Cessna Corsair Model 425

The 28-volt electrical system is pow- ered by a 24-volt, 39-ampere-hour nickel cadmium battery for starting and emergency operations and two 250-amp engine-driven starter genera- tors. Each of the generators powers its own bus; if one fails, the other will pick up the load. The separate avionics bus is split, also. The battery is reached easily (not always the case) through a bay on the starboard side of the nose. The engine cowling is easy to re- 118 • MARCH 1981 move for inspection, and access to fuel pumps and plumbing is good. The in- board leading edge of the wing is re- movable for access to the bleed-air sys- tem, which provides pressurization and heating and drives the pressure gyros, pneumatic leading-edge deicing boots and the pressure regulating valve. The pressurization system is set for a five-pound per square inch differential, which provides a 10,000-foot cabin al- titude at 26,500 feet and just under 12,000 feet at 30,000 feet. Either engine set at Flight Idle will provide sufficient bleed air to maintain pressurization, so loss of pressure is not a concern during Mosf pilafs who sfep up from pisfan fwins fa fhe Corsair will find if easier fa operafe and fly. maximum rate descents. The balance of the systems and the airframe appear to reflect the same attention to simplicity, accessibility and maintainability. The powerplants seem to be a good choice for the airframe. They are fairly far out on the wings, and the slow- turning propellers (1,900-rpm maxi- mum) have nearly two feet of clearance between the tips and the fuselage. The PT6A is a proven design-and is offered in quite a range of power. Rec- ommended time between overhaul is 3,500 hours. The engine in the Corsair installation is flat-rated to 450 hp, which it can maintain to 17,700 feet or at DO' F at sea level. The installation is clean; Cessna claims that it is the most drag- free and provides the highest inlet- pressure percentage of any, which means there is less performance loss. The PT6 is a free-turbine design. There are two independent turbines. One drives a compressor and the other the propeller through a reduction gear box. The compressor and the power turbines can be inspected, serviced and overhauled separately. The free-turbine has some character- istics of more direct interest to pilots. In the event of an engine failure, there is less propeller drag than on a direct- drive engine. Also, feathered or wind- milling starts can be done in flight. On the other hand, a propeller can be feathered without shutting down the engine. This is an advantage during simulated engine failures. It is also an advantage during ground operations. Although idle speed is only 600 rpm, the residual thrust can result in higher than desired taxi speed. Feathering the propeller of one engine helps keep the speed down-and saves wear and tear on the brakes. Three-bladed propellers are stan- dard, as are synchrophasers, electric deice and reverse (beta) mode. Anti-icing and ingestion are quite simply handled on the installation. The air inlets are heated constantly by ex- haust gas; there is no need to engage a system. Engine moisture and foreign- object ingestion are prevented by an inertial air-separation system, which, when engaged, moves vanes into the intake duct to separate air from heavier particles. The air passes on into the en- gine-air inlet; the foreign matter is di- verted through a by-pass duct. Other standard equipment includes air conditioning, copilot flight instru- ments, heated dual pitot-static sys- tems, engine-bay fire detection and warning (fire extinguishing systems are optional), corrosion proofing and emer- gency oxygen system (11 cubic feet; a larger capacity system is optional). There are a lot of options left to buy for the Corsair. Operational ones in- clude a known-icing package ($18,855) and additional avionics. A basic package of ARC 400 series avionics-dual nav/com, dual glide- slope, automatic direction finder, dis- tance measuring equipment, marker beacon receiver, transponder, encoding altimeter, 