Boeing woes

[Grumpy Git]

I see the Boeing Starliner rocket failed to reach the ISS, due to a software fault.

What with this and the 737 Max8 disasters, is there any evidence that Boeing were subcontracted to write the software for the Northern Rail and TPE rosters?

 

[DaleCooper]

Good news possibly?

Boeing fires boss Muilenburg amid 737 troubles

https://www.bbc.co.uk/news/business-50893490

Boeing has fired its chief executive, Dennis Muilenburg, a move the board of directors said "was necessary to restore confidence" in the firm.

David Calhoun, Boeing's current chairman, will take over as chief executive and president from 13 January.

Mr Muilenburg had faced calls for his resignation over the company's response to two deadly crashes involving the firm's best-selling 737 Max airliner.

The jet has been grounded since March.

Last week, Boeing said it would halt production of the plane while it waited for regulators to certify the jet's safety.

"The board of directors decided that a change in leadership was necessary to restore confidence in the company moving forward as it works to repair relationships with regulators, customers, and all other stakeholders," Boeing's statement said.

Boeing added that Lawrence Kellner would become non-executive chairman with immediate effect.

 

[Peter Mugridge]

That same BBC report goes on to point out that Boeing have merely appointed a long-serving insider in Muilenburg's place, a fact which has been met with dismay by campaigners.

Speaking personally, I would be more confident in the MAX if the entire board of Boeing were to take to the air in one once the type is cleared to fly again.

 

[furnessvale]

That same BBC report goes on to point out that Boeing have merely appointed a long-serving insider in Muilenburg's place, a fact which has been met with dismay by campaigners.

Speaking personally, I would be more confident in the MAX if the entire board of Boeing were to take to the air in one once the type is cleared to fly again.

One selected at random from the lines of parked up 737 Max's by members of the public, NOT one selected by the board!

 

[Peter Mugridge]

One selected at random from the lines of parked up 737 Max's by members of the public, NOT one selected by the board!

Yes, agreed!

If they refuse to fly on it, then it would mean they have no confidence in the software upgrade.

 

[Grumpy Git]

The 737 Max8 is inherently unstable due to the forward positioning of the engines. It's like a 220 seat Typhoon.

 

[DaleCooper]

The 737 Max8 is inherently unstable due to the forward positioning of the engines. It's like a 220 seat Typhoon.

Don't worry, there's a sensor (just one) that deals with that.

 

[Grumpy Git]

Don't worry, there's a sensor (just one) that deals with that.

Unless you paid extra for another one.

 

[edwin_m]

The 737 Max8 is inherently unstable due to the forward positioning of the engines. It's like a 220 seat Typhoon.

Do you have a source for that (or better still two sources that need to agree...)? I haven't been following the saga too closely but I've only seen mentions that the different positions of the engines changes the handling characteristics and the software in question modifies the trim so the MAX is (intended to be) sufficiently similar to older versions not to need re-training of the pilots. Plus I think the MAX still has traditional control cables, and you really need fly-by-wire to get the fast automated control inputs necessary to keep an unstable aircraft in steady flight.

Inherently unstable is good if you need to do extreme manouvres in a fighter jet but I'm not sure there is any benefit for an airliner, or at least not enough to make it worth trying to convince potential passengers.

 

[Gooner18]

Do you have a source for that (or better still two sources that need to agree...)? I haven't been following the saga too closely but I've only seen mentions that the different positions of the engines changes the handling characteristics and the software in question modifies the trim so the MAX is (intended to be) sufficiently similar to older versions not to need re-training of the pilots. Plus I think the MAX still has traditional control cables, and you really need fly-by-wire to get the fast automated control inputs necessary to keep an unstable aircraft in steady flight.

Inherently unstable is good if you need to do extreme manouvres in a fighter jet but I'm not sure there is any benefit for an airliner, or at least not enough to make it worth trying to convince potential passengers.

