Mooney M20L PFM

fuel mixture of 16:1 at every power set- ting except full power. The system does a marvelous job of thinking for itself. If the OAT rises a degree or two, fuel flow decreases a tenth of a gallon an hour. At full power, a microswitch on the power control activates a second air-density regulator in the Bosch fuel injection unit, enriching the mixture to a best-power ratio of 12.5:1. An Enrich switch is used for starting whenever CHTs are lower than 25 de- grees Celsius. Flipping the switch and engaging the starter squirts fuel into the intake manifold. Cold or hot, the engine routinely starts in one or two revolutions of the prop. Two high-pressure electric fuel pumps supply the engine. A third emer- gency pump is switched on for takeoff and landing. Fuel pressure is high enough to preclude the formation of va- por locks. Hot starts are not even men- tioned in the POH. Porsche has certified a 209-hp version of the engine for auto fuel use, but it is not available in the Mooney Porsche. The engine is the first for general avia- tion to be certified with electronic igni- tion. The heart of the dual, independent Magneti Marelli ignition systems is a pair of microprocessors that continu- ously adjust timing based on crankshaft rpm, absolute manifold pressure, piston top dead center, and intake air tempera- ture. The only moving parts are the dis- tributor rotors. The airplane has two 24-volt batter- ies, two 70-amp alternators, and two in- dependent electrical buses. If a problem should develop on one bus and trouble- shooting proves unsuccessful, the drill is to lift a large red guard at the top of a forest of circuit breakers on the right side of the panel and push the crossover breaker underneath. This pulls the plug on the affected bus and transfers the load to the other. Next, find an airport. With one bus out of the loop, redundancy is lost, and a problem on the remaining circuit could leave you with no electrical options other than battery power to the elec- tronic ignition and electric fuel pumps. ~ The greatest challenge in flying the Porsche Mooney is learning the intrica- cies of the electrical system and memo- rizing emergency procedures. TBO on the engine is 2,000 hours, but with experience, Porsche hopes to reach a 3,OOO-hourTBO. One reason is fan cooling. Air enters the engine plenum through a flush duct on the lower right side of the cowl and cools accessories at the back of the engine before it is sucked into the fan. The fan directs the air through a shroud and over the finned cylinders. The air exits into the slip- stream through louvers on the bottom of the cowl. Two engine-driven V-belts turn the fan, so its speed and, therefore, the vol- ume of cooling air in the shroud is pro- portional to engine rpm. The advantage of the fan and shroud arrangement is that CHTs are consistent and stable, even on a hot-day climb or with gross changes in power. Chop the throttle for a precipitous descent, and fan speed drops in concert with engine and propel- ler rpm. With no ram airflow, shock- cooling ceases to be of critical concern. What burden does all of this new-to- general-aviation technology place on the Porsche Mooney pilot? None, and that is the point. Operating the engine is almost as easy as stepping on the gas pedal in a car. To start it, switch on the master, the two battery switches, and the two fuel pumps, and turn the key. Push the power control in to go, pull it back to slow down. Even shutting down is different. Flip off the two fuel pumps, and the engine and propeller instantly stop as if they have seized. The Hartzell prop is made of Kevlar and is very light, so there is little flywheel effect. Engine and interior furnishings aside, the PFM is much like other Mooneys, which is to say efficient and highly per- sonal. You don't so much climb into the cockpit as slip it on. The seats sit low to . the floor, and the rudder pedals are re- •. cessed deep in the foot wells. The cabin may feel somewhat confining initially, but a Mooney grows on you. Cruise speed on our trips was a con- AOPA PilOT • 41 with experience, Porsche hopes to reach a 3,OOO-hourTBO. One reason is fan cooling. Air enters the engine plenum through a flush duct on the lower right side of the