1000 series autopilot with slaved HSI (horizontal situation indica- tor) and yaw damper-is standard. Two alternate packages are offered. One is an ARC 1000 series, which in- cludes a radio magnetic indicator (RMI) for $16,630. The other is a Collins sys- tem, including a WXR 200A radar sys- tem, for $69,350. Two Pilof staff members flew the fourth production Corsair, N98817. Its list price is $928,815 (the current base price is $825,000). More than $62,000 of the difference is for additional avionics. It probably is representative of the way the average 425 will be equipped. There are enough avionics, equip- AOPA PILOT· 119 .•_-~-~--- - .•--.-...--.•..•----..-- - --- ..........•.... - . , continued ment and interior options to keep someone planning, checking weight and the bank balance for weeks. Some add weight but increase performance; others trade weight and space for com- fort, convenience and privacy for the folks who ride in the cabin. The standard seating arrangement is for six with a club design in the back. There are two seven-place and two eight-place options, plus a multitude of dividers, tables, toilets, refreshment provisions, storage drawers, adjustable seats and entertainment features. The Corsair is being presented as an airplane that makes the transition from piston twins to turboprops easier. This is not really true, since the transition to practically any turboprop from a medi- um piston twin is easy. Yes, there is more power; yes, things happen faster. But power management and, usually, fuel management are simpler; and, gen- erally, cockpits are more intelligently organized and systems are both better and simpler. The truth is that most competent pilots who step into a 425 from, for instance a 310, a 340, a 414 or a 421 will find it much easier to operate and fly. It is also smoother and quieter, 120 • MARCH 1981 so the insidious fatigue they cause is much reduced. The 425 is very well mannered and pilot workload is comparatively low, which lets the crew concentrate on the important things. That is, so long as the pilot(s) is trained properly, fully cur- rent, very meticulous in flight plan- ning, preflight and all operations; so long as maintenance is good ... and so long as everything is working properly. One of the best pieces of standard equipment that comes with the Corsair (and, today, most other turboprops) is training for two crew members at Flight- Safety International. It encompasses system training, simulator training and actual flight in the customer's aircraft. This should be followed up with a regu- lar recurrent training schedule. Our flights in the Corsair were really A well-appointed cabin allows passengers to ride in comfort and in style. ~ :~ -~.'" just introductory, although we did sample some of the eme.rgency proce- dures, some operational variations, in- strument meteorological conditions and approaches and missed approaches. Once again, however, if first impressions are to be trusted, the combination of intelligent design and good systems means that a pilot has a lot of things working for him when things go wrong. For instance, in an engine failure im- mediately after takeoff, with the com- bination of autofeather and basic good flight characteristics, the Corsair is eas- ier to handle in single pilot operation than most piston twins. A pilot with no turbine experience has quite a lot of new terms, concepts and other things to learn-Mmo (max- imum operating speed expressed in percentage of Mach number); tempera- ture compressibility effects; ITT (inter- turbine temperature); Ng and Np (gas generator rpm and propeller rpm); flameout; torque. And then there are those things in the cockpit that look like throttle, mixture and prop, but are called power, condition and fuel levers. They function basically the same way (except the fuel control is left alone in normal operations from the time the engine is running properly to the time it is shut down. Look, mom- no leaning. It has only two positions: Off and Run); they just require a lot less fiddling with in flight. Preflight