A) Adding two more angle-of-attack sensors so a pilot can be reasonably sure of auto-adjust will work. Retrofitting those would be expensive, of course. B) Put the two buttons back the way they were and add a "light" indicator an angle-of-attack sensor failure. C) More pilot simulator training so pilots know what to expect in the unusual situation that the system fails.
I suspect the answer would be: "Even now we're not willing to bite the bullet and pay all the expenses we were dodging before".
Searching, it seems Southwest already did something like this (after the first crash, in fact). The problem might be that if Boeing does this on their dime then Boeing would be essentially giving every one of their "bargain" customers the features of their "luxury" customers, which I would speculate might be a vastly expensive proposition especially if it sets precedent going forward.
https://theaircurrent.com/aviation-safety/southwest-airlines...
And it's worth pointing out that 737s already have two of these sensors, but don't use them both for MCAS (?!?!).
"1.6.9.1 Probe heating The probes that are installed on the aircraft are heated electrically to remove water by vaporisation when the aeroplane is on the ground and to protect them from icing in flight."
Reference: https://www.bea.aero/docspa/2009/f-cp090601.en/pdf/f-cp09060...
Even if the pitot tube is heated (mandatory), very often airframe icing leads to a blocked static port, rendering even more indicators useless.
0.00001 * 0.99 = 0.0000099
0.99999 * 0.01 ~= 0.01
P(failure|alarm) = P(alarm|failure)*P(failure)
---------------------------
P(alarm)
= 0.99 * 0.00001
----------------
0.0000099 + 0.01
~= 0.001
For the noise sensor scenario, is the sensor failing or is the ancillary (and single point of failure) noise sensor failing? What happens when you have a false positive like that and a false negative on another sensor?
For the correlation scenario, when you have two systems that disagree, how do you determine which one is failing? Are their precisions and tolerances sufficiently close that you’ll get a warning at a useful point in time?
This system is critical to the Max 8 remaining classified to 'fly the same' as the 50+ year old 737 air frame design so it's critical to pilots being certified to fly the plane at all. Ergo it is a critical system and needs more redundancy or the Max 8 needs to just have a new type certificate and pilots certified to fly it as well.
Boeing REALLY REALLY doesn't want to do this because it would require airlines to retrain their pilots to use it in their fleets making them less attractive to airlines. The whole fiasco is a confluence of 1) Cost of retraining pilots on a new air frame 2) need from airlines for a more efficient plane 3) the old 737 design not having any more room below the wing for a bigger engine (which is pretty much the main way we get more efficiency these days).
While true I don't think that airlines and regulators will go for it, if there's even the slightest risk of an additional accident. No matter what.
And Boeing's "communcation strategy" after the incidents doesn't really help to instill confidence in the plane.
There's also the possible hardware fix to add an additional AoA sensor and change the software to limit the total deflection allowed + add a way to disable the MCAS only while keeping the electronic trim. The plane itself isn't irredeemable by a long shot though.
The engines are mounted incorrectly, so much so that Boeing believed pilots need the assistance of MCAS on take-off now.
The bug isn't with its algorithms, rather the need for MCAS to begin with. They can't "address" it. That's why I'll be very careful not to ever book a flight on a 737 Max, probably easier to simply stick to Airbus-only airlines: Jetblue, Alaska/Virgin, etc.
This overstates the issue. The engine mounting changes the flight characteristics enough that the MAX 8 needs to be flown differently in certain corners of the flight envelope. The MCAS was added to avoid having to re-train pilots or trigger a new type certification.
The engine mounting certainly does not make the plane unsafe.
I don't think this is a very...'precise' statement. what is "safe" in the context of aviation? If you had no MCAS, then this plane has a very bad propensity to stall. I hope we can both agree that's an unsafe airplane. You can't just say "don't do that [pull up too much] and then you're fine". The aircraft "wants" to pitch up too high and stall, which predicated the MCAS system itself. So to me, yeah the engine mounting (in and of itself) makes this plane quite unsafe.
Now, with a properly functioning MCAS it may be "safe", but when the MCAS is itself another point of failure, my opinion is that the aircraft is only safe on paper, while in practice it's just got too many hacks and kludges for it to be practically safe for the millions of safe flight hours that these things are expect to deliver.
Airbus aircraft are “safe” despite the fact that dual conflicting pilot input is averaged without stick feedback (see the Airfrance flight from Brazil). If electronics being used to fly the aircraft upsets you, you’re going to be in for a real shocker on any airbus.
The parent comment and entire thread is 100% correct. There is nothing inherently unstable or unsafe about the MAX 8. It has a pitch-up characteristic that's mild compared to some other commercial jets like the 757.
The only reason MCAS was put on that plane was to allow the MAX 8 to share a type rating with the rest of the 737 family, to make it so that it handles like any other 737 despite the pitch-up characteristic.
Go ask any commercial pilot, go watch any of the commercial pilots on youtube who have commented on this, go look on stackexchange. The notion that the MAX 8 is inherently unstable, or unsound, or dangerous, is a laughable myth to anyone in the industry. I get that the news cycle is financially rewarded for fearmongering, but I really expected people who frequent HN to know better and do some cursory research into the topic rather than posting comments that perpetuate bullshit.
