The 787 is a replacement for my 767 (currently a pilot on the aircraft) and in 1991 a Lauda Air 767 suffered a failure in one of its thrust reverser and it became activated during cruise. The aircraft was destroyed in flight.
The thrust reversers should not activate during flight (a air/ground sensors prevents that) but as it is a catastrophic failure, having the engine shut down automatically seems like a great fail safe device.
In this case it seems that the 787 engines were reversed before the air/ground sensor had sensed ground and it is a potential problem.
"The safety system automatically cut the power to the engine suffering the thrust reverser malfunction. There was no alarm in the cockpit to indicate that a thrust reverser had been accidentally deployed. The crew had no way of knowing what the true problem was. The copilot, seeing the right engine power lever automatically move to the closed position, thought that the lever had slipped back and pushed it back to the full power position alongside the left engine throttle lever. Once again, the automatic safety system closed the right engine throttle and the captain, who was conducting the takeoff, called for the autothrottle system to be switched off. After switching off the system, the copilot again pushed the right engine power lever fully forward and forcefully held it there."
He was severely burned in a Formula 1 race at the Nurburgring, and despite still suffering badly scarred lungs and weeping wounds he was back in the seat before the end of the season and only lost the championship that year because he refused to go out in the pouring rain to race the Japanese Grand Prix as he decided it would have been foolhardy.
> The EEC commands shutdown of the affected engine when the:
> • airplane is on the ground, and
> • thrust lever is at idle, and
> • engine is above idle speed and not decelerating normally
> The EICAS caution message ENG FAIL (L or R) is displayed with an aural beeper once the engine falls below idle speed.
What I don't understand is why does the reverse thrust input from the cockpit even influence the engine control when the air/ground sensor doesn't sense ground? It seems like an obvious lockout mechanism to have in place, if the result is shutting down the engines when the combination occurs.
Then just have a manual air/ground sensor override should that thing fail and you know you're on the ground and require reverse thrust.
Do you get scared when you drive to work? Or take a train? Both are more risky. (Driving significantly so.)
More specifically... The pilots have extensive training, modern airliners have fail safes everywhere, and the amount of research and engineering spent on aviation safety is mind boggling.
My point is, there's plenty of accidents caused by things that happened while the plane was in the air, that has many survivors or just some injuries. The news article at  has some examples, and it's possible to search for more. Granted, if you exclude the cases where the injuries or casualties were caused during an attempted landing or a forced landing due to malfunction, the picture would probably look much more bleak, but then you would also have ruled out a large portion of the accidents that happened.
It's thankfully _extremely_ rare that it's been impossible to make an honest attempt at a controlled landing or ditching during an accident, and in a large part of the cases where this was possible, things turned out okay for most passengers.
When you’re in an automobile, you could choose to drive faster or slower, safer or more aggressively. You can tell yourself that you are more alert or a better driver to the people who die in fatal car accidents. You can tell yourself that you have a superior ability to avoid that drunk driver who might suddenly veer into your lane from oncoming traffic. And once your car comes to a stop, if you’re not seriously injured, you can just get up and walk away.
In an airplane there’s none of that. You can make vanishingly few choices to affect the safety of your flight. And you’re stuck in that tin can until it’s on the ground and you’re either alive or dead.
Then there is this image:
Another thing I do is to remember the physics when I'm on a bumpy. Thanks to momentum, planes don't just fall out of the sky, and even bad turbulence is not likely to result in deaths.
(because if, when having a mulfunction of the detector's "feature" in mid-air the engines switch off you still have some time to fix/override it, but on the other hand when not having it if your reverse-thrust engages you're screwed immediately - and even if the feature fails nearby the ground you're still be slow & low enough for at least some passengers to have some chance to survive)
See this episode of Mentour Pilot:
It is still better to lose all engines than to have thruster reversers deploy in unsafe situations. You may stall without an engine at low altitude in a landing configuration, but you should still be able to glide for some time. Deploy reversers (or even a single reverser) and you fall like a brick very quickly.
