitted.

But this isn't really "avionics and surface control" more than automatic lane keeping is a critical control system for the car. MCAS is a convenience feature that counteracts the plane's tendency to pitch up more than you want when climbing. Sure it can improve safety, so can lane keeping in a car. Neither are critical to operation. You can fly/drive perfectly safely without them so they need not be super hardened ag…

MCAS is a convenience feature that counteracts the plane's tendency to pitch up more than you want when climbing. Nope, MCAS is required to meet the requirements set forth by the FAA. That's not a convenience thing. Various nannies may seem like convenience things in a well balanced car, but they become far more important in a powerful, poorly balanced car like a Porsche 911 or Dodge Viper — cars that have earned rep…

Whatever is a car nanny?
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