A new and detailed theory suggests that a potential bird strike plus pilot error, coupled with faulty sensors, resulted in the ET302 crash.
I’ve been following the ET302 crash closely as we all try to better understand what happened and how to prevent it in the future. Pointing fingers will not bring back lives. After Boeing CEO’s confession last week, it won’t stop the lawsuits either. But wouldn’t you feel better stepping onto a 737 MAX if pilot error or bird strikes played a big role in both crashes?
Reuters published a fascinating piece entitled, “How flawed software, high speed, other factors doomed an Ethiopian Airlines 737 MAX.” We all know the working theory. The plane took off, the pilots retracted the flaps and slats, and a sensor began feeding incorrect information to the Boeing’s Maneuvering Characteristics Augmentation System (MCAS). The crew lost control of the aircraft and it shortly crashed.
But there may be more to the story. Experts who have reviewed the black box recordings and studied the trajectory of the aircraft have offered a different theory.
The engines remained at full take-off power as the airline’s youngest-ever but highly-experienced captain, a 29-year-old with 8,122 hours of flying time, and his 25-year-old co-pilot, with 361 hours, flew the aircraft out of its initial climb.
That would be an unusual step in a regular flight, according to the experts and five current and former pilots interviewed by Reuters, most of whom were not authorized to speak publicly. “You would never, ever have full power for the whole flight,” said Hart Langer, a veteran former senior vice president for flight operations at United Airlines.
The reason the engines continued at full take-off power was not given in the report. But it is not part of a usual procedure for pilots dealing with the loss of key information such as the sensor data, the four experts said.
Set aside the age for a moment, because I know some 20-somethings who are far more mature than people twice their age. Was ET302 continuing at full take-off power because they were fighting MCAS the entire time?
By the end, the aircraft was traveling at 500 knots (575 mph, 926 kph), far beyond the Boeing jet’s operating limits.
This contradicts Ethiopian Airlines’ statement last week, which claimed: “no excess speed was noted at the initial phases of the flight.”
Downward trim (triggered by MCAS) plus the increased speed (potential pilot error) may have been the lethal combination, not the MCAS alone.
And why did this happen? Did the plane simply malfunction?
A sudden spike in black box data was consistent with a bird or other debris hitting the plane as it was taking off, shearing away a vital airflow sensor, said the four experts and two U.S. officials briefed on the data.
What if debris or birds took out one of the sensors, leading to the chain of events that caused the crash?
With a potential bird strike triggering faulty sensor data, the MCAS system forced the nose of the aircraft downward. The black box recording has the captain yelling at his co-pilot to “pull up” but the force required was so strong he could not muster the strength to pull back on the yoke. The captain also instructed his co-pilot to trim the plane using the manual backup wheel in the center console. But that too they could not move.
Desperate, the pilots re-activated the electric trim system, which reactivated MCAS. That went specifically against Boeing instructions and was also left out of the Ethiopian Airlines report. In other words, the crew knew the MCAS was faulty, turned it off, but turned it on again out of desperation, which only hastened the crash.
CONCLUSION
This is but a theory, but a well-developed and highly-plausible one. There are even details in the story I linked to above. As the investigation unfolds, we may soon establish that it wasn’t just a lemon of an aircraft, but a bird strike and two critical cockpit errors.
> Read More: Boeing CEO Accepts Blame For 737 MAX Crashes
Ok, I’ll bite. Why is this “explosive”?
Explosive as in startling. It presents a totally different narrative than what we have been told thus far.
Cranky Flier had a good piece on this as well. He mentioned due to the high speed the trim couldn’t be manually adjusted. Which may have left to the pilots re-enabling automated trim which in turn let’s MCAS adjust trim.
I didn’t see it, but will check it out.
sounds like boeing dropped some $$ and is trying to regain their grip on the narrative… We’re edging too close to “Boeing was at fault” for their comfort…
The initial report from the Ethiopians was widely expected to be a rush job designed to exonerate the airline and the pilots. The airline is too important to the country, in terms of both prestige and income, for authorities there to place blame anywhere but on Boeing.
As usual, the facts will prove the incident was complicated and caused by multiple factors.
