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R44 Stuck Exhaust Valve @ 300 Hour Check


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Hey Everyone -

 

I have been reading a lot about shut down and cool down procedures for the R44 to help with sticking exhaust valves. I came up on my first annual and 300 hour check and the #5 exhaust valve had to be reamed out...it was pretty tight according to the IA.

 

In a discussion with the mechanic as well as the owner/pilot of the shop, we walked through pretty much every facet of how I fly the 44. In addition, I have an EDM 800 which showed nothing weird in the temps. The #5 did show a little lower EGT but normal CHT.

 

Since I own the bird, I rarely push her above 21" MP pressure in cruise and most of the time I am at 19 or 20". Several times over the last year I found myself near or at MP redline and have since taken great pains to stay out of that area of operation. I run 7 quarts of oil all the time and only use about a quart of oil every 5 to 6 hours. The oil and filter are changed every 50 hours and oil testing shows nothing abnormal. I am fanatical about the care of my ship and (much to his dismay I am sure) question my mechanic about every little thing on my ship.

 

When I first bought the R44, I did spend a lot of time flying to and from Phoenix, but the EDM never showed any high temps on any of the cylinders.

 

On the cool down I was taught to land, roll the power to 60% to 65% and cool down for two minutes followed by a clutch disengage and an additional 30 second cool down and then pull the mixture.

 

Later I was told to wait for a big drop in CHT, so I started doing that. So now I cool down by landing, rolling the power to about 65% and waiting until the CHTs drop by at least half of what they were. As you can see by my EDM while in flight, they don't run that high. My cool down typically takes 3 to 4 minutes. I own the bird and I am never in a rush to shut down.

 

edm_in_flight.jpg

 

I guess it really bothers me that the valves are sticking at 300 hours when I am the only guy flying the machine. It leads me to believe that I am doing something wrong in how I fly my bird and that is bothersome since I figured I was taught right from the beginning and in my mind, I have been babying her, not running her hard and putting her away hot.

 

I guess I am looking for advice from other operators/mechanics of R44s. What is normal..? What about a good cool down procedure. I read somewhere that you should cool down at 75% no less to keep the air moving across the engine and then 65%.

 

:huh:

 

 

Thanks in Advance

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I don't have any 44 time, and only a couple of hours of robbie time. However, I feel I should point out that sometimes things just break for no good reason. A stuck valve could just be a stuck valve, and not caused by anything you did. Of course that doesn't invalidate your question or concerns. My best advice is, how does the RFM say to cool down?

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I worked with a robby mechanic and he told me he reams the valves out at 300 hours all of the time as part a preventative maintenance so he obviously had a valid enough reason in his mind to to that. Of course what one mechanic says is pretty tight and what is ok could be a question. What was the thickness of the gap and what is the minimum and what is normal? These are questions I would ask the mechanic.

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I think to answer your question about how to prevent a valve problem we must first ask was your valve bent? If all the mechanic did was ream the valve guide than I would think that the problem is most likely carbon build up. A number of reasons can cause excess carbon build up. Running with the mixture too rich will add to build up of carbon as well as running at lower manifold pressures for extended periods of time. It is possible that doing a longer than necessary cool down may also add to build up.

 

It is my understanding that the engine on the 44 is actually rated for a higher horse power than it is run during normal operations. As long as you keep the MP anywhere in the normal operating range you should be fine.

 

I know you are concerned and you have a right to be. You have a beautiful helicopter that anyone would be proud to own. I would be a little concerned to have a mechanic do work on my engine and not give me at least a reasonable explanation to what would be causing the problem. You have too much invested to not get answers.

 

I am not an A&P but I have been around engines for a long time. Just my 2 cents.

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I had a problem with a stuck valve in a 22, (three mornings in a row) it turned out the CFI that was flying the afternoons before was doing quick shutdowns. I watch for CHT to be at or below 275 before pulling mixture. The POH only says "CHT drop" but I have had no problems with stuck valves using thie 275 shutdown.

 

I will be interesting to see what that valve guide looks like at the 500hr on your bird.

