Airtest – Cessna Corsair

And now, having evaluated the type, we can only add our own praises to the chorus . . . The snag is to find the proper, factual and meaningful words without descending to, “Beautiful,” “Lovely,” or, to use an all-enveloping but totally inadequate Australian word, “Nice”.

Perhaps one of the most significant reasons for the Corsair is the slot it fills – basically between the 421 and 441 with the added foresighted bonus of propjets and undeniably updated technology.

As Rex Aviation’s chief corporate pilot Frank Bonnor put it shortly after arriving in the Corsair, it’s both an excellent transitional aircraft for pilots and owners bridging the gap between reciprocating engines and propjets, plus the fact that it’s a latest state of the art type.

Wichita’s marketing philosophy trained its guns on the Beech C. 90 and Piper’s Cheyenne II when aiming the Corsair’s thrust. There is little doubt it will score as near a direct hit as makes no difference, using cost, ease of operation, overall practicalities of ownership and actual cruise economies at height – which is where the corporate hip pocket nerve is situated when trying to sell a corporate twin of any sort.

Cessna already had a winner with their Conquest, despite tail problems and subsequent groundings. Marketing foresight demanded a regression of the series, a hand-up for the smaller operators who would undoubtedly one day have to go propjet or progress inexorably backwards.

The 425 design team already had an excellent basic airframe from which to grow – the Golden Eagle’s wide-oval cabin geometry. What they had to do was fulfil a number of demands:

• They were given the task of producing a six- to eight-place cabin turboprop exec. transport with exceptional fuel specifics at operating altitudes.

• They had to play midwife to a type having handling characteristics and systems designed to obviate heartburn by pilots who had hitherto flown piston-engine twins.

• Most importantly, the team had to bring forth a “step-up” type for 400 Series Cessna owners who more often than not had to buy from the other shop across the road to get initial turboprop experience.

What has come out of the Wichita labour ward is a healthy, bouncing and most excellent child in the 425 Corsair.

About the only first-glance similarity to the 421 is in general atmosphere when one approaches the aircraft.

But there are many new features: structural redesign in fuselage, wing and tail assembly – plus those beautifully cowled PT6s by Pratt & Whitney of Canada Ltd – makes the Corsair a unique type indeed.

By the time the Cessna product gets to normal operating height around or above FL 250 it becomes the fastest kid in the street – and the most fuel-efficient.

And it gets to that altitude fast, as AUSTRALIAN AVIATION’S evaluation team found out during a test flight . . .

One can’t get to operating height and crank up a handsome rate of knots without a good wing to get one there. So Cessna’s 425 team went to a relatively high aspect ratio wet wing with much bonding in the metal-to-metal department.

While on the bonding bit, the Corsair’s specs detail bonding in the inboard wing leading edge panels, upper and lower interspar panels, ailerons, wing trailing edge (the outer flap area) and the upper skin panel in the wheel-well region.

And we might as well mention at this early stage of our evaluation report that Cessna has really hit the jackpot in the Corsair’s finish; apart from a comparatively “rough” look around the nose area, the Corsair is a real credit to Wichita’s workshops and their new policy of quality control.

For the purists, the 425 has 5ft-odd more wingspan than the 421, plus more skinning than its Golden Eagle sister.

Not only is the inner wing beefed up in the Corsair, but the tail assembly has come in for strengthening mods while keeping that same 12-degree dihedral on the horizontal tail as have the Citation and Conquest.

There didn’t seem any good reason for changing the sweep-up of that horizontal tail; that dihedral, according to Cessna, improved Dutch roll qualities and moved a significant portion of the tail out of the propwash thus providing a smoother ride.

Other subjects in our Top-Mark department include:

• Installation design of the purposeful PT6A-112 lightweight free turbines is brilliant. A sealed inlet passage increases total ram air pressure into the compressor section. An inertial air separator system sorts out foreign objects, ice and snow from intake air.

Air picked off the exhausts is fed to each nacelle lip for de-icing – in detail, the exhaust gases are bled off the lefthand exhaust stack, shunted through the stainless steel lip and sent out the righthand stub.

