Jump to content

300C Autorotations and stuck Valves

Recommended Posts

It is time to send this story winging out there in hopes that it will help keep my fellow 300C pilots safe and to find out how many of you have had problems with sticking valves.  I have owned 56PH for about one and a half years and spared no expense in maintaining her in top condition.  She is a 1990 machine on a second run engine which was about mid-time.  We had recently completed a 1200 hour inspection and installed a new MR driveshaft.  I always work along with my mechanic.  It was never mentioned to me that this bird had a potential problem with sticking valves.  Only after my emergency did I find that other pilots and mechanics more knowledgeable and more experienced had either had problems or knew of others having problems.  My bird showed no early warning signs such as "morning sickness".  It had run perfectly until that moment.  At 1000 feet AGL, I had about 40 seconds from the first "pop" and loss of power to the time I was on the ground.  I can tell you that instinct learned through practice is what brought me and my grandson to a safe landing.  Fortunately we were not hurt but the bird certainly was.  I had just bought my new 406 mz emergency beacon several months earlier for just such an occassion.  Anyone flying over or landing in desolate areas must have one of these.  Although we were spotted by local campers who contacted us in about 15 minutes, I had already activated our 406 beacon and a search had begun with 5 minutes.  My ELT which I installed several months earlier did activate.  My cell phone did not work and my handheld radio did not function because I was unable to see it clearly because I lost my glasses in the rollover.  I had a flare gun which I used, a strobe beacon which I used, and really wished I had a spare pair of glasses.  It is hard to think clearly when you cannot see clearly!!!


After removal of the airframe to my FBO for inspection by the NTSB, mechanics were able to start the engine and it ran perfectly all the way up to 3100 rpm.  Such is the nature of transient valve sticking problems or so I am told. Some have said that adding more throttle can sometimes unstick a valve.  40 seconds does not give you much time to sort through engine problems.  Although I did retest the engine one time just prior to entering full autorotation, I found it still not producing flying power and popping unmercifully.  At that point my full attention was focused on getting my bird on the ground in very heavy forrested conditions.  I am interested to find out how many other 300C pilots have had experience with this problem in the 300C.  Why don't we hear more about it?  What can we do to prevent it?


I am in the process of putting my bird back together.  We will both fly again another day.  I need lots of parts.  Anyone having any (especially main rotor blades) give me a call or email at 562-458-8317 or Rgrafty@direcway.com.  




Accident Chronology July 9, 2004



After clearing US customs in Bellingham Washington, we departed for Arlington Airport north of Seattle.  Time of departure was approximately 19:30 hours local time in VFR conditions with unrestricted visabilities and a few clouds.  The route of our flight was to take us along the I-5 corridor with a relatively short cross deviation direct to Arlington when the I-5 diverged from our route to the west.  I was in contact with FSS to inquire about camping availability at Arlington.  At about 15 miles outside Arlington and at about 2500 to 3000 MSL, I attempted to contact the temporary tower set up at Arlington because of the airshow that weekend.  I was told by another pilot that the tower had just closed and I then switched frequencies to the multicom frequency to make further more specific inquiries about camping locations on the field.  I reached a pilot who was unable to advise me of camping because I was a helicopter.

My grandson and I heard a "pop" and I felt a yaw to the right and a loss of power.  I immediately sensed a problem with the engine and entered partial auto-rotation to take power demands off the engine.  I observed the engine running at about 2000 rpm and attempted to increase collective to restore flying power.  The engine did not respond properly and was miss firing and running roughly.  Due to my initial elevation which I judge to be approximately 1000 feet AGL and the fact that I was loosing elevation rapidly, I decided to enter a full auto-rotation and lowered collective.  The terrain below was extremely rugged with coverage of trees.  I spotted a clearing behind and to my left.  It appeared to be a clear-cut and was the only suitable choice to attempt an emergency auto-rotational landing.  I made a 180 degree turn to the left while descending in auto-rotation mode.  I was too busy surveying the landing zone to do any further assessment of the engine capability.  I do feel that it was probably still running but I made no further demands on it.  When we cleared the trees at the edge of the clearing, I noticed a large stump immediately in my path and diverted the aircraft to the left slightly to miss the obstruction.  As I neared the ground, I pulled in collective and flared for a landing expecting to touch down and skid to a stop.  The ship touched down in a leveled configuration and immediately stopped and rolled over onto the nose and left side of the aircraft where it came to rest.  The landing surface turned out to be a bog or swamp.  The surface which appeared from the air to be firm was more like a sponge.  A thick green carpet of grasses and small shrubs covered a mass of downed logs and branches which were floating or lodged in a watery pond that was approximately a foot to a foot and one half deep where we landed.  There was no possibility that the aircraft was going to be able to make a normal full down auto-rotational landing.  Something grabbed the skids and immediately rolled us over.


