Finnoff PC-12 Upgrade

By Fred George fred_george@aviationweek.com
Source: Business & Commercial Aviation

The extra cruise thrust boosts maximum cruise speed by 3-4 kt. at standard day temperatures and as much as 7-10 kt. on warm days, according to the Finnoff Aviation AFM supplement.

These data were verified by flight tests conducted by Arthur C. Barth in manufacturer's s.n. 273 ([MSN 273) at Flight Test Associates in Mojave, Calif., before it ceased operations. They are based on an aircraft with average paint and drag polars, intermediate CG, and factory spec rigging of control surfaces, external doors and landing gear.

Let’s Go Flying

We strapped into the left seat of MSN 273, a PC-12/45 model with a 9,921 lb. MTOW, accompanied by contract pilot Randy Schneider, president of Randolph Aviation, at Boulder City Airport at Boulder, Calif. With 2,704 lb. of fuel plus Finnoff as a passenger and various spares aboard, the aircraft's ramp weight was 9,880 lb.

Finnoff explained that the engine conversion adds about 40 lb. to aircraft empty weight. The -67P, because of its more robust components, weighs 21 lb. more than the -67B. The -67P also is fitted with a second 300A generator on the accessory gear box in place of the belt-driven, 115A standby generator, thereby adding another 19 lb.

The -67P requires more current for starting than the -67B. Pilatus' optional dual battery system is recommended for frequent short cycle operations or for battery starting the aircraft at high density altitude airports. Use of a GPU is recommended for aircraft fitted with single batteries.

Finnoff is developing an STC for a simplified, dual lead acid battery retrofit package to upgrade aircraft that were originally delivered with single battery systems. The firm also is developing a 300A buss tie conversion kit to replace the original 150A buss tie that was fitted to aircraft delivered with -67B engines. This will enable the electrical system to take full advantage of the 300A secondary generator.

While not part of the original Finnoff -67P conversion, MSN 273 also is equipped with a five-blade composite MT propeller that is approved for installation on all PC-12 models. Finnoff Aviation is the exclusive North American after-market distributor for MT Propellers. The $58,500 MT prop for the PC-12 is 2.7 in. smaller in diameter than the original equipment Hartzell four-blade prop. The five-blade design results in lower thrust loading per square inch and the composite structure allows more optimum airfoil shaping for better root to tip lift distribution. The changes result in slower tip speeds and lower blade tip loading than with the Hartzell propeller.

Martin Albrecht, engineer and test pilot at MT Propeller Entwicklung GmbH in Atting, Germany, says the MT prop produces 10% more static thrust than the Hartzell, thereby reducing takeoff roll by 15%. He also says that climb performance is improved and that cruise speeds are up to 5 kt. higher. However, there are no FAA or EASA-approved AFM supplement documents to support such claims.

Still, the MT prop does weigh about 20 lb. less than the Hartzell, has better vibration damping characteristics and FAR Part 36 noise levels are 4 db lower. The composite blades are built from ultra-thin beech and spruce laminates, covered with a carbon fiber skin and protected by nickel cobalt leading edge abrasion strips. There is no life limit on the blades and the prop is reparable in the field. Albrecht also claims that interior sound levels are 6 to 7 dB quieter, but, again, there are no FAA or EASA documents to support such claims.


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