Cessna 337 Skymaster - Aero Resources Inc

choice before feather- ing a prop. Single-engine climb is nothing to crow about on any of the models, falling in the 200- to 400- feet - per- m in u te range, depending upon installed power and maximum gross weight. These numbers are in line with those of other light twins. Single-engine service ceiling is very good, better than conven- tional twins. A non- turbo 1967 model has a single-engine ceiling of 7,500 feet with the rear engine out, and 9,500 AOPA PILOT. 87 1979 Cessna P337H Average new cost, equipped: $171,205 Current market value: $96,000 Specifications Powerplants Two Continental TSIO-360- CB, 225 hp at 2,800 rpm Recommended TBO 1,400 hr Propeller McCauley constant -speed, full-feathering, 76-in diameter 29 ft 10 in 9 ft 2 in 38 ft 2 in 202.5 sq ft 23.21b/sq ft 1O.4lb/hp 5 10 ft 7 in 3 ft 6 in 4 ft 2 in 3,2181b 4,7001b 1,4821b 5941b 151 gal (148 gal usable) 9061b (888 Ib usable) 8 qt 89 KIAS 139 KIAS 1,010 fpm 375 fpm engines Rate of climb, sea level, one engine Rate of climb, 10,000 feet, one engine 245 fpm Max level speed, 20,000 feet 212 kt Cruise speed/endurance w/45-min rsv, std fuel (fuel consumption, total) @ 75% power, best economy 186 kt/4.9 hr 10,000 ft (26.3 gphlI58 pph) @ 75% power, best economy 205 kt/4.8 hr 20,000 ft (26.5 gph/159 pph) @ 65% power, best economy 177 kt/5.6 hr 10,000 ft (23.3 gphlI40 pph) @ 65% power, best economy 192 kt/5.6 hr 20,000 ft (23.3 gphlI40 pph) Service ceiling 20,000 ft Landing distance over 50-ft obstacle 1,675 ft Landing distance, ground roll 795 ft Limiting and Recommended Airspeeds Vx (best angle of climb) 69 KIAS Vy (best rate of climb) 95 KIAS VYSE (best single-engine rate of climb) VA (design maneuvering) VFE (max flap extended, one-third flaps) 165 KIAS VFE (max flap extended, full) 110 KIAS V1\0 (max structural cruising) 169 KIAS V1\E (never exceed) 205 KIAS VS1 (stall, clean) 65 KIAS Vso (stall, in landing configuration) 60 K~S All specifications are based on manufacturet's calculations. All performance figures are based on standard day, standard atmosphere, sea level, gross weight conditions unless othenvise noted. 12 kt 945 ft 1,500 ft 1,170fpm Oil capacity, ea engine Length Height Wingspan Wing area Wing loading Power loading Seats Cabin length Cabin width Cabin height Empty weight Maximum gross weight Useful load Payload w/full fuel Fuel capacity, std Performance Takeoff distance, ground roll Takeoff distance over 50-ft obstacle Max demonstrated crosswind component Rate of climb, sea level, two engines Rate of climb, 10,000 feet, two feet with the front engine shut down. A 1971 turbo 337 will claw its way up to at least 14,400 feet (17,200 on just the rear engine), while a 1980 P337 can climb to 18,700 feet on just one engine. For most naturally aspirated light twins, the single- engine ceiling is any- where from 4,000 to 6,000 feet. The differ- ence is, naturally, that the Skymaster can chug along with one feathered without having a huge rudder cocked into the breeze or any of the other aerodynamic compro- mises inherent in a conventional twin running with an engine shut down. The big Cessna can be brought down final approach at surprisingly low velocities, too. For the heaviest airplanes, Cessna recommends a nor- mal approach of 80 to 90 knots, with short-field procedures calling for just 78 knots over the fence. The lighter, earlier models can shave about 4 knots off that figure. Count on optimum cruise speeds for the normally aspirated models in the 165-knot range at 5,000 feet, burn- ing 23 gillions per hour total. That's a bit slower and a bit thirstier than con- ventional twins packing a pair of 180- hp engines. Cruise speeds of the T337 show a best of 190 knots at 25,000 feet, burning 22 gph total, while a 1980 P337 (225 hp each engine) tops out at 204 knots, using 26.6 gph at 20,000 feet. The later 1337 and P337 models are only certified to 20,000 feet, whereas the earlier turbo models have no such limitation, a quirk of changes in the certification standards that took place in the 1970s. While the 337 is no speedster, at least the cabin has the stretch-out room to make the journey comfort- able. Cessna called the 337 a six-place airplane (and the P337 a five-placer), but to carry a half dozen people means having them hold their luggage on their laps because there's no room left for baggage. (Unless, of course, you find a 337 with the optional cargo pod, which will give you room for 88 • JULY 1993 MAJOR ACCIDENT CAUSES three "two-suiters," according to Cess- na.) Really, the 337 is a marvelously comfortable four-person airplane with room and payload for baggage. From the cabin, two items stand out as examples of the best and worst traits of the 337. Excellent visibility from the front row of seats is the high point; because the wing is well aft and the windows are large, the pilot and copilot have an almost unobstructed view of the outside. The low point is noise. Engines attached to each end of the cabin create quite a racket at high power settings. Reducing engine speed helps tremendously, but you'll still want to have comfortable, quiet headsets aboard. Useful load on the various models runs from 1,500 pounds up to about 1,700 pounds on the early airplanes. It's only when you load the later, large-tank airplanes full of fuel (888 pounds worth), that you really have to watch the weight and