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Comment by omginternets | Hacker News Reader

Is there any way to know what kind of aircraft you'll be boarding when purchasing tickets? I've never paid attention until now, and the 737-Max is definitely a non-starter.

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Just curious, what would it take for you to get on a 737-Max?

European and American regulators have gone over it with a fine tooth comb at this point and allow it to fly. There is always gonna be people that will say the plane shouldn't fly. Arguably the amount of attention this plane has gotten will probably make it one of the safest in the industry going forward.

Honestly? Nothing. The issue is that I don't have enough time to evaluate whether the shoring-up job on the Max is sufficient.

Since the plane is aerodynamically flawed by design. I'll never step foot on one.

But its not?

But it is? I think the parent was talking about:

>Travis is unequivocal in his assessment of the Boeing 737 MAX. “It’s a faulty airframe. You’ve got to fix the airframe [and] you can’t fix the airframe without moving the engines” back and away from their current position.

>The root problem with the engine-forward design is “once this thing pitches up, it wants to keep pitching up,” said Travis. “That’s a big no-no,” he continued, because pitch-up on an aircraft increases angle of attack.

https://www.eetimes.com/software-wont-fix-boeings-faulty-air...

FYI - Background on the guy being quoted

"Gregory Travis, a veteran software engineer and experienced, instrument-rated pilot who has flown aircraft simulators as large as the Boeing 757"

I know a few veteran software engineers that are instrument-rated and frankly I'm not sure I would listen to any of them over the FAA or aeronautical engineers. Probably good for some perspective, but not exactly a great source for determining if an airplane is "aerodynamically flawed by design".

I agree with you, aerodynamics and airframes are not something so trivial to understand.

"who has flown aircraft simulators as large as the Boeing 757"

Talk about a big aircraft simulator, those that I know are the size of a car, not of a 757 (jk)

That article, and Gregory Travis' assessment, offer zero actual evidence that the design is unstable. Lot of hand waving and "the engines are different so it must be dynamically unstable" but no actual evidence, which is obvious because no independent engineer/pilot is going to be able to effectively assess the upset aerodynamics of an airliner and come to a different conclusion than both the FAA and EASA about whether or not the aircraft is dynamically unstable.

He's somewhat right on other details, but that doesn't make his assessment of the aerodynamic issues correct.

Airfoils pitch up by default. Its how they work.

Aircraft are designed to not let that happen in an uncontrolled fashion. Software has been used to do this since the advent of computers in airplanes

Maybe we should also start boycotting A320neo's too

https://www.flightglobal.com/programmes/a320neo-also-potenti...

Aerospace controls engineer here - while the airframe might not be passively stable (as is common for civilian aircraft), dynamically unstable aircraft have been stabilized with control software since the 70s [0]. If you've flown on an MD-11, you've flown on an 'aerodynamically flawed' aircraft. Most real systems are dynamically unstable without some kind of controller (implying software) in the loop.

[0] https://en.wikipedia.org/wiki/Relaxed_stability

Boeing has kind of a poor track record for software lately, from the Max to the SLS. Time will tell if this has resulted in real change.

Ah - I didn't say Boeing's ability to write and test that control software was particularly good (in fact, I think their current track record says exactly the opposite.) I just hate when non-domain experts make judgements about things being 'fundamentally flawed.'

Insufficiently tested and documented? Sure. Bad UI/UX? Most definitely. Irredeemable 'because of aerodynamics' according to some private pilot that flew a 737 once in sim? Absolutely not.

Amen. If we don’t focus on the root cause it will be harder to solve the problem. And understand that we have actually solved it.

(Student Pilot and Mechanical Engineer here)

>> because of aerodynamics

But yes. MCAS was put in place due to concerns over aero. If that was just to avoid the need for extra pilot training then it should have been scrapped since new training will be required now anyway. But since great effort has been made to fix MCAS we can conclude that the root problem is aerodynamic.

Can aerodynamic issues be compensated for with software? Sure. I need to read up on the final hardware/software/instruction solution before passing Judgement.

You're completely ignoring that flying the 737 MAX without MCAS is not an automatic death sentence. Meanwhile a malfunctioning MCAS is actually an automatic death sentence.

The big flaws are in the software, not in the hardware. So stop focusing on that.

The qualifier of 'automatic' on death sentence is fun.

Would the software even be necessary if the airframe was better designed?

The MD-11 that was so crashy that airlines eventually sold their airframes to freight companies because cargo can’t refuse to get on one?

I don't think the flight safety record of the MD-11 bears that out[0] - most crashes of significance were either cargo flights (which are much more prone to dynamical issues than passenger flights) or flights in conditions that exceeded design specs (landing in typhoons). It sounds like most airlines sold it because it missed range/fuel burn targets, not because of safety issues.

[0] https://en.wikipedia.org/wiki/McDonnell_Douglas_MD-11#Accide...

My Dad was a frequent business traveller in the 1980s and 90's and I remember him commenting on the MD-11 and saying that he hated them because they were noisy and had lot of vibrations at the back from the center engine.

He said that was the the reason airlines switched to using them as cargo planes.

I realise this is just an anecdote, though.

