Hacker News new | past | comments | ask | show | jobs | submit login
Where Boeing’s 737 Max Planes Go When They’re Grounded (bloomberg.com)
134 points by pseudolus 84 days ago | hide | past | web | favorite | 98 comments

A fix is being flight-tested.[1] The authority of the auto trim adjustment system is being limited. All planes that don't have it already will get the "AoA Disagree" detection, and a disagree will lock out automatic trim adjustment. Pilots will get more training on handling the aircraft with that system inoperative.

How bad is the handling with that system inoperative? The need for this came from adding bigger engines to a small airframe, which required putting them too far forward so they'd clear the ground.

[1] https://www.wsj.com/articles/boeing-plans-fixes-to-make-737-...

> How bad is the handling with that system inoperative? The need for this came from adding bigger engines to a small airframe, which required putting them too far forward so they'd clear the ground.

My limited, layman understanding from the assorted coverage and posts by people who seem to understand this thing is that almost all the time the bigger, more forward engines do not cause a problem and MCAS doesn't have to do anything. It is just that on those very rare occasions when you get into a situation where it does make difference, MCAS helps you recover safely.

So, if the system can detect a problem with the AoA data and lock out MCAS, and tell the pilots that MCAS is disabled (and the pilots understand that this means some protection is gone), they should be able to finish the flight safely with at most a need to avoid pushing any limits that might get it into a situation where they do need MCAS.

Only those very very rare situations where the plane both gets into a situation where it needs MCAS and it simultaneously has an AoA sensor problem would be a problem.

I think this is why they can get away without triple redundancy and majority voting on the AoA sensors for MCAS. Losing MCAS is not an "Oh my god we are going to die!" situation. It's a "fly more conservatively for the rest of the flight" situation.

I don’t know specifically about the MAX, but based on the thrust vector if a pilot in a stall put in more power before nosing down the plane would pitch up and you’d be put into an even deeper stall. The MCAS is there to nose down automatically for you if a stall is detected.

My understanding is that in the 737-8MAX, pushing the control column fully forwards isn't necessarily enough to recover from stall (or potentially even a near-stall AOA).

MCAS was designed to trim the stabiliser down in a high AOA situation, to give the pilots a bit of extra downwards control authority and help them recover from a stall.

To compensate for flying with MCAS inoperative, pilots will need to manually trim down when recovering from a stall. I assume they will just train the pilots to always trim forwards when recovering.

I hope this results in both Boeing and Airbus rethinking their approach to balancing computer and pilot control.

The scales are too often tipped in favor of coddling pilots (handling too much for them), with the trade-off being that emergency checklists multiply and become longer - to handle situations where plane systems and sensors fail.

While I heard many stories of pilots who could get out of dangerous situations due to "extra training/knowledge acquired in their spare time", the big question is how many pilots did not get into dangerous situations because of the computer taking care for them. My gut feeling says we are better off with computers...

Just because I can handle a car, prefer manual shifting and electronic helpers rather irritate than help me, I would never dare to demand we shift control back to the drivers. In effect, I am /safer/ when oncoming traffic manages to stay in it's lane...

> how many pilots did not get into dangerous situations because of the computer taking care for them

Agreed, that kind of computer control is helpful and good. The problem comes when either (a) those secondary/contingent systems aren’t built to the same standards (redundancy, fault tolerance, etc.) as the primary systems; or (b) their reasons for existence are to artificially alter the flight characteristics of the plane, for no other reason than to make the plane fly “like another plane” or in a more familiar way — so the perceived aviation experience is effectively an abstraction, and a leaky one at that.

I’m not against abstracting away some of the flight characteristics, given that in doing so, proper due diligence is done to make the resulting system reliable and fault-tolerant.

The major problem I see here, is that no amount of software will make flying a shoebox a good idea. The primary systems were at fault too here.

> Pilots will get more training on handling the aircraft with that system inoperative

Sounds like the expense they were trying to avoid if the plane were reclassified. Is the plane now going to fall under a reclassification?

With two fatal crashes partly due to pilot error in the face of undpcumented features I think the classification is largely moot: every pilot is likely to refuse flying without extra training.

> All planes that don't have it already will get the "AoA Disagree" detection

It makes me wonder... if all planes had 2 Angle of Attack sensors, why was the disagree indication an extra option?

Was it almost pure price discrimination on the part of Boeing? A $4 light/buzzer for equipment, wiring and firmware already present, but only wired in for clients willing to pay an extra $10k per plane for the safe version?

