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

[SiliconWizard]

This part says a lot though:

In the event of multiple MCAS activations with repeated electric trim inputs
by flight crew without sufficient response to return the aircraft to a trimmed
state,  the  control  column  force  to  maintain  level  flight  could  eventually
increase to a level where control forces alone may not be adequate to control
the  aircraft.  The  cumulative  mis-trim  could  not  be  countered  by  using
elevator alone which is contrary to the Boeing assumption during FHA.

[bw2341]

That's absolutely abnormal and yet the crew never recalls the runaway stabilizer trim memory items nor calls for the runaway stabilizer checklist.

Warning! I’m not involved in aviation in any way. My posts may be mistaken.

My impression is that retrimming the plane is like breathing for a pilot. You climb, descend or turn and you retrim. A few minutes pass while on autopilot and you retrim. You scratch your belly and you retrim.

If you’re always adjusting the trim on instinct, what threshold do you need to notice that you are trimming more than normal?

A pilot’s insight would be enlightening. How often is normal for manual trimming? Also, how often does MCAS and the previous Speed Trim System normally activate?

My impression is that MCAS and STS would make detecting runaway stabilizer very difficult. You’re manually flying along and the trim motor activates briefly. Without hard guidelines of what’s normal, how would would you know if it’s too much?

[sokoloff]

It is close to breathing in terms of how much concentration it requires to activate, but it’s also quite normal that trimming occurs primarily around speed or configuration changes. Raise the flaps? Might need to trim. Accelerate to second stage climb, might need to trim. It’s not the case that you’d be trimming over and over, only to have the airplane trim against you (with associated audible and visual indications) right afterward.

With that amount of trim activity required without any associated configuration or speed change, it would be flagged as abnormal to most pilots.

For context only, I have about 1300 flight hours in several different high performance single and twin piston airplanes but only have somewhere around 20 jet hours, including around 5 in a level D full motion 737 sim.

[bw2341]

Wow!

Thank you for your direct insight and knowledge.

The report suggested that the stab trim motor may have gone unheard due to the noise from the continuous stick shaker activation. I found that very alarming. Wouldn’t incorrect activation of the stick shaker be serious enough to declare MAYDAY right away?

The crew of the previous flight who successfully recovered the same faulty aircraft decided to fly the whole flight with the sticker shaker activated! That seems crazy to me.

[bw2341]

To bring this report on topic on ”The biggest T&M forum on the net”, the incorrect use of an angle measuring instrument led to the faulty repair of the AoA sensor.

The approved instrument was substituted with one that had an extra switch labeled REL/ABS. If the instrument was switched out of absolute mode into relative mode by mistake, it would lead to an AoA sensor carefully aligned to a completely random incorrect angle.

[floobydust]

The repaired AoA sensor left it with a 21 degree offset, which was not noticed by Lion Air's maintenance team.
Xtra Aerospace was not qualified to do the repair of the AoA sensor in the first place, now the FAA revoked their repair certification license.

https://www.aviationtoday.com/2019/10/28/lion-air-737-max-final-accident-report-cites-aoa-sensor-mcas-as-contributing-factors

[Gyro]

Xtra Aerospace was not qualified to do the repair of the AoA sensor in the first place, now the FAA revoked their repair certification license.

In fact their web site no longer appears to exist and their parent company, Wencor Group, has no mention of them on their website. Not surprising if you get your certification pulled I suppose.

[AG6QR]

Wouldn’t incorrect activation of the stick shaker be serious enough to declare MAYDAY right away?

Probably not Mayday, perhaps Pan-pan, or maybe a routine return to the departure airport.  Particularly when combined with inappropriate trim activation with an unknown (at the time) cause, it's a matter of serious concern.

The crew of the previous flight who successfully recovered the same faulty aircraft decided to fly the whole flight with the sticker shaker activated! That seems crazy to me.

Yes, you aren't the only one who sees it that way.

[sokoloff]

The priorities, in order, are aviate, navigate, communicate.

Aviate: don’t crash the airplane
Navigate: take it where you want to go
Communicate: let ATC know what’s going on

In this case, saying or not saying Mayday has no practical effect. They were already getting everything they needed from ATC (nothing more would help). I doubt either pilot of either crew had any doubt that they were facing a serious emergency.

