Hi,

I am trying to design a twin EDF aircraft (with two rear fuselage mounted 110mm fans) and going by the 3 views the engines will need 2.7 degree positive incidence (up), and also 1 degree toe out (rotated outboard at the front).

Can anyone tell me the implications of this setup?

Obviously the positive incidence will result in a nose down moment, however the stab is mounted at a negative angle of attack so this should countetact that moment somewhat (by providing a nose up moment).

I have no idea what the toe out would do to the aircraft. I would assume the engines may "fight" against each other?

Thanks!

Yes they will fight against each other. The idea of toe out or in on the engines is based on better handling in a one engine out scenario. But with electric motors the chance of a one motor out issue is vanishingly small to the point where you can safely scrap it and just make them parallel when looking down from above.

But for up or downthrust you'll still need that.

Toe out is normally associated with landing gear on a tail dragger. Is that what you are asking about or are you asking about left or right thrust line on the engine?

Right thrust is also used to compensate for the prop's p-effect. So of course a ducted fan won't need that.

But your phrasing brings up a question. You say you're designing, yet you mention 3-views. If you are working from 3-views of a full scale airplane, then consider that the full scale was developed with what you see on the 3-views. There was a reason what you see wound up on that a/c. Keep in mind that 1degree won't do a lot of anything so this isn't going to be of much importance.

The pitch thrust, on the other hand, may have a lot to do with the cruise attitude of the airframe and wing on a full scale jet. You'd want to consider much the same things you'd consider concerning the wing's incidence.

Hi All,

Thank you for your replies. Yes - i was referring to an offset in the thrust line of the engine (toe out was the wrong choice of words!)

There would not be a huge difference to the scale appearance of the model if i didn't put the 1 degree outward change to the thrust line, however if there is going to be no negligable difference between having the 1 degree, and not having the 1 degree then i would go for it.

Has anyone had any experience with 'toe out' or change of thrust line outward of a twin edf?

Thanks in advance.