Another Indonesian aircraft down

[3WE]

Recurring Ignorant Outsider Asshat Safety Suggestions:

SOME sarcasm here, but a shred of seriousness.

Why not flashing yellow lights and a gentle hostie ring tone:

-Airspeed a little bit slow
-Engine power a bit unbalanced and wonky

We seem to be ass-uming that fat-dumb and happy flight suddenly went to hell (startle factor) and the stupid cowboy pilots botched it.

Several possible replies to this:

-There’s really nice and obvious airspeed and power indicators that the pilots might want to glance at.

-Similar (or adequate) systems already exist and we should STFU.

-In spite of incredible efforts, excrement transpires...we(no italics) can’t fix everything.

-Unintended consequences and 3BS’s gentle warning systems CAUSE distractions, confusion and crashes.

[Evan]

Which would be unfair, in this case. An engine can roll back for a number of reasons. FADEC, mechanical failures, bird ingestion, fuel contamination, the oil-fuel heat exchanger getting clogged, furl management issues, cnd autothrottle issues. Engine failures is probably the most-frequently practiced abnormal / emergency condition. We put 2 engines in the plane precisely in case one fails. If we cannot sustain flight with one engine, we would be better off with a single engine (since 2 engines double the probability of an engine failure).

Until we get to the fully autonomous planes, we need pilots, pilots that can manage some reasonable level of malfunctions, not paid passengers in the front seats.

Yes, unfair. But stealth, Gabriel, is the common factor I'm expecting. Not an abrupt, recognised asymmetry but a gradual one, building a gradual roll in IMC and, of course, pilot error, pilot disorientation, bias toward senses over instruments. But even if this turns out to be the case, the public can't understand these things. They will only understand that a computer malfunction 'caused' the crash.

[Gabriel]

Despite having nothing in common with the -Max crashes, if the report finds that another computer-related failure led to pilot disorientation and upset, this really isn't going to play well for Boeing in the public opinion.

Which would be unfair, in this case. An engine can roll back for a number of reasons. FADEC, mechanical failures, bird ingestion, fuel contamination, the oil-fuel heat exchanger getting clogged, furl management issues, and autothrottle issues. Engine failures is probably the most-frequently practiced abnormal / emergency condition. We put 2 engines in the plane precisely in case one fails. If we cannot sustain flight with one engine, we would be better off with a single engine (since 2 engines double the probability of an engine failure).

Until we get to the fully autonomous planes, we need pilots, pilots that can manage some reasonable level of malfunctions, not paid passengers in the front seats.

If any stupid technical failure will startle them to the point where they loose the capacity to keep the plane aloft, then we are doomed.
Unfortunately, we will never get rid of these cases. Fortunately, they are very infrequent. But we cannot just accept the impossibility of getting rid of all the cases or be happy with the low frequency. We need to keep improving the pilot selection, training and performance monitoring to train these situations out of the cockpit or weed the untrainable pilots out of the cockpit. We will never get to zero, but nothing above zero is acceptable.

[Evan]

Despite having nothing in common with the -Max crashes, if the report finds that another computer-related failure led to pilot disorientation and upset, this really isn't going to play well for Boeing in the public opinion.

[Evan]

Makes sense. To early to say "most plausible", in my opinion, given how little is known so far. But the scenario seems to fit the little that is known.

I meant most plausible autothrottle scenario, not most plausible of all possibilities. But there was further detail that the issue on the prior flight was thrust asymmetry, so I'm leaning towards that direction.

[Highkeas]

From today's AIAA newsletter:

The FAA issued an order in 2001 that 737-500 operators “replace the autothrottle computer after reports of unequal thrust.”

Bloomberg (1/20) reports that officials from the National Transportation Safety Board, the FAA, The Boeing Company, and GE “have traveled to Indonesia to help with the investigation.” Authorities expect to publish a preliminary report on the crash in 30 days.

[Gabriel]

The autothrottle was producing more thrust in one of the Boeing 737-500’s two engines than the other shortly before the plane carrying 62 people crashed into the Java Sea, said the person, who is not authorised to discuss the matter publicly. The device had been having problems on previous flights, the person said.

Issues involving the autothrottle on the 737 have led to incidents in the past, and a similar malfunction on another aircraft model was a cause of a fatal crash in 1995 in Romania.

