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chrisg

Problems with the 737MAX ?

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The 737 Max8 was created with trying avoid FAA re certification tests in mind to cut costs and time to get to production because they got in a panic when the A320 came out.

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Well,

 

The 320 is a family of aircraft that Boeing have been in competition with for years J. Whilst Airbus have jiggled around and produced different versions, the 319 for example, they are nonetheless all of the 320 family and through Airbus' initiative of fbw all of the aircraft do have a real high degree of commonality so moving between members of the family has been easy.

 

In reality it has never been quite so simple for Boeing through the tyranny of installed base, the 737 is a much older aircraft but Boeing have kept on and kept on upgrading it including moving from analogue to glass cockpit. That alone did so I discovered require a degree of re-training although not much in the way of re-certification. I don't pretend to know all the ins and outs of the FAA certification process but  there is a division between commonality of airframe and training for fairly obvious reasons.

 

Boeing fought hard to keep Airbus out of their core market, the U.S. but lost out quite strongly when American began buying 320s in large numbers - the airline particularly liked the flexibility of the various models to cover its diverse route map.

 

Overall the two companies have been neck-and-neck for years in the space that their competing products address but it would be fair to say that Boeing have been on the back-foot for a great deal of the time through not having the luxury of a clean sheep of paper that Airbus did. Boeing has stayed in the race mostly through the inertia of incumbent airlines staying with the brand and crew familiarity. The latter has long been moot though with Airbus now well entrenched in the market.

 

With hindsight Boeing probably should have bitten the bullet and moved to develop a new replacement for the 737 a long time back but instead they have kept on trying to wring more life out of the design.

 

It's ironic really that the 737 has lasted for so long in the Boeing line up when the 727,757, 767, even the 717, although that was really just a warmed over DC-9 post the merger, have come and gone. With the 747 now at or very close to EOL Boeing  are down to the 777 family and the 787 Dreamliner apart from the long, long lived 737.

 

It really is time for a new model, there is too big a gap between the 737 and the Dreamliner. The 797 might be it but that aircraft remains a bit of a mystery. Boeing had expected the MAX range to fill the gap at least for a while and the massive order book certainly supported that belief. Whether the MAX can survive the very bad press of the past few months will have to remain to be seen.

 

Cheers

 

 

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I don't blame the engineers or designers, they were put in this situation by the upper management who made these decisions. They wanted product that could be pushed out to production quick bypassing FAA time and money consuming checks. They got it, it had an Achilles heel but I suspect the people who designed the plane didn't have a real say with that MCAS fiasco.

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Totally agree, it was all driven by upper management.

 

Unless, and I doubt it, there is something hidden away about there having been any issues with MCAS during test flying then the engineers, and test pilots, would have signed the aircraft off without issue.

 

There almost certainly however was a degree of complacency involved both within Boeing and within the FAA.

 

Boeing had released multiple models of the 737 at a rather furious pace as they reacted to the Airbus initiatives, all without incident. Humans are humans, they expected nothing to go wrong, business as usual, so it was. Aircraft however have in the past, and probably will in the future, a disquieting tendency to have issues crop up down the track that were completely missed during test and development. The DC-10 was probably one of the worst but certainly not a sole example.

 

Upon reflection it might have struck people that the MAX is not simply another stretch of the venerable 737, by changing the engines and thus having to rethink their location to accommodate the long completely unnecessary low stance of the aircraft (designed that way before air bridges became the norm) several critical parameters were changed. That should really have been enough to go deeper into the certification process but the FAA trusted Boeing, who were likely not being duplicitous, simply under pressure to get the design out the door and begin filling orders.

 

Cheers

 

 

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Posted (edited)

Boeing need to change the MCAS so it can be disabled in case the sensors are bad.

The FAA have a lot of blood on their hands after past failures with other manufacturers anyway.

Edited by Jeruselem

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Hmm,

 

MCAS needs proper redundancy, AND the ability to easily disconnect it if required. I'd be more relaxed about it if the MAX were demonstrated to be safely controllable by a mundane pilot (if you can find one!! 🙂 ) with MCAS totally out of the loop.

 

That then of course begs the question why is it needed in the first place.

 

FAA is not perfect, nothing is, but it is not a very good reflection upon the industry at all that they have indeed been seen to be somewhat tardy in enforcing tighter air safety regulations even after they have passed into law.

 

It's been a subtle change that has taken decades, the UK's CAA was long regarded as the premier body in air safety but as the UK's aviation industry has faded so too has the influence of the CAA.

 

Cheers

 

 

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Yeah...

 

Definitely not a good look, especially being given 10 days to replace them on a grounded fleet - not sure of the logic of that particularly when Boeing have given no updates on looking for return to service.

 

It is going to take Boeing a damned long time to repair the brand damage and the longer the grounding goes on the longer it will take.

 

Cheers

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Geez what other faults have Boeing been hiding from us ...

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I guess the planes aren't flying so they can go fix this issue ...

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...Explains the 10 day requirement if NGs are also affected, those aren't grounded.

 

Probably not terribly serious , slats are a "nice to have" most of the time rather than essential, they just let you fly slower.

 

It does depends what the failure potential is though, jamming would be one thing mechanical failure another.

 

Cheers

 

 

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20 hours ago, Jeruselem said:

Then you got the "optional" warning lights ... if you paid for it ... it was a standard item but it was a "premium" item.

Would be odd for them to believe that as the warning light can only operate if there are two AoA sensors and I thought the standard fit out only had one AoA?

Does point more and more to Boeing have some major in house systemic failures though.

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It's murky in that regard Ali, as rather a lot of it is.