There are several major issues with what boeing has done, such as the alleged failure to reclassify MCAS as a critical system after flight testing. But instead of discussing these legitimate issues, public debate seems to have been directed towards a bullshit myth about the airframe being inherently unstable. This has been eye-opening and dispelled my notion that HN had above-average quality of discussion on technical topics.
So, what do you have? NO TRAINING on this airplane, a bugged software system, poor aerodynamics, poor design choice, stress on elevator, etc. The ethiopian airlines plane had such force that pilots were not able to manually turn the trim control wheel. Do you know how much force that plane had to have that the jack screw couldn't be operated manually? THAT is a severe design flaw. THAT is what is being investigated. Who is investigating Boeing? Boeing is investigating Boeing. Boeing on 5/7/19 admits it knew they had a severe problem but it can still be fixed. Who certified the fix? Boeing. But now the FAA is investigating that fix which was promised by April. Again, this is a severe design flaw with still many unknowns yet to be found.
Do you have any personal experience with or references for this claim?
Personally I won't fly on one in my lifetime.
I'll leave the analysis of why to others to figure out why I fly on other airplanes.
Incidentally I have seen pilots argue that the max is inherently unsafe on this forum which is probably why people are reiterating it.
What is your area of expertise and what is your opinion?
It's perfectly rational to look at the results, regardless of "why", and decide that the risk is just too great.
In this plane which is not "fly-by-wire" the pilots are part of the safety loop and are given a certain short amount of time to respond to an emergency.
Troubling to me is the footnote in the manual which there are times where the manual wheels for the trim require 80 lbs or 100 lbs or more of force. This amount of force would potentially preclude female pilots on these planes to handle these sorts of emergencies.
This is completely false. The 737 MAX does not have relaxed static stability in the manner of a fighter jet. It just has different handling characteristics than earlier 737s at high angles of attack -- a region of the flight envelope that the pilot should never take the plane into in the first place.
Fighter jets of the kind you're referring to require continuous and precise adjustments of the flight control surfaces merely to avoid departing from controlled flight. This is absolutely not the case for the 737 MAX.
Okay, how's: you can use thrust to pitch up a 737 beyond the authority of the elevator.
Airbus aircraft are “safe” despite the fact that dual conflicting pilot input is averaged without stick feedback (see the Airfrance flight from Brazil).
There is an aural warning (DUAL INPUT) on Airbuses with conflicting input.
The precise wording would be that it is dynamically unstable, and the ball is with Boeing now to prove it's not the case. Also after all we discovered on the last weeks, Boeing better make a good case, or they won't convince anyone.
The US aviation industry is about to change. I don't know into what, but it's not in a stable situation.
Airliners are very safe. They're not in dynamic stability like jet fighters and don't need active measures at all times to stay airborne. Having sensors and systems that coordinate to keep the aircraft flying optimally to remove pilot load and increase safety margins is a good thing and has been in use for decades.
The problem here was a badly implemented system without redundancies and without enough training so that pilots were actually aware of the flight profile and MCAS. Also aircraft do not have millions of flight hours, they wouldn't reach a million even if they flew 24 hours a day for 100 years.
- it is difficult for pilots to understand how MCAS works, and how to diagnose failures. They are not programmers or engineers. And MCAS doesn't provide any debugging information about its work anyway. And pilots don't have time to analyze it.
- it adds new points of failure
- sometimes there are situations when automatic systems shut down and pilots have to control everything manually. With MCAS, they would have more things to look after. Pilots who got used to flying with autopilot are usually not comfortable with manual flight, and systems like MCAS only make things more complicated for them. An example is a recent crash of SSJ100 in Moscow where experienced pilots failed to land a plane manually after autopilot has turned off.
So I think that plane designers should be very careful with adding more automatic controls. Especially if their purpose is only to save money at cost of making place less safer.
If I remember correctly, the behavior you promote as "fine" is forbidden by the regulators, and not accidentally.
Without the active MCAS the plane would have not been certified because the behavior of controls is then not inside of the prescribed limits.
If the plane must have natural behavior, then MCAS would not allow it to be certified because it's artificial control.
At high angle of attack, the MAX-8 is more unstable than pilots were trained to expect. And the MCAS has done an absolutely miserable job of fixing this. Worst case scenario bad: it caused the loss of two airplanes that, if the MCAS had never been added to the MAX-8, would have reached their destinations just fine.
Until the it flies predictably in every flight profile (including high AOA), it's demonstrably wrong to say "the aircraft flies fine." Maybe it will eventually "fly fine" but Boeing's got quite a bit of work to do first.
The specific design of MCAS and not adding any new procedures, was to lower the training requirements. Specifically, anyone certified on the old 737 was still certified on the max.
If they had improved the interface of MCAS and changed the procedure for runaway trim, it would have required more training. However, without MCAS or another remedy for the 'decreasing stick pressure at increasing pitch' problem, the plane would not have been allowed to fly at all.