Those typically aren't approved for civilian air-transport though, are they?

The MD-11 is a passenger aircraft.

Right, but that's quite atypical, isn't it?

It’s “atypical” because it’s a 30+ year old superseded model and there are more efficient designs available. KLM, a flag carrier, was flying them up until just a few years ago. If it’s certified for carrying passengers, it’s certified. There are no special concessions made to airworthiness regulations for aircraft that sell few in number.

The MD-11 has been certified for air transport since it was introduced, was flying in revenue service until 2014, and as far as I know, that certification has never been revoked.

Is it not an intrinsically imbalanced aircraft?

No it is not. No regulators has yet been prepared to certify a fixed-wing aircraft that is intrinsically unstable, even after decades of proven fly-by-wire development.

The 737 Max has different yoke force during pitch-up than predecessor 737 models, such that at higher angles of attack it does not natively require increasing yoke force to continue to pitch up. That doesn't mean it would pitch up uncontrollably. MCAS was designed to provide pitch-down force in these high-AoA cases so that yoke forces would be equivalent to 737 NG models and minimal training would be necessary to fly both.

https://en.wikipedia.org/wiki/Relaxed_stability#Unstable_air... indicates that the MD-11 (which regulators certified) is aerodynamically unstable. (That plane has a compensation system, similar to the 737-MAX.) Is "intrinsically unstable" different from "relaxed stability" in some subtle way?

And while military planes are quite different from commercial planes, many (most at this point?) military jets are aerodynamically unstable.

There are different kinds of "relaxed stability", largely depending on which axes of the aircraft are affected, and the magnitude of the instability.

Longitudinal stability is something of a special case, in that essentially all swept-wing aircraft are vulnerable to "Dutch roll" instability and are generally fitted with yaw dampers. Since such stabilizers are, practically-speaking, omnipresent, regulators are OK with using them in what is now a well-understood domain. While it can be unpleasant, all of these aircraft can be flown with a failed yaw damper - notably the 707 family has a particular proclivity for yaw instability, and while almost all civilian users opted for the yaw damper, the largest fleet user, the USAF, did not fit their KC-135s with dampers until well into their service life.

For good reason, pitch instability is a much more serious issue, and there has been very little interest in trying to bring to market a transport aircraft that required active pitch stabilization. Many, if not all, modern clean-sheet airliner designs are fly-by-wire due the the safety, performance, and efficiency improvements to be had, but they are all safely flyable in an "alternate law" (or equivalent) fallback mode.

Combat aircraft, generally speaking, aren't certified aircraft (they have no need be), for good reason - if you're flying a modern fighter and the FBW computers die on you, it's over, you eject. Understandably, that's not an option in a transport aircraft.

I suppose it boils down to whether you have confidence in the FAA of 2020 to make a decision that would be strongly against the financial interests of Boeing and many US carriers.

I think the Max will crash again. Excuse me, the 737-8 will crash again.

European regulators now allow the plane to fly after conducting their own investigation so it's more than just the FAA.

If pilots can disable the malfunctioning MCAS during emergencies then this type of accident won't happen again. The 737 max might suffer from more emergency landings than usual though.

Nothing more than approval by relevant authorities. Once I use a different treshold than that, it becomes very difficult to fly at all.

I mean all else being equal (Two planes to London leaving at almost exactly the same time and exactly the same cost) then perhaps I'd prefer the A32X. But the point is all else isn't equal. It becomes a matter of how many hundred you want to spend to fly the Airbus. Or how many hours you want to spend at the airport waiting for the non-Max flight. And I'll happily take the MAX if it saves me 30 minutes or $20. And I'll take my family along too without hesitation.

At the very least new training for the pilots.

The whole thing has been badly handled. The FAA/EU agencies should have declared at the very outset that airlines will need to bear the cost of retraining the pilots who will be flying this. It was the attraction of not having to retrain pilots that was the biggest incentive for Boeing to pull the shortcuts they did. At a bare minimum the aviation agencies should have pulled that benefit away.

Every airline will show you the scheduled aircraft when booking tickets, usually right next to the airports and travel times. Nothing guarantees they won't change it at some point before the flight though.

Be aware of the alternative aircraft code 737-8, which is a bit similar to the "good old" 737-800.

AA seems to show "7M8-Boeing 737MAX 8" though.

See https://onemileatatime.com/american-737-max-flights/ and https://onemileatatime.com/boeing-737-8/

certainly nothing guarantees, but American did at least say they wouldn't rebook non-MAX to MAX flights

The short answer is no. The longer answer is that you can see the planned type of aircraft when you book your ticket which doesn't typically change. But airlines can and do sometimes switch aircraft types at the last minute up to the point where you're already at the gate.

ADDED: And I'm guessing things are more fluid than usual in the current situation.

It really depends on the route (and the airline). Some routes I've flown are scheduled for different types throughout the day; it's not uncommon to fly on the other type. As a bonus, different types have different premium rows, if you reserve a non-premium seat and the type is changed, you may keep the seat number and get a premium seat.

If I saw 737MAX pulling at the terminal I would have cancelled the trip, but usually airline shows plane at itinerary and you can check flightradar what planes fly that route.

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