I am designing and building a twin-engine aircraft. What design parameters are required as to whether the engines are positioned absolutely parallel and equal, or is there a requirement for angling the engines to improve the flying characteristics of the aircraft if one engine quits, to allow a single engine landing?

J:

Do a quick search for the posts of "Ed Moorman," He is a great proponent of out thrust, and has settled (I think) on eight degrees out for each engine.

This is great if you want engine out to fly exactly as the plane does with both running, only less speed.

I just don't like the sight of the engines pointing out sideways, mine are all dead away except my very first twin, and the ARFs that come with side thrust built in. When I lose an engine it's throttle down time, crank some rudder in, and land.

Your choice.

Bill.

I have several twins...I place the left engine at zero and the right engine at 2 degrees right thrust..

works well

Ty

I have done lots of testing with engines out and with different size engines and out thrust will keep your plane from making the big yaw and roll if an engine inadvertently quits. I can literally keep doing acro with one engine out.

Go to the twin forun and do some research. The tri-engine Savoia-Marchetti, .91FS in nose and 2 .61FS in outboards, lost 1 outboard and crashed. The twin Sig Somethin' Extra lost 1 engine and crashed. I hate to see nice planes destroyed. That's the reason I got started on the out thrust experiments. You might not like the way it looks, but it dang sure works.

As for designing a twin, probably the most reliaboe design from a handling standpoint would be a pusher-puller, either on a long fuselage or with tail booms. The nest best would be a twin fuselage design. The fuselage channels the air flow more straight aft so you tend to get less yaw with an engine out. Finally would be 2 nacelles, which is the most common design.

If you are a very experienced pilot and know how to use your left hand on the rudder, build then straight ahead. Make sure you have enough power with 1 engine to overcome the drag of full rudder and still maintain level flight. If you are under powered, you may be in trouble.

From my experience, you need engine reliability first above all else. I get the feeling that many inexperienced pilots start off running their engines pretty well, slightly rich, and they don't have much trouble. After several successful flights, they crank on the needle a little for some more performance and one engine may quit on a partial tank. This is where they get into trouble.

In the final analysis, it's pay your money and take your chances.

Ed,
The Savoia was my airplane. The reason I lost it was that altitude. I lost and egine (I think) low over the trees on a slight up hill grade. If there had been no obstruction I could have gotten it to the field. Having to climb underpowered got me.
I have flown the Savoia on 2 engines when I cut the right engine trying to do a touch and go to help a gear legt to get unstuck. When I did the T&G i dropped low enough to cut off the right engine.
I then proceeded to climb out and go around for another landing. It was taxing but I made it.


Ty