[bw2341]

The report addressed this topic. Yes, the pilots should have ignored ATC and kept all their attention on handling the aircraft. Instead, the pilots responded to the eight heading instructions given by ATC.

Declaring PAN PAN or MAYDAY would have kept ATC quiet, reducing their workload. ATC would have gave them priority, keeping other aircraft out of their way.

[bw2341]

Xtra Aerospace was not qualified to do the repair of the AoA sensor in the first place, now the FAA revoked their repair certification license.

This is aftermath, but the events leading up to the mistake are more subtle and insidious.

Xtra had to justify the substitution of the angle measuring equipment with documentation. The people who wrote the test equipment equivalency report were either incompetent or unqualified as they missed the extra mode switch and lower accuracy of the substitute equipment.

The report was accepted by the local FAA Flight Standards District Office, who also missed the problems.

[AG6QR]

Something to remember is that, in previous generations of the 737, a faulty AoA sensor could not cause the plane to crash.  It would cause one AoA display to be wrong, and perhaps activate one stick shaker.  That's not critical.

Only when MCAS was introduced did Boeing give a faulty AoA sensor the power to cause trim changes.  And they didn't tell anyone about it, at least not pilots or operators.

So it's understandable that people who didn't know about MCAS would be a bit unconcerned about an AoA sensor.

[bw2341]

and perhaps activate one stick shaker.

Reading these kinds of reports has made me appreciate the finer details. Yes, this kind of faulty sensor will signal a single computer out of two and activate a single stick shaker out of two. But, as mentioned in the report, both control wheels are physically linked. A single stick shaker will be felt on both wheels. It may not be possible to distinguish a single shaker versus a double shaker activation.

Only when MCAS was introduced did Boeing give a faulty AoA sensor the power to cause trim changes.  And they didn't tell anyone about it, at least not pilots or operators.

So it's understandable that people who didn't know about MCAS would be a bit unconcerned about an AoA sensor.

The previous STS uses the same methodology as MCAS.  Computer controlled trim is used to enhance control feel during manual flying. It does not use the AoA sensor as an input.

As fly-by-wire is becoming the norm, perhaps more work is needed to improve AoA sensors and fault detection. Airbus had a few upsets and one crash where two stuck AoA sensors caused the rejection of the third.

https://www.flightglobal.com/news/articles/analysis-how-airbus-fought-its-own-pitch-battle-457574/

[floobydust]

This isn't failed engineering, needing improving sensors and fault detection.
It's unbridled corporate greed and corruption, at the executive level.

MCAS had already been properly engineered. From Muilenburg's testimony before Congress this week:
"Michigan Republican Representative Paul Mitchell asked why the 737 Max’s version of MCAS had key differences from a midair refueling tanker Boeing supplies to the U.S. Air Force. He pointed out that the Pentagon required that the KC-46 tanker’s MCAS system activate only once, when the civilian application could -- and did -- fire repeatedly, he said.

“Why the difference? What motivated that?” the lawmaker said.

John Hamilton, chief engineer of Boeing Commercial Airplane division, cited specifications set by the Air Force. Muilenburg said the tanker’s MCAS system was designed for different flight scenarios than the 737 Max’s version. The Air Force has said the KC-46’s MCAS systems incorporated data from two angle-of-attack sensors, rather than one sensor as originally designed on the 737 Max."

When your customer tells you how to do airplane engineering safety 

He's still among the highest paid CEO's at $23.4M, including a $13.1M bonus, 27% increase from the previous year.
Imagine getting paid that much despite killing 346 people and $9B in losses.

[chickenHeadKnob]

This isn't failed engineering, needing improving sensors and fault detection.
It's unbridled corporate greed and corruption, at the executive level.

MCAS had already been properly engineered. From Muilenburg's testimony before Congress this week:
"Michigan Republican Representative Paul Mitchell asked why the 737 Max’s version of MCAS had key differences from a midair refueling tanker Boeing supplies to the U.S. Air Force. He pointed out that the Pentagon required that the KC-46 tanker’s MCAS system activate only once, when the civilian application could -- and did -- fire repeatedly, he said.