This is all just incredibly sad. I watch Mentour’s YouTube videos and he said something that I’ve yet to see contradicted in any accident ever- the theory of Swiss cheese in catastrophic accidents- that it is only when a series of unlikely things happen and line up perfectly to override all the safety features planes have and training pilots get, just like trying to fit a straw through several slices of Swiss cheese, it is only possible when you line up all those holes that it is possible (sorry for the poor explanation). In any event, it is more likely than not that any one thing might have been recoverable but a series of medium-sized problems compounded to make an enormous tragedy. That does not mean that Boeing shouldn’t fix their operations, testing, and roll out of MCAS and other safety features, it just means it was not solely MCAS at fault.
If a foreign object, such as bird(s) and/or debris damaged the sensor, simply means it is the fault of designer/manufacturer of aircraft.
I took notice that all of your articles regarding this issue always try to put blame in the pilot, whether subtly or blatantly. Do you have personal vendetta or something against the deceased?
Try to calm down prior publishing articles. Just like Reuters instead of Retuers.
Do you have a personal vendetta against Boeing? You are quick to immediately blame Boeing in every post I do on this topic, despite evidence that suggests it wasn’t Boeing alone. Meanwhile, I have presented an even-handed approach to this issue and am open to the possibility that Boeing shares the majority of the blame. If birds damaged the sensor, then this is not a known design flaw, but a freak accident. If the pilots increased rather than decreased speed and re-activated the MCAS, they share blame in this crash.
Bull Shit. Maybe you should be the pilot and try to deal with the control column vibration and all the other signals that the pilots are being confronted with. And add a paper manual that you have to read to try to solve the problem.
IF (emphasis intended) birdstrike is involved, it’s not “a freak accident.” There are over 700 records in the FAA database of bird strikes to Pitot, TAT, or AOA sensors, many with damage. Birds are linked to many a crash (Dornier in Nepal 2012, Hudson river 2009, and Ethiopian Airlines where Speckled Pigeons brought down a 737 and took the life of 35 people in 1988 – just to name a few). There is much the industry should do to improve mitigation of strike risk – but because people see it’s just a “freak” event, its diminished as an inconsequential aviation risk…….
Birds hitting the sensor should not bring down the plane. Its a poor design. They could have used both sensors as an input (in fact should have been 3). Furthermore, the software shouldn’t have been as aggressive even if it was good data that it was getting. The erroneous angle of attack was so high, that even if it was correct, MCAS wasn’t going to be able to save the plane from stalling anyway. Whats worse, instead of designing a good body plane, they used software to adjust for its hardware problems. If my car keeps pulling to the left, I want it physically fixed. I don’t want a secondary thing/software that adjusts it back.
A single sensor that can cause huge changes to how a plane flies, enough to cause it to crash is a design flaw. Relying on the best possible outcomes to occur when planning is the worst mistake the designers can make. Now with the background that the design was rushed because Boeing was caught napping adds more gravitas to the argument that corners were cut.
THIS. It goes against everything in aviation design. Which, I might add, we owe a lot of gratitude to Joe Sutter of Boeing for insisting upon redundancy. Even a modern passenger car can handle a sensor failure without crashing the car.
Even a modern, FULLY AUTOMATED car can handle this type of failure gracefully — I know from first-hand experience. The gas pedal sensor in my car started putting out erroneous data. Rather than go full-throttle and run me off the road, the car immediately set all automation systems on the car to INOPERATIVE and refused to even attempt to turn them on again. Even basic things like the brake hold feature were disabled.
Airbus handles this by having 3 of everything. If 1 sensor or system disagrees and 2 agree, that one sensor/system is flagged as bad and the system resumes normally. If all 3 disagree, you’re having a bad day, but it won’t crash the plane.
Fundamentally, the fact that MCAS so dramatically affects the aircraft based on the readings of one sensor is the fatal flaw in the system. A bird strike should not have lead to the situation they were in.
Now, they appear to have made some mistakes in recovering the situation, but I would ask, were they even in a recoverable situation?
Sounds like a “theory” from a Boeing apologist which will blow up spectacularly in Boeing’s face. How fickle is the plane If a bird strike can bring down the max?
Reaching… I’ll wait for the full unadulterated report before passing any judgment.