none where it would deploy the reverse thrusters and probably crash regardless of other inputs to the system(could be one or more of many inputs wheel speed, slats deployed, airspeed, elevation, throttle position, etc.)
turning off the engine (presumably you want this because you are on the ground but your ground sensor is failing so you want to cut engine and apply brakes which is less preferable than the reverse thrusters but manageable normally.)
ignoring the input altogether.
not a failsafe at all and an unexpected failure mode of the system (I think this is probably the case since they couldn't relight the engine on the ground)
the point i was making is that if you have the failsafe turn off the engines under normal operating procedures it should be able to relight when in flight and it's not good if a software glitch turns your heavy into a glider without possibility to relight. (i am not a pilot but it's my understanding that you still have the turbines spinning and all you need to do is give it some fuel and fire up both ignition plugs. might need to use the compressor to spin them up to full speed but i doubt it.)
If it gets pulled in normal flight you would lose both engines but that's fine because you can glide and restart the engines. if the altitude sensor/ground sensor was broken and you want to override the reverse thrusters you have a conflicting goal there.
If you accidentally pull it during the approach you lose your engines and probably don't have time to relight before landing. in that case you might be able to still land by backup systems(FAU or just the ancillary tail turbine?) and glide?
I guess it boils down to how much trust you place in the pilots to not do the wrong thing or how much trust you place in the machine to not do the wrong thing/malfunction. It's a difficult question without a perfect solution imo.
If it's on the approach, I'd be worried. I imagine that that, at an airport like ORD, that might result in more risk than anyone really wants of the plane unexpectedly touching down on an interstate highway or something like that.
If it's like what Boeing described in the bulletin, where the engines only get shut down after the wheels are on the ground, that's maybe not super worrisome, but I can still see some room for concern. My reconsidered but still totally uninformed reading on the situation is that it takes some time for all the aircraft's systems to get the memo on whether the plane is on the ground, and that what's really going on here is that the order in which they get the memo isn't quite right. So the question of whether or not to allow a Lauda Air type situation isn't really at play here, but perhaps a related glitch to the one that caused this event could interfere with something like aborting a landing at the last minute.
If the engines quit, you still have control.
I've worked with several pilots in my career. Unless you have a ton of experience, IT pays better than flying.
This is an ANA aircraft, which means it's probably maintained well and flown by competent pilots. Looking forward to a good analysis on this.
Most large aircraft have a "weight on wheels" switch, activated when the aircraft is on the ground. There might be some bad interaction between the "weight on wheels" sensing and the thrust reverser protection. Pure speculation: initial touchdown, pilots deploy reversers, small bounce into the air, weight on wheels switches open, engine controller detects flight condition with thrust reversers deployed and shuts down engines.
The other side of this kind of failure is dealing with unintended thrust reverser deployment in flight. Here's an overview. Historically, it wasn't a big deal at altitude, but on some newer aircraft, it is, and so stronger steps have been taken to avoid it.
In that case, the aircraft touched down, reversers were deployed, a runway obstacle (a snowplow) appeared, and the pilots attempted to go around. They got airborne and cleared the obstacle, but as they lifted off, the "squat switches" on the main gear opened. One of the reversers was still deployed, and with the squat switches open, was no longer powered, and could not retract. The aircraft was uncontrollable, and crashed.
In that case, shutting down the reversed engine would likely have been preferable, although if we're doing counter-factuals, telling the snowplow driver about the airplane's revised arrival time is your go-to move, I think.
I really do find the inability to restart extremely interesting though. I'd bet it's a bug somewhere, but it would be alarming if Boeing programmed in a lock-out on the failed engine(s) (I've heard it talked about as a solution to the sudden deployment of reverse thrust in flight) .
The bugs in the Therac 25 were only discovered after the machine had been in production for a while (you had to be typing "too quickly" in order to get the software to trigger the bug with the safety interlock).
But it is entirely possible that nobody pulled the reversers while still airborne in 9 years, because it's a very strange thing to do. A bit like opening your car door while still driving 60 mph... Nobody does that in normal operation.
You don't open and shut a door when you notice it didn't fully close because you can hear the wind?
It made a grinding noise and I yanked it back into drive.