Was it almost pure price discrimination on the part of Boeing?


A $4 light/buzzer for equipment, wiring and firmware already present, but only wired in for clients willing to pay an extra $10k per plane for the safe version?

Nope, EICAS literally a warning message which is just text on the LCD.

> Was it almost pure price discrimination on the part of Boeing?

In at least one other case I vaguely recall, monitoring two sensors required bus bandwidth that was unavailable without a physical refit of cabling or electronics, so that could well have been the issue with AOA sensors and MCAS. I have no knowledge either way.

I imagine after the design of the 737 Max was completed, some customers requested that feature, and Boeing said "For just $100k extra, we'll design and build it for you". They then set an engineer to build and test the feature, probably costing nearly $100k. That airline then got the feature they'd paid extra for, and other airlines/groups of airlines didn't get it because it isn't officially part of the design.

Any proof for this interesting theory?

I imagine not.

That is indeed exactly what the nytimes article suggested

I guess this article? https://www.nytimes.com/2019/03/21/business/boeing-safety-fe...

But my question was more like this: If it cost, say, $10k to buy the option, how much did it cost Boeing to actually enable it? If it was $8k, ok, but if it was $8 or $80, then they're more culpable.

I worked for a company making small electronic devices with LCD screens. There were two models of the device, a cheap one with a smaller screen and an expensive one with a bigger screen.

After a careful look it turned out it was cheaper for the company to put a bigger screen in both models, but as a plastic cover on top to make it look small.

It didn't compromise the safety though.

I remember CD burners were like this. You could turn a 2x burner into a 4x with a firmware upgrade.

Overclocking brings up similar circumstances: The market may have been 50/50 for the low-speed and the high-speed versions of a chip, but the yield may have been 70, 80 or even 100% for the high-speed, but the manufacturers still wanted to create a low-end and a high-end market.

Overclocking brings up another example - a lot of AMD CPUs have extra cores that can be unlocked. They're manufactured as the higher-end chips, then just have cores disabled. Sometimes due to defects, but often they work just fine.

I recall some video card where you could change a resistor and fool the card into realizing all of the extra capacity it was built with and had available.

Much of that is related to binning rather than price gouging - https://www.tomshardware.com/reviews/glossary-binning-defini...

If that was 100% true, then Intel wouldn’t multiplier lock its chips.

TIL: binning

The Sennheiser HD 595 headphones from several years ago were exactly the same as the HD 555's except for being $150 more expensive and missing a piece of adhesive backed foam stuck to the inside of the ear cups behind the drivers that were put there to give the cheaper pair a worse frequency response.

Back in the late 80s, we ordered a $100.000 upgrade for a minicomputer system. The technician literally used a pair of pliers to cut a wire on the board, and the upgrade was complete.

There are 5 Southwest MAX8s parked at Chicago Midway (MDW). I took this photo of them just the other day:


Southwest is in the process of moving all of its MAX8s to the Victorville, the airplane graveyard in the desert. I doubt they'll scrap them but it smacks of long-term parking.

> I doubt they'll scrap them but it smacks of long-term parking.

Oh please, they're not being scrapped. But a working airport is not a proper place to store large jets.

Oh please, they're not being scrapped.

Which is what I said.

But a working airport is not a proper place to store large jets.

Short-term it's fine. If the expectation is that the MAX will be allowed to fly in a few weeks it makes sense to keep the airplanes at strategically chosen airports. This'll make it easier to bring them back into service. If the assumption is that the MAX will be grounded for a long period of time it makes more sense to stash them at a graveyard like Victorville.

The weird thing is that the GP quoted your comment that the planes won’t be scraped, and then he tried to one-up you... by agreeing that the planes won’t be scrapped.

Utterly bizarre.

Probably costs them a pretty penny every day they are there.

The 5 at Midway are parked at a Southwest maintenance hangar, so it’s probably a bit cheaper than public airport space.

Are the MAX8s grounded from flying altogether, or just from carrying passengers?

In the United States ferry flights are allowed (and you can watch as Southwest moves their planes to the desert). In other countries it'll vary. There are definitely some MAX8s stranded in out of the way places in Europe.

The article answers this.

They have something like 34 total, just under 5% of their fleet. So, notable, but not a huge problem.

Given the thresholds and margins at which airlines operate, I'm quite sure that it's a huge problem.

