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Comment by sosodev | Hacker News Reader

A commenter in HN thread covering the initial crash mentioned that the left engine detaching might have been the cause https://news.ycombinator.com/item?id=45821537

The referenced AA Flight 191 is shockingly similar. It makes me wonder if aviation really is back sliding into a dangerous place.

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40 years between severe accidents is fine in terms of expected failures. It's also not a good comparison because in the 70s maintenance crew were using a forklift to remive engines, improperly stressing the engine pylon. This was done as a shortcut

I don't know if it's "sliding back" as much as it is that this plane is also fundamentally from the 1970s.

The MD-11 was developed after that crash. Shouldn't its design and maintenance procedures have been informed by the incident?

The MD-11 is nothing but a re-engined and a re-named DC-10. They share the same type certificate.

https://www.easa.europa.eu/en/document-library/type-certific...

Maintenance was informed by the earlier incident. It's why we haven't seen even more DC-10/MD-11 failures sooner. Designs too have kinda been informed by this -- it's not like Boeing or Airbus make trijets anymore.

Aside from the engine detaching, it doesn't appear that this incident is in any way similar to the previous incident.

How do you figure? They're very similar planes. The left engine and its pylon detached in both cases during takeoff rotation. Both incident reports stated that proper maintenance would have prevented the detachment.

The way the situation played out is different but the failure mode seems to be very similar if not the same.

The NTSB report itself even references AA-191 as the only "similar event".

The root cause does not appear (at this stage) to be the same: incorrect maintenance in AA191 as opposed to fatigue cracking here.

Where does this report say proper maintenance would have prevented the incident?

The report doesn't say that because it's just reporting the facts not drawing conclusions. In my opinion, if a catastrophic failure happens that is a maintenance failure. Either the inspections failed to notice the fatigue or the inspection guidelines were too optimistic.

AA-191 was caused by improper maintenance (dreamed up by people who were made to cut corners and was never compliant with manufacturer spec) damaging the pylons holding the engine.

If someone did the same thing again, that would be rather unfortunate. Just more deaths for profit, even though we know it was dangerous.

The parts that seem to have fatigued and failed were only like 80% of the way through their inspection period. They were to be inspected after 28k cycles. They were at 21k cycles.

It sure looks the same from "Engine pulled itself off and flew away" angle, but if there is any similarity under the surface that's very bad. Flying was much much less safe in the 70s.

> The referenced AA Flight 191 is shockingly similar. It makes me wonder if aviation really is back sliding into a dangerous place.

I think it's cut throat capitalism at its best. Surely it was much too safe before, let's see how far back we can scale maintenance on the operations front but also how far back can you scale cost during development and production and then see where it takes us. If that changes the risk for population from 0.005 to 0.010, the shareholders won't care and it's great for profits.

I think we can see both but especially the latter with Boeing.

The entire MD-11 project was a budget-limited rush-job to try to capture some market share before the A340 and 777 came into service.

It produced an aircraft that failed to meet its performance targets, was a brute to fly and was obsolete the moment its rivals flew.

Douglas* by the early 1990s was a basket-case of warmed-over 1960s designs without the managerial courage to launch the clean-sheet project they needed to survive.

* as a division of MDC

And then they merged with Boeing...

Are you referring to AA 191 in 1979? That seems like low enough frequency event to not be worried about it.

The murder suicides in the last few decades seem more concerning.

Rather the opposite: if the cause is similar to AA 191, why weren't the actions taken after AA 191 to prevent a repeat effective? If we can get a repeat of that incident, what's preventing the industry from repeating the mistakes from all those other incidents from the past decades? Why aren't they learning from their past mistakes - often paid for in blood?

I understood the post I responded to to be referring to the cause as the engine detaching from the same type of plane, not the root cause for why the engine detached. Per the “investigation section” in the wikipedia article, I would be surprised if it was the same root cause:

https://en.wikipedia.org/wiki/American_Airlines_Flight_191

I assume the erroneous maintenance procedures that led to the loss of AA191 were rectified a long time ago.

>rectified a long time ago.

There's no such thing as "This is fixed forever". If lax maintenance oversight has led to companies re-introducing known dangerous maintenance procedures or departing from known good ones, then we will be back in the 70s in terms of airplane safety and people will have to die again to relearn those lessons.

Someone's always trying to claw you in the less safe direction. It's a constant battle to not regress.

But IDK, hopefully this plane just got some sort of "unlucky" about fatigue somehow, and it doesn't have far reaching consequences.

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