Increased parasite drag by dirt and bugs
Thread Starter
Joined: May 2017
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From: Atlantic Ocean
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!
Thanks!
Last edited by Jimmy.; 6th May 2018 at 09:24. Reason: Grammar correction
Joined: Sep 2002
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From: Great South East, tired and retired
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.
Joined: Sep 2017
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From: Canada
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.
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.
Joined: Jul 2002
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From: Somewhere, Over the Rainbow
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
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
Joined: Sep 2004
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From: Canada
The smaller the blade chord the greater the loss of lift..500s were famous for this...dirt, bug, ice contamination or sand erosion and useful load was lower.
Brand new 500...stump puller...2-300 hrs in a sand environment..not so good.
Luv the 500, great aircraft, so no criticism intended.
Brand new 500...stump puller...2-300 hrs in a sand environment..not so good.
Luv the 500, great aircraft, so no criticism intended.
Joined: Sep 2002
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From: Great South East, tired and retired
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.
At helicopter speeds, it won't make much difference, though a shiny aircraft will impress the customers more than a dirty one.
Joined: Nov 2017
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From: earth
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.
At helicopter speeds, it won't make much difference, though a shiny aircraft will impress the customers more than a dirty one.
Thread Starter
Joined: May 2017
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From: Atlantic Ocean
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.
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.
Joined: Mar 2009
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From: Canada
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.
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.
Time to take on more responsibility me thinks.
Joined: Aug 1999
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From: Gold Coast, Australia
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!
So, the initial fuselage polish was predominantly responsible for the improved performance, all from an asthmatic C20!
Thread Starter
Joined: May 2017
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From: Atlantic Ocean
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.
Joined: Mar 2012
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From: steady
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.
Avoid imitations
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From: Wandering the FIR and cyberspace often at highly unsociable times
Typical PPRuNe...chap asks a question about practical aerodynamics and soon ends up getting told how he should run his operation. 
Joined: Mar 2012
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From: steady
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?
Jimmy, have you compared the values prior and after a much needed cleaning?
Thread Starter
Joined: May 2017
Posts: 103
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From: Atlantic Ocean