Other than the noise nothing bad happened.
You'd certainly struggle to do it by accident.
(I might try to pull it more shut while moving. But not open it.)
Here's the first video I found but there are certainly others https://www.youtube.com/watch?v=-RO66a_nvus
That's overstating the case a bit. I'm 100% a layman here but I'd agree that the behavior seems like some sort of bug. But…… some planes (typically not commercial, although the Concord is one notable exception) call for reversers in flight under certain circumstances. Additionally there are definitely circumstances where a pilot might deliberately think reversers before touchdown are a good idea.
Also, the robots would have to bash at the speed of a human: The point is to mimick human inputs not necessarily test every code path (Which you could do in software)
I spent a lot of time at new job (well 18mths now) on making the software side more resilient, we still had a site wide outage of internet access and comms and internal systems because one of the women in the sales office unplugged a socket in the ingress comms cabinet to plug her hair straighteners in.
Coincidentally my request to have physical access control on all the comms cabinets shot right up the list.
The boundary layer between software and hardware itself has to be tested, the real world is a messy place :).
I'd pay quite a lot of money to camp out in the desert for a week watching fuzzing robots try to crash airliners...
That sounds like an odd safety override. Surely a better solution would be to just not activate reverse thrust. Unlike car engines a jet engine can’t just be quickly restarted if it accidentally shuts down. It typically takes 30-60 seconds to get going.
This and earlier incidents are highlighting the dangers automation can add to mission critical systems. No pilot wants to hear notices about “hey, so in case you didn’t know our programmers added some code that does this strange uncommanded thing when you push buttons a certain way”
If so, I'll take back my words but considering the manufacturer doesn't know exactly why this happened, and the engineers on the ground said it seems like a "software bug", it seems a bit presumptuous and frankly a bit comical to start saying things like:
"Surely a better solution would be to just"...
Ah well, glad a 5 sentence comment on the internet can resolve an issue in a hardware, software, and social engineering challenge decades in the making.
"For every complex problem there is an answer that is clear, simple, and wrong." -- H.L. Mencken
One of the things I have experienced in my career is the mind boggling complexity of the software in systems that are capable of killing people. The more people it can kill the more complex the software.
As a result when I read articles like the one posted I find it tantalizing to speculate about the requirements behind the story. Taking the story at face value that Boeing has thought a lot about it and that is how the software has to be, what prevents the other solution of disabling the reverser? My guess is that you want the reverser to work in the event of software failure so it has to always work, but if the pilots pull it while you are flying that would probably rip the engines off the plane. Perhaps the compromise is to take the reverser off during flight and relight the engines using aerial pressure to spin up the engines. (which has me wondering if airlines still have a turbine they can drop down to start an APU which can then be used to start the engines). Which leads me to wondering if the pilots turn off the reverser right away do they have enough residual engine power to relight? Versus when they got to the end of the runway and had nothing? Clearly the 777 doesn't have an APU running when it lands since they would have used that to do an engine start at the end of the runway or if it does, it isn't running.
It is one of those things that my like minded systems friends could sit around lunch and make a good hour and a half discussion out of.
A reverser only redirects thrust, and only generates about 60% of max thrust pushing backwards.
It's only on for a limited time on the ground because under a certain speed, you run the risk of blowing FOD into the intake path, putting the engine at risk.
I'm not aware of any reason to outright lockout a reverser in flight other than to hedge your bets against a very, very poor set of configuration choices by the pilot (reversing near stall speed too low to recover). I could foresee scenarios where being able to use reversers in the air could save the aircraft with the right combination of subsystem casualties.
Not a pilot or engineer, but absolutely LOVE aviation.
[EDIT remove "roughly speaking an order of magnitude"]
No. No it is not. 787 approach speed is 145-153 knots. It does not cruise at 1400+ knots.
What would you like to call the factor? 3? Call me a weasel, but I was hoping "roughly speaking an order of magnitude" would go down to 3. I suspected it was comfortably above 2. Am I right about that?
I'd call that half a order of magnitude, considering log₁₀(3) is around 0.477. So you're off by more than a factor of two.