Immediately after the landing and subsequent roll-over, we accessed our situation and found that neither one of us was hurt and departed the helicopter.  Some fifteen feet from the aircraft, I further assessed our physical condition and determined we were both OK.  At that point, I went back to the aircraft to switch off the master battery switch because avgas was dripping from the vent tube on upper tank.  I also retrieved my emergency signaling devices including a 406 mh PLB, hand held transceiver, and cell phone.  I activated the  manual trip on the PLB and attempted to reach someone on the transceiver tuned to the multicom and 121.5 frequencies.  I had no luck with the radio and attempted the cell phone which did not have decent reception.  


After about 15 minutes, we heard a voice from across the clearing and began preparations to walk out to that location.  We walked through some exceptionally difficult terrain and reached the person in about one hour.  It took about an hour to walk the one-fourth mile because of the terrain and vegetation.  We were then met by the fire department which had been summoned by the campers that heard our engine trouble and saw us auto-rotate down.  We were transported on four wheel drive quads to a dirt road some two miles away and then taken by pickup truck to an ambulance waiting at the main road.  Transport was then made to the local hospital where we were checked over and released.


Link to comment
Share on other sites

I had 2 stuck valves a couple of years ago with a student. Yaw was to the LEFT, manifold pressure increased, I took control and entered autorotation. Unlike you we had a fairly level feild to go to. I treated it like a power recovery at the bottom cause I knew there was some power in the engine and I might as well use it. Landing was uneventfull, no damage, engineer drove out to feild and reemed the valves, I flew it back to base alone(student quit) and they replaced the engine. The time left on engine was 9 hours from 1500 air time, probably close to 2400 hours flight time, thats if you believe whats in log book! The valves at that point had been sticking like crazy and the owners wanted to squeeze every hour out of it, we decided that no student would go solo in this ship (C-GNAB). I quit working for them a month later, to cheap and dangerous.
Link to comment
Share on other sites

A major reason for sticking valves is insufficient cool-down. Specifically, shutting down the engine before the CHT is at/below 300 degrees. This will cause the oil to "coke up" in the exhaust valve guides, causing the valve(s) to stick in high-power operation. It won't show in a run-up unless you get the CHT up to a high/normal temp.


Good on you for walking away from the wreck - I hope you get your ship back flying soon!

Link to comment
Share on other sites

Every 300 hrs you're suppose to do the "wiggle" check on the valves.  Lycoming service bulletin (can't remember the number--sorry.)


Take the valve cover caps off, use the special tool to remove the two springs per valve, and move the valve around.  They make some $500 device to measure it, but you don't really need it.  If it drags or you can't wiggle the stem inside of the guide, you need to ream it to .5000".  Start with a .4990" if they're really bad, otherwise a .4995" will do the trick.


Someone here suggested using fishing line to drop the valve into the cylinder.  I always used the grabber tool and magnet method, but I'll try that next time.  Otherwise, just follow the directions.


In the Robinsons, I'd always ream the valves around 300-400 hours TT.  After that, they really never needed it again.  But that was because.......


One thing to help prevent it--dump in a can of AvBlend at every oil change.  At $20 a can, it gets expensive, but I never had a problem after using it.  You can't do this in your fuel injected 300C, but in the Robinsons or Cb, get an AutoGas STC.  NO LEAD = NO VALVE STICKING.


Sounds like a scary experience.....awesome job on saving your butts.



Link to comment
Share on other sites

I would like to hear more about AVBLEND. I've known about it for years but know of only one flight school that uses it in their Cessna 172's. They complain of chronic oil leaks. Does anyone else really think avblend helps? What about brand of oil or time between oil changes? Of course as Flingwing stated proper cool down is a must! I see the stuck valve happened in July. Proper cool down in my H269A takes forever on a hot summer day, one small oil cooler.

Maybe we should start a poll?

Engine Model?

Brand of oil?

Brand of filter?

Time between oil changes?

Time between filter changes?

Oil additive used?

Have you experienced stuck valves with this combination?


I'll start:

HIO 360 B1A

Phillips x/c 20w50

Champion filter

Oil- 25hrs

Filter- 25hrs

No additives

No stuck valves " knock on wood "


Link to comment
Share on other sites

300CB (2001)



300CBi (2004)



Shell 20-50 Synthetic blend, no additives

Oil & filter every 25 hrs, Champion filter


ALWAYS cool to/below 300 CHT before stopping the engine.

All good!

Link to comment
Share on other sites

My experience was with R22 B/BIIs, R44 A/Rs.  All had ADC spin-on oil filter STC adapters for Champion filters.  We ran Aeroshell 15W-50 in the below 40 degrees, 80W from 40-50 degrees, and 100W-Plus anytime it was over 50 degrees.  AvBlend at every oil change.  Ran a 50/50 mix of 100LL and 93 Premium (no ethanol) on a HJ-Fuller/Peterson STC.  Mandatory TWO minute cool down regardless of OAT.  No valve sticking problems with those ships.


