Increased parasite drag by dirt and bugs
 

Does anybody have sources with data about the subject? On a quick research I just have found airplane information and few or no numbers.
Thanks!

Dirty rotor blades - salt, bugs, dust - can make the torque requirements go up quite a bit. Ice is even worse. Data? None, sorry, but I have seen the Tq go down when I have cleaned and sprayed the blades with WD40.

before anyone goes and lubes up their blades so that they may lift humongous loads with ease, be sure that the product is acceptable for use by the manufacturer, especially on a composite blade. I'm sure I don't need to be telling people that, however...Ive seen some really stooopid !!!! over the years.

My story on the subject involved 500's with ice and horse flies. No matter the season, the buildup did have an effect, most noticeably on the torque.
With so many blade shapes, designs and sizes, to do a comprehensive data collection would be an enormous task, and I don't think it's worth the time do to so to simply find out dirty blades effect performance and to what degree.

Simple solution is to clean them when they are dirty.

I've found it matters quite a bit when performance margins are close. I carry a rag in my bag for this exact reason. Using water out of my bottle I always have anyways usually does the trick and keeps the mechanics from yelling at me. Don't forget the tail rotor.

When I was taught to do it, twas at flight school in a salty environment with 22s. Seem to remember it could drop your MAP at a hover by an inch or more if I'm remembering correctly, but it's been a while.

Mike

Just read the title again and Jimmy is after Parasite Drag, rather than Profile Drag, so I suspect he is more interested in dirt on the fuselage.
At helicopter speeds, it won't make much difference, though a shiny aircraft will impress the customers more than a dirty one.

So, wipe the bird !!!! off the blades, but leave the dead bugs on the windshield.

Thank you all for the answers. Ascend Charlie is right, I was thinking about the fuselage.
Despite the logical way to don't worry about this is to keep it clean, when you are not directly responsible for the cleaning/washing and need to make an argument on reducing intervals, some data or case study could help.

Many moons ago I operated 206L on low skids with skid fairings, which got along fairly well at about 108kias. A complete professional polish with an approved Teflon polish put the cruise up to ~115kias, and later a further polish of the blades (after much checking with Bell for approval) nudged the cruise up to 117kias, all with the same power and OAT, etc.

So, the initial fuselage polish was predominantly responsible for the improved performance, all from an asthmatic C20!
http://www.eacott.com.au/gallery/d/4...hurst+1987.jpg

I agree. However, sometimes a pilot could be fliyng in a company with a tight flight schedule -45 minutes between flights, down to 30 in some occasions-, where pilots are not allowed to clean or wash the helicopters and the maintenance perform preflight inspections -pilots just performing turnarounds.

Well if you trust these chaps with your preflight then you might as well just trust them with how thoroughly they clean the thing.

Typical PPRuNe...chap asks a question about practical aerodynamics and soon ends up getting told how he should run his operation. :rolleyes:

Just pickup a few rolls of this to smooth things over.


https://multimedia.3m.com/mws/media/...l-tape-425.jpg


http://www.flystickers.com/media/cat...spdtape-bl.jpg

Shy, you are right. No insult intended. It just appeared a bit like he was looking for a scientific way to tell his footmen to keep his toy nice and shiny.

Jimmy, have you compared the values prior and after a much needed cleaning?

No, when started to think about I posted here. I'll to do that on my next shift and post. Thank you all.
:ok:

Blade tape also hampers performance.