A new five-blade composite MT propeller is in flight testing for supplemental type certification (STC) on Twin Commander turboprops.
Mike Laver of Air 1st Aviation Companies, Inc. in Aiken, South Carolina, is flying a TPE-331-10-powered 690B with the MT props to obtain FAA STC approval for Twin Commander models 690, 690A, 690B, 690C, 690D, 695, 695A, and 695B. He already has European approval to install the props on Twin Commanders. In 2013 Laver earned FAA STCs for the same MT props on the Mitsubishi MU-2 Solitaire and Marquise. Air 1st is the exclusive North American distributor for MT propellers for the MU-2 and Twin Commander.
Air 1st operates a fleet of 19 MU-2s that are used in simulated combat training at Tyndall Air Force Base in Florida. He also has extensive Commander experience, having bought and sold the Australian government fleet of Commander 1000s.
Laver said initial flight tests with the props on the Commander have shown a 10-percent increase in climb performance and a 6 dB drop in noise level in the cabin when compared with Hartzell props. Cruise speeds are comparable to the Hartzells, he added.
The Air 1st website (http://www.air1st.com) says the MT props “consist of highly compressed laminated beech wood that has a tensile strength similar to steel. The core is reinforced by layers of carbon fiber and glass and sealed with layers of acrylic polyurethane paint; the blade is protected by a nickel leading edge, which is five times harder than an aluminum blade and also corrosion free.”
Laver says the MT propellers on the Commander should provide the following benefits:
Reduced take off roll- Enhanced cruise performance
- Significant cabin noise reduction as well as outside noise reduction
- Nearly vibration free propeller operations
- Cooler engine starts
- Better erosion protection
- Unlimited blade life
- Superior ramp appeal
Laver said he installed a set of the MT props on his MU-2 in 2013 before flying it around the world. He has logged several hundred hours in the airplanes, and says the advantages of the composite props “are quite amazing.”
Laver bought the 690B with Hartzell wide-chord props, did flight testing to establish baseline performance specifications, replaced one Hartzell with one MT prop to confirm there were no unusual flight characteristics, then replaced the second Hartzell and installed test equipment for full flight testing.
He said he expects to obtain the FAA STC soon.
