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chrisg

Problems with the 737MAX ?

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Hmm,

 

Seems to be a lot of caution about just how effective the software fixes are going to be in this article:

 

https://www.bloomberg.com/news/articles/2019-03-15/piece-found-in-crash-wreckage-said-to-show-jet-was-set-to-dive

 

It seems to me Boeing are avoiding making any attempt to go back to basics and adjust the change in the flight characteristic the new engines introduced in the first place. Hardly surprising, that would need a substantial rebuild of all existing aircraft.

 

It does give the feeling though that MCAS is in a way a band aid, one that keeps falling off.

 

They COULD adjust for the nose up tendency by changing the centered position of the empennage but that would probably increase drag. Being the MAX is all about increased fuel efficiency and thus longer range that would not meet with much approval.

 

At core there is a primary design fault in this airframe that was set in concrete well before the prototype rolled out. Very difficult to correct for that but scrambling around now being a cat covering shit is still not producing an outcome I have much confidence in.

 

Buried at the bottom of the link is another link to an article about the crash evidence that led to the grounding. The jack screw that moves the horizontal tail was set to push the nose down, right up to impact whilst the crew fought against it.

 

Pretty hard to deny that was the main cause of the crash...

 

Cheers

 

 

 

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Interesting discussion I came across of why Boeing did not finalise 737 production at the NG, if not before, and move to a new design.

 

Essentially all about business. In the decade it would have taken Airbus would have taken over the lead with the A-320 and its descendants, Boeing could not allow that.

 

The same discussion mentions, quite correctly, that the present issues with the MAX are not insuperable and will be resolved. Simply put there is a long history in aviation of an aircraft being certified and flaws only turning up when a large enough population were in daily use. A hard lesson has been learned but the MAX can be expected to go on to a long career but Boeing are quietly saying there will be no new further evolved 737. It is indeed time to pull out a fresh sheet of paper and there will be time whilst MAX sales keep them in profit to fund the new initiative.

 

Strangely like many other articles the 737 is always referred to as the most produced airliner in history. That is not strictly correct, whilst only a few hundred DC-3s were built the essentially identical C-47 production went to over 16,000, the 737 is around 10,000. What is often forgotten is that the DC3 was preceded by the DC-2 which had a real balance problem, it took  dead weight in the nose to make it stable. The DC-3 design addressed that, evolution in action, but it was quicker to get a new model in production in those simpler times.

 

There was never anything of note wrong with the -3 that is why some are still flying. I cut my flying teeth on that beautiful aircraft. It was just in today's terms too slow and too small. Nonetheless it has often been said that the only replacement for the DC-3 is another DC-3.

 

Perhaps that will be the case with the 737 replacement but with all Boeing has learned about FBW and composites plus new more efficient engines the new aircraft will likely be the seed for a new line of designs. Just that line, as has happened with aircraft since, like the 747 and 777 especially, will be baked into the new design. The 737 never had that luxury, especially with the original decision to have the low ground clearance that came to haunt it.

 

What comes out of Boeing over the next several years should be extremely interesting, especially as Airbus are much earlier in the evolution cycles with the 3.xx family.

 

A tragic way to force the next step but rarely does some good not come out of the bad.

 

Cheers

 

 

 

 

 

 

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On 3/17/2019 at 10:36 AM, chrisg said:

The jack screw that moves the horizontal tail was set to push the nose down, right up to impact whilst the crew fought against it.

YI yi yi, that's not good at all.

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No Ali.

 

Not the same thing at all but an Alaska Airlines crash back in 2000 was caused by the elevator jack screw.

 

In that case it was poor maintenance of the mechanism so nothing like this crash but if anything is going to survive a near vertical crash, caused by excessive pitch down, which was the case With Alaska, it will be sturdy stuff in the tail area. A jack screw is a very solid item.

 

I don't know if it was recovered from Lion Air or if it was intact enough to reveal it was causing strong pitch down.

 

Cheers

 

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Wow....

 

https://www.news.com.au/technology/innovation/inventions/how-a-confused-ai-may-have-fought-pilots-attempting-to-save-boeing-737-max8s/news-story/bf0d102f699905e5aa8d1f6d65f4c27e

 

The Seattle Times is usually very supportive of Boeing, major employer in the area, but their people are very aviation savvy as well

 

Sleepless nights coming in Chicago, if they were not already.

 

Boeing moved the HQ there some years ago, tax reasons I think but major manufacturing whilst very distributed, centres on Seattle.

 

Cheers

 

 

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On 3/18/2019 at 11:05 AM, chrisg said:

Simply put there is a long history in aviation of an aircraft being certified and flaws only turning up when a large enough population were in daily use

 

Maybe so, but their QA/Product Validation testing at R&D level when they were looking at signing off on a single sensor hence being the critical input signal device is demonstrably flawed.  That should never ever have happened or even be allowed to happen, particularly if there's already been an example of this sensor acting up in the wild.

