Plane & Pilot
Tuesday, March 27, 2012

Living Large


Transitioning from a piston to a turbine



In a turbine aircraft, there's no vibration, shock cooling or mixture control to worry about. Turbine engines are smooth, powerful and easy to operate.
Making the transition from a fixed- gear piston into a turbine isn't easy, cheap or quick, but it's possible. For those with the means, jumping into the left seat of your own turbine aircraft opens up an amazing world of performance and capability. High-performance turboprops like the TBM 850, the PC12 or a King Air easily climb to FL 300 (and above) at speeds ranging from 250 to 300 knots. Light jets like the Citation Mustang or the Phenom 100 will transport you high above the weather, cruising at speeds ranging from 340 to 390 KTAS at altitudes up to FL 410. The move into a turbine is a big one and made a little less daunting if you know what to expect. Here's a look at some of the issues facing the first-time turbine pilot.

Engine and Systems

Forget about vibration, shock cooling, and fiddling with mixtures—turbine engines are smooth, powerful and easy to operate. Starting most turbines basically involves engaging a starter motor, spinning up the turbines and introducing fuel. Starting a turbofan equipped with fully automatic digital engine control (FADEC) is virtually a single-button operation. Unlike starting a piston, you never even think about starting with a weak battery. It takes a lot of juice to get things safely up to speed, and monitoring temperatures, particularly during the start, is a big part of operating any turbine. Once running, a single lever controls power—although, you'll have to get used to the relatively slow "spool-up" time needed to go from idle to full power, which can range from two to eight seconds, depending on the engine. On the other hand, pulling the power to idle happens rapidly and is harmless.
Making the transition into a turbine isn't easy, cheap or quick, but it's possible. Jumping into the left seat opens up an amazing world of performance and capability.
Turbine power will quickly transport you into the flight levels, and once you fly with pressurization, it's hard to ever go back. Cabin pressure is provided by a small amount of air siphoned from the engine through a "bleed valve." This air is cooled and fed into the pressure vessel at a continuous rate. Pressure-relief valves, usually located at the rear bulkhead, regulate cabin pressure by controlling the cabin-leak rate. Normally, two valves provide redundant operation with a safety valve to prevent overpressurization. Operation is simple, and many light jets like the Mustang are totally automatic, requiring only the field elevation to be input.


Cessna Citation Mustang
Most high-performance turbine aircraft incorporate numerous other systems, like redundant electrical supplies, ice protection systems, hydraulic systems, radar, data-link capabilities, terrain alert and warning systems (TAWS), anti-skid brakes, stick shakers, angle-of-attack indicators, flight management systems and sophisticated autopilots. Learning how to operate all this stuff is a big part of any initial training program and one reason many training courses require so much time.

Multi-Engine Turbine Considerations

In the multi-engine turbine world, checklists cover every procedure, and all landing and takeoff speeds are computed for every flight, taking into account aircraft weight, temperatures and field elevation. There are three critical speeds for takeoff; V1, Vr, and V2. V1 is called decision speed. Experience any kind of failure before V1, and you stop on the runway. Lose an engine going faster than V1 and you keep going. Accelerate to rotation speed (Vr), rotate, establish a climb, lift the gear, accelerate to the best single engine climb speed of V2, and at a predetermined safety altitude, accelerate to a "single-engine enroute" speed and raise the flaps.



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