A counterexample is Air Canada abandoning their financial guidance for the year as a result of the 737 Max issues: https://www.bloomberg.com/news/articles/2019-03-15/air-canad...

That's a different problem. They are a bigger percentage of Air Canada's fleet. Also Air Canada's fleet is widely varied. With other aircraft that are notably larger or smaller. And crews can only work aircraft they are qualified on. This wiped out basically a whole subset of their operation.

Southwest can more easily substitute any of their other aircraft, lease more non-max models, defer non-essential maintenance activities, and use any other crew to fill the holes. They fly all 737s.

It's a much bigger deal for Westjet: They don't have much transoceanic capacity that the 737MAX was used for.

I don't think their 737 non-MAX fleet can even make the trip from Halifax to Paris like the MAX fleet can.

And transoceanic birds need other safety features not required for standard continental fleets, like life jackets.

Sure, but having to do all those things on very short notice is probably a huge problem for a couple of folks at Southwest.

I met a maintenance supervisors/leader type for United Airlines last weekend. He said that the grounding of the 737 Max was annoying, but manageable. Their are all sorts of tricks companies can use to keep up with hiccups in aircraft availability. For example, not all of an airlines planes are flying at once. An plane sidelined for maintenance can be serviced more quickly, and returned to operating status faster than it was initially scheduled to be back in the air.

I'm worried that quicker maintenance will in the end lead to less secure air travel.

Even if you're not interested in the story itself, this is worth a quick look just to see the way they present the information. It's very nicely done.

(Scroll down to see the graphics.)

Totally. Reminded me of that addictive flying game where you have to land airplanes when the first iPhone just came out.

Successful small studio, bought by EA, and never heard from again.

They were merged into Firemonkeys Studio, and are still a going concern (their last three games - Real Racing 3, The Sims Freeplay, and Need for Speed: No Limits - are still getting updates).


Not quite though there future doesn‘t seem that bright. https://en.m.wikipedia.org/wiki/Firemonkeys_Studios

X-Plane Carrier was also a lot of fun, and by all accounts very realistic.

The current version of that experience is (I think) available as an add-on to X-Plane 10 mobile: https://www.x-plane.com/mobile/

Yes, that’s the one!

That is a beautiful data visualization. I'd love to see more articles with that level of quality

6 Southwest planes have gone to storage at VCV: https://flightaware.com/live/airport/KVCV/arrivals

KVCV, to be pedantic. Flightplans are filed with ICAO codes.

Without any passengers or baggage the IATA code VCV would not have been used at any point of their flights.

Total is up to 10 now, and 3 more on the way (1pm PT Sun).

If you want to see the one still flying: https://flightaware.com/live/aircrafttype/B38M

That'll be a Boeing test flight. Their Max's will likely be up and down all the time.

Well, the one shown up near Seattle is a Boeing test flight.

I have my doubts about the other 13 it currentlu shows around the world, especially the ones whose flight plan calls for landing far from where they start, like the Norweigian Air flight from Dublin, Ireland to New York, or the Globus one on the way from Russia to Hong Kong.

What's going on here? Airlines still working on getting their grounded planes to where they want them to sit things out?

Looks like by far the most of them are Southwest, flying from a variety of airports (Baltimore, Los Angeles, Oakland, San Jose, Chicago), which is what one would expect for a "move planes to storage" operation, but the destinations are also all over the map, too (Victorville, Burbank, Indianapolis, Houston, Dallas, St. Louis, Denver). Stashing a few at each of their smaller airports?

It's a data problem on flightaware. Check swa2738 on flightaware [0] and then check on flightradar24 [1]. It's being flown by n8648a which is not a max.

[0] https://flightaware.com/live/flight/SWA2738/history/20190324...

[1] https://www.flightradar24.com/data/flights/wn2738

I highly recommend everyone suggestion engineering solutions to watch this video from an actual pilot performing a runaway stabilizer procedure in a 737 simulator.


What happened is a series of failures; this video frames it perfectly.

I wonder if the pilots had the right to refuse to fly them after the official announcement was made. Regardless of the criticality of the flaw, there is one flaw causing the planes to crash and even one flight is 1 more than you should fly with them.

Every pilot has an absolute right, and responsibility, to refuse any aircraft they deem "not safe for flight in all weather and conditions". Period.

Of course, you may have a long and uncomfortable conversation with your chief pilot regarding the nature and quality of your judgement, but every single pilot is supposed to make an informed and independent evaluation of each aircraft before every flight.

