Boeing 737 Max. Would you fly in one?

[mistermack]

I'm not here to knock Boeing. They have achieved fabulous stuff in the past. Great planes, breaking new ground, setting records.

But there is no way I'm ever going to take off in a 737 Max. 

From what I can glean from the two crashes that grounded the fleet, the design is cobble up, and needs everything to be right, in order to keep flying. 

I want a plane that nearly flies itself, not one that needs special software, and top quality piloting just to keep it from crashing. 

I believe that the whole problem is due to moving the engines forward, and enlarging the intakes, in an effort to compete with the equivalent Airbus A320. This apparently affects the handling so much, that a special bit of software had to be installed, to prevent stalling. The software is triggered by a sensor, and when it goes into action, it overrides the pilot, and pushes the nose of the plane down. If the sensor fails, down you go, and that's what happened in the two crashes. And, I believe, it happened in other cases, where the pilots were able to cope with it and a crash was averted. 

 

I'm usually fairly trusting of technology. In cases like this, if a fix could be demonstrated to be foolproof, I would normally have no qualms about flying in the plane. But the way that this scandal has developed has created a picture of today's Boeing having a fundamentally flawed culture, where big money is more important than safety. This was a known problem, very well understood by the company, but the fundamental fix, to redesign the plane, would cost absolute megabucks. The fix that they came up with might have worked, with a thorough foolproof anti-stall system, but that cost too much as well. And it could even have worked if they had TOLD the pilots of the problem, and retrained them on how to fly through the problem. But that was too much money as well, (and might have looked bad, if it had leaked out).

So they crossed their fingers and hoped. And even after the two crashes, they STILL didn't want to do anything, till they were forced to.

So no, no bargain price would get me up in a 737 Max, when they start flying again. And I have a feeling that a lot of people will be saying the same when they book. 

[zapatos]

I'd be happy to be on the first commercial flight once they are are again certified. If Boeing and the FAA say it is now safe, and pilots are willing to sit in the front seat, that's good enough for me.

[mistermack]

1 hour ago, zapatos said:

I'd be happy to be on the first commercial flight once they are are again certified. If Boeing and the FAA say it is now safe, and pilots are willing to sit in the front seat, that's good enough for me.

All of that applied before the last crash though. After the first crash, Boeing and the FAA said it's safe, and the pilots continued to fly it till they were all grounded after the second crash.

If I was getting a pilot's salary, instead of paying for a ticket, I might be more willing. 

What's quite disturbing, is that when they tried to shift the blame onto the pilots, it emerged that in the event of the anti-stall forcing the nose of the plane down, the pilots have only four seconds to decide what the problem is, and flick the switches to disable the electrical power to the trim on the tail. After that point, the force is so great on the trim, that the manual override can't be worked by hand.

Four seconds to include thinking time, diagnosing the problem and acting on it. It's just not reasonable. It obviously can be done, and has been done. But it's not a great margin for error.

[iNow]

Yes, I would. The funny thing is that it’ll probably be one of the safest jets up there after all the attention and updates. 

Now, ask me if I’d fly Spirit or Jet Blue Airlines and I’d probably tell you no way. 

[zapatos]

2 hours ago, mistermack said:

All of that applied before the last crash though. After the first crash, Boeing and the FAA said it's safe, and the pilots continued to fly it till they were all grounded after the second crash.

 

That all applied, but a lot has changed since then. Don't ignore that.

2 hours ago, mistermack said:

What's quite disturbing, is that when they tried to shift the blame onto the pilots, it emerged that in the event of the anti-stall forcing the nose of the plane down, the pilots have only four seconds to decide what the problem is, and flick the switches to disable the electrical power to the trim on the tail. After that point, the force is so great on the trim, that the manual override can't be worked by hand.

Four seconds to include thinking time, diagnosing the problem and acting on it. It's just not reasonable. It obviously can be done, and has been done. But it's not a great margin for error.

But presumably that will all be changed, right? It will have no impact on future flights.

5 hours ago, mistermack said:

I'm not here to knock Boeing.

All evidence to the contrary.

