Defiant's two engines = SAFETY

October 1989

Dear RAF;

My Defiant now has 350 hours on it and I've had a couple of experiences that remind me of why I built the Defiant, i.e. I've had to go single engine twice and it was a piece of cake as far as safety goes and ease of flying the airplane. The first instance was last Spring when my rear engine broke and exhaust valve that then went thru the exhaust and splintered one blade of the rear prop. I was at gross with 4 aboard at 10,000 feet over hostile Arizona terrain and all of a sudden there was a pitch change and a slow degradation in airspeed. As I had been suspicious of #4 cylinder because of a wet spark plug and some "shavings" seen inside of the valve cover I was monitoring the HOT on 4 and it rapidly went from 1450 to 1200 or so and told me which engine lost power. I shut down the rear engine and turned around and flew the 20 miles back to Scottsdale uneventfully. On final, my 12 year old daughter, Sara announced that "her whole life just passed before her eyes".

The point is that this was basically a no sweat situation due to the design of the plane and with fixed pitch props and 50% power on the front engine was all that was needed to get us home with a 9.000 foot descent. Now there is a learning point here - I had my cylinder checked out with an A&P professional and was told the shavings were from the exhaust valve springs wearing on a washer and that the wet cylinder was due to the ring slots lining up. What I should have done was to have pulled the cylinder and investigated further. By the way, about 6 weeks before this I'd switched from Aeroshell to Mobile IA total synthetic oil. Aviation Consumer has an article that cautions that in engines with time on them, you may mobilize sludge and perhaps have problems.

Aeroshell is designed to keep particle sin suspension--guess what oil I'm now using. The second incident occurred this Fall when I was commuting to Santa Maria fro Scottsdale for a few weeks of work in my field of Anesthesia. I was coming home and 100 miles out over Lake Alamo, I started smelling smoke. I was at I 1,000 feet and glad I was alone and not too happy, I shut down the front engine and the smoke smell went away. I've had a nuisance oil leak for 300 hours from my front engine and since it is updraft cooling it gets on the windscreen. I'd noticed that lately there had been some black streaks in the oil and figured that it was oil that was being carbonized from cylinder head heat. So I flew the plane on home and was only able to maintain altitude at 90 KIAS without the oil temp going plus 200 with the prop windmilling.

So I stopped the prop but there was a strange air sound so I let her windmill and brought her on home and by descending to 7000 feet, maintained 110 KIAS and had adequate cooling. After investigation, I discovered 2 broken prop bolts and an almost-to-fail prop, the hub of which was charcoaled. The black streaks on the windscreen was prop wood. Now I had 40 hours on this prop from Great American and about 10 hours since re-torquing to 40 ft. lbs. I almost checked the torque when I was in humid Santa Maria but decided, if anything, the wood would have swelled and therefore any checking could be done in Scottsdale.

When I got the prop from Great American, the lug holes were too shallow and I deepened them with a plug cutter and flew all this time with what probably was a prop that may not have compressed all the way to the flange of my 8" extension. The second thing is that I relied on advice that grade 8 hardware bolts my be OK for prop bolts. I now question this and feel personally that the extra expense my be worth it, especially to all of you singe engine pilots out there. Other than these problems, the Defiant has been a delight to fly and the only advice to you other Defiant builders is that I would do a fixed windscreen for safety like Johnny Murphy did and would do a fixed front gear that would be similar to the Wheeler Express with a wheel pant. The speed penalty might be very small and the gear box could be done away with. Mike, I'll be seeing you at Jackpot.

George (Best)

EDITOR'S NOTE; Grade 8 bolts have no place on an airplane, especially as prop bolts. They are much too hard and therefor boo brittle. Aircraft bolts are ductile, not brittle!

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