Hole In Engine on NWA 757

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03-27-2009, 02:01 PM

#11

alvrb211

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Quote:

Originally Posted by AZFlyer

Wouldn't throwing a blade catastrophically disrupt the balance of the fan, causing the engine within the cowling to just throw itself apart?

Looks like a pretty violent event in this video.
Fan blade separation test:
YouTube - Blade Containment

If the video is anything like what would be typical, there doesn't seem to be enough damage to the cowling of the NW jet in the photo for a fan blade separation.

Just a guess.

Unlike the majority of 757 operators, NWA have Pratt and Whitney engines on their 757's. The fans on the PW are very thin, straight, unswept, and very inefficient. They look like sword blades compared to the blades in the video.

The Rolls Royce blades in the video are wide chord fan blades. They are swept and have a lot of geometric twist. They are also gas filled to retain their shape. They are so efficient they don't need IGV's.

In the event of a blade off, the PW fans do a very poor job of slinging debris to the outside and through the bypass of the engine. The IGV's on the PW fans would further cause debris to go through the engine core. Those skinny PW blades are much more brittle and prone to damage.

AL

Last edited by alvrb211; 03-27-2009 at 05:35 PM.

03-27-2009, 02:40 PM

#12

HerkFCC

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Position: C-130 Flying Crew Chief

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Quote:

Originally Posted by acl65pilot

If it did not throw a blade, you may not know anything. If you did chuck a blade, you would probably feel the vibration.
This looks like it could be a few things. Everything from a blade exit point, to a discharge point for some lightning.

If the 757 isn't totally fly by wire (I'm not sure if it is or not), would the crew possibly be able to tell through vibrations being transmitted through the power lever for that engine, even if for some reason the crew had no indications on their instruments?

03-27-2009, 03:08 PM

#13

rickair7777

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Quote:

Originally Posted by HerkFCC

It's not FBW. It looks like a blade or part of a blade almost certainly came off. I would think that there would have been an increase in fan vibe at the very least, but possibly not out of parameters so it might have gone un-noticed up front. There is no set normal vibe value for an engine, just a range in which healthy engines should fall, it's routine to see zero vibes, or vibes near the top of the range.

I think the vibes would have to be far out of normal to feel it up front, you would see it on the gauge first.

03-27-2009, 03:20 PM

#14

FlyDL

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edited for content

Last edited by FlyDL; 03-27-2009 at 03:54 PM.

03-27-2009, 05:35 PM

#15

H46Bubba

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Quote:

Originally Posted by acl65pilot

Yes, and it was an MD-88 that just applied TO power. Killed a mother and her child.

Now I know why they sit all us nonrevs back there.

03-27-2009, 05:38 PM

#16

acl65pilot

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Most little ones fall fast asleep back there. Not mine though.

03-27-2009, 06:18 PM

#17

bravo24

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Doubt that they lost a fan blade. The hole is forward of the fan case and a statement in the article said the inlet cowl was replaced and the aircraft returned to service. If they'd thrown a blade the crew would have probably felt it and the engine would have to have been replaced.

BTW the PW2037 and 2040 are FBW engines.

03-28-2009, 07:25 AM

#18

Sniper

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Quote:

Originally Posted by bravo24

The hole is forward of the fan case and a statement in the article said the inlet cowl was replaced and the aircraft returned to service. If they'd thrown a blade . . . the engine would have to have been replaced.

Agreed, it does appear that way, forward of the case. Though this wouldn't be the first time the media reported an inaccuracy in aviation.

Quote:

BTW the PW2037 and 2040 are FBW engines.

The term FBW is normally associated with control surfaces, not engines. What would make an engine 'FBW'? FADEC? The absence of 'throttle cables'?

03-28-2009, 11:49 AM

#19

bravo24

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Quote:

Originally Posted by Sniper

Agreed, it does appear that way, forward of the case. Though this wouldn't be the first time the media reported an inaccuracy in aviation.

The term FBW is normally associated with control surfaces, not engines. What would make an engine 'FBW'? FADEC? The absence of 'throttle cables'?

To us in the techie part of the aviation world the PW2037/2047 is considered FBW since thrust lever position is transmitted electrically to the FADEC via resolvers in the pedestal as opposed to cables between the thrust levers and the MEC. Just like FBW flight controls.

03-28-2009, 11:56 AM

#20

Sniper

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Quote:

Originally Posted by bravo24

. . . thrust lever position is transmitted electrically to the FADEC via resolvers in the pedestal as opposed to cables between the thrust levers and the MEC. . . .

Ok, so both FADEC and no cables. Got it.

The 777 is definitely FBW. Do pilots like this, or would you prefer cables and pulleys? (trying to get this thread back to the 777)