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747 Engine Inlet Sparks

Posted: Tue Dec 28, 2010 6:29 pm
by dl757md
Regarding the following picture

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Photo © Thomas Merkl



I work around engines all the time at night and I'm quite familiar with the phenomenon of static electricity discharging from the fan blades which is more common in the winter due to the lower relative humidity. This picture is the first one I've seen on Anet of the phenomenon (I'm sure there are others) and it struck me as unusual because when I've seen static discharge it's not usually localized at the blade tips as on engines 1,2 and 4 on this Qantas bird. It's usually more dispersed across the disc.
It's possible it could be the tips rubbing the abradable shroud but then why only from the 5 o'clock to 7 o'clock positions? Why is it not doing it on nbr 2 engine? Anyone care to float a theory?

DL757Md

RE: 747 Engine Inlet Sparks

Posted: Tue Dec 28, 2010 6:36 pm
by futureualpilot
Given the angle at which it appears the sun is illuminating the rest of the airplane I'm thinking its just the way the sunlight is hitting the fan, not actual discharges of electricity.

RE: 747 Engine Inlet Sparks

Posted: Tue Dec 28, 2010 6:51 pm
by dl757md
That would explain why number three has no "sparks" being that it's in the shadow of the fuselage. Thanks!

RE: 747 Engine Inlet Sparks

Posted: Tue Dec 28, 2010 10:05 pm
by EMBQA
The snow causes it ..............

RE: 747 Engine Inlet Sparks

Posted: Wed Dec 29, 2010 12:00 am
by boeingfixer
Quoting EMBQA (Reply 3):
The snow causes it ..............

Not in this case. Everything in shadow is dark indicating that this is just reflected sunlight.

Although snow can cause static electricity discharges on fans it is not as drastic as one would think. During daylight this phenomenon is all but unnoticeable.

Cheers,

John