Hopefully this will explain it for you :

 

[cactustwirly]

What I don't get, is why didn't Boeing decide to do a chopped down B757 MAX instead, the 757s newer design and greater height would mean that it would have less issues with the bigger Leap engines?

 

[Gooner18]

What I don't get, is why didn't Boeing decide to do a chopped down B757 MAX instead, the 757s newer design and greater height would mean that it would have less issues with the bigger Leap engines?

At a guess I would say due to cost and time scale

 

[Grumpy Git]

At a guess I would say due to cost

FTFY.

 

[Gooner18]

FTFY.

Ha, 50 percent there lol

 

[JamesT]

What I don't get, is why didn't Boeing decide to do a chopped down B757 MAX instead, the 757s newer design and greater height would mean that it would have less issues with the bigger Leap engines?

The 757 was well out of production by the time they decided to do the 737 Max. The 757 being a bigger aircraft was also somewhat aimed at a different market, airlines wanted a smaller plane with longer range and/or better efficiency which a re-engined 737 offered.
I expect shortening an existing design is also very much trickier. The original design will have made various trade offs depending on the length, especially the location of components which may have to move.

 

[Grumpy Git]

The 737 design is like a modern day Morris Minor compared to an A320.

I suspect the Max8 is a lot cheaper than an A320 neo as well, hence the greater sales?

 

[TrafficEng]

Hopefully this will explain it for you :

I suspect that isn't the kind of source edwin_m (or anyone else who really wants to understand MCAS and the Max issue) had in mind.

MCAS isn't a system to prevent the aircraft stalling. It also isn't anything to do with the Max being "inherently unstable".

 

[TrafficEng]

<Snip>
Plus I think the MAX still has traditional control cables, and you really need fly-by-wire to get the fast automated control inputs necessary to keep an unstable aircraft in steady flight.

It does. There is a direct mechanical link from the control column to the elevator. A system of clutches allows the elevator to be operated and trimmed by a powerful electrical system, but still allows mechanical control by one, both or either of the pilots in the event of a failure in the electrical system.

The simple test of the assertion the Max is "inherently unstable" is that a truly inherently unstable aircraft of that size would be unflyable without computer operation of the control surfaces. Switch the computers off and you will crash. The Max can be flown manually using pulleys and cables. And the appropriate action to take if this system misbehaves is to turn the 'computer' off (strictly speaking, isolate its output). If the 'computer' had been switched off at the correct time the pilots would have had a perfectly flyable aircraft in all three incidents.

What I don't get, is why didn't Boeing decide to do a chopped down B757 MAX instead, the 757s newer design and greater height would mean that it would have less issues with the bigger Leap engines?

In addition to the points JamesT made, the 757 is not a 737. That's a lot of very expensive retraining the airlines would need to give all their pilots to allow them to fly a totally different aircraft type. The airlines - quite understandably - don't want to make that kind of investment.

 

[TrafficEng]

Don't worry, there's a sensor (just one) that deals with that.

Unless you paid extra for another one.

There are two (as standard) on every Max. But only one at a time is feeding data used by MCAS.

Why? Because with two data sources there is no way of knowing which one is wrong if one or the other fails. The system was designed to alert the pilots to a disagreement between the two sensors and allow them to decide what to do next. (i.e following standard procedures to neutralise the fault).

Adding a third sensor and associated processing systems could allow voting to take place, but even this is not completely safe. It could be possible for two faulty sensors to out-vote the one which is actually telling the truth. If you think this is improbable, Airbus will unhappily tell you otherwise.

 

[edwin_m]

Hopefully this will explain it for you :

Thanks for posting. It's a useful summary, although I still don't understand why moving the centre of thrust upwards relative to the centre of drag would cause the plane to nose up at high thrusts, as simple mechanics says it should be the other way round.

I suspect that isn't the kind of source edwin_m (or anyone else who really wants to understand MCAS and the Max issue) had in mind.

MCAS isn't a system to prevent the aircraft stalling. It also isn't anything to do with the Max being "inherently unstable".

