E.U.’s Biggest Economies Ban Boeing Max 8 Jets • Hacker News Board

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#261

Post by wikiwawa » Tue, Mar 12, 2019, 7:47 PM UTC

kharms wrote: post #189

oppositelock wrote: post #137

Earlier quoted context omitted.

The FAA and Boeing need to investigate this, but you can't make such statistical inferences, since you simply don't have enough data points. There could be no more crashes for the next few years with those 350 planes. The FAA and NTSB are very good at what they do, one of the very few examples of government services that work well together with industry, give them some time.

We have some idea of a crash rate for safe airplanes. Something like: P(Crash|Miles Flow & Hull Age) If we assume this airplane is safe, we can apply that probability to it and then ask P(2 Crashes|N Miles & 350 New Planes). You would then have a probability for this just being bad luck, and compare that against your prior that this is a safe plane. I haven’t done the math, but my gut says it would point to grounding…

The mean of a Beta Distribution (2, 348) (https://www.wolframalpha.com/input/?i=beta+distribution+(2,+...) is roughly half a percent, much higher than the 1 in 11 million across all flights (https://www.quora.com/What-is-the-probability-for-an-airplan...).

(You can pretty much always make statistical inference, with uncertainty going up with the lack of data)

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#262

Post by VBprogrammer » Tue, Mar 12, 2019, 7:48 PM UTC

sokoloff wrote: post #161

sfilargi wrote: post #146

I urge people to read the discussion by pilots regarding the 737 MAX. https://www.airlinepilotforums.com/safety/120514-ethiopian-7... It all comes down to this: "There are far too many aerodynamic bandaids that are permitted to pass the current standards. Not just this particular airplane, but a whole bunch of airframes. If the basic aerodynamics won't pass without the pushers, pullers and now AOA induced changes to…

Almost every (or perhaps every?) swept wing jet has active/positive anti-stall systems, at least a shaker and often a pusher. The wings need to be swept for efficient travel much over Mach 0.6 and these aero aids are needed for swept wings. At this point, pushers and shakers are well-accepted fixes for aero that is not inherently recoverable.

Stick pushers go all the way down to the PC12 (a single engine turboprop). Honestly there is no putting that genie back in the bottle. Getting benign stall behaviour out of a highly efficient wing is very difficult.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#263

Post by dpe82 » Tue, Mar 12, 2019, 7:49 PM UTC

nraynaud wrote: post #185

oppositelock wrote: post #137

Earlier quoted context omitted.

The FAA and Boeing need to investigate this, but you can't make such statistical inferences, since you simply don't have enough data points. There could be no more crashes for the next few years with those 350 planes. The FAA and NTSB are very good at what they do, one of the very few examples of government services that work well together with industry, give them some time.

You just can't have more data points, because flight travel is too safe. And no, the FAA is not really that good, general aviation pilots die all the time from negligence and the FAA doesn't enforce the rules when pilots violate them (in particular low altitude flying).

General aviation is actually quite safety focused. The entire culture is centered around safety; a large amount of private pilot training time is dedicated to the subject; human factors in particular. Go to any fly-in breakfast and talk to the pilots and inevitably at some point during the conversation you'll hear something about being a safe pilot.

That being said, the government gives general aviation pilots a fair amount of freedom once they get their license. There are rules and they are enforced; particularly when violations put the general public at risk. But there's also recognition that it's quite possible to regulate GA out of existence like a lot of other countries have, and that has pretty negative consequences in terms of pilot availability for other purposes. Therefore, regulations scale with the amount of danger the public is exposed to.

For example, ultralight aircraft (single place, =12,500 lbs, those that land on water, those that have old-school landing gear, etc. etc.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#264

Post by jakelarkin » Tue, Mar 12, 2019, 7:49 PM UTC

sfilargi wrote: post #146

I urge people to read the discussion by pilots regarding the 737 MAX. https://www.airlinepilotforums.com/safety/120514-ethiopian-7... It all comes down to this: "There are far too many aerodynamic bandaids that are permitted to pass the current standards. Not just this particular airplane, but a whole bunch of airframes. If the basic aerodynamics won't pass without the pushers, pullers and now AOA induced changes to…

"the plane should never have gotten the green light to fly."

this is an overstatement. airframe fuel efficiency is a undoubtable good thing vis a vis climate change, costs, etc. Obviously they've reached a point were the aerodynamic profile of a modern, efficient airframe is difficult to control via manual pilot input alone in some scenarios. This was the case for stealth technology with fighter/bomber designs.. the B2 for example has no vertical stabilizer and would not be controllable at all without fly-by-wire. Of course pilots will lament complexity and the loss of manual input. Regardless, the FAA wanted MCAS in the 737Max. Augmenting human input in the face of instrument failure and possible human failure is an extremely hard problem and uncharted territory for the industry. Doesn't at all mean its a not a worthy goal or that the designers or regulators had ill intent or negligence.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#265

Post by AWildC182 » Tue, Mar 12, 2019, 7:50 PM UTC

zanmat0 wrote: post #252

AWildC182 wrote: post #219

Earlier quoted context omitted.

It's a bit more complicated than that even. The 737 was originally designed for a very different mission than it's being used for right now. If you find pictures of the original 737-200s they look very different from the MAX line of today. It was built in an era when it was assumed that 707 and soon after 747 class airliners would serve the hubs and then smaller 737s would serve the small regional airports. As such t…

>if you do as the pilots want and achieve very high aerodynamic stability through the air-frame instead of stability control systems (fly by wire essentially) it reduces the aerodynamic efficiency of the airliner It's crazy to me that that would be an acceptable compromise.