balance. The center-of-gravity range is generous. Most Skymasters have pretty good range, too, with long-range tanks available from the start. Airplanes through the 1972 models had 92 gal- lons usable standard, with 128 gallons According to the AOPA Air Safety Founda- tion's General Aviation Accident Analysis Book-For the Years 1982-1989, the Cessna 337 series had a total of 79 accidents, resulting in 63 major injuries and 33 air- craft destroyed; 56 of those accidents were determined to be pilot-related. Most acci- dents occurred in the cruise phase oftlight, 39.3 percent; of those, 21.4 percent were caused by fuel exhaustion (an additional 3.6 percent from fuel mismanagement), and 12.5 percent were weather related. Landing-phase accidents accounted for optional. In the long-range airplanes, fuel was carried in two interconnected main tanks in each wing, plus an aux- iliary tank between the cabin and booms; the pilot has to switch between the main and auxiliary tanks. Starting in 1973, the auxiliary tanks were plumbed in with the mains, eliminating the need to switch tanks except to turn the fuel off or to cross- feed. Standard tanks for the 1973 and 1974 models remained 92 gallons usable, with a long-range option total- ing 118 gallons; in 1975, the extended- range tankage was increased to 148 21.4 percent, with 7.1 percent attributed to failure of the pilot to lower the landing gear, 5.4 percent were hard landings, and 3.6 percent were overshoots. A total of 8.9 percent of the accidents were related to approaches gone awry. 3.6 percent in VFR conditions and 5.4 percent in IFR condi- tions. Mechanical mayhem was the prima- ry cause in 10 accidents; two 337s came to grief after engine failures, five from landing gear or brake problems, and three from fuel system maladies. The accident cause for an additional 13 is unknown. 0 gallons usable in four interconnected wing tanks a side. Finally, starting in 1976, the standard tanks were reduced in capacity to 88 gallons usable, while the long-range option stayed at 148 gallons. The fuel system merits discussion because it seems to be the source of the 337's most common accidents. According to a study compiled by the AOPA Air Safety Foundation, during the period of 1982 to 1989, fuel starva- tion or exhaustion accounted for the largest single category, with 15 acci- dents. These ran the gamut from fail- ure to change tanks to simply running out of fuel before reaching the desti- nation. Two additional accidents stemmed from fuel system malfunc- tions, one a fuel leak and the other a jammed selector valve. On paper, the 337's fuel system is not particularly complex and far simpler than, say, a 31O's or a 34o's. And while the 337's fuel system has at least been reliable, such praise can- not be lavished upon its engines. Early on, the 10-360s gained a reputation as hot-running, crack-prone power- plants. Before the B-suffix engines were introduced in the late 1970s, there were numerous reports of bro- ken crankshafts and connecting rods. Even today, service difficulty reports point to cracking cases, sheared crankshafts, head-to- barrel separa- tions' and general engine mayhem. The normally aspirated 10-360s have a published time between overhaul of 1,500 hours, but don't bet big money on it. Most operators report needing top-end work enroute to TBO. Maintenance matters get worse with the turbocharged or pressurized airplanes. The early, 210-hp turbo air- planes do better than the later 225-hp •The 337's cabin has stretch-out room and good visibility; noise and lack of baggage space are low points. models (which get that power from 37 inches manifold pressure and 2,800 rpm), but neither powerplant will win any longevity awards. Continental lists the TSIO-360s' TBO as 1,400 hours, but once again, savvy owners will not bank on getting to that number with- out at least some interim top-end ministrations. Another systems headache, accord- ing to owners and service difficulty reports, is the gear system. All 337s have full gear doors, and the hydraulic system has been the bane of many a mechanic. We're told, however, by the Cessna Pilots Association, which maintains the P337 photographed for this report, that with proper mainte- nance, the 337 gear can be reliable and not terribly expensive to main- tain. The trick is to get the system debugged first; this is a prime shop- ping point for any 337 purchaser. Don't even consider putting money down on a Skymaster unless you've had the gear and engines gone through thoroughly, and even then, be sure to budget liberally for the first year's ownership. We are told, also, that the later model years are better as Cessna replaced the engine-driven hydraulic pump with an electric power pack. The bottom line seems to be that the basic 337 airframe is the strong, simple type, but the airplane's engines and systems can really hog out a checking account. Joining the Cessna Pilots Association or a 337 club can give you the knowledge to make main- tenance matters more reasonable. Still, maintenance problems don't seem to matter much to those individ- uals who have spent the time and effort to debug their airplanes. For them, the 337 represents a reasonably economical, safe multiengine airplane. They truly seem to love the Skymas- ter-and will shoot daggers at those nonbelievers who dare call it anything other than three- three-seven. 0