R22 & 300 Performance Examples...
As far as engine performance is concerned, the O-360-J2A (Lycoming engine for R22 Beta II) was designed at 180 BHP; however, Lycoming only tested it at 145 BHP because they thinned-out the cylinder heads and used Aluminum pistons to save weight (and for liability reasons). The engine is fully capable of producing 180 BHP, but the data plate says 145 BHP. So that's what we go by. If you stay within POH limits, you should not exceed 131 BHP. Why did RHC specify 131 BHP in their design?
In piston engines, you loose about 7 horsepower for every thousand feet (roughly). It's the pilot that derates the engine by staying within MP limits, which affects your angle of attack on the blades. There isn't really a mechanical device that "derates" the engine... just the pilot.
Therefore, at 7000' you have every bit of that 131 horsepower available to you...
180 HP
- 7 (thousand feet) x 7 (horsepower) = 49
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131 HP
Schweizer's web site claims the 300 has a HIGE of 10,800 feet. This is a sneaky advertisment because this is at a weight of about 1400 pounds... one person and an hour of fuel. At gross weight, the Schweitzer can only handle 5,900 feet.
Piston helicopters that operate at their maximum horsepower at all times are not high altitude performers. Specifically, the performance power available to their engines is extremely limited when compared to the Beta II at the same altitude because you are subtracting from an available horsepower figure that was running at maximum at sea level! In other words, they don't have the same altitude "buffer" that the R22 Beta II does.
The Beta I and Beta II are almost the exact same aircraft. A few minor changes, but the biggest difference is the engine. So if you fly mostly at lower alititudes, you will NOT have ANY performance increase from a Beta II vs. Beta I. If you fly at higher altitudes, you will need the Beta II.
Also, there is TON of information you can research concerning carb ice, manifold pressures, fuel injection systems, turbo chargers, and so forth. What topics are you specifically looking for? If you want to compare turbine and piston reliability, look up an article from the March 2003 Rotor & Wing magazine (pages 36-37). This is about the extent of my limited knowledge. Hopefully, some of the Enstrom, Brantly, Hiller, and Schweizer Gurus will chime in with additional details and data.