How so?

When I say stability control, we're not generally talking about unstable or "relaxed stability" airframes where the system failing would cause a pitching moment to accelerate rather than converge and the aircraft would tumble and disintegrate. From an efficiency and handling standpoint, this would be ideal, but it's only used in tactical military aircraft where the crew can bail if there's a problem.

In most cases, we're talking about preventing stall in a swept wing aircraft. Swept wings are necessary to cruise efficiently beyond ~300mph at high altitude so they have to stay obviously, however they have VERY poor stall characteristics. As such, we have to do some things to prevent the aircraft from stalling such as playing with trim, using a stick pusher, etc.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#266

Post by VBprogrammer » Tue, Mar 12, 2019, 7:51 PM UTC

VBprogrammer wrote: post #102

The more I think about it the less likely I think the most recent crash will end up being attributed to the MCAS system. Why? Because with what we know now I could have prevented the Lion Air crash. Any airline flying these planes would have been criminally negligent to have not issued guidance to all of it's crews pointing out the system, the potential danger and the workaround. Any pilots who've gone through their…

Honestly, I'm not sure what's wrong with that statement. There is plenty of president for aircraft which went through special airworthiness investigations, the MU-2 for example, and came out the other side without fault.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#267

Post by anovikov » Tue, Mar 12, 2019, 7:51 PM UTC

zanmat0 wrote: post #252

AWildC182 wrote: post #219

Earlier quoted context omitted.

It's a bit more complicated than that even. The 737 was originally designed for a very different mission than it's being used for right now. If you find pictures of the original 737-200s they look very different from the MAX line of today. It was built in an era when it was assumed that 707 and soon after 747 class airliners would serve the hubs and then smaller 737s would serve the small regional airports. As such t…

>if you do as the pilots want and achieve very high aerodynamic stability through the air-frame instead of stability control systems (fly by wire essentially) it reduces the aerodynamic efficiency of the airliner It's crazy to me that that would be an acceptable compromise.

Obviously stability has to be achieved through fly by wire tech. Doing it through natural aerodynamic stability is a waste of resources of insane proportions as such airframes induce more drag and burn more fuel. If this sounds too scary for people in a forum of software developers it only puts a shame on our profession, from ourselves.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#268

Post by Maken » Tue, Mar 12, 2019, 7:53 PM UTC

hexane360 wrote: post #239

freehunter wrote: post #220

Earlier quoted context omitted.

The FAA is not an agency that should be assuming something is safe by default. It is an agency that should be assuming something is unsafe by default and demanding the manufacturer prove it is safe. If it's random chance, Boeing should be able to prove it is random chance. Until then, the FAA should ground them.

How do you suggest Boeing "prove" that there are no links between the events? You can't prove the null hypothesis.

They can prove the causes were different in each case.

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#269

Post by DuskStar » Tue, Mar 12, 2019, 7:55 PM UTC

outworlder wrote: post #192

anoncoward111 wrote: post #135

Earlier quoted context omitted.

I agree, in my eyes it is debate between "the plane is not safe to fly by anyone" and "the plane is safe to fly with additional training, when given" If the 737 MAX planes remain in the air in the USA, Boeing and US Govt are de facto saying "third world pilots clearly just don't understand how to fly our planes". If they ground the planes, they de facto admit there is an actual safety issue.

> "the plane is safe to fly with additional training, when given" Here's the thing. The additional training is not strictly necessary. The same procedures pilots are already trained for in previous models should have saved the aircraft. Unless investigations turn up a new problem. Of course, one could argue that, by disclosure changes to the system, that the pilots would be able to react faster. But that's not really…

It feels to me like Air France Flight 447 [0] - there was a flight computer behavior that the pilots didn't know about, but nonetheless following normal procedures would have prevented the crash. (For AF 447 that would have been "point the nose down to recover from a stall", for Lion Air 610 it was "check the trim wheel - you know, that thing that moves right by your knee - if pitch control is abnormal") Unfortunately, as we add more and more safety systems to planes people seem to be forgetting how to compensate for when the systems fail...

0: https://en.wikipedia.org/wiki/Air_France_Flight_447

Re: E.U.’s Biggest Economies Ban Boeing Max 8 Jets

#270

Post by erokar » Tue, Mar 12, 2019, 7:55 PM UTC

jakelarkin wrote: post #264

sfilargi wrote: post #146

I urge people to read the discussion by pilots regarding the 737 MAX. https://www.airlinepilotforums.com/safety/120514-ethiopian-7... It all comes down to this: "There are far too many aerodynamic bandaids that are permitted to pass the current standards. Not just this particular airplane, but a whole bunch of airframes. If the basic aerodynamics won't pass without the pushers, pullers and now AOA induced changes to…

"the plane should never have gotten the green light to fly." this is an overstatement. airframe fuel efficiency is a undoubtable good thing vis a vis climate change, costs, etc. Obviously they've reached a point were the aerodynamic profile of a modern, efficient airframe is difficult to control via manual pilot input alone in some scenarios. This was the case for stealth technology with fighter/bomber designs.. the…

That's not really the problem with the B737 MAX though. It's not inherently unstable like e.g. a fighter. The issue is that they had to fit the engines in front of the wings, and this will create a significant pitch-up if thrust is added abruptly, e.g. in a go-around.

To counteract this they introduced the MCAS system. They would not have needed this if they hadn't "retrofitted" big engines on an old airplane design, but instead started from scratch. The B737 MAX is not really a modern aircraft, but a heavily modded old design.