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UPS plane crashes near Louisville airport

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Re: UPS plane crashes near Louisville airport

#71

Post by loeg »

CPLX wrote: post #66
roygbiv2 wrote: post #22

Earlier quoted context omitted.

Looks like a compressor stall on number two engine two seconds into the video.

I would say it does not, in fact, look like a compressor stall. It looks very much like an uncontained disassembly, presumably from fan blades that suffered a catastrophic failure and broke up in a way that exceeded the limits of the engine's containment. Obviously impossible to tell from some cell phone type videos. Being struck by something is also possible. But it sure does look like an uncontained engine failure.

I think you're looking at engine number 1, while GP is talking about engine 2.

https://news.ycombinator.com/item?id=45818448

Re: UPS plane crashes near Louisville airport

#72

Post by loeg »

FabHK wrote: post #70
loeg wrote: post #33

Earlier quoted context omitted.

I think you're looking at the left wing (number 1) engine; GP is talking about either the tail or right wing engine. (I think tail is number 2 on MD-11.) There's a brief explosion visible through the smoke at about 1-2 seconds in, to the right of the engine visibly on fire; that's probably what he's talking about. Freeze frame: https://imgur.com/a/c3h8Qd3

And having 2 out of 3 engines fail (or underperform) would explain the insufficient climb thrust.

Right!

Re: UPS plane crashes near Louisville airport

#73

Post by appreciatorBus »

loeg wrote: post #33
appreciatorBus wrote: post #25

Earlier quoted context omitted.

I don’t know, that looks like a lot more than just a stall. There was a ton of flame that looked like it was coming out of the front or top of the engine, rather than just something shooting out the back.

I think you're looking at the left wing (number 1) engine; GP is talking about either the tail or right wing engine. (I think tail is number 2 on MD-11.) There's a brief explosion visible through the smoke at about 1-2 seconds in, to the right of the engine visibly on fire; that's probably what he's talking about. Freeze frame: https://imgur.com/a/c3h8Qd3

Yup makes sense. Now seeing photos of the entire left engine on the ground by the runway and the implication that however it failed it might have damaged the tail engine.

Re: UPS plane crashes near Louisville airport

#74

Post by namibj »

TylerE wrote: post #59
gizmo686 wrote: post #32

Earlier quoted context omitted.

> they tried to take off instead of accelerate past the runway at ground level Do runways have some sort of barrier between them and the next "important" thing. It seems like that would be prudent both for cases like this, and breaking failures following landings.

Security/debris fencing yes, but that's like, orders of magnitude short of what would stop the amount of energy we're talking about here. You also don't particularly want it to be catastrophically effective as there are real world cases where planes have clipped the fence and then NOT gone on to crash, or at least to crash in a fairly controlled manner with the majority onboard surviving. Hitting a brick wall at 180m…

Yet a reinforced concrete wall of e.g. triangular section and anchored with "long enough" piles would be about the only not-that-expensive way to turn a short strip of "airport land" past the EMAS into a V1 stopping supermarket.

Re: UPS plane crashes near Louisville airport

#75

Post by mannykannot »

positron26 wrote: post #52
octaane wrote: post #35

Earlier quoted context omitted.

Unless you have a berm several dozen meters high with a 100 meter base, you ain't stopping something like this from a physics standpoint unfortunately. Many airports have this problem. The recent korean air disaster which echos this is another example. BTW, this is why most airports, if possible, point out to sea...

There is a dead zone between rejection and successful take-off speeds. We see it hit too often. I think pilot training is playing a factor. A normal rotation kills too much energy. One engine can climb when you have some airspeed and get clean, but if you lose too much energy on rotation, the inefficiency of the AoA for the rest of the short flight means that engine can no longer buy you any up. I've seen too many si…

Rotation does increase drag, but you need to rotate in order to achieve the necessary angle of attack. The only way to reduce the rotation angle is by going faster than the normal rotation speed for the given weight and airfield density altitude, but doing so is out of the question in this scenario.

Re: UPS plane crashes near Louisville airport

#76

Post by appreciatorBus »

chzblck wrote: post #46
octaane wrote: post #27

This is probably the worst way a plane could go down in terms of damage caused. Maximum effect in term of damage. Cargo plane apparently reached V1 (go/no go speed) on the runway, and suffered a catastrophic engine failure. They passed V1, so they knew they were going down. Engine was shedding large debris, including the housing (!!!) which is a shrapnel shield. They were on fire just as they reached V1. Plane was fu…

Sorry for ignorance but why is the right thing to continue to take off with an engine on fire?