Hi Marissa,
You can wait forever dear. There’s no way an unadulterated report ever made. Too much at stake. Credibility of Boeing, FAA, and subsequently Government of USA. The stake holders will fight all out to shift the blame.
For example, influencing people’s opinion from a media outlet such blog.
@James, honeybunny: guess you don’t understand that was a figure of speech. The fallout for Boeing and the FAA will be massive nevertheless.
I can’t believe it, but I actually agree with @Debit on something! What he said above it totally correct. Proof that even a broken clock is right twice a day! 🙂
Boeing’s rush design of this model caused them to make bad choices – and to ladle on the plastic surgery – and these bad choices contributed mightily to both crashes. Yes there may have been other factors. But when you have an aircraft that behaves unexpectedly because of the loss of a single sensor, you have a big problem and a lousy design. I can’t believe that this is the same company that designed such aviation greats as the 707 and the 747.
The stopped clock analogy holds for a consistent message that no one agrees with all the time but everyone agrees with over a few limited instances. My consistent message has been white Republican males are scum. That message is particularly relevant with the chimpanzee in the white House and the obsequiousness ( I knew that word, promise 😉 that white Republican males defer to that chimpanzee, even at the expense of the country, the law or basic decency.
Thank you for agreeing with me.
Personal vendetta, none. I do read various sources news and analysis tough. I only stated the facts. If you have the slightest idea that I blame Boeing, because the facts put Boeing in that position. As for the blame, you unconsciously thought so simply because you disagree strongly with the facts, or have different agenda against the facts.
How come you called yourself giving an even handed approach while you set anonymous pilot who (admitting it him/herself) never flown a Boeing (specially a 737) to write an elaborate articles to tone down the facts of grounding 737 Max8 around the world? You even going so far as suggesting a political move behind PRC’s as the first one done it?
All these time and facts, the best you can come up is “open to the possibility that Boeing shares the majority of the blame.”? You clearly steering the opinion of the readers to be in favour of Boeing.
Anyway, if a sensor can be damaged by stray object means a design flaw in the sensor and/or its placement. The damaged sensor causing a catastrophe, means flaw in system design.
You want to blame the pilot? Well… They were trained on ipad as per Boeing requirement. That’s a fact. Everything leads to Boeing.
it is well known from the beginning the aircraft was too fast and altitude too low, as it can be seen in the initial Flightradar 24 data. The aircraft was so fast it probably will disintegrate sooner or later at this phase of flight. however, most media people does not understand any of these. They lock on a narrative that is easy to understand and potentially explosive (50-year old design, profit over people, government corruption, Boeing incompetence, etc.) and runs with it. and the rest follows. In reality, the truth is always way more complicated.
This article is crap… Playing the old card with pilot error. This is just cheap speculation as the pilots literally had no way out of this, and btw, the not only the AOA sensors were feeding faulty data but also the airspeed…
Is Boeing the source of the theory?
lol did Boeing feed you this crap . it doesnt matter if it was a flying dragon that hit the sensor . The Boeing System is a joke . Their air worthiness directive is a joke . It never took in to account the very condition that the Lion Air and Ethiopian Air flights faced . but above all people like you are a joke . Your expertise is flying around in a plane as a passenger . Shame on you . your theory is not explosive . its laughable .
Time will tell…
The reason for full power was they had just taken off, they were low and wanted to climb. You need power to climb.
If they were able to pop the nose up a lot of power would be needed in a hurry to stop it from stalling. The 737 Max pos lemon should have been retired long ago. It’s just lipstick on an old 60s pig now.
Nader is right. Go get ’em.
Google “Ralph Nader Calls For Recall Of Boeing 737 Max Jets After His Grandniece Was Killed” on NPR.
Google “Ralph Nader on Boeing 737 Max: “Those planes should never fly again”
Only if they corrected the aerodynamics so MCAS isn’t needed (like every other airliner) and it’s recertified by someone other than Boeing and the FAA should it fly again.
Another critical software error was found regarding the flaps. Boeing only checks for errors after crashes? What else is wrong with it?
Southwest had a deal with Boeing that no training would be required or it would cost Boeing $1 million per plane. That explains why the bad aerodynamics and MCAS was kept a secret.