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Guest pokey

Lycoming engines are notorious for stuck valves & Lycoming knows it. They have several service instrux. addressing this problem. Poke around their website & I'm sure you will find alot of info about this problem. I ream the guides in the 300's every 300 hours regardless. I would recommend that you go back & have your mechanic ream ALL of the guides, (not really a fun job trying to get that valve back in its hole w/ the cylinders installed, but? it can be done). BTW? What type of oil are you running? I run the aeroshell 50 PLUS, (B4 they came out w/ the PLUS, i used the aeroshell 50 w/ the Lycoming additive) The additive was supposed to help w/ sticking valves--but? they still stuck.

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I think to answer your question about how to prevent a valve problem we must first ask was your valve bent? If all the mechanic did was ream the valve guide than I would think that the problem is most likely carbon build up. A number of reasons can cause excess carbon build up. Running with the mixture too rich will add to build up of carbon as well as running at lower manifold pressures for extended periods of time. It is possible that doing a longer than necessary cool down may also add to build up.

 

It is my understanding that the engine on the 44 is actually rated for a higher horse power than it is run during normal operations. As long as you keep the MP anywhere in the normal operating range you should be fine.

 

I know you are concerned and you have a right to be. You have a beautiful helicopter that anyone would be proud to own. I would be a little concerned to have a mechanic do work on my engine and not give me at least a reasonable explanation to what would be causing the problem. You have too much invested to not get answers.

 

I am not an A&P but I have been around engines for a long time. Just my 2 cents.

 

The mechanic and the owner (who is also a pilot) said if they did not know me personally they would have thought that I was not cooling down long enough. However since they both know me and know how I treat my helicopter, they were at a loss as to why it might be happening. They rent a 44 and have never seen the valve sticking problem in over 1000 on their ship.

 

The valve was not bent, just very tight and had to be reamed out. We went through 30 minutes if discussions about how I operate the helicopter and could not come up with any ideas as to why it is happening.

 

This is the first time I have heard that too long of a cool down could cause the same problem. When its very hot out, I sometimes cool down for 10 minutes, could this be the issue...?

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Lycoming engines are notorious for stuck valves & Lycoming knows it. They have several service instrux. addressing this problem. Poke around their website & I'm sure you will find alot of info about this problem. I ream the guides in the 300's every 300 hours regardless. I would recommend that you go back & have your mechanic ream ALL of the guides, (not really a fun job trying to get that valve back in its hole w/ the cylinders installed, but? it can be done). BTW? What type of oil are you running? I run the aeroshell 50 PLUS, (B4 they came out w/ the PLUS, i used the aeroshell 50 w/ the Lycoming additive) The additive was supposed to help w/ sticking valves--but? they still stuck.

 

 

I am running Aero Shell 15W-50 which is the same as all of the other Robbies in that shop. I do not any additives in the oil or fuel.

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The mechanic and the owner (who is also a pilot) said if they did not know me personally they would have thought that I was not cooling down long enough. However since they both know me and know how I treat my helicopter, they were at a loss as to why it might be happening. They rent a 44 and have never seen the valve sticking problem in over 1000 on their ship.

 

The valve was not bent, just very tight and had to be reamed out. We went through 30 minutes if discussions about how I operate the helicopter and could not come up with any ideas as to why it is happening.

 

This is the first time I have heard that too long of a cool down could cause the same problem. When its very hot out, I sometimes cool down for 10 minutes, could this be the issue...?

 

 

the factory will tell you no more then two minutes. During the summer i might wait 3 or 4 but i always am at least 2. I would run the manifold pressure as stated in the POH. Don't baby it, their designed to produce that amount of power. The several r-44's i have flown get the SB valve inspection and have never had an issue. I do know that all of those helicopters have been worked, meaning no one has babied them. I don't mean any offense to the babying of the helicopter but it might be a cause, because day in and day out you are only asking for 20 inches and then every once and while you pull up to 25 inches she might not be used to that. I had a similar issue in an r-44. Had the valve inspections everything was good. This day was 95 degress with 100% humidity, the student QUICKlLY added collective just below red line and a valve stuck. ran rough and lost a little power but came back. No big deal they will stick from time to time.

