Blum und Voss BV P-170 experimental 3 engine bomber

   that's one uguly plane

Bob, I think what Andrew was referring to is the torque amplification by moving the engines to the wingtips. Usually, the engines are mounted as close as possible to the fuselage, to minimize effects of torque. Feet away from fuselage center line times thrust in pounds gives you foot-pounds (ft-lbs) or in modelling sense, inch-ounces (in-oz). You triple that distance, then it is 3 times as strong.

With all engines running, the left and right outboard engines cancel each other out if they are at or near the same RPM. Lose an engine, then this is where the concern comes in.

You are right though, you have both engines run out of fuel first starting with the outboard, then inboard, finish with the central engine.

However, if one engine by happen-chance quits prematurely, this is where the concern comes in.

I suppose one could simplify things by putting two weaker engines outboard, say 2 Pee Wee's or Babe Bee's, and a larger / stronger say Tee Dee in the middle. Prop accordingly for outboard weaker thrust.

I wonder if this particular plane was intended for propaganda purposes. Since Allies apparently never heard of it, I suppose not, just some thinking out of the box.

rsv1cox wrote:Flying the pictured tri-motor would be rather hairy.

However, observing the "need for speed" crowd here, It appears that anything that raises the question of being "hairy" is enough of a challenge to give it a shot.

andrew wrote:
I saw that today and thought it could be a pain getting all three engines running and tuned, plus the tanks would need to be topped off before flying.  I suppose, depending on which outside engine quit first, it would either crab around the circle pointed to the outside or come barreling in scaring the bejesus out of whomever was flying it.

I think I would prefer to watch rather than stand in the circle -- I would hate my obituary to read, "Old man apparently died of fright while being chased by a toy airplane!"

The trick to three at the same time is making sure you have your three most reliable engines. You want to use Tee Dees running on bladder pressure so you don’t have any fuel delivery problems. Start the outboard first so it runs out first.

https://www.coxengineforum.com/t8882-headed-to-tucson?highlight=Tucson

Jim, you have a point there. BTW, you missed the following post, because it was posted a couple days ago and other threads have since bumped it down:

CEF: Happy Birthday jpvelo/Jim Roselle

I would think the obvious answer to engines quitting would be to use different size tanks....largest for the center, next largest for the inboard, smallest for the outboard. Test by seeing what run times are off each tank, to confirm run times BEFORE flying.

Or, start them in sequence. outer to circle first, then inner, then middle. Fuel burnt would cause the outer to quit first, then inner, left with the middle one running.

It would be interesting for someone to scale this down to half-A and put 3 .049's on it. Then I suppose one could put two Babe Bees as the outer engines and one Golden Bee as the inner. It would be a fast flyer though, as one would want to make sure it could finish out on the one Golden Bee, which would limit its wing area.