corroded nose cowls

[Mariner]

Who knows how rough the surface of the nose cowl of a high bypass engine is allowed to be?

Most business jets have nose cowls I can use for a shaving mirror, but most airlines have them not nearly so shiny.

I recently saw nose cowls, which were quite rough in certain places caused by surface corrosion from short term storage. Especially the top and bottom of the inlet, with runoff stains along the sides.

Are we just talking esthetics here, or would a certain amount of roughness create flow distortion, thereby reducing stall margin somewhat?

I do assume that roughness would create some extra drag, and thereby higher fuel consumption.

I was told there are no AMM limits for it.

Anyone?

[Ultralights]

the roughness of the aluminium of the nose cowl would be below the boundary layer in most circumstances. most of the surface conditions would be a result of the tooling used to manufacture the part. any turbulence caused could actually improve the aerodynamics of the airflow into the cold stream duct,well, until it passes through the blades themselves.
as for effecting stall speed? i seriously doubt it would make any difference.as for corrosion damage, the SRm would state tolerances and minimum thickness of original material before it requires repair.

[lomapaseo]

Any pics ?

I can't ever recall seeing corrosion on a nose cowl

Some lip roughness due to erosion (sand, rain, ash, etc.).

Never heard of a problem over lots of operators

[glhcarl]

The information requested can be found in the Structural Repair Manual Chapter 54-30 Figure 801 Negligible Damage Limits!

[Mariner]

Thanks guys.


The nose cowls had been polished a few months earlier, during RTS from a 2 yr storage in the desert. Following a D-check & another 4 mo storage, they had stained again significantly. Light surface corrosion, roughness (like 300 grit sandpaper), stained and with run off stains.
All caused by storage outside in definitely-not-desert conditions.

No decent pics.

Irr it turned out to be no big deal, as plane & engines performed nominally during the 1st flight.