Indeed. As your later post points out, the Max isn't in fact inherently unstable. I don't believe Airbuses are inherently unstable either, although they have eliminated the mechanical linkage to the control services in favour of "fly by wire". This simply means that the controls are implemented electrically rather than mechanically, with the risk that loss of the relevant circuits would render the plane uncontrollable. But if left with the control surfaces static in their normal flying positions an Airbus will also continue to fly, whereas a Typhoon will fall our of the sky.

 

[Gooner18]

Thanks for posting. It's a useful summary, although I still don't understand why moving the centre of thrust upwards relative to the centre of drag would cause the plane to nose up at high thrusts, as simple mechanics says it should be the other way round.

Maybe due to the engine sitting up above the wing somehow effects the lift characteristics causing the nose to lift higher than a 737-800 in the same situation, hence the need for MCAS to make the 737 max act like a 800 thus reducing training costs etc.

 

[Peter Mugridge]

Maybe due to the engine sitting up above the wing somehow effects the lift characteristics causing the nose to lift higher than a 737-800 in the same situation, hence the need for MCAS to make the 737 max act like a 800 thus reducing training costs etc.

The engines are further forwards, hence the centre of gravity is moved further forwards - that's the main issue.

 

[Gooner18]

The engines are further forwards, hence the centre of gravity is moved further forwards - that's the main issue.

surely If that was the only reason it would have the opposite effect as someone put earlier I.e the nose wanting to pull down all the time ?

 

[RichT54]

Interesting reading in the Guardian yesterday about how Boeing had reluctantly released more documents about the development of the 737 MAX, including more reports about senior company test pilot Mark Forkner, who had described the erratic behaviour in flight simulator tests of the MCAS anti-stall system and apparently requested that information about MCAS be omitted from flight manuals and pilot training.

 

[TrafficEng]

Maybe due to the engine sitting up above the wing somehow effects the lift characteristics causing the nose to lift higher than a 737-800 in the same situation, hence the need for MCAS to make the 737 max act like a 800 thus reducing training costs etc.

I've not yet seen a definitive explanation (I don't think Boeing have released full details) but some sources I believe to be reasonably reliable suggest the issue is a combination of the engine size and position causes a different aerodynamic response compared to the older models. It appears the larger engine nacelles and a longer lever arm generate unhelpful nose-up forces which increase as the angle of attack increases.

I've also read that the specific issue is a non-linearity in the control feel - the effect of the nose-up forces is to reduce the amount of force needed on the control column to maintain the same flight path. This seems to be contrary to a certification requirement, not just a training issue.

This makes sense. Otherwise Boeing could have dealt with the post-accident situation through pilot retraining (and scrapping MCAS) which almost certainly would have been a cheaper and faster solution to getting the aircraft flying again.

surely If that was the only reason it would have the opposite effect as someone put earlier I.e the nose wanting to pull down all the time ?

Yes, moving the centre of gravity forward would have a nose-down effect. It could also be dealt with by making other changes to restore the centre of gravity (E.g. adding some ballast at the rear of the plane) rather than adding complicated control systems.

 

[DaleCooper]

surely If that was the only reason it would have the opposite effect as someone put earlier I.e the nose wanting to pull down all the time ?

Is it because the engines are of a larger diameter which lowers the centre of thrust?

 

[TrafficEng]

...who had described the erratic behaviour in flight simulator tests of the MCAS anti-stall system...

I'm not sure there is anything 'new' about that. It has also been pointed out that those comments are about a flight simulator, not an actual aircraft.

...and apparently requested that information about MCAS be omitted from flight manuals and pilot training.

This isn't entirely inconsistent with the modern approach of pilots not being trained in detail to understand how systems work, and instead to focus on identifying symptoms and following the correct procedure for the situation.

The linked Guardian article states the omitted information "render[ed] the pilots of both the doomed Lion Air and Ethiopian flights helpless when the system kicked in". This is simply inaccurate. Not knowing about MCAS wouldn't prevent the pilots from identifying the symptoms and selecting the correct procedure - as demonstrated on the flight before the Lion Air crash. Furthermore, the Ethiopian pilots did have the information. They knew what MCAS was and had specific instructions on what to do in the event of an erroneous MCAS activation.

