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Compressor Wash RR C250-20B

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Compressor Wash RR C250-20B

Old 24th Apr 2016, 10:16
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Compressor Wash RR C250-20B

I am based 6km from the coast. How often would you good people on here recommend I perform a compressor wash on a C250-20B engine?
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Old 24th Apr 2016, 14:36
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A fresh water rinse at the end of each days flying is recommended, but not always practical to do. Don't leave the engine without one for more than a few days and try to have a chemical wash regularly done.

There are plenty of guys around the UK who can tell you stories of their compressor failures (I know of at least 4 in the UK in 2015) all of which were due to corrosion at the vane roots.

It may be the last thing you want to do after a long or late days flying, but is it not worth a few more minutes before you jump in the car.
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Old 24th Apr 2016, 18:25
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Comp Wash

Allison/RR prescribe the water wash at the end of any day's flying in the UK. The rationale is based on their assessment of a 'hostile environment' defined as anywhere in UK given that the maximum distance from the sea on our island is 70 miles. In addition to this are the sulphur-based contaminants emanating from industrial sites (albeit less than previously).


The advice is wise, if a compressor lets go, it will be inconvenient (of course) and seriously expensive. ~ VFR
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Old 24th Apr 2016, 20:13
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Well here's one for you

Have lived in SW with C20B's for 25 years. The only time they are washed is every 100 hours at maintenance checks. Never had any corrosion and case halves have lasted about 3 to 4 years ( new carbon fibre ones so far into year 5 !!) The 500's fly around 300 hours a year. When D and C Plod had the 105 they chemical / water washed every day, compressor case halves were doing just over a year and 600 hours.
As most compressor wheels are now coated they have a fair degree of protection. Not sure if it is a consideration but all my 500's have had filter barrier systems tor particle separators . Cant see why it would help but .....
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Old 24th Apr 2016, 20:29
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Sulfidation: High temperature turbine blade corrosion

It's not just about the compressor, the daily water wash helps with the turbines as well.
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Old 24th Apr 2016, 21:01
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Hughes 500. Agree totally , I have operated C20Bs for over 25 years less than 40 miles from the coast( and often at the coast ) never comp. washed except at the annual (even before the days of coated wheels) and never had a problem. Not a fan of leaving all that water in there.
However at annual/100hr we inspect the compressor wheels very carefully, for corrosion not just the case halves but never found any. Last case halves served 9 years ! Always kept in heated hanger at min 15c
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Old 24th Apr 2016, 22:38
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Sent a C20 compressor to Heliwork a number of years ago and received a phone call asking for a little more information on it's history. As it happened removing the compressor for overhaul was our first job on this 206 which had just been purchased by the owner.

Eric T the maintenance manager said " You know how we check for corrosion pitting with a magnifying glass, well with this one we don't need it, it looks like a swiss cheese".

They sent me all seven scrapped wheels back to have a look at. I had never seen anything that bad.

In the end you pay your money and take your chance. Water is cheap compressors are expensive.
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Old 25th Apr 2016, 16:03
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Better safe than sorry - a water rinse every evening and a chem wash every 50 should do you
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Old 26th Apr 2016, 19:22
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Dont use plain old water out the tap unless you have to according to the
Rolls Royce O&MM chapter 72-30-00 page 232 calls for highest quality water available, preferably distilled, de-ionized or de-mineralized.
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Old 27th Apr 2016, 04:19
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I keep my jet ranger within 2 miles of the Tasman Sea. My first machine I water rinsed everyday and then annoyed my neighbours by a 5 minute drying run. In 700 hours replaced three compressors . Bell reckoned I wasn't drying enough!

My next jet ranger was the one I flew around the world . On advice from a crusty old engineer at Bell in Fort Worth only had the compressor washed at the 100 hourlys. Compressor lasted over 600 hours on that unit before exchange even though over 10,000 mn over the ocean at low levels.

Most owners I know just get the compresser split at each 100 hourly and do no washes in between. Get maximum life and safety even though in a coastal environment .
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Old 28th Apr 2016, 23:15
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Thanks guys for your comments.
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Old 28th Apr 2016, 23:30
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Hughes 500 consider this - if, just if a christmas tree joint fractures or a blade goes for a walk (as it did with me one night over a city) and god forbid you had to land - causing serious injury to third party or your pax - you had better be ready to argue why you didnt find the need to follow the maintenance manual re: comp washes (including using deionised and not tap water.

The same applies to the manufacturer who refurbs your compressors - what would you do if they told you that due to you not following the maint manual, your warranty was null and void?

