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Aviation History
1987
1987 - 0026.PDF
*v*»-« Idle 4,000 cam B 5,300 rp.m Propeller governor Slnflle-levf-uoiiti oi, operating principle Power ISA OM 1,000 .^ I Throttle 3,000 5,000 Engine speed "o °° Propeller | *t governor < Single-lever-control in practice Idle position Increase throttle Throttle butterfly closed, hydraulic propeller governor at low- speed position Throttle butterfly opens Engine r.p.m. increases Propeller governor maintains low r.p.m At 2,500 r.p.m (approx 40 per cent of take off power) butterfly fully open Pilot controls propeller pitch via governor Decrease in propeller pitch reduces drag, increases r.p.m., and increases air to cylinders Fuel demanded via air metering unit Power increases and stabilises Activates rich mixture switch Engines runs on rich side of peak exhaust Gas temperature (EGT) for best power Decrease throttle Decreases propeller pitch Dag increases Airflow to cylinders decreases Air metering unit demands fuel Power decreases and stabilises De-activates rich mixture switch for economy Engine runs on lean side of Peak EGT Further increase throttle Full throttle propeller r.p.m. Fuel flow is indicated on a clear digital display, which is a handy feature for flight planning. It can read consumption in kilograms or litres per hour, fuel used (which is retained for next flight), and propeller speed. A quick call to Donaueschingen tower, and we taxi out along the perimeter taxi- way. The PFM.3200 gives a low throaty rumble and sounds like the car engine, which is hardly surprising. Take-off checks are standard with fuel and both electric fuel pumps on—one as a backup. Engine run-up is at 3,000 r.p.m. with normal ignition checks. Opening-up for take-off gives one a vivid feeling of power, though there is a slight tendency, easily checked, for the aircraft to leave the centre line. Power is verified by noting maximum r.p.m. and 66 lit/hr fuel flow. We lift-off at 65kt, establish a 90kt climb, and climb through the overcast at 850ft/min. The standby fuel pump is switched off once we are airborne. The simplicity of the engine controls allows more attention to airmanship, especially in the circuit. There is no propeller or mixture to set after take-off as we enter low stratus, and no cowl flaps, engine temperature, or r.p.m. limitations to worry about, either. Most pilots are probably unaware of just how much time is spent with eyes down in the cockpit at times of high workload and airspace congestion. The Porsche pilot merely decides how much power he needs by fuel flow and r.p.m. Normal cruise is flown at 152kt, burning 381it/hr. Maximum range cruise at 120kt with 251it/hr consumption gives lOhr endurance. For maximum endurance a miserly 251it/hr gives one llOkt, ideal for holding patterns. We soon clear the tops of the low-lying scud. Up ahead a distant speck grows larger as we close in on the turbocharged Porsche Cessna 182 test bed aircraft for photography. Close formation gives me a chance to try out the vernier throttle. Pressing the central button on the throttle releases the vernier control, allowing free throttle movement. With so much reserve power and immediate response, I quickly revert to using the vernier control for small but precise power changes. It is the nearest thing to flying a jet. Forward for "go" and rearward for "slow". Power changes are smooth, thanks to a patented damper system which Porsche declines to detail. The low-level rumble of the PFM.3200 makes for easy conversation without headsets, and I can image that the low pitch engine note would allow long flights without fatigue. The single-lever control would be ideal for an aerobatic machine. Plans are afoot to produce an engine cleared for inverted flight. The power response and constant-speed propeller would reduce workload and optimise performance for the competition pilot. Returning to base, we have to make an unofficial cloud-break procedure on the Donaueschingen NDB. Being a triple first for Flight's reporter—first time in a Mooney, first with the Porsche engine, and first at this airfield, it is a good test of the engine's advantage for IFR flight. The Mooney is stable but responsive, and with precise power control an instrument approach poses no problems, despite the weather. Engine shutdown is simply a matter of switching off both fuel pumps, followed by the ignition. Oil quality can be checked before shutdown by a press-to-test oil warning light which extinguishes within 3sec if quantity is sufficient. First impressions of the PFM.3200 are of low noise and vibration, smooth and accurate throttle response, and simplicity of operation, with accurate monitoring of fuel consumption. The quality of engine sound, pitched lower than a Lycoming, is pleasing, as you would expect from the engine's pedigree. The Mooney 231 which made the world flight has now flown l,800hr, and is being used in a daily flight-test programme and on routine passenger flights throughout Europe. The world flight achieved a TBO of l,000hr, and with a recent overhaul this has now increased to 2,000hr. The Robin DR.400 has already made 300 glider-towing flights at gliding cham pionships in Austria and West Germany, and interest in the aircraft has been very encouraging. Porsche enjoys a close relationship with Pierre Robin, and the PFM-powered DR.400 will be the first Porsche delivery this month. The company has set up a Porsche retrofit and service centre in Gailsburg, Illinois, under US sales manager Don Krull. The PFM.3200 is the first of a family of engines, and deserves the closest consideration. O FLIGHT INTERNATIONAL. I April 1987
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