Partial Engine loss on Climb-out in Piper Arrow

grabidou

Tried to Google this several different ways and have had no luck with a solid explanation.

Scenario: Hot July day, High Density Altitude, Full Fuel, Single Pilot, Piper Arrow II.

Just arriving at an airport on this hot July day to drop off a friend to pick his plane up from maintenance. The Arrow had sat on the ramp for about a half an hour, most likely heat soaking in the 98 degree humid day. Ready to take off again, Called Ground, taxied to the run-up area, normal run-up, called tower, and cleared to go. Here is where it happened. Rolling out and rotated fine, broke ground and started climbing Vx. After about 200 feet AGL, Rough Engine, Partial Power loss, shaking airframe... Calling the tower to explain, and let them know it will either be off field on a close by highway or back to the airport. Clearance either way! First thing was to keep airspeed going. Trying to hold best glide with a shaking airframe and partial power (almost like it was running on 2 cyls or less). Leaned out the mixture in case in was fowled plugs (which is what it felt like). Thinking back, that was probably a bad idea. After a few minutes full power was restored and was able to gain some altitude. a couple minutes and a couple hundred feet more, happened again. At this point a turn back to the airport straight line was possible. With enough altitude and power to make it back, there was an uneventful landing on the opposite runway. Cleared the runway, Did a Run-up (NORMAL!!) Confused!?!?!

Things that where checked (by two maintenance shops):
all 8 plugs - almost flawless
compression check - high 70's across all cyls
Everything else looked mechanically sound

Aux Fuel pump WAS used (well still trying to remember!!) Common motion to roll up mixture before run-up and hit the fuel pump switch "On" at the same time.

Flew after this for a good 15 hours with no issues...

Looking to this forum to see if there had been any similar issues, or thoughts on Why!?!? With all tests coming back normal, its hard to grasp.

Talking it over with numerous pilots, mechanics, reading forums, there have been a couple of could be...
-Vapor Lock (Understand this issue fully on startup, but cant comprehend it after startup, taxi, run-up, take-off roll)
-Detonation (100LL fuel was being run, full rich on take-off, and it was off a 200ft AGL airport), Maybe?! Seems far fetched

flyguydon

Have the fuel servo and fuel distributor OH. I had some issues like this a number of years back. I did all kinds of $$ work before OH the fuel servo and had no issues since. I realize you do not want to fly this kind of issue to have it happen again, but if you did, if it were the servo you would see very strange fuel flow indications during the event...

grabidou

Thanks for the reply, the fuel servo was replaced/OH earlier this year. Also the electric fuel pump was replaced this year. Not saying one of those could be to blame. I have had replaced and OH parts go bad with low hours on them.

flyguydon

It could be a sticking valve. Mags... nah... not at all likely both would fail to only a few cylinders at exactly the same time. Fuel pressure, perhaps, but with both pumps on it is not likely. You would need to see the indicated pressure during the event. Fuel spyder... maybe but probably done with the servo??

smalone

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smalone

Given what you described I would wonder about some bad gas (i.e. water, contaminate, etc). Had you taken on fuel during the stop? Many pilots do not redrain their tanks after a fuel up "assuming" the airport fuel is contaminate free, which sometimes its not. You did not mention a pre-flight but I also "assume" this was done.

grabidou

Yes, fuel was taken on before I took off from the first airport. I did a thorough preflight then, and also check fuel and oil at every stop including sump.

Curious about the sticking valve, and spyder valve. With the loss of power, I can't imagine one sticky valve would cause that? Maybe more than on? What are the chances? For the spyder valve, I'm no 100% on how the mechanics work on that? Does it get out of sync like timing?!

Thanks for the replies!

smalone

How about a temporary loss of one of your mags? Maybe a loose wire or moisture?

JoeB

Vapor lock would be my first suspicion. The engine and everything attached to it was already heat-soaked, and it was a hot day. You don't cool it off any taxiing and doing your run-up because there's very little air being pushed through the cowling by the inner section of the prop, then you open the throttle takeoff and really heat things up before the cooling air gets flowing via airspeed. In normal operations you see your highest engine temps right after takeoff. Then, for airspeed, you picked the slowest one possible (Vx). Conditions were certainly ripe for the fuel to boil in the engine.

I can't say for sure it wasn't a transient mechanical defect or bad fuel - but don't rule out the notion that it was just too hot.

grabidou

A quick update. I did send a note to Lycoming and they responded with doing a Valve Wobble Check. We haven't done that yet, but will in the next few days if I can get up there. Also, not sure what symptoms would show to check something like that?

greghughespdx2

I'd say the same things already mentioned: Valves, water in fuel (did you sump all the sump locations?) and mixture being the tops. Also whether or not the air/induction system has any leaks, and (because it can happen in high temps and you mentioned high humidity) carb ice is a real possibility if there's a wait between runup and departure. What was the outside air temp at the time, and the humidity/dewpoint spread I wonder?

n36601

Sounds a lot like what happened to me, TWICE. My Warrior stuck a valve on one cylinder while I was at altitude. I was able to hold altitude but it was shaking pretty good. Landed at the nearest airport, uneventfully, and had the cylinder replaced. About two months later, again at altitude, but beginning a descent, a second cylinder valve stuck. This time it bent the pushrod and tube, so it was easy to identify, after landing at the airport I'd just passed. Both times, shook a lot, but I was able to hold altitude, 2,000 MSL. Two months, later I bought a Lycoming rebuilt, zero-time engine, with the new roller tappets. It was like buying a brand new engine at a rebuilt price. It's been flawless for the last 500 hours. My 2¢ is on a sticking valve. Besides, I don't know anything about injected engines.