0: Uniform, linear and logarithmic are obvious candidates, but depending on the domain you can end up with some really wierd scales (eg floating-point ULPs, which can look logarithmic or linear, but aren't either).
1: hence > So you're off by more than a factor of two.
roughly 10x going down to 3x would also mean it would go up to 17x. That's a pretty wide range, so I don't think that order of magnitude is going to ever really be similar to 3x of something on the basis of what it means.
In fact, the reversed kicking in would decrease the loading on the aircraft by decreasing it's airspeed.
This isn't a case of acceleration being able to break the mount from the frame. If it ever could, one wouldn't want it on the plane in the first place.
Doesn't mean you couldn't ruin your day with it, but it isn't an instant catastrophic failure either.
Read the accident report and follow up on Lauda Air Flight 004. Boeing specifically was forced to issue a statement that it was virtually impossible to overcome a catastrophic failure outcome from a thrust reverser deploying at cruising speed.
That counts as a pretty serious thing to avoid :-).
Ideally, yes. I submitted a recent incident where the RAT deployed on a 777 because it's so unusual (and was also not due to lack of fuel):
What I find is you start with several viable approaches, pick one and go down the path enough to figure out the downsides. At which point you need to decide to backtrack or keep going. That’s the hard part not simply coming up with a seemingly simple solution.
(Somewhat frighteningly, two of those people are doing that at Facebook right now...)
These groups are not mutually exclusive, membership can only be assigned by a domain expert and is finally irrelevant if the other is right.
Generally when one is very close to the problem, one sees the environment as immutable. Because, well you spent very many hours building that environment, for very good reasons. And your complex solution "has to" work within the constraints of that complex environment.
Whereas, the "mind of a child" that doesn't grok the environment, also doesn't have a fixed notion of it. This is anecdotal of course, but maybe half the time what I see happen is that it's easier/better to change the environment and this can only be seen with fresh eyes.
It's not the spoon that bends, and it's not you that bends around the spoon. There is no spoon.
Anyway, he hit an example of the issue, and wanted to just put in a bug ticket to one team, and didn't understand why that was not useful or necessary.
My analogy is that it's like showing up at NASA in 1965, and wanting to submit a ticket that says "Your rockets can't actually go to the moon. Fix rocket so that it can go to the moon."
Things are complicated and rarely as simple as they seem.
On the other hand, I've worked on things for hours before for someone to glance at the problem and solve it. Always a humbling experience.
It is less appreciated when people phrase things in a condescending manner, though.
When the "they" is at least another expert in the same field and not a total stranger completely ignorant of pretty much every relevant detail, and the "you'd expect" part starts at a baseline of nearly 0% for people walking in out of the street unfamiliar with the specific problem at hand, then yes, "they" are right more often than I'd "expect."
If you use anything other than non-SPA, Go, PostgreSQL then it's over engineered and doomed to fail.
Quite a few turboprops have beta range that is supported for use in-flight. The purpose is to increase the rate of decent, similar to slipping the plane. So it's not always an invalid input; it's make/model/phase of flight specific.
There are a number of YouTube videos with people who have tried it. The answer, in a modern car: pretty much nothing. It just stays in Drive. On one car, it turned on the backup camera display!
If the connecting rods had fled the engine that would indicate that someone succeeded in getting it into a gear it didn't want to be in.
Talking about an odd safety override. It's kind of a self-destruct button.
It's not a self-destruct button, it's anti-destruct limit.
As for the thrust reverser, there are many integrated systems on the aircraft. It's possible that the cockpit detected weight-on-wheels, but the flight mode hadn't yet transitioned for the engine controls.
On the other hand, a runaway engine fire or uncontained turbine failure is much much more likely to cause a crash.
So almost all jet engines are designed to have a shutdown (sometimes helped by the built-in fire extinguishers) as a worst case outcome. The quick response drill for an engine overspeed or temperature past certain limits is to shut it down immediately and pull the fire extinguisher handle.
