May 1, 1994
HIRO PATRICK YAMOTO
As an aircraft mechanic and pilot, I've performed many cylinder break-in flights in aircraft ranging from Cessna 150s to cabin-class twins. I've had several real in-flight emergencies during this kind of maintenance flight, as well as during regular business or pleasure flights.
Most causes were mechanical, such as broken pushrod seals, a stuck carburetor needle valve, a broken fuel line, a defective mixture cable connection, etc., although some were human errors, like finger-tightened spark plugs that came loose in flight.
Each time I have such an experience, I always make sure that it will not happen again by paying more attention to these problem areas during the preflight check. Minor problems add up to major ones when ignored, as was the case on a recent flight.
I was assigned to break in a newly overhauled Lycoming engine installed on a Piper Archer. After a careful engine runup, I took off from Watsonville Municipal Airport on the central California coast. I flew over the airport for a while to make sure nothing was abnormal and questionable.
There were only two minor squawks reported for my airplane: a sticking left fuel quantity gauge and a slight leak at the left fuel drain valve. The fuel gauge needle was easily unstuck by tapping the face of the gauge, and the leak at the drain valve was only a few drops an hour.
So I headed for Vacaville, about 90 nm to the north. It was an uneventful, pleasant flight. Upon landing, I removed the engine cowling to inspect the freshly painted, shiny powerplant. Everything looked great.
I departed for Porterville in the San Joaquin Valley. After landing, I checked the engine again, refueled, and prepared to leave. During preflight, however, I noticed the left drain valve leak had become much more noticeable — now it was several drops a minute.
The fuel gauge sticking problem was still there, but tapping still solved the problem. A little over 40 gallons of fuel was more than enough for the 1.5-hour final leg back to my home, even with the leak.
I left 85-degree-hot Porterville for 55-degree-cold Watsonville. My fuel selector was on the left tank, and I was going to switch midway in the flight over an uncontrolled public airport. Within 15 minutes after departure at 2,000 feet, my engine suddenly quit. I immediately raised the nose to attain 76 knots, the best power-off gliding airspeed.
I've noticed many pilots, during a simulated engine-out practice, hesitate in raising the nose to slow to best-glide airspeed. I've learned to do that to gain extra altitude. In fact, I gained more than 300 feet by doing it this time.
I remembered seeing a private airstrip on my right about a minute before my engine quit. I made a gentle right turn and started trouble- shooting by switching tanks, turning on the electric fuel pump, applying carburetor heat, checking the primer, etc.
The engine restarted in 10 seconds, leading me to believe the engine-driven fuel pump had been the problem. I had this problem before in a Piper Tomahawk. With the airport just ahead, I shut down the engine again because I didn't want pieces of a broken fuel pump entering the $10,000 engine.
Before turning off the master switch, I looked at the left fuel gauge and tapped it with my fingers. It showed about three-fourths full, but the needle didn't move at all.
I landed safely and coasted off the rough but comfortably long, paved runway. I began wondering how long it would take to replace a fuel pump at this private airstrip. But when I got out of the airplane, I was shocked to see that the left fuel drain valve was gone. It obviously came off in flight. The engine had quit not because of a pump failure, but because of a dry fuel tank. That's why switching to the right tank restarted the engine. Unfortunately, my fuel gauge stuck at the same time, masking the problem.
After thanking the owner of the private landing strip for not yelling at me for my unauthorized visit, I took off with 20 gallons of fuel in the right wing. During an uneventful flight back, however, I kept thinking, "Well, with my luck today, the right fuel drain valve might come out at any second."
I flew with two students later that afternoon and had begun to calm down by the time the second one showed up.
Hiro Patrick Yamoto, AOPA 887555, is president and chief pilot at Strawberry Aviation in Watsonville, California. A former airline pilot, he has accumulated 8,700 flight hours in 17 years and is an instrument and multiengine instructor.
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