“Why the difference? What motivated that?” the lawmaker said.

John Hamilton, chief engineer of Boeing Commercial Airplane division, cited specifications set by the Air Force. Muilenburg said the tanker’s MCAS system was designed for different flight scenarios than the 737 Max’s version. The Air Force has said the KC-46’s MCAS systems incorporated data from two angle-of-attack sensors, rather than one sensor as originally designed on the 737 Max."
--snip--

KC-46 pegasus is derived from a B767 and may have other significant mcas and pitch /trim response differences,
P-8  Poseidon is  a more recent issue naval patrol, anti-sub aircraft derived from B737-800ERX, this would be a better comparable but I don't know if it has a modified MCAS.

[BravoV]

After this saga, all fall back to a very simple fundamental question, how is Boeing better than -> Comac ?

Example Comac C919, its intended to compete primarily with the Boeing 737 MAX, pretty confident its darn cheap compared to 737 MAX.

Quote : "In 2012 the C919 order book stood at 380 units worth US$26 billion, and averaging $68.4 million. FlightGlobal's Ascend market values in 2013 were $49.2 million for the Airbus A320neo, 51% less than its $100.2 million list price and $51.4 million for the Boeing 737 MAX-8, 49% less than its $100.5 million list price. In June 2015, the China National Radio predicted a $50 million price, cheaper than the B737 or A320 list prices."



Also if the China's FAA equivalent body is proven to accept bribe or made such mistakes, guilty parties for sure will be executed with death penalty, at least this bring more confident isn't it ? 

[Nusa]

After this saga, all fall back to a very simple fundamental question, how is Boeing better than -> Comac ?

Example Comac C919, its intended to compete primarily with the Boeing 737 MAX, pretty confident its darn cheap compared to 737 MAX.

Quote : "In 2012 the C919 order book stood at 380 units worth US$26 billion, and averaging $68.4 million. FlightGlobal's Ascend market values in 2013 were $49.2 million for the Airbus A320neo, 51% less than its $100.2 million list price and $51.4 million for the Boeing 737 MAX-8, 49% less than its $100.5 million list price. In June 2015, the China National Radio predicted a $50 million price, cheaper than the B737 or A320 list prices."



Also if the China's FAA equivalent body is proven to accept bribe or made such mistakes, guilty parties for sure will be executed with death penalty, at least this bring more confident isn't it ? 

That's easy. The 737 exists. The C919 doesn't, except for a few prototypes being used for testing. FIRST delivery isn't planned until 2021, and it'll take time to ramp up production. China internal customers will dominate the output for the next decade or more, assuming no serious flaws show up in service. Some of that market is built-in, since that's an obvious result of having a state-owned aircraft manufacturer and state-owned airlines. As for mistakes, are you sure we'd ever hear about most of them? Most of the media is state-owned as well.

Also, you stopped copying wiki text too soon. Allow me to continue, directly after what you quoted:

The Chinese airlines that have placed orders for the C919 already have either the Boeing 737 or Airbus A320 in their fleets.[66] In 2013, Chinese state-owned newspaper Global Times complained that an Aviation Week editorial about the bleak prospects for the aircraft "maliciously disparaged the future outlook for the C919".[67]

COMAC aims to take a fifth of the global narrowbody market and a third of the Chinese market by 2035.[8] It expects 2,000 sales in the next 20 years.[68] China considers it as a source of national pride.[69] The Financial Times states the C919 is outdated by 10–15 years compared to the latest versions of the A320 and Boeing 737, and will probably cost more to operate.[70] Its range of 2,200–3,000 nmi (4,100–5,600 km) falls short of the 3,400 and 3,550 nmi (6,300 and 6,570 km) of the A320neo and 737 Max 8, the C919 payload-range and economics are similar to the current single-aisles, but it will compete with the Neo and Max. FlightGlobal forecasts 1,209 deliveries: 687 standard and 522 stretched variants, for 85% in China.[31]

[dzseki]

This 737Max saga cannot get any more sad, even if it is allowed to flight it really doesn't comply FAA rules fully, like clearance between control cables,

One issue is how FAA managers agreed during certification of the 737 MAX to give Boeing a pass on complying with a safety rule that requires more separation between duplicate sets of cables that control the jet’s rudder.