The original one is https://news.ycombinator.com/item?id=19568158
and was written at night, so there's some loopy phrasing in there I never corrected. Let me unpack some of it to fit the context here.
The pressure applied on the stick itself does not change. Rather, the function of how much deflection you get out of the plane per unit force applied to the stick changes.
Design regulations state an airframe for which this curve at any point goes negative cannot be certified as a civil transport airplane.
That means, there should be no point in the flight envelope where the sensitivity of the controls drastically changes. It should be a predictable increase in force required to get more deflection, all the way to stall.
With the MAX without MCAS, this rule is broken at high AoA when the engine nacelles start making lift.
MCAS is meant to compensate for this necessary breakage by inducing some mistrim.
The effect of mistrim in that case is to cause the controls to require more force to induce those last few degrees of deflection, using the AoA sensor as the primary indicator as to whether the system should activate, in order to bring the curve into compliance.
The problem, as hinted by the response to my post in that thread, is that an honest to god stick-pusher would be more akin to the system you'd want for that. Adding the AoA sensor as a single point of failure is insane, due to the consequences should that sensor start spewing garbage data in normal flight.
Most of those are realizations I came to after stumbling across a Royal Aeronautics Society interview of D.P. Davies, a British test pilot for the ARB, the aircraft certification authority for the U.K., which I believe I linked in the comment.
At the time I wrote it I was in the midst of a deep dive into the more arcane aspects of control systems. I have some literature tucked away somewhere that I was referencing, bit I'd need to dig rather deep in my browsing history to recover all the context.
An interesting historical note: MCAS is similar to a system McDonnell Douglas implemented in MD-11's (LSAS, Longitudinal Stability Augmentation System) for the same reasons as Boeing eventually implemented MCAS: to be able to claim that the new aircraft flew just like the old MD-10.
Makes one wonder if someone brushed the dust off something that really shouldn't have been emulated again after the merger.
Pilots are trained extensively not to trust what motion feels like, and to use the horizon and instruments. An adjustment in stick pressure is not a notable new threat, they just need to be trained for the plane's behavior.
It seems that what you claim is "not a new threat" is actually forbidden by the regulations, because it was recognized to be a threat.
I'm not quite sure how that is related to beginner flight lessons. (?)
Most commercial planrs fly 3000 hours a year. There are about 400 787-Max planes built - that's a million flight hours per year already (if they weren't grounded...)
The engine position exacerbates a problem already plaguing the 737 since the Classic. I think you're understating the problem quite a bit here.
Unless there is something about the magnitude of MCAS necessity that Boeing did not tell us yet.
Boeing's original stance of "stupid pilots should have followed runaway trim procedures" does not seem very consistent with actively removing a two-stage disable feature that already existed (and which, in hindsight, might have saved those lives). How desperate exactly were they to never ever let the pilots catch a glimpse off the real flight characteristics?
Anecdotal: I know of at least one family that booked a trip on a non-Boeing airline, at additional cost, to avoid risking being on a Max.
Imagine that after the Max is back in service, that there is a serious incident in the first few months - it doesn't have to be fatal, just a close call of some kind - how many more customers will avoid the Max at all costs?
By the time you've arrived at the airport and see the MAX at your gate, it's too late and you've already paid your fare.
1. to make certain I don't board one of these machines by mistake. I will not risk my life over this egregious comedy.
2. to vote with my dollars and punish Boeing and businesses that do business with Boeing, especially if they refuse to remove these planes from their fleet.
What Boeing committed here is leagues beyond the recent emissions scandals. It's criminal and the perpetrators should be afraid of the coming justice. This should honestly be as close to a company-ending event as one could imagine. We shouldn't treat this lightly, slap on the wrist, business as usual. This must never happen again.
i booked a boeing 787 dreamliner but ended up in a crummy 777 from a decade ago.
In a world that had actually severe consequences for corporate negligence, regulators would force Boeing to let airlines cancel/change all orders, and compensate them for the 737 Max models they already shipped to them, as they cannot be flown safely. Boeing's behavior does not indicate that they are interested in properly fixing this problem as opposed to getting it certified via corporatism / the FAA allowing them to perform a big part of their own checks.
No choice? It's a choice between risking passengers' lives and money. Be real about what the choice is.
The bugs will be addressed and they'll still fly. Airlines have no choice, there's a limited capacity in the world for airplane construction, several thousands of orders on the books for the 737 and 320 waiting to be filled. What can an airline do? They can cut back some orders but not all orders.
> I'd honestly like to see the 737 MAX taken out of service and Boeing simply ending this line.
I have an alternate history fantasy where instead of going with the MAX and then trying to kill the C-series as they did, they instead bought into the C-series. Swapping the cockpit for a Boeing cockpit design. Built the -500 stretch of the C-series, and then used the C-series to replace the 737 line in the <165 pax market. And moved ahead on the 797/NMA for which they'd have a shorter version covering the 200-270 pax market as a pure passenger mover as it's proposed.