Lion Air crash: Jakarta Boeing 737 'had prior instrument error'

[NiHaoMike]

how would you get power to the rotor without brushes? gearbox and bearing seals, why? it is a sealed unit

Brushless resolvers work with the drive coil on the stator and the rotor is just a piece of steel shaped such that it alters the coupling between the drive coil and sense coils as it turns.

[langwadt]

how would you get power to the rotor without brushes? gearbox and bearing seals, why? it is a sealed unit

Brushless resolvers work with the drive coil on the stator and the rotor is just a piece of steel shaped such that it alters the coupling between the drive coil and sense coils as it turns.

are you sure?

[floobydust]

AoA sensors seem to experience wide temperature swings, water, ice, birds, lightning and static discharges - so they don't use semiconductors in them. Old Russian AoA sensors use a quad wirewound potentiometer.

My beef is any loose strand of wire, plastic or metal chip can get in the gears, stick to the lube and cause troubles. There's so much manual assembly that a flake of anything could get loose. Why is it constructed like a Grandfather clock?
I find setscrews are terrible for holding something to a shaft, like a gear on a shaft. Dissimilar metals, like steel and aluminum expand/contract at different rates and they work loose. There's no chromate finish or Alodine in the AoA sensor that AvE takes apart. I could go on, but the Rosemounts look cheap and antiquated.

AoA manufacturing error  FAA directive for Cirrus jets with Aerosonic AoA sensor where the vane setscrew was not properly tightened and no Locktite applied.


Oh look, another copy pasta wall of text. Just a reminder, the stance is:
"Muilenburg insisted that MCAS system “was designed per our standards” and followed proper certification procedures."
Boeing was unable to find any "technical slip or gap" in building its MCAS software.

Relying on one sensor is going to be interesting to defend, Mr. CEO.

[GeorgeOfTheJungle]

The pilots are the last line of defense.

[dzseki]

The pilots are the last line of defense.

And the first to blame, right? 

[GeorgeOfTheJungle]

The plane had a fault but did not have to crash... Blame Boeing for the fault, blame the pilots for their wrongdoing.

[GeorgeOfTheJungle]

Russian style AoA sensor, 4 potentiometers:

[dzseki]

The plane had a fault but did not have to crash... Blame Boeing for the fault, blame them for their wrongdoing.

It would be interesting to see statistics about airplane incidents with percentages divided between:
where the plane...
- had "minor" fault and the pilots did not manage to solve the problem (but they "should" or "could").
- had NO fault, but the pilots still crached the plane.
- had major fault (there was no way to save the plane by pilots).
- had "minor" fault but the pilots saved the day.

I don't have any number at hand, but I feel that the great majority of the accidents fell into the first two categories.

[chris_leyson]

I wasn't surprised at what AvE found in his teardown of a Lockheed C130 AoA sensor. Nearly 50 years ago I scored a cockpit direction indicator for not very much that I found in a scrap bin at a local electronics retailer. Made by Smiths Industries, it had two resolvers a rotary damper and a two phase motor lots of gearing and generally mechanical porn. The damper was just a copper cylinder mounted on a shaft with a permanent magnet stator to generate eddy currents and the 3 phase brushed resolvers were built in the same way as in AvE's teardown. The AoA sensor in AvE's teardown would have been electrically, pressure, humidity and temperature tested and probably a lot more. Maybe some of the design parameters would have been tested during development and would be "guaranteed by design", like a bird strike for example. The aircraft industry have been using 3 phase 400Hz resolvers for what must be 80 years or more without any problems.

[floobydust]

Don't fall into the same trap Boeing is exploiting - some old design or product must be safe because of very few or no incidents over many decades.

The problem with that mindset is any engineering changes bring you back to square one, where you have to evaluate their impact on safety, from scratch. Even though it has the legacy model number, or uses proven physics, that one change can make something unsafe.

Re-evaluating or doing a new safety assessment is time consuming and expensive so it's best to workaround it. This is a common management ploy to rush getting product to market.
Another method is to under-categorize the system change as nothing important, doesn't affect safety, the pilots should be able to handle it, kind of thinking.

You end up with a non-redundant (sensor) MCAS system that flies under the certification radar and avoids the full safety assessment it required.

We don't know the AoA sensor changes over the years, but what cost-improvements have been done to them?
Since 2004, over 200 reports of AoA sensor problems, much fewer for Boeing: FAA Service Difficulty Reporting

Why are they malfunctioning so often? Cheapness? Killer birds hitting them?
Or an industry content to sit on it's ass and do nothing to improve the design and manufacturing.
If only 0.001% of the litigation dollars was instead spent on R&D towards better AoA sensors.

[soldar]

The pilots are the last line of defense.