Google “cnn boeing-737-max-production-cut/”
Most terrible accidents are caused by a series of unusual events. Think of the loss of the TITANIC, which would not have cost 1500 people their lives IF the sea hadn’t been so calm that no tell-tale waves were breaking around the iceberg… IF the lookouts in the crows nest had been supplied with the binoculars that were locked in a closet no one onboard had a key to… IF the steel shortage in Britain had not resulted in sub-standard steel being used in TITANIC’s hull… IF the White Star Line had followed the ship’s builders’ recommendation and installed twice as many lifeboats… IF the nearby CALIFORNIAN had not turned-off it’s wireless for the night… IF, IF, IF…
When arguments failed, try to turn it into a joke. Hello there…
This theory is so unlikely/far-fetched that NONE of the ( always looking for an explosive angle) mainstream media has picked it up. Not a single one.
In the context of the recent admission by Boeing that there are indeed issues with the MAX, has the creepy CEO now apologised for lobbying Trump not to ground it?
What about my source, Reuters?
Ok, I missed that. But only one.
Thank you for admitting you only sourced articles/news with content in favour of Boeing.
Hehehe….
Take a look at who owns Reuters.
Nowadays one has to compare notes from many sources as the regular sources (CNN, BBC, Fox, Reuters, most european news channels to mention a few have become selective and biased). While I still read them, I compare with Asian, Russian and Indian sources, even Al Jazeera.
Each on his own is biased, reading them together sometimes shows something of a real story.
This angle is being picked and will certainly be a part of the final report. Although serious design issues are the crux of these disasters (no redudancy on such a critical system??) the pilots certainly contributed to the cascade of events by maintaining such a high speed thus limiting their options vis a vis critical control surfaces. None of this exonerates Boeing. It simply lumps these crahes with the vast majority of the rest in aviation history as not being simple, single cause events.
Seems a lot of people have already made up their minds,
Indeed.
Yup. Some based on facts, some… Well… Persistently defending Boeing it would be stupid if were not compensated.
The article indicates: By the end, the aircraft was traveling at 500 knots, far beyond the jet’s operating limits.’
You indicate: ‘This contradicts Ethiopian Airlines’ statement, which claimed: “no excess speed was noted at the initial phases of the flight.”’
There is no contradiction – the Ethiopians are describing the “initial phases of the flight”, the article is describing the end of the 5min flight. The airspeed went from normal in the beginning, to way too fast in the end. Both are accurate
The First Officer tried to trim the aircraft manually, and replied that the trim was not working. Be interesting to know why he could not trim the aircraft manually. Perhaps the young first officer didn’t realize the physical force reqd? At that time, the aircraft was near its max operating velocity – perhaps the aerodynamic forces made the already difficult task of manual trimming impossible? Perhaps the manual trim system had some other defect?
Either way, the crew appears to have turned the trim cutout switches back on, allowing the crew to electrically trim the nose back up. Interestingly, the crew only very briefly trimmed the nose back up – only about 1 or 2 seconds. Not sure why the crew’s trim up commands were so brief – the horz stabilizer hardly moved. Would think they would have pressed the electric trim up switch – and held the sw pressed trim up – for something like 15 or 30 seconds, not just one or two seconds. . . . Then, once done using the electric trim, why didn’t the crew flip the trim cutout sws back off, again disconnecting the MCAS system before it could counter with trim down?
Still more to learn here . . . .
When I was in college, in order for me to write a proper and balanced paper, I had to search for various sources and references thoroughly. It appears that the author of this article failed to do that. Over the past few weeks, I read articles written by Leeham News which I feel is the most authoritative regarding technical aviation matters and I also went through nearly every article from a Seattle Times, NY Times, and WSJ related to the crash and Boeing’s bringing forth the MAX and nearly all of these articles squarely point to Boeing as being at fault with this crash. Even Crankyflier who I respect regarding aviation matters presented a brief but detail analysis (not as thorough as Leeham News) and even he had a change in mind with his most recent article pointing at Boeing. The pilot may have made errors but no way should they have been placed in that situation initially. Even if it was a bird strike, why would Boeing not build redundancy so that the plane would not be subjected to the effect of MCAS resulting in a crash? Absolutely ridiculous to point finger at the pilot.