Bleed air supplies numerous systems including cabin pressurisation, cabin heat and air distribution, power for pressure gyros, drives the ejector for the cabin pressure regulating valve, inflation for pneumatic de-icing boots and pressurises the door seal.

The engineering gurus have even thought up a way to keep the cowlings clean immediately near the exhaust stubs. Antisoot louvres on the cowling provide a layer of air which separates exhaust gases from the engine nacelles in a neat boundary layer demonstration which makes for minimum cleanup needs and maximum paint protection.

Before we leave the powerplant department, let’s look at the placement of the tri-blade Hartzells and their parent urging department: the props are set well forward of the cockpit and cabin, making for a quiet environment that is enhanced by a high-ratio reduction gearbox.

The reduction means that at full bore the mighty props are spinning at only 1900 rpm. In cruise prop settings can be as low as 1600 rpm.

TBO (time between overhaul) for Pratt & Whitney’s PT6A is listed at 3500 hours.

The undercard features a trailing link assembly plus an air-over-oil shock strut. The trailing link does much to improve pilot ego by almost reaching out for the ground and gently hugging it to the wheels.

Retraction time for the undercarriage is booked at 4. 5 seconds – 7. 5 seconds during single-engine operation. Maximum gear extension speed is Manualled at 175 knots indicated – the same speed as the first-stage extension of the split flaps.

Our walkround included a peek into that long-nosed compartment which not only takes the air-conditioning compressor, optional avionics and a 20-cell nicad battery, but can make up the weight to 600 lbs in baggage.

On board through the clamshell doors, one gets a fuller idea of Cessna’s quality control policy amid a vision of leathers, fabrics and vinyl set out in a wide-body theme. Passenger seating ranges from four to six in a four-option departure from the standard four-seat club seating configuration.

The five-a-side windows lend added space to the interior. Other options include hardwood dividers between cockpit and cabin, digital readouts of height, airspeed and outside air temperature on the divider, a choice of biffys, refreshment centres and tables.

The flight deck of this specific model, suitably optioned and worth about $A916,000, is a model of correct neatness – or neat correctness if you wish, exuding the essence of professionalism.

Your Corsair’s cockpit is businesslike and simple – which speaks volumes for the claim of it being an excellent transition type.

Most pilots agree that the Corsair’s panel is a cinch if you’ve had a taste of other instrument panels in the big 400 Series; there are some who fall on one side or the other when likening the Corsair’s overall cockpit layout with either the Citation or 421.

Fuel management is among the simplest of the lot: On, Off or Crossfeed. Thirty-five eye-level annunciators give “first glance” system status information to the crew. Logical layouts form functional groupings of systems switches, flight instruments, avionics, powerplant controls, cabin climate controls and circuit breaker panels.

Your standard Corsair comes equipped with Cessna 400 Series avionics – dual VHF Comm and Nav, marker, transponder, DME, an audio panel and the 1000 autopilot which includes a yaw damper and air data computer input.

Options include RNAV (area navigation) radio altimeter, altitude alert and pre-select, a 1000 Series flight control system, mono/colour weather radar – and a checklist display option for the colour radar.

Before we fired up the Pratts, the AUSTRALIAN AVIATION team listened to Frank Bonnor’s factual rundown on the ferry flight to Australia. It made sense of many claims aired during our pre-flight briefing.

With typical thoroughness, Frank & Co. kept a detailed performance log en route – we took only those spanning more than 1000 nm. as examples. Here they are:

Wichita-Montreal. Dist 1164 nm. Time 5 hr 5 min. Fuel burn (lbs) 1884. Av. Speed 229 kts. Av. I/flow 370.

Goose Bay-Reykjavik. 1338 nm. 5 hr 44 min. Fuel burn 1823. Av speed 227 kts. Av I/flow 318.

Luxor-Dubai. 1247 nm. 5 hr 5 min. Fuel burn 1768. Av speed 245. Av. I/flow 348.

Dubai-Bombay. 1044 nm. 5 hr 3 min. Fuel burn 1886. Av speed 206. Av I/flow 373.

