Bell VTOL (oz13608)

About this Plan

Bell VTOL. Free flight model for twin Jetex power.

QUote: "BELL'S VTOL was a design study of a vertical rising jet air-plane which could take off and land on a 'dime'. I was fortunate in being able to see movies of actual flight tests, and it worked very well. The machine lifted, turned 360° over the spot, progressed 200 ft down the field, landed on a spot, minimum flying speed was zero mph. Maximum was rumoured as 300 mph, but the aircraft was not designed for this speed; it was intended only as a stability test bed.

The success of any aircraft is entirely dependent on stability, and this is the paramount problem for all VTOL aircraft. In hovering flight the Bell ship utilised compressed air ejected from nozzles at the wing tips and tail for control in all three axes. Powerplants were two Fairchild J-44 turbojet engines of 1,000 lb thrust each, and they could be rotated from vertical to horizontal for varied flight attitudes.

The aircraft had a span of 26 ft, a length of 21 ft and weighed 2,000 lb. Note the marginal thrust to weight ratio - no heavy eating for the pilot!

Your model is not intended for hovering flight, although you can gain some interesting experience by attempting to turn your Jetex engines as near vertical as possible and still retain flying ability, then you will appreciate some of the problems the full scale people had.

The plans tell most of the story on construction, but be careful to keep the tail end light, use quarter grain balsa for all flying surfaces, and take care to avoid splitting when bending the camber into the wings. No dope is required. To mount the motors drill a hole in the centre of the Jetex mounting clip and find a short machine screw that will just protrude enough to take the nut on the other side. The model should balance at 50 percent wing chord, and I used chuck glider techniques for trimming.

For initial flight tests use only one engine, and adjust for a slight circle on the glide, with the loaded engine on the inside of the glide turn. When using two engines always light the inside (of circle) engine first. Make small adjustments one at a time - this is a fast moving model.

I have had flights of up to 3 min and distance of, as the old-time magazines would put it, 'flies 5,000 ft.'"

Direct submission to Outerzone.

Quote: "Hi Steve & Mary, From Model Aircraft January 1956, an interesting little Jetex twin by Larry Conover. Cheers,"

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