I just made 3 flights on my Outsider twin with 8-9 degrees out thrust on each engine. The idea behind the project was something I read 15-20 years ago that if you use 8-9 degrees out thrust on twin engines, you will have very little, if any, yaw from an engine out. I guess I should ask if anyone else has tried this.

Plane: Goldberg Tiger 2 ARF, 61" span, 680 sq in area
Engines: 2 OS .46AX with APC 11-6 props in nacelles added to wing. Ernst thrust plates behind each engine mount to adjust out thrust.
Weight 8 lbs 15 oz.

1st Flight on 2 engines: Excellent. Fast and still aerobatic even with the additional weight. Landing good, but fast.

2nd flight: The plan was to take off on 2 engines, shut one down and check the yaw and flight characteristics on 1 engine at full power. Even though I am using 2 channels, I could not get the right OS to shut down in the air. The plane handles well with 1 engine at idle and the other at full power. This is probably the worst case since the full prop disc is causing drag. This configuration did require some rudder. On landing, the right engine quit. (About time, I thought.)

3rd flight: Well, I had one engine running and my buddies were asking for a try so I lined up and gave it full power. Lots of left rudder needed on take off roll. That's different. Take off roll was nearly double, but since we have several thousand feet of hard surface I wasn't worried. After lift off, I made a slight right turn. The wind direction was causing me to have to make turns into the bad engine for a pattern. This is normally the worst case, so it would be an additional test to see how the plane handled. I had been holding a little rudder, but after I circled back and lined up with the runway, I released all of it. There was a little yaw, but not much. There was some cross wind so this could have caused the yaw. I was still at full power on the running OS AX and the plane was handling good.

I circled a couple more times and tried a few rolls. Rolls toward the good engine, left rolls had about the same roll rate as with 2 engines. Rolls toward the bad engine, right rolls were faster! There was at no time any hint of uncontrollability.

I made a right hand pattern, again, toward the bad engine, flew a fairly fast final approach and touched down fast with a bounce. The plane seemed to have more of a sink rate on 1 engine.

If the weather cooporates, I'll get some more flights next weekend. I'll also take the Twin Air out and compare the 2 with an engine out. Just from a few flights, I like the out thrust. It didn't seem to affect the speed, although I can't say for sure, but the plane was fast enough for me. The handling with the right engine out was excellent, considering I took off, made turns into the bad engine, rolled both directions and made a landing pattern with turns into the bad engine, all without a hitch.

More Outsider photos

Even more photos

I have zero thrust on my Duellist engines. Had a couple engine out flights during it's short 6-flight existance. As long as there was enough air speed it flew just fine on one engine. Had a couple missed approaches on one engine and was able to go around. The fuse is rebuilt and as soon as it's warm enough to paint and fly next spring I'll get to have more fun with it.

My twin Uproar has no out thrust either and never is a problem. I'm building a twin Ringmaster and not using any thrust in that either.

From what I have experienced, as long as there is enough speed to keep the wing with the dead engine flying you shouldn't have a problem regarless of out thrust. Rudder use can be just as effective as the thrust and something you can control.

Ed I have a twin ugly stick that I built some 20 years ago. Back then that was the thing to do is offset the motors. I still have it ,haven't flowen it for years. I had an engine out all the time and it wasn't hard to fly at all. I had more fun with that old ugly plane than anything I have had. Now I build the twins with the motors staight . Rich

Great job Ed!!! I've always put in 3-4° except I also account for torque by decreasing the left engine offset and increasing the right and none of this applies to the planes that have a contra rotating on the right.

Tim, one of the worst twins I ever had was the first Duelists I built. It was built per plans, no retracts and I used two Royal .45's. The Royals were not reliable and after the third spin in I destroyed the plane into a garbage can. On the other hand one of the best twins I've had was the second Duelists, on this one I had spring air retracts, moved the engines in one rib bay towards the fuselage and used new OS .46FS with a standard on the left and a contra rotating on the right, that was a great flying twin....

evan,
I did in fact move the engines in one rib and have mechanical retracts. The wing survived the crash and I built a new fuse from the M.A.N. plans. Can't wait to fly it again!

For what it is worth I did not put any out thrust on a three engine Kadet Senior. I have been flying on outboards only for most of the last 12 or so flights. The last four flights have deliberately been with mid range synchronization off by 1200 RPM (7200 and 8400). There is remarkably little difference in flight characteristics.

For experimentation I prefer to shut one engine back to idle in the air. It just seemed safer to have the protection of being able to throttle up if things started going haywire. Needless to say the switches sometimes get flipped the wrong way and one engine will shut down.

In my opinion the key is to acquire engine out experience in non-emergency time and with an inherently stable airframe.

Bill

I had a very lucky twin that I sold after 11 years. Forgive my bragging.


I put only about 1 1/2 out in the right engine and none in the left.


It was very tame flying on just the left engine. The right one is the one that usually got me in trouble.


I thought I had started something when another member at the feild built two twins. Both had considerable out thrust, probably in the range of what yours have. And both lasted only a few monthes.


Although I believe your experiment is a good one, I wouldn't call it a complete success until you attempt flying on the right engine.
( and I would never tell anyone to kill the left engine on purpose )

Good Luck and keep us posted as I have two Rockwell Commanders waiting for me to go mad again .

Hello Ed,

I have built and flown two Pilot Twin Ace models. The first was powered by OS 25 FP's and had 5 degrees out thrust on both. Engine outs were not too much of a problem. The second had 2 degrees out thrust and was powered by OS 30FS engines. This was a real handful on one engine and I eventually gave it away after yet another prang.

I have come to the conclusion that 5+ degrees out thrust on both engines helps in engine out situations. I will also avoid overpowering twin engined models in the future.

My $.02 worth.

Col

Col

One of my test objectives was the high power on a twin question. That's the reason I put 2 OS .46Ax's on a .46 size plane. I could have gone with a .61 size plane which would have been less of a problem, but I thought it would be a better test with max power in the plane.

This build was not to be a plane I would fly for the long term, it was purely to test out thrust for future use. That's the reason for the ARF and some "quick & dirty" large box nacelles. Nothing fancy. Get it built quickly and test fly.

I have flown with the right engine out and, if the weather holds, I'll try the left engine out this weekend. I did rolls, but want to do some loops, Immelmanns, Cuban-8s, and most of all, 1-engine flat spins toward the bad engine. I plan to write all the results up in my April column. (I am just sending in the March one.)