I built my Pelican PL with a Rotax 914 turbo engine. I wanted to get the most performance out of my aircraft, as I live in a mountainous region. The 914 turbo charged engine lends itself to a prop like the Airmaster, as the constant speed function permits one to fully utilize the full power of the engine through all phases of flight, and especially for take-off.
As I live very close to the Rotech Canada facility in Vernon BC, [distributors for Rotax engines in Canada and the USA] I have had been able to get a lot of useful insight and information regarding my engine and propeller combination from them. My prop was factory set for t/o, climb and cruise at 5700, 5500 and 5000 rpm respectively, as per Rotax recommendations. However, I now only use t/o and cruise settings for my everyday flying. The Rotax 914 max rpm is 5800, the engine redline. My Grand Rapids EIS RPM warning setting is set for 5700, so I rarely exceed the 5800 rpm limit, and if I do, it is for a few seconds only. I get 39,9 inches of boost[MAP] and 5700 rpm for t/o, and the Airmaster keeps it there, or within 50 to 80 rpm of that figure.
After my initial climb out, usually for 3 to 4 minutes, or to a safe altitude, I set the Airmaster controller unit to climb mode, which settles the rpm in at 5450 to 5500at 35 inches. [max continuous operation boost.] When talking to a Rotax representative from Austria a while back, he said how much the 914 likes to operate at this rpm range, and how 5000 rpm is too slow, and tends to “lug” the engine along. So I took his advice, and have been using the higher rpm ever since.
The neat thing is, the Airmaster keeps this rpm up there even at lower MAP settings, so I now cruise along at between 5400 and 5500 all the time, and get really good airspeed results to boot. I can typically maintain 5450 rpm at MAP settings at even 28 inches. The 914 - Airmaster combo permits me to get sea level performance up to 16000 ft. It is nice to have the turbo power in an emergency, and a prop like the Airmaster, which responds so well to a full power scenario when one needs it.
Airmaster has been awesome with customer support, and the unit is a joy to work with, and easy to maintain and service. A really quality product. I have 145 hours on the prop now, and love it. I would be happy to chat with any owners who would like to talk props.
Thanks, Rupert Gruen.