Related, British Airways Flight 268, a B-747, when taking off from LAX had a problem with one of it's engines so they shut it off, and continued flying all the way to London, albeit to Manchester instead of Heathrow, with one less engine. https://en.wikipedia.org/wiki/British_Airways_Flight_268
But what if a thrust reverser self-activated, without being commanded? The previous safety mechanism wouldn't help because it's being bypassed.
So there is a secondary safety system that detects such situations. Something along the lines of "I think the trust reversers shouldn't be activated right now, yet they appear to be activated. The engine is clearly malfunctioning, lets shut it down"
It appears that this secondary safety system has been activated. There was probably a bug, or a sensor malfunction that triggered it.
But it is still possible for the pilots to deploy reverse thrust too soon, after touchdown but before there there is enough weight on the wheels to provide sufficient steering. I'm guessing the pilots deployed too soon, and discovered a new corner case.
It's a vent that opens to blow exhaust gases to the front instead of behind.
On this particular occasion the system is thought to have malfunctioned in some way (e.g. it might have not registered the application of reverse thrust) triggering a shutdown.
The sane choice would be to not engage reverse thrust at all (until the pilot has reset the reverse thrust throttle) or to only engage reverse thrust once the landing gear has weight on it.
Having reverse thrust depend on a sensor that could fail seems like a poor choice. What if the landing gear don't drop? Is there a situation where you would still want reverse thrust without landing gear?
Actually, maybe some ex-Soviet airliners can still do it. DC-8s being used by cargo airlines could possibly still technically do it, but don't use the ability.
> What if the landing gear don't drop?
I don't think that there is need for reverse thrust in such a scenario.
> Is there a situation where you would still want reverse thrust without landing gear?
Even if there is, there could be a manual override.
How do we slow down planes that still need to come down despite a stuck landing gear, then?
Indeed, a manual override must exist.
It's also a sensor that you can simply put on each wheel to determine if there is weight applied.
Or if the manual override is turned on.
That sounds like apple's "you are holding it wrong" when "antenagate" happened. Not something I want to hear from an aircraft company where people's lives depend on it working.
They may have to fine-tune that system, but from a safety perspective, this event had a good ending, and making its decision system more complex also carries risks, so, maybe, nothing has to change.
More apt would be "when the computer is not sure that isn't really, really dangerous".
I also think that the phrase "too X" is polysemous. Depending on how it's used, it may imply a notion of blame. But it can also just be a way of describing an incompatibility. "This clearance is too low for that truck" and "This truck is too tall for that clearance" are entirely equivalent statements, IMO. Neither implies that the truck or the bridge is wrong, just that the driver would be wrong to try and drive under it.
Even further out there, when describing a timing-based bug that isn't known to be 100% deterministic as, "If X is happens too quickly after Y, Z might happen" seems to me like it's just a much more straightforward way of saying, "If X happens within some unspecified interval after Y, then Z might happen." Nine syllables shorter, same meaning.
There's "beyond a certain speed", but still something of a mouthful.
I'm not a lawyer; couldn't tell you where the fault would split in that case, but if my hunch about the lack of a failsafe for a given instruction is correct... it's still a surprise to me. I'd expect existing avionics production procedures to catch this sort of thing.
The older I get, the more I believe your expectation is wrong. Lessons learned are rarely transferred to new people who were not present when the lesson was initially learned.
I've even worked at companies that try to compile a database of "lessons learned", but they never instruct anyone to read through the whole thing. Even if they did, when confronted with a large amount of material how much of it actually sticks?
The we move on to more procedural methods like fault-tree analysis, FMEA, etc... That's great and can help a lot, but it's still a GIGO process and new people need to learn how to do it well. There are always new people learning new things.
Aviation usually encode them on checklists. They have a much higher degree of success (probably because of culture, not medium), but failures happen some times too.
Or as my neighbor says: "I've dealt with hundreds of engine fires!" (He flies A320s.)
In a jet engine though, you have a nozzle on the back, so the input area is greater than the output area. Heating the air also causes it to take up much more volume. These put together, mean that the output velocity is much greater than the input velocity, so there is a momentum transfer from the atmosphere to the plane.