Which is why you would want them to get all the training they can use and yet Boeing denied any training was necessary because this NEW plane handled just like the OLD plane. Which was a lie. A lie that cost lives.

[MT]

MCAS assisted by faulty AOC caused 737 Brax to slide into river! Its awful! Pilots rescued plane and passengers! Hallelujah!

[soldar]

I believe the plane in Florida was a regular Boeing 737 and not a 737 MAX. It seems it skidded along the runway and into the river so it was not anything to do with flight. It landed in a storm on a wet runway and could not stop in time.

[tooki]

MCAS assisted by faulty AOC caused 737 Brax to slide into river! Its awful! Pilots rescued plane and passengers! Hallelujah!

No, I can guarantee you that the aircraft in question did not fail because of MCAS, because it didn't have MCAS, since it's not a 737 MAX, since the FAA has not un-grounded the MAX yet.

[windsmurf]

MCAS assisted by faulty AOC caused 737 Brax to slide into river! Its awful! Pilots rescued plane and passengers! Hallelujah!

Trump?

[Brumby]

MCAS assisted by faulty AOC caused 737 Brax to slide into river! Its awful! Pilots rescued plane and passengers! Hallelujah!

What a stupid thing to say.  Shows you have NO understanding.  Your credibility is now officially zero.

[Yansi]

The "rat" look is sometimes what people want. Metal chips, coolant, oil, grease are messy. AvE's slang also seems to be part of a rough, unrefined approach contrasting the precise works that he's looking at. I've seen a few youtubers take on a persona to stand out.

That particular AoA sensor is primitive engineering by any means.
The slip-ring on the Litton resolver looks like something out of a cheap toy motor, with a bit of gold plating. Why isn't it brushless?
Open gears? Put them in a gearbox so any particles don't jam the sensor. How about a double seal on some bearings.
I bet the thing is worth a small fortune but reliability isn't there. Something is wrong with the Rosemount/UTC AoA sensors on the max.
ET302 suspected a bird hit it and broke off the vane but the engine intake is nearby with no fan damage? and the erroneous readings are not consistent with a broken vane.

how would you get power to the rotor without brushes? gearbox and bearing seals, why? it is a sealed unit

They have provably used the same sensor for 50 years with no issues

Brushless resolvers are the industry-wide standard these days, used in many many servo-motors, where absolute position sensing is required.

[windsmurf]

Boeing Knew About Safety-Alert Problem for a Year Before Telling FAA

[BradC]

Boeing Knew About Safety-Alert Problem for a Year Before Telling FAA

So if I'm reading that right the AOA disagree alert was supposed to be a standard feature that just didn't work? I'm having difficulty with that concept. Not because it isn't plausible, but the enormity of what that actually means. "We knew it didn't work correctly (or at all), but we let it slide". Surely that's erroneous.

[Gyro]

Also reported by the BBC:  https://www.bbc.co.uk/news/business-48174797

Boeing has admitted that it knew about a problem with its 737 Max jets a year before the aircraft was involved in two fatal accidents, but took no action.

The firm said it had inadvertently made an alarm feature optional instead of standard, but insisted that this did not jeopardise flight safety.

How do you 'inadvertently' turn a standard feature into an extra cost ($80k/plane) option? 


EDIT: A case of 'please don't request this option, it doesn't work', or 'please fund us to make it work on your plane'(as an individual variation of the standard s/w)?

[floobydust]

Is it possible the Flight Control Computer is out of memory?

Guessing it's some 80x86 redundant, fault-tolerant clunker that was not redesigned for the 737 max in the rush to compete with Airbus.

This is the only reason I can come up with that the AoA DISAGREE annunciator does not work, known over a year ago and no fix issued. Optional AoA gauge. And the old MCAS kindergarten-grade software.
I've seen what happens when legacy embedded computers get dragged along into new products.
The clock speed is too slow, not enough RAM or FLASH- so adding features becomes a minefield. You have to cut some to make room for others.

[MT]

MCAS assisted by faulty AOC caused 737 Brax to slide into river! Its awful! Pilots rescued plane and passengers! Hallelujah!

No, I can guarantee you that the aircraft in question did not fail because of MCAS, because it didn't have MCAS, since it's not a 737 MAX, since the FAA has not un-grounded the MAX yet.

Tooki have been Honk Honk'ed!

[Yansi]

has been what?

[Gyro]

Has been Trolled seems to fit.

[raptor1956]

MCAS assisted by faulty AOC caused 737 Brax to slide into river! Its awful! Pilots rescued plane and passengers! Hallelujah!

There are no 737 Max AC permitted to fly outside of Boeing and there testing program -- this was not a 737 Max AC and thus did not have the MCAS system -- troll somewhere else!


Brian