Just another example of journalists telling a story rather than reporting facts.

 

[edwin_m]

Is it because the engines are of a larger diameter which lowers the centre of thrust?

They are larger, but they had to be lifted up because of the limited ground clearance. So I presume the bottom of the engine is about where the bottom of the old engines was, and therefore the centre is higher.

The linked Guardian article states the omitted information "render[ed] the pilots of both the doomed Lion Air and Ethiopian flights helpless when the system kicked in". This is simply inaccurate. Not knowing about MCAS wouldn't prevent the pilots from identifying the symptoms and selecting the correct procedure - as demonstrated on the flight before the Lion Air crash. Furthermore, the Ethiopian pilots did have the information. They knew what MCAS was and had specific instructions on what to do in the event of an erroneous MCAS activation.

As far as I recall the Ethiopian pilots did deactivate MCAS but they'd left the throttles on full thrust, were going too fast and the forces on the control surfaces were too great to operate the manual trim so they switched the automatic system on again. This sounds like a workload or focus issue with the problem distracting them from other things they should have done. Any system that might intervene in an unpredictable manner could lead to that type of brain overload even if there's a recognized and known way of getting round it.

 

[TrafficEng]

As far as I recall the Ethiopian pilots did deactivate MCAS but they'd left the throttles on full thrust, were going too fast and the forces on the control surfaces were too great to operate the manual trim so they switched the automatic system on again.

That is more or less the sequence of events, although I believe it is not clear (in the information published so far) whether the pilots were attempting manual trim using the mechanical system (using the cable-connected trim wheels) or were attempting to manually operate the electrical trim (using the control column switches). There is some ambiguity in the words extracted from the CVR transcript and either interpretation is possible. As far as I know the data which should provide a definitive answer hasn't been published yet.

This sounds like a workload or focus issue with the problem distracting them from other things they should have done. Any system that might intervene in an unpredictable manner could lead to that type of brain overload even if there's a recognized and known way of getting round it.

This is an interesting point. MCAS is in fact predictable, it can only operate if certain conditions are met, and when it operates it applies nose-down pitch that the pilots would be able to sense in the control column feel. (this sense may be degraded due to the operation of the stick shaker which is another potential aspect of the overload situation).

One of the things lost in the press coverage is that it wasn't MCAS itself that 'failed', it did as it was designed to do. The problem was with a failed AoA sensor and the way in which the system was designed to handle that situation. The AoA sensor feeds into other systems, including the computation of airspeed. The first the pilots knew of a problem was just after the point of rotation where they began getting warnings consequential to the two AoA sensors not agreeing. One of these would be 'airspeed unreliable'.

At this point in the incident, MCAS is not in the equation because the flaps were extended and the flaps being fully up is one of the requirements for MCAS to work. Therefore MCAS would not have been adding to workload. However, there were other things the pilots needed to be doing and overload appears to be a factor in these not being done.

It is arguable (we will never know exactly what the pilots were thinking) that concerns about the risk of MCAS coming into play led to the pilots being distracted away from completing the basic initial tasks. For example, attempting to engage the autopilot was an error in an unreliable airspeed situation, but might have been thought of as a sensible protection against MCAS starting to operate.

And it is for this reason that modern practice and training emphasise following procedure
rather than having detailed systems knowledge and trying to 'engineer' the aircraft in flight. That's why it might have made sense to some people not to mention MCAS in the pilot manual and training, even though that seems counterintuitive to us.

 

[JohnMcL7]

The Channel4 documentary on the 373 Max is worth a watch particularly as they have some pilots recreating the flights to show what it would have been like for the pilots of the doomed planes:

https://www.channel4.com/programmes/boeings-killer-plane-what-went-wrong/on-demand/70508-001

As times goes on and more information about what Boeing knew and how the plane was certified it gets a lot more worrying.