Without the T, the pipe moved as you'd expect. With the T directing the airflow in equal proportions perpendicular to the axis of the pipe, the pipe stayed still as if the fan wasn't on at all.
Here's my caveman f=ma thought experiment:
1. make it 2-d.
2. replace the fan with a person sitting on a chair on a frictionless surface.
3. instead of air it's an endless field cinder blocks ahead of him.
the person reaches out, and pulls in a cinder block. f=ma says they each move toward the other while the center of mass of the combination of them does not move.
Now, if he throws the cinderblock behind him, he moves further forward - this would be analogous to an airplane propeller. or a fan in an open pipe.
If he, um, splits the cinderblock in two and places each half directly off to his sides there is no net force exerted on him by this. This is the fan in a T-shaped pipe.
the fan+pipe grabs air from ahead, moves this mass backward and then sets it aside. it's not a jet-engine, but it is moving the air mass toward itself and must be moved equally and oppositely.
I don't think it's essential to worry about how the air/blocks rearrange themselves after this - but if the blocks surround and jostle, that's just another effect layered in super-position over this one, and if we don't agree so far then it will only make things more confusing
With your concrete block example, as I start pulling the block towards me I experience an impulse forward. But when it approaches my body I slow it down to zero speed, creating an opposite impulse. So although I might have moved forward a few inches during the motion, my momentum is zero at the end. When you scale this up to large numbers of air molecules, the result is the same.
if the demo was mainly to show that it's the jet of air expelled out the back that's providing thrust, then, fine it does that and its a valuable lesson. I guess I'm hung up on the technicality that there is actually a real movement of air mass even without that rearward jet and that has to be felt by the apparatus - I guess it's just unnoticeably small in the real world demo.
anyhow, my confidence in physics intuition has been shaken. thanks bunches.
The exiting flows out the sides neatly cancel. So what's happening from front-to-back? There is air flowing in at some velocity x cross-sectional area x air density. this momentum has to be balanced completely for the pipe to stay still - but there is no source of momentum in the other direction so the pipe will feel this force and move.
if the pipe was open at the back, there would be momentum exiting the pipe balancing the incoming momentum - or even over-balancing (as in a jet engine)
here's a video going through the math on a similar problem which is a little more complex in detail, but the same in principle: https://www.youtube.com/watch?v=hXApWf1r0Eo
I think the important thing to consider is the relative velocities of the intake and exhaust air (the latter being much larger).
here is a thermal image of a modern jet with thrust reverses on :
The force on the plane is in the opposite direction.
I am surprised to say the least.
I have always imagined avionics developers in a different way. Like having a thick rulebook to go through to add a new line to codebase etc.
From what I remember, the first time 4 USAF F22 were flying across international date line to deploy to Hawaii(?), they had software related issues. As they flew across the international date line (first time in a real flight), all computers on the jets crashed, including navigation/etc.
Luckily they were flying in close formation with a tanker, signaled with flashlights, and were able to follow the tanker back to another base safely.
I believe USAF requires a multi jet (usually tanker) to accompany small jets when they are flying across the ocean.
You mean killed 189 people, right? https://en.wikipedia.org/wiki/Lion_Air_Flight_610
The final problem that brought the aircraft down - the trim run-away - happens all the time in airliners you've flown in. When the run-away starts, the pilot is supposed to flip two switches to disable the trim system motors. In the Lion Air crash, it is indeed believed that a software bug from the misbehaving sensors started the run-away, but again, handling trim run-aways are something that pilots are supposed to train for and deal with.
737's are even safer here than many airliners, because after you disable the electric trim motors, you have manual wheels in the cockpit that you can rotate to set the trim back to what it should be. Some other airliners in common use don't have these manual trim controls - you have to disable a trim run-away in time, or it's game over.
It doesn't. A trim run-away is a very very serious incident for any pilot.
There are procedures to deal with it, and we check trim override in pre-flight checks, but it's absolutely not an everyday thing.
> 737's are even safer here than many airliners, because after you disable the electric trim motors, you have manual wheels in the cockpit that you can rotate to set the trim back to what it should be. Some other airliners in common use don't have these manual trim controls - you have to disable a trim run-away in time, or it's game over.