is straightforward, although a bit more involved. The pre-takeoff check list uses up 18 pages of the oper- ating manual, for instance, and the emergency procedures use 48 pages. Cessna has a good method of de- scribing emergency procedures in its operating manuals, by the way. Steps that must be committed to memory are boxed. Useful information, cautions and warnings-actions that, if taken, can really ruin the day-are further flagged. The process makes it easier for pilots to determine what they must do before they have the leisure time to reach for the check list. There is an annunciator panel under the glareshield with 33 items to call the pilot's attention to emergencies (red), hazard (amber) and safe or normal con- ditions (green or white). Now we get to the good part: flying. Once all the preliminaries have been completed and the passengers have been seated and briefed and the air- stair door secured, the fun begins. The before-start check list is uncom- plicated, as is the normal start. In fact, most starts-even in cold weather- will be easier than with a piston en- gine. Before taxiing and before takeoff, there are a lot of systems and settings to check, but, again, it is just that there is more, not more difficulty. Ground handling is good. The main- gear track is wide, and the action of the trailing-link gear smooths out most 122 • MARCH 1981 ~ The frailing-beam gear is easy fa care for and makes landing an evenf worfh looking forward fa. rough spots. Nosewheel steering is fairly light. It is preferable to get the engines "on the bit"-the propellers developing 1,900 rpm-before brake release to avoid differential thrust, which makes directional control look a bit sloppy and bothers the passengers. Torque is the governing condition on takeoff (1,244 foot-pounds maximum) for the CorSrtir (with some powerplants, temperature is the limiting factor), and / care must be taken to avoid passing through the value, since it will increase as speed increases. Lever movement must be measured and smooth. Gross weight Vmc (minimum control speed with critical engine inoperative) is 90 knots indicated airspeed; the Cor- sair will accelerate through quite quickly, and a bit of back pressure through 98 knots will provide lift-off at 102 KIAS, which is Vsse (minimum in- tentional one-engine inoperative speed). Tap the brakes, and retract the gear. It will be buttoned up in less than five seconds (the book says 4.5, 7.5 with one engine out). Speed and alti- tude increase quite rapidly, and the critical configuration and the time of exposure for engine failure are passed very quickly. The best-rate-of-climb speed, 115 KIAS, fills the windshield with the nose. A comfortable cruise climb speed is 150 KIAS. Turbine engines are noted for their high fuel consumption at lower alti- tudes. The climb performance of the Corsair is good, so there is no reason to stay low even for relatively short trips. We tried a time-to-climb on one flight. With three aboard and 1,400 pounds of fuel, the aircraft was 740 pounds below maximum takeoff weight. The time to climb from brake release at Wichita Mid-Continent, 1,332 feet, to 26,000 feet was just under twelve and a half minutes using an ini- tial climb speed of 120 KIAS. The ini- tial rate of climb was more than 2,200 fpm (sea level rate of climb at maxi- mum weight and 115 KIAS is listed as 2,027 fpm). Fuel flow averaged 434 pounds per hour (pph). Leveling at cruise and establishing Ba,.;;ed on manufacturer '.