[MigL]

The changes made to the MAX to accommodate the more economical higher bypass engines, necessitated different engine-to-wing mounts ( because of their larger diameter ), placing them higher and farther forward.
The altered CoG/ CoL characteristics made the plane very slightly unstable in pitch, such that excessive nose-up angle would diverge and stall the wing.

Now this is nothing new, just about every military fighter plane since the 80s has been unstable in pitch as it makes them extremely maneuverable. But since all new planes ( even airliners ) are fly-by-wire, it is easy enough for computer software to control a humanly unflyable plane. The computer software does the job that a human would not be able to do.
A Eurofighter Typhoon is so unstable, trying to fly it manually has been described as "sitting on the hood of a car doing 100 mph, holding a bike backwards, by the handlebars, and trying to keep it going straight".
The 737 MAX is nowhere close to this and is easily controlled by the pilot.

But since this is a commercial airliner and extra precautions have to be built in, to control the pitch-up moment on the 737 MAX, Boeing added MCAS ( Maneuvering Characteristics Augmentation System ), which receives information from two Angle-of-Attack ( attitude ) sensors, and if they deviate too far in pitch, the MCAS software forces the nose down.

The problem in the two crashes ( shortly after take off, with nose high pitch ) was that one of the two sensors wasn't working and with no pilot notification, the MCAS could not be over-ridden by pilot control, and it re-applied continuously, eventually crashing the plane  into the ground.
The 'fix', all in software, is to compare the two attitude sensors and if one isn't working notify the pilot. Make the input from MCAS weak enough so that it can easily be overridden by the pilot. And apply MCAS control only once, as that should be enough to get the pilots attention to a possible problem.

The Boeing 737 MAX series are good planes, and maybe suffered from Boeing trying to make them idiot proof by putting too many roadblocks on the pilot flying the plane. I understand Boeing is considering re-naming them to get rid of stigma associated with the plane ( as demonstrated by Mistermack ), but I'm not sure if it'll work.
They may have to introduce a replacement for it.

[zapatos]

I believe about 400 planes have been delivered, another 300 built (if I read that right) and about 5000 have been ordered. I don't know that a replacement for the 737 MAX is reasonable for Boeing or the airlines. The airlines won't be able to return the 400 that have been delivered, and while they may not like the plane's reputation at this point, they surely like just about everything else about it.

[mistermack]

42 minutes ago, MigL said:

Now this is nothing new, just about every military fighter plane since the 80s has been unstable in pitch as it makes them extremely maneuverable. But since all new planes ( even airliners ) are fly-by-wire, it is easy enough for computer software to control a humanly unflyable plane.

There's a big difference though, in the miles and flying hours that fighter jets clock up in their lifetime compared to passenger jets. And the requirements are different. Manoeuvrability  isn't a requirement for passengers. But stability and safety is. Fighter jets don't have people walking around not strapped in for one thing.  And they have ejector seats and parachutes. They are a bit like formula 1 cars, compared to family saloons. The odd crash doesn't really matter, it's performance that counts.

It will be interesting to see what they propose as a fix. They are due to start flying again soon. There's going to be mega-scrutiny this time of what measures have been taken, unlike after the first crash, so it will have to not just be good, but be seen to be good. 

I still won't be flying in one. When I get on a plane, it's comforting to tell yourself that it's safer than driving etc, when you get up to 300 mph and a thousand feet up. The last thing you want is the thought of diving head first into the ground in your head.

[Danijel Gorupec]

3 hours ago, MigL said:

The 'fix', all in software, is to compare the two attitude sensors and if one isn't working notify the pilot. Make the input from MCAS weak enough so that it can easily be overridden by the pilot. And apply MCAS control only once, as that should be enough to get the pilots attention to a possible problem.

This is the part that I don't understand... If they asked me, I would tell them exactly the same. You have two sensors, so compare them. Don't make electronics bossy, but assisting....  How come they didn't think of it? I am sure they did - I bet somebody intentionally decided otherwise, and this somebody did not act as an engineer when making the decision.

(That said, I think regulatory bodies share the same responsibility in this case as the Boeing.)

[mistermack]

3 hours ago, Danijel Gorupec said:

This is the part that I don't understand... If they asked me, I would tell them exactly the same. You have two sensors, so compare them. Don't make electronics bossy, but assisting....  How come they didn't think of it? I am sure they did - I bet somebody intentionally decided otherwise, and this somebody did not act as an engineer when making the decision.

