Denny,

My buddy, Carl "Flaps" Laffert, and I have built 25 twins. We heard so many "old wives' tales" that we decided to test a couple out to make sure. One of the first ones we tested was engine out thrust. I was flying a Twin-Air 45, low wing sport twin powered by 2 Magnum .52 2-strokes with 11-6 props. I was at full power doing a Cuban-8. When I used aileron to roll upright in the first half of the maneuver, the plane snapped. That got my attention. I throttled back, recovered and slowly added power. Sure enough, one engine was out. I then landed safely.

On the way home and later, we talked about what we could do about an unexpected single-engine situation. I remembered from maybe 20-years ago reading that out thrust would cure the problem. I seemed to remember 8 or 9 degrees out was the specified amount. That looked like a lot, but Flaps said he would modify a kit for the test, if I would buy it.

I ordered a Goldberg Tiger 2 ARF (.40-.46 size plane). I also had 2 nearly new OS .46AX engines we could use. Flaps built 2 nacelles from lite-ply and mounted them on the wing. He also closed in the nose and finished the kit with my radio. It was a little heavy at 8 1/2 lbs, giving it a 32 oz/sq ft wing loading, but I felt it would be OK.

The first 2 flights, I trimmed and got the feel of the plane. It did need to be landed a little faster, but nothing outrageous. For the third flight, I filled one tank (I forget which) to half full and the other was filled completely full. I took off and proceeded to stay at full power and do my usual acro. I did have fellow club test pilot, Mark Pfeiffer, standing with me as a witness. There were other fliers up so I couldn't hear the engines that well. After around 7 minutes, Mark said, "Ed, you have lost an engine." I hadn't noticed anything. I flew around a bit more, then landed. Next, I shorted the other tank and repeated the test. This time, I was watching closer and did notice a drop of speed just before Mark informed me of the engine out.

At no time on either flight did I ever feel the plane was out of control or even hard to control. The engine failures were a "non-event." I got so confident flying with out thrust that on a later plane, I had an engine quit on take off. Rather than abort, I just finished the take off, flew around for a couple of minutes, then landed. Granted I had plenty of power, since most of my planes are over powered, but, even so, to take off on one engine does show the benefit of out thrust.

I did take my out thrust twins to several twin meets and the first question I am always asked is, "Don't you lost a lot of forward thrust with that much out thrust?" Actually, no. I'm an engineer and the math tells me that at 8 degrees, I still have slightly greater than 99% of my forward thrust. I know the angle looks extreme, but the math tells me that's true. The cosine of 8 is .99027. My experience in testing confirms this number, as best as I can tell.

Anyway, Denny, I did write for R/C Report magazine for 10 years. You can find my twin notes in back issues from their on-line site. You can also search this Twin Forum for "Ed_Moorman" that's Ed underscore Moorman for my old posts. Drop me a PM with your email and I'll find those old notes and send them to you.