Boeing installed a clearly defective MCAS system, and are certainly responsible for the Lion Air crash. Responsibility for the Ethiopian crash is less clear. Certainly the Ethiopian pilots had to deal with a defective MCAS system. Did the pilots deal with the system correctly? It’s not clear if they did. Did the aircraft have some other defect in addition to the MCAS system? We don’t yet know.
Hence, it is too early to declare the pilots were not to blame – we don’t yet know.
I should say, too early to declare the pilots don’t share some of the blame. I agree w/ Al – most of the fault rests with Boeing. Whether All the fault rests with Boeing, we don’t yet know.
Agree 100% It’s actually interesting — and a bit sad — that so many, media and public alike, want to jam these disasters into a preconceved narrative rather than evaluate them on a factual level. The rush to develop a “bigger” inevitable results in rejected some facts that don’t fit in favor of others that do.
If the facts of this case establish that the pilots — who were clearly placed in a very difficult position by Boeing design choices == made poor decisions, so be it. All that emerges is a clearer picture which indictes clearer specific areas for improvement and ultimately improved passenger safety, And that should be the goal. Not some grander agenda.
Regardless it seems crazy to me that a system that has the ability to nose down the plane only relies on one sensor input. That is literally the reason there is redundancy built into all critical airplane systems.
I’m not sure as to why Boeing implemented the system that way. But it’s telling that they are changing it in the update.
Even if chance and pilot error played their part here, it certainly seems as if this systems design contributed to rather than helped the situation.
Truly scary that my cell phone using accelerometers knows if it is pointed towards the ground but a complex, modern commercial airliner can lose that ability if just one sensor relays bad information. Component failure due to bird strike, poor maintenance, or other cause is emminently forseeable. Thus the need to employ redundant systems.
Boeings choices here are truly shocking…
Thing is, as a designer, for something so important, you have just one system and no backup for it – why would the pilots be blamed. Whether full speed or not, was there a way out for these pilots anyway? What kind of engineering is that, they don’t have a backup system? What kind of rush is that. If something is 90% the fault of the manufacturer and 5% the fault of the pilots – why are the pilots to blame? It is nothing new also that someone could panic when there is an imminent danger ahead – try thinking clear when the plane you are in is falling down hundreds of miles an hour.
If you look at the preliminary investigation report,
report is here:
http://www.ecaa.gov.et/documents/20435/0/Preliminary+Report+B737-800MAX+%2C%28ET-AVJ%29.pdf/4c65422d-5e4f-4689-9c58-d7af1ee17f3e
Pg 26 of the Report indicates the aircraft was level or climbing for 5min & 30sec of the 5:45 flight. Only for the last 15 seconds or so was the plane falling down hundreds of miles an hour.
Any mistakes the pilots might have made were made while the aircraft was level or climbing; a time when the pilots were (hopefully) level headed, not panicking.
Clearly the automated MCAS system was faulty (I believe even Boeing concedes that). But automation systems on aircraft do fail. When they do fail, pilots are trained to disconnect those systems and continue to fly the aircraft. These pilots did disconnect the faulty system, but were unable to continue flying the aircraft. Why they were unable to continue flying is an important issue that needs to be resolved.
theory
What is the point in guessing – wait for the final report. Oh, clickbait
Because minds are made as the narrative unfolds.
Dear author, how much were u paid to write this article?
You can’t attack the argument, so you attack me?
Disgusting.
Matthew, let’s just be tactful and say you’re no Woodward and Bernstein.
You are beyond ignorant …..you are arrogant to boot.
I agree with you Matthew. While Boeing has a fair bit of blame in the design contribution to the accident, Pilot error is certainly a significant factor here. First, NEVER, EVER re-engage a faulty trim system once it was disconnected for what could only have been interpreted as a runaway trim condition. Secondly, If the speed builds up out of control, pull the throttles back. There is some basic airmanship that was missing here. There is no reason that control of this aircraft could not have been re-established with a crew of average capability.
I find it criminal that BIG media is out to crucify a BIG corporation just because they are an easy target. Boeing is not in a position to defend themselves in a way that doesn’t make them look to be insensitive to the families and people lost in these tragedies.
