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

seattletimes.com

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

#121

Post by skybrian »

CydeWeys wrote: post #106
skybrian wrote: post #97

Earlier quoted context omitted.

Just putting the safety record into context. Actually, I think if the planes can be fixed (and I'd be shocked if they couldn't), the two crashes before the fix will no longer be relevant for assessing safety.

This isn't a valid way to put it into context. It doesn't matter which countries the planes crashed in; the causes were the same and lives lost are lives lost. And air travel is so globalized these days that one crash anywhere can kill citizens of dozens of countries.

Yes, it doesn't matter which two countries it was, but it's fine to point out that many airlines in many countries didn't see these problems. The planes flew in many places every day with no trouble.

You are calling me out over nothing. This is uncharitable, to say the least. Why make trouble?

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

#122

Post by JudgeWapner »

bushido wrote: post #112
skellera wrote: post #76

Earlier quoted context omitted.

Most people don’t even think about the plane they’re flying in. It will not be that big of an issue to continue using them unless some group actively tries to warn passengers about flying in those specific planes.

It seems like this is becoming a concern now - per: https://www.cnbc.com/2019/05/07/barclays-downgrades-boeing-s... The primary reason for the downgrade being: Barclays’ survey of airline passengers says many people will avoid the 737 Max “for an extended period” once the aircraft is flying again.

this is what marketing people are paid to solve. they'll rebrand it, have some feel-good TV commercials like BP did after they dumped millions of gallons into the gulf, and somehow get on with life.

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

#123

Post by AnimalMuppet »

nwallin wrote: post #83
deskamess wrote: post #57

Earlier quoted context omitted.

Why would they not have gone with a, say, 757 MAX - it seems to fit the bill spec wise. Is it that global pilot pool is not as great for the 757 as 737?

The 757 "max" is a 767. 757s and 767s share a common type rating. It's not so much that the pilot pool is lacking, it's that a lot of airlines have a pool of existing 737 pilots already on their payroll. If you need to lay off half your employees, and replace them with an entire new pool of people, half of them are going to be terrible employees, and it will take you years to weed out the bad ones. For better or wors…

If I understand correctly, if you wanted to switch from 737s to 757s, you don't lay off your pilots and hire new ones. You take a few pilots at a time off of 737s, and spend months re-training and certifying them for 757s.

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

#124

Post by JudgeWapner »

hirowan wrote: post #101
skybrian wrote: post #97

Earlier quoted context omitted.

Just putting the safety record into context. Actually, I think if the planes can be fixed (and I'd be shocked if they couldn't), the two crashes before the fix will no longer be relevant for assessing safety.

You're putting the safety record into chauvinist context, to be exact. An AoA failure is sufficiently rare for it to have only occured in a couple of occasions in - shockingly - only a couple of countries.

actually you're being really ignorant to the fact that tons more flights originate in the US and UK so if they all have an equally-likely probability of failure, we should have seen one there first. Ethiopia and Indonesia had the first incidents. Boeing is mostly at fault here, but it may not be a coincidence that countries with lower standards of certification had the first incidents.

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

#125

Post by cesarb »

mcsoft wrote: post #44
techslave wrote: post #27

Earlier quoted context omitted.

basic principles? i think that’s a bit far. the plane isn’t inherently unstable is it? i thought it’s just the black box of MCAS that is the problem and MCAS is there to avoid a lengthy type certification. it’s completely explainable. and it wasn’t seemingly insignificant. it was for fuel efficiency. it was significant and they knew what they were doing.

They had to install MCAS because the plane was unstable in high AoA mode, i.e. during takeoff. And it was unstable because larger CFM engines could not fit under the wing anymore so they had to put it further forward and a bit up. This increased the pitch up moment when a full power is applied. Also, can't really see how the height of the fuselage above the ground affects fuel efficiency.

> They had to install MCAS because the plane was unstable in high AoA mode, i.e. during takeoff.

Forgive me if I'm missing something, but isn't MCAS disabled while the flaps are extended, which is the case during takeoff and landing?

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

#126

Post by quickthrower2 »

oldmantaiter wrote: post #59

Off topic, but oh man does that website embody everything that is wrong with display advertising. Left the site open for 6 minutes: 8000 requests, 100MB transferred and a memory footprint of 700MB for that tab and climbing. Absolute garbage.

Yeah each day I’d feel less and less guilty using adblockers and router rules.

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

#127

Post by jsjohnst »

TheOtherHobbes wrote: post #37
rootusrootus wrote: post #21

Earlier quoted context omitted.

But at least one aircrew in the real world actually succeeded.

Debugging flight systems while the lives of 189 people are hanging in the balance is not something that should be encouraged.

Depends on your definition of “debugging”. That’s actually the entire job of a pilot in the plane during flight, to be ready to respond when something goes wrong.

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

#128

Post by breatheoften »

Taking a forward view — I think FAA needs a way to defray the impact of operational costs by incentivizing the uptake of changes that produce safety improvements.

The ultimate economic reasoning for the 737 MAX was entirely to reduce operational cost: “give us a plane with better fuel efficiency that we don’t have to pay to train pilots for!”. This is actually a deeply broken incentive that, I think this case shows, should not exist. The plane delivered is objectively far worse than it _could be_ were it not for the need to reduce operational cost.

Ultimately — some large portion of that operational cost is induced as a result of the need to comply with safety regulations. That creates downward pressure on unecessary experimentation but also has created this very perverse incentive to design planes that are _deliberately_ not as safe as they could be given application of some approximation to “our best engineering knowledge”.

Pretty early on in the design process for the 737 MAX — there shouldve been a meeting with regulators. The regulators should’ve been presented with this option and the design and economic reasoning for it — and they should’ve also been presented with another option wherein there was a relaxing of the need to defuse operational costs. The regulators should be empowered to then say “don’t build this broken plane, build the safer plane and we will introduce tax credits sufficient to help offset the airlines retraining costs.”

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

#129

Post by WrtCdEvrydy »

alexis_fr wrote: post #53
djsumdog wrote: post #33

Earlier quoted context omitted.

I'm actually wondering if the 737 MAX will make it back into service. Every single one of these planes will need to be flow back to one of their maintenance centers (like the one south of Seattle) and undergo retrofits. Hopefully it will result in Bowing being required to make this a new plane and a lot of pilot re-certification. If it does return to the market, I wonder if they'll be forced to rebrand it. It's obvio…

Bugs tend to appear in Poisson law of probability: 2 big bugs immediately, 2 others a few weeks later, but that means there are hundreds of them to discover over a period of 5 years (until the D-check). So, in all probability, we don’t even know the list of fatal flaws even yet!

It's a 737 with lower engines.

The flaw is using software to fix a hardware issue.

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

#130

Post by Obi_Juan_Kenobi »

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…

> These engines moving made the plane more vulnerable to a stall situation.

I don't think this is correct. A lot is being made about the engine move with regard to aerodynamic behavior, but it doesn't seem at all outside of the bounds of what is considered standard. Pilots report that a similar 'light stick feel' at high AoA is already present in aircraft like the 757.

It's not that the aerodynamic change was worse or better, it's simply that it was a change at all. MCAS was there to satisfy the type rating. MCAS is not anti-stall.

The crucial mistake appears to be the extreme failure mode of the system; it is permitted to input high stabilizer trim angles without limit. Without any kind of restriction, the failure goes from annoying (pull up on flight stick + fiddle with stab control until you solve it) to the deadly crashes we've seen where pilots are in extremely tricky situations.

The fix could be as simple as making MCAS cutout in the case of an AoA disagree (no real hardware changes here) as well as limiting the input of extreme trim angles.

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