Tindal-Toowoomba. 1356 nm. 4 hr 56 min. Fuel burn 1801. Av speed 275. Av I/flow 365.

(Time represents take-off to touch-down and includes circuit and any holding. Fuel represents total fuel burn engines on to engines off).

We used an outside power source for engine start after settling into the lefthand seat of November 67744 – “You’d better fly it from the proper seat, to make sure that what I’ve told you about the Corsair being an easy transition aircraft is true,” commented Frank.

In all our past jousts we’ve never known Frank to even stretch the truth. He was correct once again as we went about the start drills; all that happened was that we checked props clear, flipped the fuel boost pump on and checked the aux. boost pump annunciator ON and fuel pressure low light OFF, popped the START switch on and when N g (gas generator rpm) hit 12 per cent moved the relevant fuel control lever to RUN.

Monitor ITT (interturbine temp) and N9 for a max 1090C and flip the Start switch OFF when Ng hit 52 per cent.

Power was increased to 68 N g and that was that – the motor was off and running, singing low and sweet while we brought power back to flight idle.

Same for the other side, and we began the taxi. More surprises – the ride was better than average, and ground roll speedup was controlled by pulling up the reverse thrust locking cams on the Corsair’s power levers and coming back into Beta a fraction. Optional taxi drill is to pull one or both props back to Feather, or taxi on one Pratt, to save the brakes; and your Corsair can roll very easily to beyond a fast running pace.

A nosewheel-rudder interconnect gives positive control up to 18 degrees either side or free turning up to 55 degrees.

After runup we armed the Corsair’s autofeather system – a magnificent device which, if it senses a power loss on either powerplant, feathers the offending engine’s prop and locks the running engine’s prop out of feather.

At the take-off point N67744 had three souls on board and a take-off weight of 6,700 lbs. The outside air was +18C.

We increased power against the brakes, hesitated briefly around 1900 prop rpm to let the Pratts approach stabilisation, advanced the power levers to match torques to take-off limits of 1244 ft lbs, then let go of the anchors.

The roll was immediately brisk, as one would expect, and it got brisker in almost your old Beaufighter-like style (without the swing) until rotation was initiated at a fraction over 90 knots on the clock in a performance departure. The Manual recommends 98 indicated for normal rotation.

Wheels up (no flaps for this take-off), the evaluation Corsair whined upwards at 115 knots, VSI coming round at a fast rate of knots to better the 2027 fpm (gross figure) brochure mark. Cruise-climb of 135 indicated still gave us better than 2000 fpm.

There was unfortunately no time for a workout at the Corsair’s fighting height of just under FL 180 when it would have got up and flown at 264 kts TAS.

Even at our modest height we felt the Pratts working their mouths gently against their derated bits, wanting to get into their stride.

And we certainly endorsed the maker’s assertion that the Corsair is a fingertip aircraft . . .

Almost perfect balance between the control surfaces means a smooth ride, a touch of pressure here and there to make coordinated manoeuvres a thing of ease and pleasure at all times.

Normal setting for climb to cruise is max. continuous, 1244 ft lbs torque or an ITT value of 680C – whichever comes first, providing the best performance and range. After that one hardly touches the power quadrant at all.

In the cruise, one usually sets up prop synch manually and Disregards the synch control. Max. cruise torque, says the Good Book, is just below 695 on a new engine.

Turns up to max rate opened our handling evaluation; no sweat, just a great deal of professional feel coming through all over.

Stalls are announced with considerable and increasing buffet feeding in through the control surfaces.

A clean condition stall occurred right on book figure of 88 knots with the twin Pratt & Whitneys at Flight Idle. The buffet built up to moderate as stall speed approached with a sharper buffet building in and shaking the stick.

In dirty condition, gear down and full flap, the Corsair again became irritated as 79 knots neared but only produced a light buffet in response to an unwelcome manoeuvre.

Asymmetries were performed to a deliberate drill. As this was our team’s first tryout of a new type, we followed the Manual’s recommendation by keeping about 120 on the clock.

The Vmca demo started by checking flaps and gear UP, power levers at take-off, airspeed at Vsse (intentional one-engine operative speed) down to 102 IAS minimum.