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I have my ship serviced by Rich Carter in the Seattle area, he personally owns and least 40 Robbies and regularly maintains at least that many more, he's an excellent mechanic with a lot of experience. He has seen that reaming the valve guides at 300 hrs, proper cool down and fresh oil of the right kind is the best insurance against valve sticking.

 

I use Aero Shell 15-50 during the winter and W100 plus in summer months, both contain the anti wear additive. Since new, I have changed the oil and filter every 25 hours per his suggestion. At 100 hrs I had the side clearance check done and all ranged either .019 or .020, in the middle of the range. Rich has had recent experience with ships that were running Exxon Elite (never hear of it) where the valves stuck so badly that they went through the top of the piston, I don't know if that oil has an anti wear additive.

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<snip>

I have been reading a lot about shut down and cool down procedures for the R44 to help with sticking exhaust valves. I came up on my first annual and 300 hour check and the #5 exhaust valve had to be reamed out...it was pretty tight according to the IA.

<snip>

In addition, I have an EDM 800 which showed nothing weird in the temps. The #5 did show a little lower EGT but normal CHT.

<snip>

I guess it really bothers me that the valves are sticking at 300 hours when I am the only guy flying the machine. It leads me to believe that I am doing something wrong in how I fly my bird and that is bothersome since I figured I was taught right from the beginning and in my mind, I have been babying her, not running her hard and putting her away hot.

<snip>

What about a good cool down procedure. I read somewhere that you should cool down at 75% no less to keep the air moving across the engine and then 65%.

<snip>

 

Unless you had noticeable power loss and/or significant engine vibration then I suspect you did NOT have a stuck exhaust valve. In my experience, one definitely notices a stuck valve (closed or open) and your EDM800 should also have recorded the event, presuming a reasonable sample rate. The fact your mechanic had to ream the exhaust valve guide only indicates "insufficient clearance" was measured, but that is what Lycoming SB388C is supposed to detect, and before things become problematic (read: stuck).

 

First 300-hour check? RHC's published maintenance schedule indicates SB388C be performed at the first 100-hour inspection, and thence every 300 hours.

 

If you operate a Lycoming engine in a warm environment it will at some point probably require exhaust valve guide reaming per their Service Instruction 1425A. More info on stuck exhuast valves, from both operational and maintenance perspectives, is available online at:

http://www.lycoming.com/support/tips-advic...ints/index.html

(next time you are near KTOA drop in and ask an RHC Tech Rep's for a hard copy - they are part of the maintenance course curriculum)

 

Both the R44 and R44II POH's recommend cooling down at 60-70% rpm, while the R22 POH recommends 70-75% rpm, so 70% rpm works for all models. The POH's also do not specify a cool-down time, only "CHT drop", and several minutes cool-down is typically required in a hot environment before thermal equilibrium is reached i.e. the CHT stabilizes. Conversely, in colder environs comparatively less cool-down time is required.

 

As to the 50-hour oil changes, that falls within the published schedule but it may not be sufficient for your specific operation. Check out this article:

http://www.avweb.com/news/savvyaviator/194208-1.html

 

I have never flown an R22/R44 with an EDM800 so I cannot comment on the typical intercylinder EGT spread, but you might exchange the #5 cylinder's fuel injector nozzle with that of another cylinder to determine if the "little lower EGT" is due to the nozzle.

 

You will enjoy a turbine engine, but sometimes even they require reaming (of an oil passage).

 

Fly safely.

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Unless you had noticeable power loss and/or significant engine vibration then I suspect you did NOT have a stuck exhaust valve. In my experience, one definitely notices a stuck valve (closed or open) and your EDM800 should also have recorded the event, presuming a reasonable sample rate. The fact your mechanic had to ream the exhaust valve guide only indicates "insufficient clearance" was measured, but that is what Lycoming SB388C is supposed to detect, and before things become problematic (read: stuck).

