Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Boeing 737 Max pilots complained to feds for months about suspected safety flaw

dallasnews.com

Post reply on HN
Print view View original

201–210 of 307 posts

Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw

#201

Post by inferiorhuman »

siwatanejo wrote: post #133
lsh123 wrote: post #101

Earlier quoted context omitted.

Incorrect analogy. Runaway trim is a common and known problem with a solution to pull the electric trim breaker. MCAS failure is very similar in appearance and have exactly the same solution.

Can you think of a better car analogy? I'm genuinely curious.

All cars that drive only the front wheels experience a phenomenon called torque steer: as the engine produces more power the car tends to veer off into one direction or another. This is typically only a problem with more powerful engines.

Many manufacturers will use different length driveshafts to each front wheel, maybe they'll use fancy mounting hardware, maybe they'll reduce the maximum power at low speeds, maybe they'll apply the brake on one wheel as you start to move in a direction other than where the steering wheel is pointed.

Let's say a car company put out a little front wheel drive car so powerful that simply applying the brakes or cutting power would make the car much less fun to drive. So let's say our miracle company decided to have the computer steer the car in the opposite direction when you press the accelerator pedal instead.

Then one day the dongle that determines how far you're pushing the accelerator pedal breaks. The wiper on one of the potentiometers is dirty and instead of sending no signal it's sending an erratic and inaccurate signal. It's not a problem for the engine computer, there are two pots and it's picked the good signal and limited engine power just in case. For some reason cruise control doesn't seem to work, but other than that the car seems to drive fine.

But the torque steer doohickey is using the bad signal. The bad signal is erratic and makes the computer think you're trying to accelerate rapidly and yanks the wheel to the left for no apparent reason. You yank the wheel in the other direction and the car drives fine for a bit so you continue. As you accelerate onto the freeway onramp it happens again. You yank the wheel the other way and keep going. Then you try to change lanes to pass a slow truck in front of you. It happens again, only this time as you're trying to turn left you can't counteract the insanity. Instead your car tries to make a ninety degree turn at freeway speeds.

Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw

#203

Post by [deleted] »

rootusrootus wrote: post #117
sfilargi wrote: post #99

For a car analogy, imagine Tesla creates a new model that under certain conditions tends to over-steer left. To prevent any accidents because of that, they have added a system that turns the steering wheel clockwise. To disable the system it is not enough to try to prevent by force the steering wheel from turning, but you have to press a button that disables electric steering assistance. Notice they have never briefe…

I feel like every time someone insists on making a car analogy, it just piles on more evidence that car analogies never work. At least you don't have to get a new endorsement on your license for every model of car.

[deleted]

Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw

#204

Post by smdyc1 »

balaksakrionon wrote: post #107
jashkenas wrote: post #53

Earlier quoted context omitted.

Great links! Here are the three 737-related ASRS reports that mention MCAS: ACN: 1597286 "Day 3 of 3 departing in a MAX 8 after a long overnight. I was well rested and had discussed the recent MAX 8 MCAS guidance with the Captain. On departure, we had strong crosswinds (gusts > 30 knots) directly off the right wing, however, no LLWS or Micro-burst activity was reported at the field. After verifying LNAV, selecting ge…

In ACN 1597380 - why would MCAS kick in if he wasn't manually flying (pilot states autopilot was engaged specifically to avoid MCAS)?

I'm wondering if the autopilot contains the same correction algorithm that MCAS is using.

I'm wildly speculating here, but since wing loading is also a factor in calculating the angle of attack at which a potential stall condition could occur, I'm also wondering if it relies on the accuracy of the weight and balance the pilots enter into the flight computer. Pilots have missentered such critical information before.

Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw

#205

Post by ezconnect »

dajohnson89 wrote: post #195
privong wrote: post #145

Earlier quoted context omitted.

> So 20 MAX-related issues out of ~850. How is that significant? To build on what @ggm and @siwatanejo noted. The 737 debuted in 1967, so it is 52 years old now. The 737 MAX is 2 years old. In terms of number of issues per year since the aircraft was introduced the 737 is at ~15 incidents per year and the 737 MAX is at ~10/year. But as @ggm notes, it's important to look at when in the life cycle many of the non-MAX 7…

So then why did I get downvoted so hard?

You don't seem to know how to do math

Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw

#206

Post by black-tea »

varenc wrote: post #150
dpwm wrote: post #91

Earlier quoted context omitted.

1555013 is pretty damning in telling how the airlines treated the MAX as the same type as the 737-800: "I had my first flight on the Max [to] ZZZ1. We found out we were scheduled to fly the aircraft on the way to the airport in the limo. We had a little time [to] review the essentials in the car. Otherwise we would have walked onto the plane cold.My post flight evaluation is that we lacked the knowledge to operate th…

Wow... I wonder how much of this could have been avoided if the 737-Max had just been given an entirely new model name like "738". I'd assume that when the 777's came out even pilots with experience on the 767 and other Boeing planes were still given ample training beforehand. The minor difference in the Max's model name disguises the seemingly large difference in their operation.

Generally airline pilots only fly one type of aircraft at a time. So yeah, when 777 came out some would have become 777 pilots.

Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw

#207

Post by azernik »

mobilemidget wrote: post #163
dpwm wrote: post #91

Earlier quoted context omitted.

1555013 is pretty damning in telling how the airlines treated the MAX as the same type as the 737-800: "I had my first flight on the Max [to] ZZZ1. We found out we were scheduled to fly the aircraft on the way to the airport in the limo. We had a little time [to] review the essentials in the car. Otherwise we would have walked onto the plane cold.My post flight evaluation is that we lacked the knowledge to operate th…

As a passenger I would feel safer knowing that last information and instructions are not send a day before the flight but a pilot gets actual training? Maybe that’s just me

In theory, regulators agree.

However, Boeing seems to have marketed this plane under the regulatory fiction that it was the same plane as the 737, and that therefore no retraining was needed.

Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw

#208

Post by fsloth »

selectodude wrote: post #56
jrockway wrote: post #49

Earlier quoted context omitted.

1593699 is amazing.

Probably southwest pilots. If it’s not analog it’s too much for them.

The appeal of the 737 MAX for airlines was that it was intentionally made so that you could take crews with a 737 qualification and put them in.

I.e the airlines could save money on training.

The main design constraint on that bird was that it should pass most of the old paperwork so that Boeing nor airlines would need to go through expensive training and quification.

Yet, they modified the plane quite a bit - but they could not modernize several systems since they would have to then go through rigorous and expensive testing. ..

Nobody seems to underline this fact.

I bet that's the actual reason they didn't put the automatic pitch modification system to any documentation - it would not fit on the description of "just old 737 nothing new here hop in".

Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw

#210

Post by mprev »

rectang wrote: post #171
jussij wrote: post #129

Earlier quoted context omitted.

It really does not matter what spin Boeing comes up with regarding the cause of these crashes. The reality is in a very short space of time two 737-MAX have fallen out of the sky. You only have to look back at the McDonnell Douglas DC-10 to understand once a plane gets a bad reputation, it is doomed. For an example of how this can go bad so very quickly, here in Australia this issue has become so new worthy, it's now…

The DC-10's infamous cargo door was a grievously poor design choice, violating well-understood safety principles for the sake of a little more cargo space. It's everything you fear about psychopath executives rolling the dice on safety because what do they care? The DC-10 deserved its ignominious reputation and the McDonnell-Douglas deserved every bit of the scorn they received and more.

It might turn out that the MAX situation is a similar roll of the dice.
Post reply on HN