Any ships that came in that ran on 100LL or didn't do proper cool downs ALWAYS had sticking valve around 300-400 hrs TT.


And Flingwing is absolutely right......Cool downs are the secret to prolonging engine life.  We had this one 400hr R22--the owner NEVER warmed it up or cooled it down.  He would run it up to 100% as soon as the clutch engaged, and would give it about a 30 second cool down if that.  He was too important and busy to waste that time, right?  We bought it from him with about 500 hrs on it and had to replace ALL FOUR cylinders.  The exhaust valves were disfigured and beat up the seats and guides.  Luckily I caught it before the engine "ate" itself.  Of course we took that off of the purchase price of the ship.


Another thing to keep in mind.  JUST BECAUSE its 10F outside, doesn't mean you can cut your cool down time.  When you land, the CHT is showing something like 300F when on hotter days it's up around 350-375F maybe?  Well OF COURSE because the OAT is 50-75F lower than it normally is.  I'd get these solo students on super cold days that would shut it down secods after they lowered the collective because the temp was "all ready down" around 300F.  Thats 300F difference from ambient!  Normally, I'd try to get it around 200-225F difference from ambient.  So on hot summer days, get it at least one needle width left of the 350F line.  IN ANY TEMPERATURE, this almost ALWAYS took 2 minutes.


That was my experience.

Link to comment
Share on other sites

At the end of the day, however, there's no way to know what caused the problem. It could just as easily have been contaminated fuel, or an injector problem, or a wire that has an intermittent open.


We always cool down three minutes, one minute at operating RPM and two minutes at 2000. Always. Now I know why.

Link to comment
Share on other sites

IgorS brought up something we haven't discussed, cool down procedure.

My Shut Down Check List is very vague on cool down procedure. It says to run at 1850rpm until oil temp stabilizes. My old H269A likes to run high oil temps, 200o to 220o. This always concerned me but people with more knowledge than me say this is fine. I've been in 300Cb's that couldn't get the temp over 170o and that is not warm enough to cook out the moisture, the dip stick was even rusty.

So is there a right way and wrong way to cool down?


Link to comment
Share on other sites

I want to thank everyone for giving my post some serious thought.  I sure wish I could have seen this discussion before my accident.  As I suspected there are many more instances of valve sticking problems than we might think.  I am really surprised the factory has not addressed this issue.  I can find nothing in the HMI that addresses a "wiggle test" or even a reference to Lycoming's discussions of the problem.  This is a problem critical to flight safety and I think it is happening far more than we hear about.  On going maintence of this critical valve system needs to be addressed in the schedule of periodic inspections--perhaps the 300 hour inspection.  The NTSB is well aware of this issue and one of their investigators sent me copies of some pages that appear to come from a Lycoming maintenance manual which address the problem and on-going maintenace to prevent it.  Unfortunately, I do not know the source manual where this information originated.


In reviewing the replys to my post, several things come to mind:


1.  Cool down is obviously important.  Whether that was a factor in my incident, I am not certain.  As a student and subsequently as an owner, I religiously cooled down below 300 degrees which took sometimes almost 5 minutes on hot days.  I only put 150 hours on 56PH so I cannot vouch for cool downs prior to my ownership.


2.  I follow a strict oil change schedule.  I change oil every 25 hours with Shell 15w-50, new filter, oil analysis every change.


3.  I have not used any additives but my FBO, after the accident, said they had some valve sticking problems with their training ships and started putting Marvel Mystery Oil in the crankcase.


    Ironically, I was on my way back from Canada where I had just purchased an Enstrom which had the same engine.  I wonder what Enstrom or their owners experience with this problem has been.

Link to comment
Share on other sites

  • 10 years later...

I have a 2003 S300C with 1150 squat switch hours. From 200 hours till 1000 hours the ship was used as a trainer... Lots of startups, shutdowns, autos...work! At my last 300 hour check my mechanic found my #4 had very low compression...20. He reamed and got compression back to normal. I never felt a stuck valve thinking as engine heated up the valve would release. Since then I added the 300 hour ream as standard procedure. I switched from aeroShell 15w-50 to Phillips x/c 20w-50. I also installed. Jpi 700 engine analyzer just left and below my ignition key on side of console. I found my #4 runs hottest ....100 deg f at normal operation..hotter than lowest cylinder #1. Then #2 is hotter then #3 third hottest. I noted that the console sensor gage for CHT uses the #3 cylinder. So i..( and all the other students) have not been using the hottest cylinder to determine when the magic 300 deg f is reached for cool down!!! So now hat I am using the hottest cylinder I hope I will never have this coking issue.

George 425.652.5601

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...