(That said, I think regulatory bodies share the same responsibility in this case as the Boeing.)

I'm guessing here, obviously, but it looks likely that a real stall is just as dangerous as a fake one. So the electronics in that situation are vital, to take action quicker than a pilot would. Otherwise, you could easily fix as above. Just when a stall is indicated, play a recorded message to the pilots, indicating the proper series of actions for that situation. It can only be time that prevents that from being the solution. 

The best answer is to have a plane that doesn't want to stall. 

How do other planes survive without electronic anti-stall? ( I don't know ). 

My own fix, off the top of my head, is to design a visible air speed indicator that works on physical principles rather than electronic. 

I would put a carbon fibre bendy rod, like a fishing rod, on the nose, where the pilots can always see it. The bend in the rod would give an unmistakable indication of air speed, and as it's always there, the pilots would know at a glance if the plane was about to stall, or not. After a few hours flying, your mind would match the shape of the rod to the indicated air speed. 

[StringJunky]

3 hours ago, mistermack said:

I'm guessing here, obviously, but it looks likely that a real stall is just as dangerous as a fake one. So the electronics in that situation are vital, to take action quicker than a pilot would. Otherwise, you could easily fix as above. Just when a stall is indicated, play a recorded message to the pilots, indicating the proper series of actions for that situation. It can only be time that prevents that from being the solution. 

The best answer is to have a plane that doesn't want to stall. 

How do other planes survive without electronic anti-stall? ( I don't know ). 

My own fix, off the top of my head, is to design a visible air speed indicator that works on physical principles rather than electronic. 

I would put a carbon fibre bendy rod, like a fishing rod, on the nose, where the pilots can always see it. The bend in the rod would give an unmistakable indication of air speed, and as it's always there, the pilots would know at a glance if the plane was about to stall, or not. After a few hours flying, your mind would match the shape of the rod to the indicated air speed. 

From what I understand of the cause, there needs to be some kind of redundancy in the critical sensors.

[MigL]

A 'stall' isn't necessarily about speed; you can always give a plane more throttle to regain speed ( unless you are touching down ).
So airspeed is not that serious a problem.
On the other hand, a wing that exceeds a certain angle of incidence, experiences delamination of the airflow over the top of the wing.
The resulting loss of lift causes the plane to 'drop like a rock' unless it can be levelled out.
Unfortunately at such high angles the tailplane loses control authority to force the nose back down, and you crash.

MCAS was designed to prevent such a departure before it got serious.
It turns out it was a little too aggressive.

[mistermack]

3 hours ago, MigL said:

A 'stall' isn't necessarily about speed; you can always give a plane more throttle to regain speed ( unless you are touching down ).
So airspeed is not that serious a problem.

Theoretically that's right, but in practice, the emphasis is on airspeed. This is what wikipedia says about stalling :

"This graph shows the stall angle, yet in practice most pilot operating handbooks (POH) or generic flight manuals describe stalling in terms of airspeed. This is because all aircraft are equipped with an airspeed indicator, but fewer aircraft have an angle of attack indicator. An aircraft's stalling speed is published by the manufacturer (and is required for certification by flight testing) for a range of weights and flap positions, but the stalling angle of attack is not published."      https://en.wikipedia.org/wiki/Stall_(fluid_dynamics)  

What happens in practice is that if the nose is wrongly pointed up, the plane loses airspeed AND the angle of attack is increased towards the stall angle, so both factors are going in the stall direction. The airspeed indicator should still give an indication of imminent stalling for that reason. 

You would think that the angle of attack could be measured using a mechanical indicator, since the wings are fixed in line with the body of the plane. A pendulum would show if the plane is level or nose up or down. 

Maybe in a severe updraught the effective angle of attack could be changed though.          

