Check Those Oil Leaks By William B. Heilig, EAA 5492 R. 2, Box 375, Scottsbluff, Nebr. O YOU have a small oil leak in an aircraft engine D that you cannot pinpoint? If so, be suspicious of a cracked cylinder causing the leak. Many homebuilts are tightly cowled, and excessive ground operation when first testing them by long taxiing can create excessive cylinder temperatures. This, in turn, can cause the steel barrel of the cylinder to get hot enough to lose its normal temper and cause a minute crack. From this small, invisible crack, oil will seep out a drop at a time, and it appears to be but a minor thing. When the airplane is put away, a few oil spots will form on the hangar floor beneath the engine and that is when to start looking seriously for that oil leak as it may be the very beginning of a small cylinder crack that is going to get worse as time goes by. It may take as long as 100 engine hours before it develops into a crack large enough to cause the entire cylinder to break, but the chances are very great that it will progress to that stage eventually, and this is exactly what happened to the Lycoming 0-290-G engine in my "Miniplane." HEAD TEMP REACHES 250 DEC. C.
After a major overhaul on this engine and installing it in the "Miniplane", I wanted to taxi test the airplane and run the engine long enough to gradually seat the rings. I no doubt ran it too long in this process and the head temperature would sometimes get up to 250 deg. C. Then I would shut it down to cool before more running. It leaked no oil at that time. After several test flights, during which time the engine ran perfectly, I noticed a spot or two of oil dripped from the cowling onto the floor. The cowling was removed and all hoses and bolts were tightened in an attempt to stop this slight leak. At that time I noticed that the two rear cylinders had been hotter than the two front ones, as their bases were a darker color. However, I did not think it serious enough to bother anything.
Over a total of 130 engine hours, the oil leak got only a little worse . . . about one quart every six hours, so I wrote it off as a "gremlin leak" and went happily on my way until last spring when I flew to Cheyenne, Wyo. The trip to Cheyenne was uneventful except for low ceilings and light rain, but the return trip was when I almost lost that little airplane. Twenty miles from home and over some very rough country at 3,000 ft. above ground level, the engine suddenly got very rough. Smoke filled my cockpit! I have a canopy, so I opened it at once in order to breathe, and I thought the airplane was going to pieces. I closed the throttle to keep the engine from shaking loose, looked for a place to land, but couldn't find one. So, I opened the throttle gradually and found that I could get maybe 25 percent power without too much vibration. I then established a long glide toward my home airport which is Scottsbluff, Nebr. CROSS WIND LANDING
It turned out that this little bit of power and altitude proved to be a perfect combination for a landing right on the numbers of a straight-in cross wind runway. The engine refused to run long enough to taxi into the parking area, so it was close. Examination proved that the right rear cylinder cracked 80 percent of the way around and, in turning the propeller over by hand, the piston could be plainly seen going back and forth in the crack which opened and closed as the piston pushed the head to the side with each compression stroke. Why it didn't push the head all the way off and then flop over and lock the engine is hard to explain. Thank God, it didn't! LESSON TO BE LEARNED? Stop all oil leaks, no matter how minor. If you notice that a cylinder appears to have been hot, be suspicious and remove it for close examination.
RAZORBACK "EMERAUDE" . . . (Continued from poge 32)
The interior is finished in black and white naugahyde with a foam base which helps to eliminate in-flight noise and makes the "Emeraude" quite comfortable, similar to riding in a roomy sport car with wings. OWNER/BUILDER GROUNDED FOR FIRST FLIGHT
The first flight was made with no real problems other than that I, as owner and builder, had to stay on the ground. I had only 25 hours on a student ticket, but
by the next weekend I was checked out and have been the chief over my own creation from that day on. Since then, it has proven to be a good flying machine. The stabilizer had to be raised % in. as the airplane wanted to fly tail low with two persons on board, and 3 deg. of engine offset was not enough to counteract the increased power, so I added a small rudder trim tab. Power stalls have a noticeable tendency to pull the aircraft to the left because of the high amount of torque from the engine, especially above 2000 rpm. Power-off stalls are smooth and straightforward, with no warning except the lessening of wind noise.
Fairings over the landing gear legs and drag braces were
added later to the airplane. The large wheel pants are also of fiberglas.
Many people have already stated their first impressions when flying their airplane initially, and I'm
one to join those who were skeptical for it was certainly a nervous affair. Therefore, I would surely advise any other person with little experience to find a competent and willing person who is familiar with small aircraft to attempt the first flight. I felt that two years of fulltime spare time was just too much to gamble on being able to say, "I made the first flight." ® SPORT AVIATION
J3
