HP and gyro design


Gold Member
Sep 23, 2004
Acampo, CA
depends on what I have sold recently
Total Flight Time
OK, so we all know that the lighter the aircraft the less required power. The better the rotors the less hp required. A few gyros made it legitimately under Part 103. Even fewer did it using the Rotax 447 of 40hp.

So it can be done efficiently in both used of materials to keep it light, and efficiency in drag.

One example is Fetter's Air Command 447. The few owners I have talked with said it flew pretty good and used the 40hp Rotax.
Other Part 103 compliant like the KB3 make it by weight and speed but need a Rotax 60 hp 532 or 582 to fly decently.

Not many tractor gyros out there, and none really made Part 103.

My Bensen/KB2 made it because I shaved all weight were I could, used a 90hp MAC (loved it) and pitched the rotor so I could not fly faster than 60 mph.

My Gyrobee made it, built to plans and used a Rotax 447. Must say though it flew ok, did not feel as solid as the KB2.

Is there any particular reason (beside best view) why there are fewer tractor gyros?
Why if you are able to make 254 lbs does that usually require more than 50hp needed?

David M.


Yamaha gyro...Oregon, USA
Nov 16, 2003
Oregon, USA
Sport Copter gyroplane
Total Flight Time
300+ gyroplane, 11 airplane, 1.5 PPC, AND... a ZILLION hours of flying in my dreams!
The original Air Command that Dennis Fetters sold as an ultralight when having the Rotax 447 as the powerplant did not weigh less than 254#.

I weighed an original style (Low Rider) Air Command that had a Rotax 503 on it.
Stock, w/ McCutchen Skywheels rotorblades. I don't recall the exact amount, but w/ the 503, it was about 20# over.

I checked one of the Rotax engine weight tables, such as here: http://www.parachutepilot.com/weights.htm

It shows the difference between the 447 & 503, (w/ "B" gearbox, manual pull start) to be 10# (82.4# for the 447 & 95.4# for the 503). That 95.4# is for twin carbs on the 503.

I wrote to DF, asking how he could have claimed the A/C 447 met Part 103 regs, since it had to have been about 10# over the weight restriction. He tersely replied that it was compliant.

I edited the weight of 503 to include twin carbs.
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