Frank whipped the starboard power lever back to Flight Idle, we took up the yaw with rudder and he feathered the “inoperative” motor’s prop. It was no problem to maintain heading with the boot plus a regulation five degrees of bank towards the dead engine.

It was possible to trim out the yaw, although we found no more trim available by the time we had the Corsair on a steady heading.

The same ease of correction and trim-out of yaw was possible on the port-engine-dead drill. Turns into and away from the inoperative motor were pure joss – even steepish turns into the silent engine.

In our lightish condition we managed to get a steady and purposeful rate of climb in excess of 500 fpm at 4000 ft.

What about the owner’s section, that luxurious cabin? Our team in the cabin had been making most audible approving noises and, on completion of our brief evaluation, had marked every section from finish to decibel level and creature comfort either Excellent or Way Above Average.

Visibility was excellent from the corporate seats; ease of movement in the wide-body cabin was likewise excellent.

Back to cruise figures; with all the fun of fuel totes, fuel flow and attendant avionics slaved to the autopilot, most of an average trip would be in a monitoring category.

With 2452 lbs fuel on board at FL 250 – a reasonable height considering the pressure differential (5 psi) – range at max. Range power could span 1575 nautical miles with 207 on the clock. That would take an average of 7. 8 hours, at mid-cruise weight, says the Manual.

Interesting combinations include:

With six people on board, range at max cruise at 25,000 ft roughs out to 1037 nm at 256 knots.

Up there at FL 300 range spans out to 1147 nm with six p. o. b. , cruising at 248 kts.

With only four on board the best figure of the lot is still attained at that FL 300; 1646 nm at 21O indicated.

The six on-board figure includes 180 lbs baggage and options, 8200 lbs take-off weight and 2097 lbs usable fuel.

The four on-board figure is attained with 165 lbs baggage and options, 2452 lbs usable fuel and a take-off weight of 8200 lbs.

Although the Flight Level 300 figure is an enviable one returning the best performance, the more realistic Flight Level of 250 is best for normal purposes – unless you want to start breathing oxygen, it’s best to stay down there where your cabin pressure equals 10,000 feet.

Back in the Bankstown circuit gear was lowered well below the max. operating speed of 175 knots, and flap came down progressively. Crosswind at 116 indicated, finals rock-steady at 100 on the clock (102 says the book at a heavier weight); check prop synch out, prop control levers forward, check three greens, autopilot and yaw damper off . . . Flight Idle at 50 ft . . .

The Corsair touched down delicately (thanks to the reach-out trailing link!) and we whipped up the reverse thrust locking cams on the power levers and came back on into Beta range. Max reverse is limited to one minute with 1244 torque ft-lbs, 101. 6N9 and 1815Np (prop rpm).

The evaluation Corsair stopped almost dead in its tracks and we turned off with braking assist backing up the reverse thrust, at the first turn-off. Our cabin team reported no more Gs than in a normal RPT arrival and in fact less actual discomfort.

In retrospect, we considered every possible angle but came up with the same answer. The Corsair is in every way a genuine pleasure to fly, both as a transition type and as a corporate workhorse.

Cockpit and cabin are two of the quietest regions we have operated in, in this class of aircraft. Other evaluation pilots in other parts of the flying world have gone the whole hog and unequivocally stated that Corsair’s cabin noise levels are the lowest in its class.

At all speeds, all heights, with or without both Pratts producing their mellow whine somewhere in the background, we couldn’t fault the machine- and after all, no pilot really goes out to fly an aircraft with the object of picking holes in it. If faults there are, they will show themselves.

With only 16 minutes booked for the climb from s/1 to 25,000 feet, Corsair can accept the initial performance penalty imposed against its immediate competitors, get on up there and really open its shoulders in a cost-effective operation.

As one of our colleagues remarked, nobody will ever come up with the perfect aeroplane, but once in every while a maker gets everything together at the right time and produces a type which becomes a standard within class – a type which gladdens pilots, passengers and company accountants.

Such an aircraft might well be the Cessna 425 Corsair.