I see you’re playing reasonable doubt card…. Oh well… Its always easier to blame dead man instead of BIG corporation. Dead man can not compensate you in anyways, but there’s always a chance in BIG corporations….
Why can’t it be both? Why must it be Boeing OR the pilots not up to the task? This stringe averse reaction to any critique of the pilots performance is interesting to say the least.
Difficult to give a short opinion. But:
1. According to the report on FDR, there was an airspeed discrepancy. The F/O and alternate speed were in agreement. This should have been noticed on crosscheck at 100 knots or even below. (Captain airspeed indication fault).
2. MCAS only became effective AFTER flap retraction.
3. Either pilot control wheel thumb switches can and will counter act MCAS input by holding the thumb switches in the nose up position.
4. The next step is a memory item which doesn’t call for pulling out a checklist.
5. During climb out with trim calling for nose down, the two electrical disconnect switches should be opened. (They disconnected the switches, BUT later reactivated them. A NO NO.
5. The Captain called for the LEFT auto pilot on, which is tied to the left (BAD) airspeed.
That is why the auto pilot disconnected automatically.
6. When the discrepancy was recorded by the left computer, it also disconnected the auto throttles. (NEITHER PILOT PULLED THE POWER BACK FROM TAKEOFF POWER at 94% N1.
7. Since power was not decreased from T/O airspeed continued to climb to the point manual control of the trim wheel was highly unlikely.
8. Had either pilot been proficient in understanding the automatic disconnects, and non normals we all train for,they could have easily returned to land.
9. They should have recognized the problem right after flap retraction. (JUST PUT FLAPS BACK DOWN), Or use thumb switches.
Very important to reduce the power to prevent excess airspeed to be able to use the manual wheel by extending the handle.
10. Had either pilot turned on the RIGHT autopilot, MCAS would have been automatically disabled.
Chris: The First Officer tried to trim the aircraft manually, and replied that the trim was not working.
Why the FO could not trim manually seems an important question.
You indicate the hi airspeed rendered control of the manual trim wheel highly unlikely; I’m guessing the theory being the aerodynamic forces (from the hi speed) on the leading edge of the horz stabilizer made manually trimming (pulling down) the leading edge too difficult?
I’ve no experience in a 737 (other than as a passenger), but in small (slow) aircraft, trimming force doesn’t seem to change much between climb out & cruise speed. That of course might change given the much larger horz stabilizer and the much higher speed the Ethiopian 737 experienced. Any knowledge or experience on your part on whether a pilot can manually trim the horz stabilizer on a 737 at or near Vmo (max velocity)?
It’s one thing to disconnect the faulty system, which they did. The problem becomes what to do then.
easy to say, fly the plane, but that seems to have not been easy.
Reduce thrust and slow down is a problem, as it will likely push the nose lower, given the design of the MAX – which you don’t want.
Lots of noise about what they did wrong, but no-one seems to have clearly articulated how they could recover.
When the MCAS system went haywire and began trimming the nose down, the pilots appear to have correctly used the Stabilizer Cutout sws to disconnect the MCAS system. (Chris suggests they could have re-extended the flaps, which would also have disconnected MCAS. Appears this also would have worked, but re-extending the flaps after take off seems a bit counter intuitive.)
(Chris also suggests the pilots could have turned on the RIGHT autopilot, which also would have disconnected the MCAS system. This too seems like it would have worked, but with the left autopilot having just disconnected, I can understand why the pilots doubted the right autopilot would have any better outcome.) The pilots appear to have just followed the procedure recommended by Boeing, and flipped the Cutout switches.
With MCAS disconnected, seems the pilots should have retarded the throttles (if your car goes haywire, very difficult to diagnose the problem when you’ve got the throttle to the floor, and the car is passing 100mph).
They should also have trimmed the aircraft back up. With the flaps re-extended, they could have used their elect trim up sws. With the Cutout sws flipped, appears the elect trim sws were also disconnected. Hence, the pilots appear to have tried to manually trim the aircraft back up, but couldn’t. Why they couldn’t seems an important question – one theory is that the very hi speed made manually trimming the aircraft impossible. Or perhaps there was some other defect?