This is to avoid the possibility that shrapnel from an uncontained engine blowout could sever all the cables and render the plane uncontrollable.
The requirement was introduced when such a blowout caused the deadly 1989 crash of a United Airlines DC-10 in Sioux City, Iowa. The 737 has never been brought into line with the requirement

.....The story listed a series of legacy design details that have been repeatedly grandfathered into the latest model each time Boeing has updated the 737, which was originally certified more than 50 years ago.
All the issues in the list were flagged by FAA safety engineers as requiring fixes before the MAX could be certified. But each was waved through after managers on the Boeing side of certification insisted that these were non-issues and managers on the FAA side agreed to let it move ahead with the requirement unaddressed.



So basically Boeing is designing non-compliant and unsafe airplanes like nothing but since it is already designed how the hell is it not going to get certified, the costs would be tremendous!!!

https://www.seattletimes.com/business/boeing-aerospace/new-questions-raised-on-safety-of-both-737-max-and-787-dreamliner/

I'd think a big part of this is just pointing fingers by FAA, as they want to appear to be the "good guys" now. The 737 family has an excellent track record in safety, in general.
Now they claim that the 737 does not comply a 30 year old rule, while obviously no accident was contributed to that non-compliance in that 30 years, come on!

[SilverSolder]

[...] they claim that the 737 does not comply a 30 year old rule, while obviously no accident was contributed to that non-compliance in that 30 years [...]

If the rule is incorrect, it should be removed.  Otherwise it should be adhered to. 

There should be no rules that are arbitrarily ignored just because someone thinks not enough accidents are happening!

[BravoV]

The problem now is not Boeing, forget any technicality talks, as its pointless.

Its just natural as they're just maximizing the profit, while the safety part is ignored heavily with the great aid and help by FAA.

For so many decades, can you imagine the bribe that FAA officials took ? And maybe politicians too for being quite all this time ?

And please don't be naive, that FAA didn't get or want any catch all by "surrendering" the certification to the Boeing to be "self-certifying" company.   

Even its pronounced & written as "Boeing" , still it has the meaning of "One Hung Low" brand inside.

[sokoloff]

[...] they claim that the 737 does not comply a 30 year old rule, while obviously no accident was contributed to that non-compliance in that 30 years [...]

If the rule is incorrect, it should be removed.  Otherwise it should be adhered to. 

There should be no rules that are arbitrarily ignored just because someone thinks not enough accidents are happening!

My 1965 Mustang doesn’t meet many current federal safety standards. Nevertheless, I can still drive it on the road. I’ve chosen to make a few upgrades (adding dual circuit brakes, not originally equipped, and will likely add three point belts [lap belts originally an option, shoulder belts not offered]), but didn’t have to.

That does not mean I think the shoulder belt or dual circuit braking or reverse lights requirements are bad laws, just that they don’t apply retroactively to machines certified or built before they were introduced.

[GeorgeOfTheJungle]

My 1965 Mustang doesn’t meet many current federal safety standards. Nevertheless, I can still drive it on the road.

Lucky you. The bureaucrats in Brussels want to end with that in Europe.

[m98]

Lucky you. The bureaucrats in Brussels want to end with that in Europe.

Rightly so. Why should the community bear the healthcare bills of individuals recklessly injuring themselves and others with unsafe cars?

That does not mean I think the shoulder belt or dual circuit braking or reverse lights requirements are bad laws, just that they don’t apply retroactively to machines certified or built before they were introduced.

This doesn't, shouldn't and has never applied to the aviation industry. As soon as anything is deemed unsafe or outdated, it needs to be changed. Would you let yourself or your loved ones fly on a "no worries mate, she'll be right"-airline?

[GeorgeOfTheJungle]

Lucky you. The bureaucrats in Brussels want to end with that in Europe.

Rightly so. Why should the community bear the healthcare bills of individuals recklessly injuring themselves and others with unsafe cars?

Since when does "the community" pay our cars' insurance bills?

[tom66]

Since when does "the community" pay the insurance bills?

Most Europeans pay taxes that pay for healthcare, a greater number of car accidents mean more hospital visits and greater costs.

Air pollution & climate change also effect everyone.