Shabby operations methinks...........it costs peanuts and 30 minutes to do a comp wash.....
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Old 29th Apr 2016, 09:54
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TC

You might indeed be correct in your thinking / what RR say but maintenance company has only washed them every 50 / 100 hours which in my case is every 4 months. They look after 20 RR engined machines and have never had a compressor let go in over 30 years. I would agree with you on the old compressors which didn't have coated wheels ( had to split the bloody thing every 6 months which in a 500 means engine out ) or a private owner flying once a fortnight.The problem with sticking distilled water through it means you have to light it off again to dry it out ( see Dick's post ) Now a turbine on a RR C20 B has on N1 1750 hours or 3000 starts so by washing after every day would almost half your starts, let alone N2 4500 hours or 6000 cycles and compressor 9000 cycles. My feeling is the less thermal shock ( start 0 to 800 degrees in a few seconds ) is better than trying to stop corrosion that in many peoples consideration does not exist or perhaps better is not what the manufacturer believes to be correct. Example would be my compressors, no corrosion in 25 years in over 10 different helicopters with about 6000 hours between them. Actually much more likely to have problems with the crap RR compressor case halves that I am sure are made of Swiss cheese, hence have gone to carbon fibre ones ( first in UK to have them ) which are streets better, only issue is sending the compressor to a RR AMC who hate seeing them as they don't need changing so often ( so no $ 10k bill ).
Only compressor problems I have had have been after overhaul where the AMC had not balanced the impeller properly , caused the anti ice seat flange to crack off the case completely n less than 300 hours. In other case the impeller cracked due to vibration due to guess what the manufacturer not making it properly !
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Old 29th Apr 2016, 21:24
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Just to bring a little humour to the thread ... in my dim & distant sales days, when helicopters meant Enstrom & piston engines for me ... my party piece was to explain to potential Bell customers what wonderful creatures the turbines were. No awkward throttle twisting, oodles of performance and always more than enough power. BUT ... the dreaded Bell JR was a firm enemy of Enstrom piston sales, so I was always at pains to explain the niceties of the factory's compressor wash requirement for the C20.

Picture the scene. Lovely wife and family loaded on board for a great night out at a posh hotel. A perfect landing on the lawn and, being the perfect husband ... you open the cabin doors and escort your lady in her finery to the hotel entrance and the envy of all around. BUT ... it's not for you to join the party yet. There's work to do. Time to don the overalls to avoid muck dirtying the DJ and, while ignoring the curious stares from your friends, you retrieve a 10 litre bucket and a hand operated stirrup pump from the luggage locker ... and make a quick search for the nearest water tap. You'll now need to mount the stirrup pump in the bucket and use the short steps you carry to gain access to the engine compartment where you disconnect the PC line and plug in the water connector from the stirrup pump. Once nicely connected, you ask a friendly local to work the pump as you engage the compressor starter. A minute or so of rapid pumping will easily be enough to ensure a really good compressor wash. But we are not quite finished yet ... even as your good lady appears to see what's going on and ask what the hell you're doing messing about with your five hundred grand helicopter. You quietly advise her to go back to her friends. You'll be joining the party in less than ten minutes. Now there's just a single drying run to complete the job.

There's actually a whisker more to it of course, but I mustn't labour the point. Just a couple of starts to record in the tech log, stow the bucket and pump and remove the boiler suit. Hey presto ... in no time you're ready to join the party for the fine dining you've booked with only a few spots of engine oil left to clean up. You're the envy of all! That's the way to make the 'Grand arrival.' ....

Personally I've always followed the advice of Hughes 500. Take care all. Dennis K.
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Old 1st May 2016, 08:34
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While I can appreciate the common practice of flushing RR 250 turboshaft engines operated in a marine environment with distilled water on a regular basis to comply with OEM warranty requirements, I don't see how it really reduces surface corrosion of compressor blades. Even after the compressor blades are washed with distilled water, in a marine environment they will still be exposed to more salt air unless the engine volume is purged and sealed.

A more serious problem presented by introducing water into the internal space of a shut-down turbine engine is migration of water past the seals and into the engine's lube system, where it will cause corrosion of bearings, shafts surfaces, etc. The labyrinth seals used in most turbine engines quit working when the flow of bleed air stops.
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Old 1st May 2016, 19:44
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refer to the Allison CSL to see if you are in a Corrosive environment as well,,if you are in a corrosive environment such as the eastern seaboard of the US, then the compressor inspection is done every 300 Hrs I think. If you dont, you have voided your airworthiness certificate, and any incident is on you,,,

Last edited by lamanated; 2nd May 2016 at 19:02.
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Old 1st May 2016, 21:21
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Hughes500, you are trying to argue with common sense and personal experience against a dogged, unquestioning military adherence of the printed word and SOP. You'll never win.

By the way, I'm sure the filter barrier gives some protection to the compressor coating from erosion from fine particles.
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Old 2nd May 2016, 07:31
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Dennis how the devil are you, just love your post a typical salesman !
KJ what I always find interesting are posts made by some, all i can say not only ask the people who fly them but ask the people who maintain them as well as the poor sod who has to sign the cheque personally ! They would then understand that manufactures try their best to take the piss on price and quality and availability.
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Old 2nd May 2016, 22:32
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All those little cracks in the compressor linings absorbing water then getting hot, & they can be there after 20 \30 hours or less of following RR to the letter
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Old 2nd May 2016, 23:50
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I concur John, I have seen AFS filters packed with salt. The seem to do a pretty good job stopping it.
One thing I learned from my insulator washing experiences. There is way more airborne salt the closer to the equator you get. I assume its just a result of more evaporation. Power companies on the gulf and southern California coasts have to wash salt from their power lines annually. In the northwest and north east. I've never heard of it.
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