The 737 Max saga reminds me of the hazards of flying on third world carriers.

The only difference between the North American carriers and the overseas ones is that they sprung for the option that tells them that the MCAS is about to point the nose at the ground hard by displaying a warning in relatively small writing on a screen somewhere near the middle.

Apart from that, which may not have made much difference there is no overall difference in terms of safety or training that would have prevented the Ethiopian crash.

Ethiopian is a state-of-the-art operation with a modern fleet. Lion Air is a bit more questionable, but their 737 crash appears to have nothing specific to that airline or being based in Indonesia.

You may have other evidence of hazards, so might I. But the 737 MAX saga isn’t it.

I feel like there could be a good amount of hollywood usage of these idling planes to make some thrilling media for us to consume.

There would be many, many more not that old aircraft out there in storage that will be much, much cheaper to organise and insure a film shoot for.

Now that everybody, even non-pilots on HN like me, know how to turn MCAS off, it doesn't really make sense to keep them grounded.

While pilots now know how to counteract this specific problem, it also highlighted how flawed the safety analysis of this plane was. It makes sense to re-evaluate to make sure there isn't a second problem that just hasn't killed anyone yet.

Plus, how much testing has the airplane gone with MCAS in an off state? Certainly less time than in the on state.

And at the next level up the causality chain, the safety analysis was flawed because of the regulatory capture of the FAA by Boeing.

Should we therefore ground and review all the planes?

The plane isn't airworthy in an MCAS upset condition resulting from faulty AOA sensor. That's because numerous contraindications are happening in the cockpit as a result, including the failed side stick shaker activating. In the Lion Air 34 and 610 flights, the stick shaker was active almost continuously. That's not airworthy.

Also, the autopilot uses stabilizer trim. If you turn stabilizer trim to cutoff, you have no autopilot. Also, the emergency airworthiness directive says it's possible a runaway continues even after stabilizer trim is set to cutoff: If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.

Once there was a second crash, with stabilizer jackscrew in the full nose down position, it was untenable to allow the planes to be considered airworthy, for the very central reason that we don't completely understand what happened and how to avoid it.

The proper response in aviation safety is not to assume pilots are doing the wrong thing upon receipt of an emergency airworthiness directive. It's to assume they are following the directive. You don't just pretend they're morons and keep on subjecting the general public to risk, while you guess at what the problem is.

It's there to solve a problem though. You can cut power to the recalled airbags in your car too.

The whole point of MCAS was to avoid pilot retraining on the different handling characteristics. To say that you can just not have that system is also to say the pilots need to be retrained for the Max planes. Something that Boeing felt necessary to avoid and thus implementing this MCAS. Now that 2 planes have crashed you can't just say "Oh Okay just turn MCAS off duhhhhhhhhh".

The misfeatures that are suspected to have contributed to the recent accidents exist in part to keep the plane similar enough to previous 737s that lengthy pilot retraining is not necessary. Now that that fiction has been dispelled, additional training seems to be called for. (probably a bit more is needed than passing on whatever knowledge 'non-pilots on HN' have picked up)

If turning it off was a fix then it wouldn't have been there in the first place.

I am sure the feature is there to help keep the plane stable. It can be flown without the system being on if the sensors don't work. You can drive your car without cruise control, but it makes it more convenient with it on.

The feature is there so pilots don't have to be retrained on the different handling of the plane. It was entirely cost avoidance on Boeings part. To say that they could just turn it off is also an admission that the plane is not the same and pilots would need to be retrained. Boeing can't have it both ways.

> the feature is there to help keep the plane stable

And we don't want that?

> You can drive your car without cruise control

Sure, because cruise control is there to allow me to be lazy, not to keep my car on the road.

The aircraft has handling deficiencies at high angles of attack due to the engines being mounted differently. The MCAS is there to correct this. It's this or redesign the plane. Only 2 things that could have helped: an angle of attack disagree light to warn the pilots of the issue, and to to retrain the pilots. The first was sold just as an optional package, the second was considered unneeded since Boeing treated the new plane as a perfect equivalent of its predecessor. Disabling the MCAS is not a fix and without it the plane is not certified to fly.

It works when the sensor works. When it doesn't you need to fly it manually.

What I'm saying is that the MCAS is there so the plane can get the certification. You can fly the plane without it but it's not considered normal (or safe) operation. Which is why it must be there and it must work.

You can fly a plane without an engine if needed but just try certifying a plane with one engine under one wing.