cowl and cools accessories at the back of the engine before it is sucked into the fan. The fan directs the air through a shroud and over the finned cylinders. The air exits into the slip- stream through louvers on the bottom of the cowl. Two engine-driven V-belts turn the fan, so its speed and, therefore, the vol- ume of cooling air in the shroud is pro- portional to engine rpm. The advantage of the fan and shroud arrangement is that CHTs are consistent and stable, even on a hot-day climb or with gross changes in power. Chop the throttle for a precipitous descent, and fan speed drops in concert with engine and propel- ler rpm. With no ram airflow, shock- cooling ceases to be of critical concern. What burden does all of this new-to- general-aviation technology place on the Porsche Mooney pilot? None, and that is the point. Operating the engine is almost as easy as stepping on the gas pedal in a car. To start it, switch on the master, the two battery switches, and the two fuel pumps, and turn the key. Push the power control in to go, pull it back to slow down. Even shutting down is different. Flip off the two fuel pumps, and the engine and propeller instantly stop as if they have seized. The Hartzell prop is made of Kevlar and is very light, so there is little flywheel effect. Engine and interior furnishings aside, the PFM is much like other Mooneys, which is to say efficient and highly per- sonal. You don't so much climb into the cockpit as slip it on. The seats sit low to . the floor, and the rudder pedals are re- •. cessed deep in the foot wells. The cabin may feel somewhat confining initially, but a Mooney grows on you. Cruise speed on our trips was a con- AOPA PilOT • 41 Mooney M20L PFM Base price: $149,900 Average equipped price: $185,000 Specifications Porsche PFM 3200-N03, 217 hp @ 2,343 prop rpm Recommended TBO 2,000 hr Propeller Hartzell composite, two-blade, constant-speed, 74-in diameter 26.92 ft 8.33 ft 36.08 ft 174.8 sq ft 16.6 lb/sq ft 13.4 Ib/hp 4 10.5 ft 3.6 ft 3.7 ft 1,952 Ib 2,1401b 948 Ib 7591b 585 Ib 396lb 2,900 Ib 2,900 lb 66.5 gal (60.5 gal usable) 399 Ib (363 lb usable) 13.5 qt 120 Ib, 22.6 cu ft sistent 155 KTAS at 2,300 rpm. Fuel flow varied between 9.5 and 10.5 gal- lons per hour, depending on altitude and ambient temperature. One flight in particular showcased the PFM's cross-country talents. The itiner- ary was Frederick, Maryland, to Keno- sha, Wisconsin, in the morning and re- turning that same evening. Winds were not a factor westbound, so 12,000 feet was the requested altitude. The POH calls for a cruise climb of 90 to 100 KIAS, but with the short prop, 110 knots works just as well. The initial climb rate with one aboard and full fuel was 1,000 feet per minute, which gradually decreased to 650 fpm at 8,000 feet. The interesting part was watching the Bosch system do its thing, reducing fuel flow from 16 gph down low to 13 gph at 8,000 feet, even though the power control stayed put. The absence of a headwind meant an early arrival for the appointment in Ke- nosha, so the extra time was used to ex- periment. The initial cruise power set- ting was 2,300 rpm, which yielded 153 knots true at 8.8 gph or 16.3 miles per gallon, according to the Arnav 50 loran. Reducing the power 1,000 rpm reduced fuel flow four tenths of a gallon at the expense of two knots. Another 1,000 rpm, another four tenths and two knots. At 2,000 rpm, fuel flow settled on 7.6 gph at 145 knots true, and the noise 129 KIAS 106 KIAS 174 KIAS 195 KIAS 65 KIAS 64 KIAS 57 KIAS Powerplant Length Height Wingspan Wing area Wing loading Power loading Seats Cabin length Cabin width Cabin height Empty weight Empty weight, as tested Useful load Useful load, as tested Payload w/full fuel Payload w/full fuel. as tested Max takeoff weight Max landing weight Fuel capacity Oil capacity Baggage capacity Performance Takeoff distance, ground roll l.250 ft from engine and prop was little more than soothing background music. Vibration and noise levels are notice- ably low in the PFM, which increases the comfort level considerably. The en- gine hangs from a three-point, low-vi- bration mount, and the gearbox is cou- pled to the engine through a fabric- reinforced rubber disk that absorbs torsional vibration. The slow-turning