It depends on whether or not, at the point in which you realize you have an engine on fire, you have room on the runway left to stop.

As I understand it, there is a low speed regime, under 80 knots, where are you stop for basically anything.

Then there is a high speed regime, where you only stop for serious issues, because you now have so much kinetic energy that stopping the plane, while still possible, will involve risk. (i.e. fire from overheated brakes.)

At a certain point, called V1, there’s no longer enough room to stop, no matter what your problem is. You’re either getting airborne or you’re crashing into whatever is ant the end of the runway. In general, getting airborne is the safer option, while obviously still not risk free.

However, this calculation also assumes that the engine fails in an isolated fashion, and its failure did not affect the other engines. If the failure of the left engine threw off debris that damaged the middle engine then we are now talking about a double engine failure. I’m sure the pilots knew there was a problem with the engine when they made the decision to continue, but it’s possible that problems with the middle engine weren’t apparent yet and that it only started to fail once they were committed.

Obviously, this is just speculation, and we will have to wait for the preliminary report at least.

RIP

Re: UPS plane crashes near Louisville airport

#77

Post by mannykannot »

gizmo686 wrote: post #32
octaane wrote: post #27

This is probably the worst way a plane could go down in terms of damage caused. Maximum effect in term of damage. Cargo plane apparently reached V1 (go/no go speed) on the runway, and suffered a catastrophic engine failure. They passed V1, so they knew they were going down. Engine was shedding large debris, including the housing (!!!) which is a shrapnel shield. They were on fire just as they reached V1. Plane was fu…

> they tried to take off instead of accelerate past the runway at ground level Do runways have some sort of barrier between them and the next "important" thing. It seems like that would be prudent both for cases like this, and breaking failures following landings.

Some runways have been extended with ‘engineered materials’ surfaces, often a form of porous concrete into which an airliner’s wheels will sink, absorbing a lot of energy and arresting the airplane without causing it to break up. It is very effective for landing overruns, but I don’t know about last-seconds aborted takeoffs.

Re: UPS plane crashes near Louisville airport

#78

Post by panxyh »

FabHK wrote: post #68
chzblck wrote: post #46

Earlier quoted context omitted.

Sorry for ignorance but why is the right thing to continue to take off with an engine on fire?

V1 is the speed at which you can still stop the plane before the end of the runway. (It is computed for each takeoff based on runway length, aircraft mass, takeoff engine power setting, flaps, wind, runway condition, etc.) When the plane reaches V1, pilots take the hand off the throttle: they're committed to takeoff, even if an engine fails. It is better to take off and fix the problem or land again, than to smash in…

Isn't there any margin? Does it calculate stopping before end of runway or before causing damage?

Surely uncertainty about the situation contributes to defaulting to committing, but what if it's a passenger plane and at V1 pilots know they've lost power? Wouldn't veering into highway at 30 mph be weighted against certain, big loss of life?

Edit: I now see that this has been partially answered by uncle comment

Re: UPS plane crashes near Louisville airport

#79

Post by positron26 »

bigbadfeline wrote: post #67
positron26 wrote: post #52

Earlier quoted context omitted.

There is a dead zone between rejection and successful take-off speeds. We see it hit too often. I think pilot training is playing a factor. A normal rotation kills too much energy. One engine can climb when you have some airspeed and get clean, but if you lose too much energy on rotation, the inefficiency of the AoA for the rest of the short flight means that engine can no longer buy you any up. I've seen too many si…

> It manages to go up a bit, so it's fast enough to get airborne. The normal looking rotation kills too much energy. Yes, it did get airborne for a few seconds but from the video below, it looks like the left wing was damaged by the fire and could not provide enough lift, then the right wing rolled the plane to the left causing the crash. https://bsky.app/profile/shipwreck75.bsky.social/post/3m4tvh...

> looks like the left wing was damaged by the fire

The wings and aerodynamics don't really care if air or air with combustion are flowing around them.

Roll is a consequence of the loss of control due to low speed and the yaw of the good engines. Speed up, rudder works, plane might maintain positive climb.

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