I think the shaft might not be long enough to mount a prop perperly.
Other wise i would had mounted a .25 car engine rated at almost 2HP on an airplan.

What stopped me was the high RPM. @ 30000 rmp..it'll rip the prop apart.

As memtioned above..threads are on the out side of the shaft for airplane engine
The threads are on the inside of the shaft for a heli.
If my hand and life depended on it...I wouldn't risk it.
I've had clutch bells come loose on my nitro car many times. The little screw
that presses against a washer to keep the clucth in place will come loose.
If a clutch comes loose..it's not life threatening.

Another thing to take into consideration is..you'll be replacing props more often. Once you mount
the clutch..it usually stays mounted unless there's a major problem.
All i know is...I get better torque with a wrench than a screw driver.

I havn't really consider it becuase heli engines are more expensive than planes engines.lol
Plus taking my heli apart...would make it less vaulable just to see if the shaft is long enough.
Car and heli use a clucth bell...so I figure it'll be short.

Heli engine also has a longer stroke (longer rod) than an airplane engine for more torque.
So...you can't really compair them to an air plane engine.

I had a shuttle once. I also horse traded it for a couple of nice .40 and .60 model built and complete....engines and servo..less RX.
Becuase the servos the heli wasn't standard and the gyro and what have ya.