Given that there was a second crash , similar to the first, I don't think this argument holds.

At the time of the second crash it wasn't as clear what the likely culprit was. If it was believed to be a defect with the aircraft at that time then most other countries would have already grounded them by then. I think that's a bad argument to make as well, but not for those reasons.

Everyone who earned a type rating to fly 737s also knew how to turn it off, by following the non-normal (aka "emergency") checklist memory items for stabilizer runaway.

It is shocking to me that the second crash happened, if they both turn out to be MCAS and stab trim sourced. How could you step into the cockpit of a 737-Max that day and not know about the MCAS issue and be primed to respond according to the checklist?

I have to add that I'd be happy to put myself or my family onto a 737-Max flown by a US-flag carrier (Southwest, American, United [Delta doesn't fly the -Max]), as I believe there's a significant variance in crew training worldwide.

Bad sensor data was represented as accurate sensor data. It is easy to solve some problem you know is occurring, it is hard to solve a problem where something weird happens and the data in front of you is telling you that what you think is happening is not what is happening. ("I think we're stalling." "Nah, the sensor that directly measures that says we're not." "Hmm, what else could it be? Get me the checklist" crash)

It shocks me that the redundant angle of attack sensor and the "disagree" light is not standard equipment. Who is buying multi-million dollar airplanes and cares about the cost of an angle of attack sensor and a lamp? Not people that care about safety, that's for sure. I know the airline industry loves nickel-and-diming their customers, but safety equipment is a little more important than priority boarding and a checked bag. It is shameful that Boeing adopted that business model.

More on angle of attack sensors: https://www.flightliteracy.com/angle-of-attack-indicators/. If you fly GA, you should get one. Having a readout of the flight energy you have available is one of the greatest safety upgrades you can make.

Agreed on the value of AoA; it’s a toss-up whether we’ll be upgrading in the next couple years. Not much sense in adding it to a plane we might be selling shortly as it doesn’t bring much increase in resale. Next airplane is likely to have it as OE.

There's circumstantial evidence this particular variety of MCAS upset doesn't look like runaway trim. The manifestation is transient, seems capricious, results in surprise.

U.S. based pilots have said they didn't know anything about MCAS or MCAS upset until the FAA issued an emergency airworthiness directive, AD#: 2018-23-51, expressed surprise and were critical to discover this after the fact. Years after the fact. And it took a crash.

A second crash, despite the issuance of the AD suggests the AD is somehow sufficient. Maybe we don't know the full range of possible MCAS upset behavior. Maybe we don't know if there are additional factors that contribute to surprise and confusion.

>It is shocking to me that the second crash happened, if they both turn out to be MCAS and stab trim sourced. How could you step into the cockpit of a 737-Max that day and not know about the MCAS issue and be primed to respond according to the checklist?

the MCAS caused almost crash the day before the first crash of the same plane - it was only that off-duty pilot who knew about MCAS and thus saved the plane. Yet the next day that plane flew again with an MCAS unaware crew. Looks like some systemic issue. Grounding of the planes would allow to correct the specific tech issue of MCAS. Whether the systemic issue is going to be corrected is yet to be seen.

Agree, seems like waste of resources to keep them grounded.

I’d prefer to waste the resources of an airline or Boeing, rather than the kind of “waste of resources” in losing whole plane loads of human beings. Turning off MCAS solves one problem and trades it in for another, it is not a waste of resources to solve all of the relevant problems.

What is a waste is pretending that wasted resources is the worst thing that can happen here when we have two fatal crashes being investigated.

What an irresponsible comment. One can't just hand-wave away safety protocol, even if the failure appears to be obvious.

The issue is more of incompetent pilot. As indicated that the day before the lion air crash, the pilot know what to do to handle the issue. At least for lion air, the airline has been locally famous for being careless about maintenance and pilot training.

So the plane's not unsafe, you're just statistically vastly less safe as a passenger ON the plane, because the pilots are much more likely to crash it, killing everyone aboard.

Well, that put me my place. I'll hop right on another one tomorrow!

You could also say that Max flights now require 3 pilots to safely manage.

No, what required is a properly trained pilot.

Oh my plane is pointing at the ground. Let me just stare at the trim indicator to see some intermittent change that only occurs every 10 minutes.

Exactly, but instead of requiring the retraining of pilots for a new airplane that flies significantly differently then the previous model, Boeing put in an automated system and charged extra for the instrumentation needed to determine if that system is failing.

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact