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

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

#101

Post by lsh123 »

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…

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.

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

#102

Post by pdonis »

jashkenas wrote: post #53
tuna-piano wrote: post #30

Some context: 1. There have been 865 737 related ASRS reports since 1/1/2018 2. I don't know how to quickly separate out 737-MAX reports from the non 737-MAX reports, as the ASRS database doesn't include 737-MAX as an airplane type! From scanning, I can say that there are more than five MAX related reports, though. [1] All 865 737 reports since 1/1/2018 CSV - http://s000.tinyupload.com/index.php?file_id=5466867979406…

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…

What I'm gathering from these reports is not encouraging:

(1) The third report says that MCAS only operates in manual flight. The second report appears to confirm that since the pilot says he engaged autopilot sooner than usual to remove the possible MCAS threat.

(2) However, both the first and second reports describe uncommanded pitch down events while in autopilot. That means there is another problem in addition to the MCAS issue, since the latter should not be engaged at all when in autopilot. (If the root problem is an unreliable angle of attack sensor, that would explain both issues, since the AoA sensor would be used by the autopilot as well as by the MCAS.)

(3) We have an aircraft type that is known to have repeated uncommanded pitch down events while in autopilot, and it's still flying. Unfortunately, we already have other aircraft types (from Airbus, not Boeing) that have the same known issue that have not been grounded either. So the system as a whole simply seems to accept the risk of this happening without warning, and hoping that pilots will be able to respond as these pilots did (well done to them) and avoid an actual incident.

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

#103

Post by oliveshell »

woodrowbarlow wrote: post #95
oliveshell wrote: post #75

Earlier quoted context omitted.

> A little scary? Perhaps, but it’s not unprecedented. The B2 stealth bomber, for example, famously lacks a vertical stabilizer (tail fin) and so is inherently unstable and relies on computerized control surfaces to maintain stable flight [1]. This seems to have worked fine, although the things definitely log way fewer flight hours than an airliner. I believe several other aircraft do this as well (fighter jets and s…

i don't know anything about aircraft, but i would be inclined to think that the lack of tail fin on a B2 isn't just a design flaw or technical debt from the previous model and that there were other reasons for it.

You’re right— the B2 was designed like it was in order to minimize radar cross-section at all costs.

One could see, though, how a Boeing engineer could point to the B2 and fighters that rely on software for safe flight and say “See? They do it and it’s fine!” as a justification. Not that I’m saying that makes it right.

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

#104

Post by [deleted] »

michaelt wrote: post #93
js2 wrote: post #73

Earlier quoted context omitted.

The alternative would have been redesigning the 737 such that it would be a different plane. There are advantages to keeping it as similar as possible to the previous generation. Boeing was in a bit of a bind. They had a plane (the 737) originally designed for different requirements (the plane is low to the ground) in wide spread use that the airlines wanted them to make more fuel efficient to stay competitive with A…

I'm not clear on why having different engines, different handling and MCAS makes it not-a-new-plane, but having the landing gear extend further down would make it a new plane?

[deleted]

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

#105

Post by mannykannot »

mimixco wrote: post #82
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 both the first two cases, the pilots knew about potential MCAS issues and discussed them with each other before take-off -- and they still had (terrifying) problems.

In those cases (if they are not two reports of the same incident), while MCAS was discussed prior to the flight, the actual incident appears to be autopilot related, and there is no mention of the trim running away and having to be disabled. In fact, the Captain's report mentions that he chose to engage the autopilot earlier than usual, "to remove the possible MCAS threat."

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

#106

Post by newacct77 »

Udik wrote: post #66
ergocoder wrote: post #62

This is off topic. But I've been skeptical of the commercial aviation accident risk compared to cars. I'm not saying cars are safer. But using accident count per mileage seems a bit odd, especially when the most risky parts of flying are taking off and landing. A plane travelling 400 more miles doesn't incur much more risk. But a car travelling 400 more miles incur a much bigger risk (e.g. fatigue, car malfunctioning…

I'd say it's accidents per person/hour. And I've read somewhere that the figures used to be similar for cars and airplanes (though aircraft safety is constantly improving, cars probably less).

Accidents? Or fatalities? Cars today are certainly safer than cars 50 years ago.

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

#107

Post by balaksakrionon »

jashkenas wrote: post #53
tuna-piano wrote: post #30

Some context: 1. There have been 865 737 related ASRS reports since 1/1/2018 2. I don't know how to quickly separate out 737-MAX reports from the non 737-MAX reports, as the ASRS database doesn't include 737-MAX as an airplane type! From scanning, I can say that there are more than five MAX related reports, though. [1] All 865 737 reports since 1/1/2018 CSV - http://s000.tinyupload.com/index.php?file_id=5466867979406…

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)?

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

#108

Post by Zarel »

lutorm wrote: post #85
ergocoder wrote: post #62

This is off topic. But I've been skeptical of the commercial aviation accident risk compared to cars. I'm not saying cars are safer. But using accident count per mileage seems a bit odd, especially when the most risky parts of flying are taking off and landing. A plane travelling 400 more miles doesn't incur much more risk. But a car travelling 400 more miles incur a much bigger risk (e.g. fatigue, car malfunctioning…

The relevance of the metric depends on what you're using it for. If you decide whether to drive or fly to a destination based on how safe it is, risk/distance is a perfectly reasonable metric. Since flying is a means of transportation, it seems reasonable to judge the risk relative to the amount of transportation you get out of it. That doesn't discount the fact that most of the risk is in take-off/landing, so if you…

I'm not sure how your comment addresses the core problem that risk/distance is not a reasonable metric if long-distance driving is less risky than short-distance driving, and you apply the short-distance driving risk to long-distance driving.

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

#109

Post by fl0wenol »

dpwm wrote: post #91
ehsankia wrote: post #64

Earlier quoted context omitted.

It would be ironic if the lack of 737-MAX category for reports is why these reports never made it to the people who needed to see them, which caused the issue to go unnoticed.

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…

If you want an RCA of the last two crashes in 737 MAX's, please see the parent. Ridiculous gyrations to avoid new aircraft regulations creates dangerous scenarios for pilots and passengers.

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

#110

Post by Gibbon1 »

CamperBob2 wrote: post #70
mrpippy wrote: post #37

Earlier quoted context omitted.

MCAS can only activate when flaps are raised, it shouldn't cause any unexpected trim changes during landing. This is why the Lion Air flight had a normal takeoff/climb until they raised the flaps.

Aren't the flaps up during landing?

Flaps are deployed to lower the stall speed of the aircraft by increasing the lift coefficient of the wing at the expense of higher drag.
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