 

My EDM did not ever show anything abnormal. The #5 EGT has always been low from the time I had the EDM installed. Several months ago I lost my aux fuel pump. After it was replaced, I noticed a definite different vibration in the helicopter. I had it checked by my A&P as well as flown by another pilot. They both told me that it was "running fine". Maybe this was my first indication and I just didn't know it.

 

First 300-hour check? RHC's published maintenance schedule indicates SB388C be performed at the first 100-hour inspection, and thence every 300 hours.

 

Yes, this is my first 300 hour check. Nothing showed at the 100 hour check.

 

If you operate a Lycoming engine in a warm environment it will at some point probably require exhaust valve guide reaming per their Service Instruction 1425A. More info on stuck exhuast valves, from both operational and maintenance perspectives, is available online at:

http://www.lycoming.com/support/tips-advic...ints/index.html

(next time you are near KTOA drop in and ask an RHC Tech Rep's for a hard copy - they are part of the maintenance course curriculum)

 

Thanks - I downloaded the reprint. Seems specific to fixed wing aircraft, but good information.

 

Both the R44 and R44II POH's recommend cooling down at 60-70% rpm, while the R22 POH recommends 70-75% rpm, so 70% rpm works for all models. The POH's also do not specify a cool-down time, only "CHT drop", and several minutes cool-down is typically required in a hot environment before thermal equilibrium is reached i.e. the CHT stabilizes. Conversely, in colder environs comparatively less cool-down time is required.

 

I cool down at 65% for whatever amount of time it takes for my CHTs to drop in half. Sometimes out in the desert this can be 10 minutes or more.

 

As to the 50-hour oil changes, that falls within the published schedule but it may not be sufficient for your specific operation. Check out this article:

http://www.avweb.com/news/savvyaviator/194208-1.html

 

OK, so for the low cost of an oil change, maybe I should switch to 25 hour changes as opposed to 50 hour changes.

 

I have never flown an R22/R44 with an EDM800 so I cannot comment on the typical intercylinder EGT spread, but you might exchange the #5 cylinder's fuel injector nozzle with that of another cylinder to determine if the "little lower EGT" is due to the nozzle.

 

You will enjoy a turbine engine, but sometimes even they require reaming (of an oil passage).

 

Fly safely.

 

Working on that one, but I really want to make sure I am running my R44 the right way in the mean time!! Thanks for the great information.

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I'm flying an 08 R2 also, and I've been changing the oil every 25 hours, 35 if I get too busy.

I've been cooling down at 65%, normally around two minutes. If it is really cold out I it is occasionally less than 1 minute before I drop to idle and disengage the clutch. But most of my LZ's are 1000-2000' drop from normally flight altitude (call it mountainous if you will), so it cools down a lot on the way down at 12-14" mp. On a hot day I normally cool down for 3 minutes or until there is a noticeable drop in CHT (must be cooler than 300), almost never more than 3-4 minutes.

During cruise I normally run it a hair under maximum continuous power, unless I'm solo I'll run it around 20".

However I've only got around 170 hours in this ship, 100 hour looked fine. Oil is 15w50 at the moment.

The other r2 I flew a lot had around 400 hours on it when I left, if I remember correctly, most of the hours were from me. It was flown and cooled down the same, no issues that I was aware of, unless maintenance found something I didn't know about. But it always ran great, just lots of track and balance sessions.

 

If you're running at high DA a lot, the ship is running rich and you're going to be more susceptible to carbon build-up. Just part of the nature of having to run it full rich all the time.

 

The school I worked at had a lot of stuck valves in the R22's, definitely much more common in the summer, we suspected from short cool-downs, excessive use of carb heat, etc. But sometimes things just happen. From what you are saying, doesn't sounds like you are doing anything wrong, but 10 minute cool downs might be a bit unnecessary.

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Lycoming engines are notorious for stuck valves & Lycoming knows it.

 

Richard- Pokey said exactly what I was going to. We run ours down to 70% for cool down, two minutes at a minimum. If temps outside are really high, like 90+ you might wait 3 minutes, then disengage clutch, 30 seconds then lean it off. Pretty much the same as what you are doing now. I would guess the problem is more Lycoming related than it is HeloJunkie related !

