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Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

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Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#221

Post by bronson »

manigandham wrote: post #210
michaelmrose wrote: post #205

Earlier quoted context omitted.

Nobody who isn't an engineer wants is terribly interested in the argument that a model of plane that has killed 2 planes full of people recently is in anyone's opinion safe. Personally I won't fly on one in my lifetime. I'll leave the analysis of why to others to figure out why I fly on other airplanes. Incidentally I have seen pilots argue that the max is inherently unsafe on this forum which is probably why people…

Actual engineers do care about the "why" since that's what matters. Otherwise don't bother flying on any aircraft since all models have crashed at some point.

Your second sentence is too glib. By just about any statistic you want to look at, the MAX-8 has an abysmal safety record. Probably worse than any other aircraft in revenue flight.

It's perfectly rational to look at the results, regardless of "why", and decide that the risk is just too great.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#222

Post by _ph_ »

bronson wrote: post #218
manigandham wrote: post #204

Earlier quoted context omitted.

The aircraft flies fine. MCAS is a stability control system that applies in certain cases (full power, high angle of attack) where the nose pitches up. It may lead to a stall but that's not what it's correcting for and it doesn't just happen during level flight. If the MCAS system was disabled then pilots handle it manually. Trim is not an exotic concept and just takes training and understanding of the operating char…

The aircraft flies fine in most flight profiles, yes. At high angle of attack, the MAX-8 is more unstable than pilots were trained to expect. And the MCAS has done an absolutely miserable job of fixing this. Worst case scenario bad: it caused the loss of two airplanes that, if the MCAS had never been added to the MAX-8, would have reached their destinations just fine. Until the it flies predictably in every flight pr…

Alternatively just train the pilots on the behavior in the domain where MCAS would activate. MCAS main purpose is to lower the training requirements.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#223

Post by avar »

cletus wrote: post #118

So a lot is known at this point: 1. The A320neo caught Boeing completely off-guard; 2. The threat of the likes of American Airlines (already a mixed Airbus/Boeing customer and the largest airline in the world) placing a large A320neo order for regional aircraft operations scared the bejesus out of Boeing management; 3. For airlines like Southwest that are pure 737, the prospect of adding a plane that didn't share a c…

    >  the plane CLEARLY flies differently to a 737[...]
There's no such thing as "a 737". A 737-600 is 31 meters long[1], and a 737-900ER is 42 meters. Both share the same type rating with the MAX[2], and have the same 36 meter wingspan.

That's going from a length:span ratio of 0.86:1 to 1.17:1, you think those sort of airframe changes don't make for a plane that flies differently?

Maybe the whole notion of a "common type rating" is foolish, and pilots should need to re-train from scratch for the smallest of changes. Change the paint job? New type!

There's a lot of "the engines moved!" discussion around the 737 MAX which seems to be ignorant of decades of significant airframe changes not impacting type, to little apparent ill effect until now.

1. https://en.wikipedia.org/wiki/Boeing_737_Next_Generation#Spe...

2. https://en.wikipedia.org/wiki/Boeing_737_MAX#Specifications

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#224

Post by sho »

massysett wrote: post #46
djsumdog wrote: post #28

What is the endgame now for 737 MAX planes? Every airline using them has had several weeks to totally reorganize to deal with these huge missing parts of their fleets. Boeing keeps talking about fixing them and putting them back in the air, but I dunno. At this point, it should be agreed the fundamental design flaws are serious, and Boeing should have simply made a brand new plane, with much more modern controls and…

These planes cost at least $100 million each. They will fix them and get them flying again.

Minor quibble - but no airline actually pays that much. A rough rule of thumb is around 50% of "list" price. In the real world, they're around USD$50-60m each.

Your point still stands, of course.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#225

Post by thereare5lights »

erentz wrote: post #43
djsumdog wrote: post #28

What is the endgame now for 737 MAX planes? Every airline using them has had several weeks to totally reorganize to deal with these huge missing parts of their fleets. Boeing keeps talking about fixing them and putting them back in the air, but I dunno. At this point, it should be agreed the fundamental design flaws are serious, and Boeing should have simply made a brand new plane, with much more modern controls and…

> What is the endgame now for 737 MAX planes? The bugs will be addressed and they'll still fly. Airlines have no choice, there's a limited capacity in the world for airplane construction, several thousands of orders on the books for the 737 and 320 waiting to be filled. What can an airline do? They can cut back some orders but not all orders. > I'd honestly like to see the 737 MAX taken out of service and Boeing simp…

> Airlines have no choice, there's a limited capacity in the world for airplane construction,

No choice? It's a choice between risking passengers' lives and money. Be real about what the choice is.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#226

Post by aerodude »

blendo wrote: post #135
hirowan wrote: post #100

Earlier quoted context omitted.

MCAS has absolutely nothing to do with maintaining commonality. An aircraft with decreasing stick force on approach to stall in its normal mode of operation would've never been certificated.