When the manual trim was not available, appears the pilots returned the stabilizer trim sws to Normal, restoring their electrical control of the trim, but also reconnecting the MCAS system.
They then only very briefly (for 1-2 seconds) used the elect trim up sw on the yoke. Holding the trim up sw for 15 or 30 secs seems like it would have greatly assisted the pilots in recovering. Holding the sw for only 1-2 seconds hardly assisted them at all . . .
Then appears the pilots made the fatal mistake, and left the MCAS system reconnected.
About 5 secs after their momentary trim up command, MCAS reactivated and trimmed the aircraft into its fatal dive.
The following article tends to support the hypothesis in the Reuters article though the author confuses AoA vanes with pitot tubes in part of the article (AoA vanes aren’t hollow and can’t be blocked by ice or other solid matter).
https://www.bloomberg.com/amp/news/articles/2019-04-11/sensors-linked-to-737-crashes-vulnerable-to-failure-data-show
Truly scary that my cell phone using accelerometers knows if it is pointed towards the ground but a complex, modern commercial airliner can lose that ability if just one sensor relays bad information. Component failure due to bird strike, poor maintenance, or other cause is emminently forseeable. Thus the need to employ redundant systems.
Boeings choices here are truly shocking…
Amen
To claim that a possibility is a fact it would be more responsible to include how likely the possibility is. How likely each factor defined, there are many, contributed might help to find answer to the question…..one thing for sure is less regulation did not help the victims arrive to their destination
Look at the prelim FDR data. Stick shaker comes on, altitude diverges and airspeed diverges all before flaps are retracted and MCAS was active. At the exact same time as this you have a pitch attitude that reaches 20 degrees than sharply falls matching the control input from the pilots. As flaps are retracted the plane is already close to maximum low altitude speed of 150 kts. As soon as the flaps are retracted A/P is kicked off and MCAS comes in. Around 45 seconds later we have the last of a series of MCAS commands to pitch down where the command is given, but pitch trim does not change. I believe it is at this point someone grabbed hold of the trim wheel preventing it from moving, but by this time the aircraft is already at it’s maximum airspeed and only getting faster. The fact that the airspeed and altitude indications began their divergence at the exact moment the AOA began diverging points to more than just MCAS. I think given that fact alone we’re looking at some sort of physical damage to the aircraft, especially considering it’s all coming from the same side. The AOA and pitots are within a forearms length of each other. It wouldn’t take anything larger than a seagull or a large owl to take all of them out. There is even a point where the left altitude reads lower than ground level. If a pitot were bent so that the airflow was passing over the entrance but not into it, it would create a suction, which also would explain a lower reading, even one that’s negative.
then* 250kts*
Not to defend Boeing in any way, their design of MCAS and complete lack of information on this new system is totally unforgivable, but they did publish an urgent emergency bulletin on MCAS behavior after the Indonesian accident. It feels sad to put some blame on the pilots as well but unfortunately very big mistakes were made. Pretty much immediately after the take off the Ethiopian pilots got all of the caution messages; unreliable air speed, unreliable altitude on the failed AOA side and continuous stick shaker etc, all listed on the Boeing’s bulletin. If they studied this bulletin carefully, at this point it should have been very clear to the flight crew what situation they are dealing with. Now if you have unreliable airspeed warning you must follow the unreliable airspeed procedure which you have to remember by heart. It is one the failures in the emergency manual (QRH) that you have to memorize. First things you do is disengage autopilot and auto throttle if engaged, select flight directors off, then you pitch for 10° nose up and set thrust (N1) to 80%. This will give you safe airspeed and a shallow climb out. Once you have everything under control emergency checklist shall be read and complied with. Emergency manual also lists pitch and power settings to fly without reliable airspeed source (airspeed from standby instruments (ISFD) should have been correct as it has it’s independent airspeed source). Then as bulletin says, if you retract the flaps MCAS will engage, so NO flap retraction. All take offs are made with flaps selected. Ethiopian crew did retract flaps causing activation of the MCAS. With take off flaps selected, unreliable airspeed procedure complied with, you have completely flyable aircraft that is under control. Then you return back for landing or divert to nearest suitable airport if weather at the take off airport doesn’t permit landing.