I have an engine question. Can you put a helicopter engine in a plane. See our club is starteing an "unlimited" class. basically race anything you want. I have found a nice heli motor and it is low profile for more aero dynamics. I was woundering will it work the same as a plane motor. thanks
Justin</p>

Justin, Make sure you can bolt a prop to it. If you can, go for it. Let us know how it works? Greg

Airwebb,I had the same question... Here is the thread..As for Me,I am still a bit confused...
http://www.rcuniverse.com/forum/m_10326329/tm.htm. Best Regards,TJ

All engines have intake ports that are for a lack of a better term, " Positioned " so that the engine makes it's peak power at a certain RPM. With a helicopter engine it is rather high. If we take a look at the math it may be easier to understand. For aerobatics, helicopters run a rotor RPM of 2,000 to 2,200. Most helicopters are geared around 9:1. so if you multiply 2,200 by 9 you get 19,800. This is the engines RPM while doing extreem 3D. So you can see how the engine is designed for high RPM use. When put on an airplane the engine must run a prop that allows it to operate at the RPM where it develops it's peak power. In most cases this prop would be too small to overcome the drag of a typical sport airplane.

speedracerntrixie , now THAT explanation makes sense..Thanks, TJ

Ive got an OS .32sx helicopter engine that Ive had on a trainer, 4 star .40 and now a GP Big Stik.. It moves out!!!  Best engine that I own by far.. Go for it!!

The OS 32H is identical to the airplane 32 except for the head and the design is about 15 years old. The new breed of heli engines are the ones timed for higher RPM operation. I guess if the OP lets us know what his specific engine is I can narrow it down a bit

Like the guys said, The heli engines are run @ pretty high RPM normally with 30% nitro AND TEHIR MUFFLERS are tunned to the high RPM

The 50s run in the 17K to 19K range, (no more) and 91 around 14.5K and 16K.

Be carefull with some of the older OS 90s, they dont like to be above 15K and anywhere near lean.
In a helicopter, All these engines run very rich because of the crappy cooling a helicopter provides, so the mixture with a prop will be leaner but dont get carried away.

Santiago

Thanks for the info guys. That all helps alot. Idont have a heli engine to use, but I am just doing research to see if it would work. Im building a race plane and Im trying to get the most bang for my buck. Most airplane engines that turn 18-20k rpm cost $4-$500 used.

Justin

Give some more info on the airplane you plan to build. Here is mine, capable of 160 and maybe higher after I finish breaking in the engine and experimenting with props. Power is a Rossi 61 FIRE that I got off ebay for 86.00. There are deals if you look enough.