CW: Plane Crash

May 25th, 1979 American Airlines flight 191 crashed shortly after take off. It's the deadliest aviation accident to occur in the US. I'm gonna talk about it because I'm weird and like to understand why things fail. Here we go! 1/X

The aircraft involved was a McDonnell Douglas DC 10. American Airlines started using this plane in 1971. Other airlines had DC 10 as well.

The captain of flight 191 Walter Lux, had logged 22,000 hours of flight, w/ over 3000 being DC10 and was also qualified for 2/X

17 other aircraft including DC-6, DC-7, and Boeing 727. The flight crew overall had experience with the DC 10 (James Dillard 9,275 hours, Alfred Udovich 15,000 hours. collectively over 1800 hours in DC-10).

Clearly experienced flight crew.

So what happened? 3/X

The aircraft had 258 passengers and 13 crew for a total of 271 souls on board.

As the plane reached take off speed and began to rotate (lift nose upward), a loud bang was heard from the left side of the plane. Unknown to the flight crew, the... 4/X

left engine completely separated from the plane, damaging a hydraulic line for flap control on the left wing, damaging the wing, and other issues I'll touch on soon.

Looks like take off speed for a DC10 is ~ 150kts, (172 MPH).

That's a lot of plane going fast 5/X

I'm not a pilot, though I'm reading a book and learning as I have an interest in a private pilot license, so forgive me if I goof anything up.

So the plane makes it off the ground, but things aren't good. It has half the thrust, and damage to left wing impacting lift 6/X

If a plane goes too slow, it stalls. Basically this means you are no longer generating lift, and it doesn't fly anymore. It's also possible for wings to stall independently IE left wing can stall before right.

SO plane is in the air, engine is gone. ALSO the left engine 7/X

is the engine responsible for generating electricity for the captain's instruments. Also the same engine powered cockpit voice recorder, radio, etc. It's worth noting that First Officer was flying the plane and did have instruments.

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Anyway, you get the point, bad situation is bad.

The plane was in the air for about 50 seconds, and reached an altitude of about 350 feet. Due to the damage to the left wing and hydraulics, the left wing stalled and caused the plane to bank left. On impact the plane was

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at a bank angle of ~112 degrees...

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50 seconds.

all 271 souls on board lost, plus 2 on the ground, and 2 significant injuries due to burns.

Why did the engine separate from the plane?

We know why, and it becomes an interesting tale.

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So this crash was a big deal, it spread in the news quickly. Eventually the FAA grounded the DC-10 and prevented international flights coming IN on a DC-10.

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The investigation into Flight 191 discovered damage to the mounting point for the left engine. They pylon (love it) is a mount. I think this sites between the engine and the rest of the air frame.

This was the major clue needed to help understand what happened.

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turns out, the plane had recently had it's engine removed, as part of routine maintenance performed end of March. The Manufacturer procedure dictated that technicians should first remove the engine from the plane, then remove the pylon.

American Airlines, Continental and 14/X

United had a different idea though.

They discovered that if the pylon and engine were pulled as an assembly, it could save ~200 man hours. All three airlines adopted this approach to this routine maintenance process.

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American and United used forklifts in this process, but if the assembly wasn't balanced, it could rock back/forth.

The damage to the mounting area on Flight 191 discovered by NTSB was due to the engine and pylon assembly damaging the air frame.

The damage was
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subtle. However, it developed into fatigue cracking, with each take off and landing cycle weakening the point further.

This is why the engine broke away that fateful day.

The fun doesn't end here though

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Investigation into the DC-10 fleets maintained by American Airlines and Continental Airlines discovered "several" additional planes with this same fatigue damage.

United used a hoist instead of fork lift when they did engine/pylon, and did not show damage.

holy shit.

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So there you have it. An attempt at reducing the labor time for routine maintenance on these planes across 3 airlines resulted in one of the worst air tragedies in US history. It also created a condition where it could have happened again. and again. and again.

and so
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Winding down our story. This crash and the grounding of the DC-10 damaged the reputation of the plane. It was later exonerated, but public opinion is a thing. The direct cause of this failure was improper maintenance procedure. American Airlines was fined $500,000 and

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The removal procedure of the engine/pylon as a unit was banned.
Further the FAA amended the plane's type certificate to state that removal of the engine and pylon as an assembly would immediately result in the plane being deemed un-airworthy.

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One of the American Airlines mechanics that last performed the work on the aircraft committed suicide.

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So that's the story of American Airlines Flight 191. There's a lot more detail to the story that I glossed over. the reputation of the DC-10 was damaged but it went on to serve as a passenger plane for 30 years after the incident. This was a maintenance issue, not design. 23/X

This story shows how important it is to be thorough in an investigation. It shows the amazing work crash investigators can do. It shows the potential catastrophe of shortcuts.

I hope this was interesting, thx for reading!

Drop me a follow or RT if you don't mind.

FIN

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ADDENDUM:

The video that inspired this thread