As I understand it, previous 737s did maintain stick force on approach to stall. The MAX, due to different engines, has decreasing stick forces when the lightly loaded, and/or with an aft center of gravity. My simple solution? Disable MCAS, keep the stick trim switches as on previous 737s, and require MAXs to only fly with a forward CG. 2000 kg of forward ballast might work. Even better, reduce aft weight by increasi…

Wouldn't both of those solutions undermine the advantage of the airframe, which is the fuel cost savings of the larger engines?

That said, I think seating pitch and spacing is definitely a conversation that needs to be had. I'm an average-sized guy, and I have a hard time with today's airline seats. I would hate to see what it's like for someone taller. There definitely needs to be more stringent regulation of airline seating to mitigate ever-vanishing personal space.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#227

Post by rocqua »

_ph_ wrote: post #222
bronson wrote: post #218

Earlier quoted context omitted.

The aircraft flies fine in most flight profiles, yes. At high angle of attack, the MAX-8 is more unstable than pilots were trained to expect. And the MCAS has done an absolutely miserable job of fixing this. Worst case scenario bad: it caused the loss of two airplanes that, if the MCAS had never been added to the MAX-8, would have reached their destinations just fine. Until the it flies predictably in every flight pr…

Alternatively just train the pilots on the behavior in the domain where MCAS would activate. MCAS main purpose is to lower the training requirements.

Not quite if I am to believe other HN comments. The thing MCAS compensates for is that, in certain cases, as you pitch up more, the pressure on the stick decreases. This feels to pilots like leveling out, which is dangerous. MCAS was designed to counter this.

The specific design of MCAS and not adding any new procedures, was to lower the training requirements. Specifically, anyone certified on the old 737 was still certified on the max.

If they had improved the interface of MCAS and changed the procedure for runaway trim, it would have required more training. However, without MCAS or another remedy for the 'decreasing stick pressure at increasing pitch' problem, the plane would not have been allowed to fly at all.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#228

Post by bronson »

Aeolun wrote: post #169
cjbprime wrote: post #156

Earlier quoted context omitted.

I can help with that -- the MAX is suffering hull losses per flight completed at a rate about 100x that of comparable planes like the A320. Totally off the charts.

It’s such a weird statistic to use though. One crash takes a really long time to recover from in that score. So even if the 737 Max was magically fixed tomorrow, the score wouldn’t change.

> One crash takes a really long time to recover from in that score.

As it should be. That's how important safety is. Boeing brought this on themselves by letting a second airplane crash before responding properly.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#229

Post by simion314 »

manigandham wrote: post #208
simion314 wrote: post #201

Earlier quoted context omitted.

>There's no fundamental design flaw, the aircraft is sound. You can claim this because now all the FAA approvals for this planes, all tests need to be redone by somebody that we can trust. Sure they but larger engines, did they improved the supports, the bolts ,FAA "checked" this updates but can you trust them? the idea that MCAS is the only subsystem that must be fixed and checked is flawed, everything needs to be t…

The fault here is complex and involves the architecture of the system, the sensors, and how the behavior mimicked the older designed which reduced the training required which meant pilots were not as aware of both the changed flight characteristics and the MCAS itself. Sure the FAA definitely needs to be questioned as to how they let this through without enough redundancy and pilot awareness but the engines are not t…

Why should I trust you or FAA that the engine, the engine mounts and all the new updates related to this larger engines were tested when we know from previous articles that hings were rushed and stuff like the fire suppression system was not OK and the engineer was changed because was objecting.

I imagine that putting a larger engine is not as easy, isn't a larger engine heavier? the forces larger? Don't you need to test the engine supports, the wings, all the related mechanical support structure.

Your theory that only MCAS is an issue is already false since it was found that without autopilot 2 humans don't have the physical force to control the plane , so probably a new requirement in the FAA should be added that with autopilot off 1 single pilot should be able to control the plane. You may say this is related to MCAS but6 it is obvious that this item was not in any checklist for things to test so even with a working MCAS but other emergency where autopilot would be turned off you would get in the same situation.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#230

Post by Dylan16807 »

rocqua wrote: post #227
_ph_ wrote: post #222

Earlier quoted context omitted.

Alternatively just train the pilots on the behavior in the domain where MCAS would activate. MCAS main purpose is to lower the training requirements.

Not quite if I am to believe other HN comments. The thing MCAS compensates for is that, in certain cases, as you pitch up more, the pressure on the stick decreases. This feels to pilots like leveling out, which is dangerous. MCAS was designed to counter this. The specific design of MCAS and not adding any new procedures, was to lower the training requirements. Specifically, anyone certified on the old 737 was still c…

> This feels to pilots like leveling out, which is dangerous. MCAS was designed to counter this.

Pilots are trained extensively not to trust what motion feels like, and to use the horizon and instruments. An adjustment in stick pressure is not a notable new threat, they just need to be trained for the plane's behavior.

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