Nurcahyo Utomo, the lead investigator at Indonesia’s National Transportation Safety Committee, confirmed that a malfunctioning throttle was “one of the factors that we are looking at, but I can’t say at this point that it’s a factor for the crash or there was a problem with it”.

https://www.scmp.com/news/asia/southeast-asia/article/3118618/sriwijaya-air-crash-indonesian-investigators-look-faulty

My thought when reading the above was stated below in the same article:

Twin-engined jetliners such as the 737 are designed to fly on a single engine during an emergency, so an autothrottle failure that produced unequal thrust should not have been enough to take down the plane by itself.

[Gabriel]

Some rumblings about the autothrottle. It had been malfunctioning on previous flights but no details as to how. I can't imagine a scenario in which an autothrottle malfunction could lead to a crash like this unless it was followed by egregious pilot error, but it could possibly lniitate a sequence that results in disorientation, a main cause of pilot error. Most plausible I think would be an undetected rollback that leads to stall and a botched stall recovery or a pronounced thrust assymetry that results in gradual roll to an extreme attitude and spatial disorientation, or some combination of these things.

Makes sense. To early to say "most plausible", in my opinion, given how little is known so far. But the scenario seems to fit the little that is known.

[Evan]

Some rumblings about the autothrottle. It had been malfunctioning on previous flights but no details as to how. I can't imagine a scenario in which an autothrottle malfunction could lead to a crash like this unless it was followed by egregious pilot error, but it could possibly lniitate a sequence that results in disorientation, a main cause of pilot error. Most plausible I think would be an undetected rollback that leads to stall and a botched stall recovery or a pronounced thrust assymetry that results in gradual roll to an extreme attitude and spatial disorientation, or some combination of these things.

[TeeVee]

I think that what you are seeing "destroyed" is the chassis with the connections and support circuitry but the memory module is a reinforced "ball" external to that.....

gotcha.

[Gabriel]

well, i'm clearly not an expert on electronics, but based on my experience with consumer electronics, i have to wonder how they think the CVR may still have viable info on it, seeing as how the memory board(s) were ejected/separated by force from their protective housing and have been submerged in salt water for days.

maybe one of you knows something about this...

I think that what you are seeing "destroyed" is the chassis with the connections and support circuitry but the memory module is a reinforced "ball" external to that.

Compare the pictures in AvHerald with this picture below (disclaimer: I have no clue if they are the same model)

[TeeVee]

well, i'm clearly not an expert on electronics, but based on my experience with consumer electronics, i have to wonder how they think the CVR may still have viable info on it, seeing as how the memory board(s) were ejected/separated by force from their protective housing and have been submerged in salt water for days.

maybe one of you knows something about this...

[Gabriel]

http://avherald.com/h?article=4e18553c&opt=0

On Jan 19th 2021 the KNKT reported that the FDR contained 330 parameters of a total of 18 flights. The KNKT have already developed a general picture of the accident, however, need further data from the cockpit voice recorder before publishing any information. Inspections of Boeing 737-300, 737-400 and 737-500 in Indonesia have been ordered.

So it was more than just pilot error....

[Schwartz]

At my office there is heavy speculation that this airline is not doing proper maintenance when pulling planes out of storage. We have been talking to our customers (airlines) and planes really like to run all the time. It's really quite unprecedented to have this many planes idled for such periods of time.

[Evan]

in the video of them "unboxing" the FDR, what they pulled out was a memory board with like 9 modules. i'm guessing the CVR is the same tech

An older analog CVR would use magnetic audio tape. The first solid state CVR came about only three years before this plane was manufactured. Would it have been integrated into an airframe put into production in the early 1980's? Or would it have been reserved for the NG's? Would a major carrier like United or Continental have taken the initiative to upgrade their older CVR's? Because I don't believe there has ever been a requirement to do so.

There have since been revisions to the Federal Register on just about every other aspect, from duration to power supply to physical separation and ELB issues but AFAIK there is still no requirement to upgrde to digital CVR units:

The replacement of magnetic tape flight recorders was not proposed in the NPRM and represents a significant change that is beyond the scope of the rulemaking. The commenters did not provide any data on the extent of usage or the cost of replacement, nor has the public (including affected operators) been allowed to comment. The final rule does not contain a provision requiring the replacement of magnetic tape FDRs.

(That being the case for FDR's, I assume it is also the case for CVR's)

As tape is significantly less durable than silicon, and survivability is a core requirement, this seems to me to be a glaring oversight.

Anyway, let's hope this one survived...