sovietjet
Posts: 2546
Joined: Sat Mar 15, 2003 12:32 am

Fan Blades Not Spinning

Tue May 13, 2003 12:09 am

If the plane is taxiing/landing/taking off why are the fan blades not spinning at all? The Il-76 and Il-62 have the same engines and I noticed both plane's engines fan blades don't spin although it's kinda hard to see in some of the pictures. Jusk look closely at the engines in the pics. Just wonderin why there are fan blades at all if they dont spin.

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Photo © Sven De Bevere



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Photo © Frederik Adam



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Photo © Sven De Bevere



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Photo © Ronny Van Belleghem



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Photo © Jorge Rocafort




 
timz
Posts: 6084
Joined: Fri Sep 17, 1999 7:43 am

RE: Fan Blades Not Spinning

Tue May 13, 2003 12:14 am

If they don't spin they're not fan blades.
 
Staffan
Posts: 3879
Joined: Tue Mar 18, 2008 9:21 am

RE: Fan Blades Not Spinning

Tue May 13, 2003 12:25 am

Why is the aircraft in that second photo hovering above the ground??

Staffan
 
bobrayner
Posts: 2038
Joined: Sun Apr 27, 2003 8:03 am

RE: Fan Blades Not Spinning

Tue May 13, 2003 12:31 am

I would be very, very surprised if they weren't spinning in at least two of those images  Wink/being sarcastic

Just because there's no motion blur doesn't mean there's no motion.
Very short exposure, maybe, whilst at relatively low rpm?

(Although, having said that, none of the above photos appear to be in very bright conditions, and the aperture can't have been really wide if most have good depth-of-field...)
Cunning linguist
 
Staffan
Posts: 3879
Joined: Tue Mar 18, 2008 9:21 am

RE: Fan Blades Not Spinning

Tue May 13, 2003 12:33 am

Jokes aside, the fan is probably spinning but it just doesn't look like it because a fast shutterspeed was used when taking the photo. Another option is that the enines have inlet vanes that give the airflow the best angle when it hits the first compressor stage.

Staffan
 
bobrayner
Posts: 2038
Joined: Sun Apr 27, 2003 8:03 am

RE: Fan Blades Not Spinning

Tue May 13, 2003 12:38 am

Oeps.

"short exposure" = "fast shutterspeed", of course  Smile
Cunning linguist
 
Staffan
Posts: 3879
Joined: Tue Mar 18, 2008 9:21 am

RE: Fan Blades Not Spinning

Tue May 13, 2003 12:40 am

Found a picture!


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Photo © Michael Van Bosch




Looks like it has inlet vanes.

Staffan
 
ben
Posts: 1369
Joined: Fri Aug 06, 1999 9:27 pm

RE: Fan Blades Not Spinning

Tue May 13, 2003 12:48 am

I'm not 100% sure about the D-30 engines of the Tu-154M, Il-62M or Il-76, but on the Tu-134, they do have guide vanes/stators at the front. This was very strange for me to see when I was less aviation-literate on my first Tu-134 flight. I thought "why the hell arent the engines turning yet" as we went screaming down the runway on takeoff.

If you look closely at the engine outside it's cowling on this page: http://www.npo-saturn.ru/old/English/d30ku.htm you will see the guide vanes/stators before the 1st stage fan and compressor.
 
ben
Posts: 1369
Joined: Fri Aug 06, 1999 9:27 pm

RE: Fan Blades Not Spinning

Tue May 13, 2003 12:55 am

Also from the same site (the manufacturer), you can see they specifically offer:

For engines in operation, we can offer reconditioning depending on the kind of a defect:
- Foreign object ingestion (Stage 1 compressor blades);
Inlet guide vanes reconditioning or replacement in case of their failure;


So I think there we have the answer.
 
exPratt
Posts: 306
Joined: Wed Mar 08, 2000 6:15 am

RE: Fan Blades Not Spinning

Tue May 13, 2003 11:23 pm

The stationary airfoils in the engine inlets are the inlet guide vanes. On first and second generation jet engines, they were standard equipment to support the No. 1 bearing and thus the front of the compressor rotor as well as to direct the flow of air into the compressor. The IGVs also contributed to jet noise as the fan and compressor blades sliced though the wakes behind each vane, similar to the way the old sirens worked. The JT8D-200s and hushkitted basic JT8Ds had a spacer case installed between the IGV and compressor case to move the wakes from the vanes away from the compressor and fan blades. Later generation jet engines like the JT9Ds, CFM56s, CF6s, and RB211 eliminated the IGVs completed and have the fan cantilevered in front of the forward bearing.

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