A good couple of questions.

It's always been my understanding that the T'Bird 1 used the upright engine. That's the way Bob flew the original, though he may have later built and flown one with an inverted engine. He did fly a radial version of the "Bird, that still exists today. It's being restored at present. He left it behind, in England, while on his world tour, and at least one version used trike gear.

There are a couple of good reasons an inverted engine is the choice of most stunt pilots today. An inverted engine gets the prop up higher, so the gear doesn't have to be as long to clear the ground. This also changes the verrtical CG, making it possible for a lower wing mounting. It affects the thrust line and the lower wing possition allows for a higher stab centerline to be used, which helps with the control geometry.

Designs that use an upright engine, therefore a lower thrust line, ussually need long spindly mains. They also should have a higher wing possition, which may nessitate having the flap horn on the underside of the wing. If the stab centerline is above the wing centerline, problems can occur when setting up the elevator horn. I think the ideal possition for the elevator in such a condition, may best be found to be at the bottom of the fuse, lower than the wing.

Planes that have vertical CG problems are hard to trim out. In the case of an upright engine, low wing design, the plane wants to bank out upright, and in when inverted. The best example of this condition I can think of would be Williams Ringmaster, an Old Time design, that is not one bit related to Sterling's Ringmaster we all know and love. iT is well known for this banking tendency. The best fix being to bring the leadouts out, above the wing. Not the prettiest solution.

John Miller

Bill,
 That is very ineresting!

Many people were also building inverted engined T-Bird I's with bubble canopies, well before the T-Bird II came out. I have pictures of two of them that were taken about 1960. They were beautiful.

Also, John D'Ottavio's Classic "Jerseyan" (Sept 2004 MA) has an upright engine. The thrustline is on the centerline of the wing. It had moments that you see on todays "modern stunters". The airplane was low slung with clipped prop blades. I have had 2 of them and they fly along with the best of the Classic airplanes.

John build a second "Jerseyan" with an inverted engine, and different rudder, but it was never flown in a contest. Seems, he let a friend use it, there was a split up and the guy's wife destroyed the airplane! I had a picture of the airplane but don't know where it is.