This is not true at all either. There are no planes with a single electric trim that you cannot override. The FAA and EASA would refuse to certify those.
Whereas a 737 has physical cables connected from wheels in the cockpit to the stabilizer jackscrew.
Both circuits are electric, but they are separate systems on separate power busses to ensure you always have control.
You'll need to cite that, since it contrary to any information I can find on the Lion Air accident e.g.:
> The chief executive officer of Lion Air, Edward Sirait, said the aircraft had a "technical issue" on Sunday night, but this had been addressed in accordance with maintenance manuals issued by the manufacturer. Engineers had declared that the aircraft was ready for takeoff on the morning of the accident
Your claim that it was "unsafe to takeoff" and had "multiple broken sensors" is pretty remarkable. So I'll definitely need to see a source backing up such remarkable claims.
> "The aircraft suffered an airspeed indicator problem for its last four flights, including the flight to Denpasar. Thinking that it would fix the problem, the engineers in Bali then replaced one of the aircraft's AoA sensors, but the problem persisted on the penultimate flight [...] [the crew] recorded a twenty-degree difference between the readings of the left AoA sensor and the right sensor."
> "On 28 November, Indonesia investigators said the Lion Air jet was not airworthy on flight before crash."
More important though is that the 737 MAX differs wildly from earlier 737s in how much it relies on the AoA data. Mechanics and pilots not experienced with the MAX were probably operating under the (false) assumption that a bad alpha vane wouldn't be the end of the world. In fact displays indicating the angle of attack and warnings about disparity between the alpha vanes is an optional feature on the 737. It's considered that unimportant.
The key differences from earlier 737s are that the MAX uses the AoA data to calculate airspeed and that the MAX may use a single AoA input to try to kill you. I believe the former was disclosed, but considered how short the differences training is may have been easily overlooked. The latter, of course, was not disclosed until the crash.
So you still haven't supported your extraordinary claim that the aircraft was:
> unsafe on takeoff.
In fact we know it was safe on takeoff.
Or rather, as airworthy as any other MAX flying around.
Not sure why you're being downvoted, as I haven't seen any evidence linked contradicting what you said.
"not airworthy" means that it was unsafe.
It goes like this:
several flights report problem
maintenance "fixes" the problem
next flight reports that another, worse problem has appeared - bad enough that regulators have now said that the plane was "not airworthy" during this flight
final flight impacts ocean at high speed
Your assertion is that since maintenance cleared the plane after the second fix, the plane must have been fine. To that, I point to the previous time maintenance cleared the plane, when it was demonstrably not fine.
“Indonesian investigators have said the Lion Air Boeing 737 jet that plunged into the sea, killing 189 people in October, was not airworthy on a flight the day before it crashed.
They further found that Lion Air must improve its safety culture and better document repair work on its planes.
The flight from Bali to Jakarta on 28 October had experienced similar technical issues to the doomed flight the next day from Jakarta to Pangkal Pinang, said Nurcahyo Utomo, head of Indonesia’s national transport safety committee (KNKT).
The pilot of the 28 October flight chose to press on to Jakarta after shutting down the plane’s anti-stall system, Utomo said.
“This is the basis of our recommendation to Lion Air. In our view, the plane was not airworthy,” he told a news conference in Jakarta.
But its investigators said that Lion Air kept putting the plane back into service despite repeatedly failing to fix a problem with the airspeed indicator in the days leading up to the fatal flight.”
So the aircraft spent several days flying with a broken sensor, sometimes without even an attempt at repair.
I've removed the multiple sensor part.
And was repaired between the two flights as I quoted above. Are you selectively ignoring the information in the very post you replied to?
Here's that information again to refresh your memory:
You and the other poster seem to be basing your whole position on time not moving forward in a linear fashion: Failure, repair, flight. In that order.
Pointing out the previous day over and over while ignoring what occurred in the interim isn't a real argument.
I didn't look into it any further, but based on that alone I would agree that this seems like a shitty feature, perhaps a loud alarm or other warning would be more appropriate than putting the plane in a dive without human intervention