[Janus]

30 minutes ago, mistermack said:

Theoretically that's right, but in practice, the emphasis is on airspeed. This is what wikipedia says about stalling :

"This graph shows the stall angle, yet in practice most pilot operating handbooks (POH) or generic flight manuals describe stalling in terms of airspeed. This is because all aircraft are equipped with an airspeed indicator, but fewer aircraft have an angle of attack indicator. An aircraft's stalling speed is published by the manufacturer (and is required for certification by flight testing) for a range of weights and flap positions, but the stalling angle of attack is not published."      https://en.wikipedia.org/wiki/Stall_(fluid_dynamics)  

What happens in practice is that if the nose is wrongly pointed up, the plane loses airspeed AND the angle of attack is increased towards the stall angle, so both factors are going in the stall direction. The airspeed indicator should still give an indication of imminent stalling for that reason. 

You would think that the angle of attack could be measured using a mechanical indicator, since the wings are fixed in line with the body of the plane. A pendulum would show if the plane is level or nose up or down. 

Maybe in a severe updraught the effective angle of attack could be changed though.          

Small single engine craft have a "stall indicator".    It is simply a little spring loaded metal flap extending out of the leading edge of the wing ( or least this is how they did it years ago).  If the angle of attack increases beyond a certain point, the airflow over the wing pushes the flap up, setting off the stall warning. 

A pendulum would not be of much use, as wing loading is also a factor in a stall.    If you are in a bank, you increase wing load and increase stall speed.  For a PA-38-112 Piper Tomahawk, the stall speed(no flaps) can increase from 48 KIAS at 0 degrees bank to 53 KIAS at 30 degrees.   In a coordinated turn, a pendulum would point in the same direction relative to the plane in both cases.

[mistermack]

Reading a bit more of what wiki says about the plane doesn't exactly fill me with confidence.

"The Maneuvering Characteristics Augmentation System (MCAS) is a flight control software system developed for the Boeing 737 MAX to provide handling qualities similar to the Boeing 737 NG, especially in low-speed and high angle of attack (AoA) flight. It lowers the nose without pilot action when it determines the aircraft is too nose-high, based on input from airspeed, altitude and angle of attack sensors. However, it is susceptible to erroneous activation, as evidenced in the deadly crashes of Lion Air Flight 610 and Ethiopian Airlines Flight 302. The 737 MAX is indefinitely grounded until regulators decide the aircraft is airworthy, pending software and instrumentation updates and revisions to information for flight crews. They may also be required to undergo MCAS training sessions in flight simulators."

This is the real meat of the problem. The change in weight distribution, by moving the engines forward and upwards, have given the plane worse handling characteristics, and MCAS is designed to take over from the pilot, when things are going wrong. When they say "especially in low speed and high angle of attack flight" they are obviously talking about low altitudes, just after take off, or just before landing. The very times when there is no margin for error, no time to pull out of a dive, even if you could.

The MCAS is a clear admission that the plane isn't safe enough to trust to the pilot to fly it, and that's why I won't be getting in one. They didn't develop that system just for fun. There must be a real risk of stalling, if it's not there.

On the commercial side, I guess if they can get a good work around, and can get some accident-free air miles behind it, people will stop worrying. That's the optimistic view. A lot depends on the media, and how they treat it. 

 

 

 

[MigL]

The FAA certification was 'rushed' because Boeing made the convincing argument that the 737 MAX had the same handling qualities as the 737 NG. So it did not need full re-certification.
They could have called the plane a 797, certified it without the MCAS software ( as there is nothing inherently dangerous about its 'raw' hanling behavior ), but certification would have taken about 2-3 yrs.
They chose, instead, to simulate the already certified handling qualities of the previous model, and got it to market a lot quicker.

It didn't work out too well.

[mistermack]

9 hours ago, MigL said:

The FAA certification was 'rushed' because Boeing made the convincing argument that the 737 MAX had the same handling qualities as the 737 NG. So it did not need full re-certification.
They could have called the plane a 797, certified it without the MCAS software ( as there is nothing inherently dangerous about its 'raw' hanling behavior ), but certification would have taken about 2-3 yrs.
They chose, instead, to simulate the already certified handling qualities of the previous model, and got it to market a lot quicker.

It didn't work out too well.

That's partly why the FAA reputation has taken a big hit over this. And they are in a bit of a tight spot. If the "cure" for another MCAS failure is to turn it off, then what they are saying is you need to turn a certified plane into an un-certified one, with the flick of a switch, to stop it from crashing. 

It's a hell of a position to be in.