 

Good catch by the mechanic though.....fix it now as opposed to getting a stuck valve in flight.

 

Goldy

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Lycoming have been known for valve problems, these are old links, but it shows the general trend.

 

http://egaa.home.mindspring.com/engine1.htm

http://www.airplanebroker.com/MARV.HTM

They might not be current engines & Lycosorus might have incorporated some or all suggestions, but is shows you are not the only one who has problems, We have with the 300 & yes we cool it as per the book every time.

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At the factory safety course they were saying that longer than needed warm ups and cool downs can lead to carbon build up. Once the gauges are in the green, start flying; don't keep it on the ground running. For shut down, keep it running only long enough for the CHT to drop. The amount it drops and how quickly will depend on the outside temp, obviously. This is what was taught to us just last week, but I'd suggest calling them for yourself.

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At the factory safety course they were saying that longer than needed warm ups and cool downs can lead to carbon build up. Once the gauges are in the green, start flying; don't keep it on the ground running. For shut down, keep it running only long enough for the CHT to drop. The amount it drops and how quickly will depend on the outside temp, obviously. This is what was taught to us just last week, but I'd suggest calling them for yourself.

 

Hey Shakes -

 

Thanks. Same thing they told me at the safety course. On the side however, Pat told me that the 2 minutes was an absolute minimum and that you should cool it down until there was a "solid" drop in CHT temps.

 

All open to interpretation by the pilot of course!!

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Richard- Pokey said exactly what I was going to. We run ours down to 70% for cool down, two minutes at a minimum. If temps outside are really high, like 90+ you might wait 3 minutes, then disengage clutch, 30 seconds then lean it off. Pretty much the same as what you are doing now. I would guess the problem is more Lycoming related than it is HeloJunkie related !

 

Good catch by the mechanic though.....fix it now as opposed to getting a stuck valve in flight.

 

Goldy

 

Hey Goldy -

 

Yea, Mike at Civic is a fantastic mechanic that always takes the time to talk to me, talk about other ships he has seen, offer advice and suggestions and answer my unending string of questions about my helicopter. In my mind, choosing a place to park your helicopter is so much more than monthly price.

 

Thanks to information from Civic, Robinson, Lycoming and everyone that replied here, I am going to make some changes to the way I warm up and cool down.

 

After reviewing all the data from my EDM800 (snapshots every 2 seconds of 28 engine parameters), the cool down process is certainly cooling the engine. Never once in all the data was the engine shut down with excessive CHTs which was the first concern by many. Nor was it flown prior to a good warm up temperature. All other parameters were good across the board. No high MP, no high oil temp, etc.

 

So cool down and warm up temps are not the issue, so I now look at all the other suggestions including too rich of mixture for warn up and cool down and maybe too long of a cool down period.

 

Starting now, I am going to lean for warm up and cool down, plus cool down to a specific CHT temperature as opposed to a "drop in CHT temperature". I just need to figure out the optimal CHT temps for shut down. Since the EDM shows the exact temperature of each CHT, I need to pick the right cylinder to measure and the exact temp I want to shut down at and manage shut down in that manner.

 

Hopefully this will cure the problem....I guess we will find out in 200 hours !!

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At our flight school we had this problem all the time(in R22's). We always used TCP fuel additive. It prevented the valves from sticking. Whenever we had a valve stick, we would ask if TCP was being used and the instructor would usually say, "the syringe was broken so I hadn't been using it."

 

We added it at every fueling, unless we fueled in the field somewhere. When we didn't, the valves would start to stick within 10-20 hours.

 

http://www.aircraftspruce.com/menus/ap/fuel_additives.html

 

 

Marc

Edited by Marc D
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http://precisionengine.home.mindspring.com/engine1.htm

 

 

I have met these people, true professionals & interesting reading. (BTW, his wife Carol is a QTpie) ;)

 

That is a really good read. A must for any owners!

 

I had always wondered why they couldn't just put in some "hardened" valve guides. This article really cleared it up.

 

Marc D.

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