propeller generates fewer decibels, and engine noise is effectively attenuated by the exhaust muffler and also by the inte- rior soundproofing. The flight took exactly four hours. The lineman replenished the tanks with 35.6 gallons. The Mooney could have flown for another two hours and still have had legal IFR reserves. Dinner was waiting at the end of the return leg, so it was flown at high power in 3 hours 24 minutes. The tanks took 41.2 gallons. With 60.5 gallons usable fuel, the PFM has excellent endurance. The com- promise is restricted payload. Our PFM can carry 2.3 170-pound souls with the tanks topped off. With four FAA-stan- dard adults aboard and 50 pounds of bags, you could depart with enough fuel to taxi out and check the ignition before running dry. Between the two ex- tremes-full fuel or full cabin-lies a fair amount of flexibility in trading one for the other. Mooney says it is working Takeoff distance over 50-ft obstacle 2,510 ft Rate of climb, sea level 1,050 fpm Max level speed, sea level 168 kt Cruise speed/endurance w/45-min rsv, std fuel (fuel consumption) @ 2,300 prop rpm 160 kt/4.5 hr 9,000 ft (66.6 pph/11.l gph) @ 2,100 prop rpm 152 kt/5.2 hr 9,000 ft (58.2 pph/9.7 gph) @ 2,000 prop rpm 145 kt/5.9 hr 9,000 ft (51.6 pph/8.6 gph) Max operating altitude 19,300 ft Landing distance over 50-ft obstacle 1,900 ft Landing distance, ground roll 900 ft Limiting and Recommended Airspeeds Vx (best angle of climb) 75 KIAS Vy (best rate of climb) 96 KIAS Va (design maneuvering) 117 KIAS Vfe (max flap extended) 110 KIAS Vie (max gear extended) 129 KIAS Vlo (max gear operating) Extend Retract Vno (max structural cruising) Vne (never exceed) Vr (rotation) Vs1 (stall, clean) Vso (stall, in landing configuration) All specifications are based 011 manufacturer's calcula- tions. All perfonnance figures are based on standard day, standard atmosphere, sea level, gross weight COll- ditions unless otherwise noted. 0 on increasing the useful load. Base price of the PFM is$149,900. Av- erage equipped retail price of an IFR- equipped one is $185,000. The price re- flects an expensive certification effort, the higher cost of the Porsche engine, and Mooney's decision to set the PFM apart with a first-class interior and instrumentation. Mooney has built 41 PFMs, about half of which have been sold. The company admits to a mistake in initially market- ing the PFM to its traditional customer base-existing Mooney owners-rather than to first-time buyers. New incentive programs are being considered to attract PFM sales. Porsche, meanwhile, has had to con- duct some damage control following a decision to sell its Galesburg, Illinois, base and discontinue its effort to reengine Cessna 172s with the PFM 3200. Porsche's aviation activities now will be handled by Porsche Cars North America in Reno, Nevada. Technical support, including parts inventory, spare engines, and customer assistance, are unaffected by the change, except for relocating to Reno. About 100 aviation mechanics have attended special PFM 3200 training classes. The announcement prompted wide speculation that Porsche would soon bailout of airplane engine production altogether. Sales of Porsche cars in the United States have declined steadily since 1986. The company has cut pro- duction of its cars and has altered its marketing approach to emphasize low volume and high exclusivity rather than volume sales. That strategy would ap- pear to fit the PFM 3200 perfectly, but a Porsche spokesman said the likelihood of continued production and develop- ment of the PFM 3200 (a turbocharged version has been tested) has yet to be determined in light of Porsche's woes. The strength of the PFM is not, as some believe, the prestige of driving up to the fixed-base operation airside ramp in a Porsche, although that is a pleasant extra. The benefits are much more prag- matic. They include the ease of manag- ing the power, fuel economy, the ab- sence of vibration and noise, instant starting, and the very real potential for longer, more reliable service. Mooney and Porsche have taken a long step for- ward with the M20L. In an cri-ena in which technology advances almost im- perceptibly, their achievement deserves a full measure of attention, recognition, and support. 0