Sparking on the 737 engine front stage

[c130jbloke]

Hi all,

I work at an airfield above the Artic circle and we use a lot of sand to keep the ramp etc free of ice.

I have noticed when 737s have their engines running, sparks / flashes around the outer part of the disc, next to the engine casing. Looks good but it got me wondering.

Is this sparking caused by sand particles being ingested into the engine when they strike the fan blades ? And as I was always under the impression that only fresh air was meant to pass through the engine, where does this fit in with FOD ingestion / damage ?

Thanks for any answers !

C130JB

[Turbine D]

c130jbloke

Your observation is correct. The fan blades are made from Titanium, Ti6-4 alloy to be exact. It is the same alloy used to make titanium golf club heads. They, too, spark when being hit from a tee that has sand accumulation or when hitting out of a sand trap, impressive at dawn or dusk!

Observing it at the fan casing is good as it means the majority of the sand particles are being flung outward and will pass through the fan by-pass instead of being ingested into the core. Over time, some erosion will result at the tips of the fan blades or in the acoustical liners along the walls of the fan casing.

Turbine D

[mitzy69]

seen sparks on fan blades in Arabia
whole inlet looks like there is a big Catherin wheel alight.
erodes the leading edge nicely.

[Gulfstreamaviator]

Please, find some sand storm, light show pics...

Glf

[Turbine D]

Gulfstreamaviator

Couldn't find any photos of sparking of the fan, but here is what I meant using the golf club example:

YouTube - Golf club sparks (http://www.youtube.com/watch?v=NO7yKaKBvQ4)

Turbine D

[ShyTorque]

A similar thing occurs on the main rotor blades on some helicopters when some types of dust/sand hit them. For example, the Sikorsky S-76, which by no coincidence, has titanium leading edge protection strips.

[ion_berkley]

A rather good link for this one, nice pics.
The Kopp-Etchells Effect (http://www.michaelyon-online.com/the-kopp-etchells-effect.htm)