••ligures The Corsair's panel is simple, yef sophisficafed. Pilof work load is low, fhanks fo cockpif arrangemenf and sysfems derived from' fhe Cifafion program. Specifications c maximum cruise power of 1,900 rpm, torque at 933 and fuel flow at 380 pph, the indicated airspeed was 169 knots, true airspeed 252 knots. The noise level was quite low. Using 1,700 rpm and higher torque lowered the noise level and resulted in practically the same speed, but higher fuel burn. Range at maximum cruise power at that altitude with full fuel is 1,265 miles at 257 knots. At 30,000, it in- creases to 1,406 miles at 250 knots. The Corsair does like altitude. The day was quite choppy, and the airplane handled it well, both at alti- tude during cruise and at low altitude and low airspeed. The controls are well harmonized at all speeds with, of course, higher effort at the upper end of the speed range. We tried a maximum performance descent from cruise altitude. With power at Flight Idle and speed at 210 knots, the initial rate of descent was 5,000 feet per minute. We tried both coupled and uncou- pled approaches with some balked landings thrown in. We also tried sin- gle-engine situations and stalls. There isn't much to say about it all. The Cor- sair is very well behaved and shows no tendency to get away from the pilot. Both gear and the (first 15 degrees of) flaps can be extended at 175 KIAS, which will do a lot to help operations in high density areas or to descend in choppy air. Maneuvering speed is a rel- atively high 154 KIAS, too, although towards the end of the flight it must be reduced (for instance, to 131 KIAS at 5,500 pounds). Normal approach speeds are well be- low comfortable speeds for quite a few piston twins. The recommended ap- proach speed is 102 KIAS, And the landings. Ah, yes. That gear does make up for more than its share of poor technique and misjudgment. It would be nice to fly such an air- plane regularly. It also would be won- derful to be able to enjoy some of the systems and human engineering devel- opments in smaller, less expensive air- craft. Those of us who spend the ma- jority of our time grinding around in the muck at lower altitudes could cer- tainly use the help and the security. It is a shame that simplicity costs a million bucks. Perhaps Cessna, ~hich has made obvious strides in the pilot's favor at the high end of the line, will put the same kind of effort into its sin- gle-engine aircraft. 0 154 kt 264 kt 259 kt 251 kt 240 kt 257 kt 2·19 kt 238 kt engine 90 kt 107 kt 115 kt '175 kt 145 kt 175 kt 175 kt 230 kt 90 kt 84 kt MJximum level speed (17,700 ft) Cruise speed (1,900 rpm, 8,200 Ib) 20,000 ft 26,000 ft 30,000 ft Cruise speed (1,800 rpm, 8,200 lb) 20,000 ft 26,000 ft 30,000 ft Cruise speed (1,700 rpm, 8,200 Ib) 20,000 ft 254 kt 26,000 ft 245 kt 30,000 ft 233 kt Rdnge @30,000 ft, 8,200 Ib tdkeoff, 1,900 rpm 250 kt 1,406 nm 210 kt 1,640 nm RJnge @ 25,000 ft, 8,200 lb t,.keoff, 1,900 rpm 258 kt 1,210 nm 206 kt 1,530 nm RJnge @ 20,000 ft, 8,200 lb tJkeoff, 1,900 rpm 263kt 1,020nm 205 kt 1,370 nm Service ceiling 34,700 ft Single-engine service ceiling 18,500 fl LJnding distdnce (ground roll) 952 ft LJnding over 50 ft 2,145 ft Limiting and Recommended Airspeeds Indicated air"'pt't'd~, nol calibrated VJ (Maneuvering) Vfe (MJximum fl,1p extended) 15' 45' Via (MJximum ge.u oper"ting) Vie (M"ximum ge.u extended) Vne (Never exceed) Vsi (51,111cle,m) Vso (St,111in I,mding configur,1tion) Vsse (Minimum intentional one-engine inoperJtive) 102 kt Vmc (Minimum control with eriticJI inoperative) Vx (Best dngle-of-climb) Vy (Best rdte-of-climb) 2,047 ft 2,341 ft 2,027 fpm 434 f pm PrJIt & Whitney PT6A-112, 450 shp, 1,900 rpm, 3,500 hr HJrtzell,3-bIJde, constJnt speed, full feJther ,md reversible, 93.4 in diJ. Hftlin 35 ft 10 in 12 ft 7 in 225 sq ft 36.44 lb/sq ft 9.11 Ib/hp 6 (7 & 8 opt) 15 ft 10 in 4 ft 8 in 4 ft 3 in ·1,870Ib 5,1861b 3,405 lb 3,089 Ib 952.8 Ib 636.81b 8,2751b 8,2001b 8,0001b 6,7401b 2,499 Ib (2,452 uSJble) 434 pph 9 qt (e,1 engine) 1,1001b Recommended TBO Propeller Performance CESSNA CORSAIR MODEL 425 BJsic price $825,000 (1981) Price JS tested $928,815 Engine Wingsp,m Length Height Wing.1reJ. Wing loading Power IO.1ding SeJts CJbin length CJbin width Cdbin height Empty weight (b,1sic JirerJft) Empty weight (dS tested) UsefulloJd (basic ,1irer,1ft) UsefulloJd (,IS tested) PJyloJd w/full fuel (bJsic airer,1ft) PdyloJd w/full fuel (dS tested) Ramp weight Gross weight (tJkeoff) Gross weight (l,mding) M,JX lero fuel weight Fuel CJp,Kity Fuel flow Oil CJpJcity Bdgg,'ge CJpJcity TJkeoff distJnce (ground roll) Takeoff over 50 ft Rate of climb (seJ level) Single-engine ROC (seJ level)