 

Balls need to be seriously nailed to the wall for everyone involved on that decision-making process.

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Totally agree Merlin, it is becoming very apparent that the FAA and Boeing have been getting far too cosy with each other.

 

For all I know that might be similar with Airbus in Europe but if so perhaps this will be a wake-up call for them as well.

 

Cheers

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FAA in the past has too slow to act when they knew of flaws in planes but took far too long to get anything done.

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Hmm,

 

Still begs the question if you need to actually turn the bloody thing off to stop it committing Hare Kiri but the aircraft is then flyable why did you need the damned thing in the first place ?

 

I'd suspect the answer is money  and motive - a redesign of the 737 planform to sort out the effect of the bigger engines whilst still giving them ground clearance would have been quite expensive and the certification would have been more thorough.

 

The 737 MAX seems to be in a way inherently unstable in some parts of the flight regime. Not badly so, an F-16 with the CCV out to lunch takes a genius to keep it in the air and down to a safe landing but it begs another question: Is MCAS actually making much smaller adjustments a lot of the time at certain flight times ? If so, and I'll keep an open mind on that then the certification should never have been treated as a rubber stamp on a stretch of an already certified airframe - it would be a long way to being a new aircraft, but done on the cheap.

 

Cheers

 

 

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Yeah J, which puts the ball back in Boeing's court.

 

I already described how experienced 737 pilots found the 737MAX manual inadequate and confusing, especially with respect to MCAS.

 

However looking up the quick-ref is not unusual when a little seen situation presents, much like check lists in a way but indexed. Apparently it was very little help with an MCAS issue and the Lion Air crew were already in dire straits when they turned to looking at it after trying everything they could think of.

 

Training or ease of transition was a major selling feature for the MAX but it is becoming apparent that Boeing perhaps even attempted to make light of the changes from the 737 predecessors to the MAX.

 

A significant engine change, a change in weight distribution and thrust line plus a new addition to the auto systems that confusingly can continue to be in the loop, or so it seems, even when the autopilot is disengaged is not "small changes" and it is difficult to in many ways think of it as a simple set of variations or enhancements of  the same aircraft.

 

The fact that a dead heading pilot knew to actually shut down MCAS to sort out the issue on the same aircraft on an earlier flight is telling in many ways. There is no mention of if the pilot was from Lion Air, perhaps not, airlines often extend a courtesy jump seat ride to other carrier's crew.

 

The fact that there is no simple means to turn off MCAS apart from killing it is frankly bizarre, also taking it out of the loop seems to leave the autopilot still available from what can be interpreted. That really makes it a separate system, not just part of the suite that is autopilot.  No one thinks of a stick shaker or stick pusher as part of the autopilot in fact those are particularly in the loop when the aircraft is being hand flown post-take off. That's where the control problems that caused these crashes presented so just why should MCAS be integrated to the autopilot but not shakers and pushers. ?

 

Incidentally those are usually combined. An impending stall is often not readily felt in power control systems so a shaker provides an artificial feed-back of how a stall feels on a manually controlled aircraft. If you ignore it the stick can be pushed forward which is the natural thing to do. But on any aircraft with those systems that I've flown you can readily turn them off if you already know and want to be riding the ragged edge of a stall .Ttight field for example or needing a steep near stall climb to avoid terrain. Even so most pushers do not operate on approach, hardly what you want descending close to the ground.

 

I had this whole debate brought up to me in my own context by a friend a couple of days ago.

 

For a time I flew a variety of Learjets on charter work.  I flew 24 and 25 series versions, very similar so no big deal to move between them. When Lear went through a series of acquisitions to now be a part of Bombardier the series went on through numerous models. Later ones bore very little resemblance to the 2.xx series. Lear however were always pedantic , 24 to 25 a minor conversion but even up to the later 2.xxs it was a full training course even though they were really not much different in the end. They also were far less successful. 3 series and beyond it is apparently from the ground up training, never flown them.  Those are rather simpler aircraft to fly than a 737.

 

It may not be a fair comparison but just how Boeing have fobbed the MAX of as being just another 737 is becoming more and more a very misleading description.

 

Airbus have the advantage of a much younger family that was deliberately conceived to be FBW and to have very high commonality across a broad number of models. Boeing's vision of the 737 way back when was nothing like that at all.

 

A hard lesson to learn, cant say I like watching Boeing wriggling  much but they have brought it upon themselves and cost lives.

 

Cheers

 

 

 

 

 

 

 

 

 

 

 

 

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Looks like China isn't buying anymore Max8s either ... as part of this trade war

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Boeing were charging extra for "optional" safety features in the Max 8s. Well if you're a tightass airline who doesn't want pay extra for anything, I guess you don't get that feature! And that feature just happened to be one which could saved the crashed planes.

https://www.popularmechanics.com/flight/airlines/a26899044/boeing-charged-extra-safety-feature/

Edited by Jeruselem

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