 

It seems there is indeed only one AoA sensor in the loop, at a time... If I read the spec.correctly, and it is difficult to believe sometimes what I'm reading there are two sensors but in the bare bones configuration only one is in the MCAS circuit. If you pay more you get the warning light - which seems to suggest they then hook up both sensors but only use one at a time unless one fails. Just what the failure rule is the spec does not say.

 

We discussed a few pages back that economically the wiring for both would just be there, connect if required, but really, talk about nickel and diming...

 

Potentially it goes further, to respond correctly to a system with sensor comparison would require a different software law to a single sensor system. Or perhaps no one thought of that and the single sensor system therefore became confused easily...

 

There is a very disquieting feeling of decadence going on here. I do not even pretend to think I know what the spec. is actually saying, because I don't. I'm not convinced the engineer who wrote it did either.

 

Cheers

 

 

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Yeah...

 

It's an interesting move being they buy for a diverse number of airlines as a holding group.

 

I will bet my bottom dollar that they received a massive discount to make this intent to purchase announcement, quite possibly below cost, after all Boeing still has inventory building up and nowhere to put them.

 

Cheers

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Hmm,

 

It seems Boeing are entertaining a re-branding of the the entire MAX line...

 

Marketing seem to think they can fool all of the people most of the time...

 

That company needs some radical change...

 

Cheers

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Hmm,

 

It seems trying to fix things in software alone may not cut it.

 

Not hugely surprising, to address all possible scenarios it is quite likely they will uncover possibilities that had not been considered.

 

Boeing are beginning to run out of room for aircraft, even though they have slowed production.

 

Cheers

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12 minutes ago, chrisg said:

Hmm,

 

It seems trying to fix things in software alone may not cut it.

 

Not hugely surprising, to address all possible scenarios it is quite likely they will uncover possibilities that had not been considered.

 

Boeing are beginning to run out of room for aircraft, even though they have slowed production.

 

Cheers

 

The problem is balance of the plane ... which was flawed, the software masks the problem.

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True enough but can it mask the issue under all circumstances ?Apparently not.

 

It's a subtly difficult problem for Boeing in more ways than one. a permanent change of trim by perhaps realigning the tailplane would most certainly fix the issue across a wide rang of airspeeds, although probably not so much at high mach numbers but it would be at the expense of an increase in drag which in turn would reduce the range and the fuel efficiency.

 

In reality most of the time MCAS isn't doing much of anything at all but when it does it is or can be too aggressive. However if it were really required rather than reacting to bad input it might actually need to be rapid and aggressive.

 

It would be nicest to just get the band-aid off the aircraft but they can't without major design changes.

 

A bit of a lose-lose situation.

 

Cheers

 

 

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Apparently the 737 had low hanging engines so they could be serviced more easily, unlike the Airbus which has their engines higher up. That in the end cause the minor change to moving the engine upwards causing the issues with imbalances Max series as the new engines were bigger and fatter.

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Um no,

 

The 737 design is old, it comes of an era before air bridges so it was deliberately built to sit low to the ground so that it was only a short climb up the steps to get on board after walking across the tarmac.

 

Boeing didn't really seem to stick to that, Adelaide had no air bridges for a long, long time, Darwin the same, so you walked out to a long climb into 727s.

 

These days in most of the world it doesn't matter but they went to very great lengths to give it a low profile, even flattening the underside of the engine nacelles.

 

Finally with the MAX they had to go to a new generation larger diameter engine and the only way to keep it a "737" was to reposition the engines forward and up but still keep the low undercarriage and, within FAA guidelines, claim it as just another 737 - minimal training needed to transition.

 

That changed the thrust line of the aircraft and began the entire software correction via MCAS in the event of the aircraft because its thrust line is non-linear should nose up sufficiently that it could reach a high enough angle of attack to stall.

 

There are many ways of looking at it but most all of them get back to Boeing being both contemptuous of pilot skills and wanting to sneak the design past the FAA - blunt but true.

 

Lots of aircraft have less than ideal trim characteristics, most require some adjustment over the course of a flight as fuel is consumed and weight shifts but 737s happen, until the MAX, to be very benign in that regard, much like the DC-3 of old if you balance it before take-off through even weight distribution you will not need to adjust trim much if at all in the course of a flight.

 

Boeing rather cynically decided pilots were so used to that they'd not bother the pilots pretty little heads about it and would use software to make it go away.

 

It is even somewhat debatable, from what I have seen, that they even made anything much of a deal about MCAS at all when submitting the design to the FAA for certification.

 

I'd suggest they should have, it's a new system, not present on any earlier 737s.

 

You could make a small case for US pilots in particular being better trained and possibly better able to deal with the control anomaly that doomed Lion and Ethiopian, but I don't really think so, the pilots in control of both had plenty of experience and it would be racist to suggest otherwise.

 

I'll make no bones about the fact that I have never liked the 737 much at all, but in general it has been reliable enough, just not as a passenger very comfortable.

 

The MAX has sort of ended that comfort factor for me.

 

I do wonder if Virgin will persist with their order because there is a very strong awareness in Australia of the MAX issues and Virgin tend not to want to wage publicity battles on behalf of manufacturers, nor should they.

 

We'll have to wait and see but right now they can walk away, although it is not quite that simple. They need, by their projections the capacity and Airbus are struggling as it is to keep up with their demand.

 

We might see quite a few older aircraft returning from the bone yards for a while and I can't say that would bother me much  🙂

 

Cheers

 

 

 

 

 

 

 

 

 

 

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Additionally the original 737 was somewhat smaller and based on the 707/727 turret, and the early engines used were low bypass turbofans which are smaller diameter.

 

I thought maybe the earliest 737 just used a turbojet, but it seems not to be the case?

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