PC-9 Set to Enter RAAF Service

Then the Government complicated the situation by re-opening tenders for the 69 production aircraft required and scrapping the A-10 program. The RAAF rewrote its specification and modified its training syllabus accordingly. Further complications arose when HdH took over CAC, in the process becoming two-thirds owner of AAC. GAF subsequently pulled out of the Consortium, and total control was relinquished to HdH.

Despite a valiant effort by HdH to resurrect the Wamira as the A-10B, the project was finally cancelled with the first prototype only a month away from roll-out. First flight of the A-1OB would have been in August 1985.

Lady Fortune certainly did not smile upon the Wamira. IF there had not been the constant bickering between the AAC partners and the RAAF, IF the RAF had chosen the A-20, IF GAF’s industrial relations problems had not affected the project, IF the Government had been more single-minded and determined about the concept, and IF there had not been so many impressive competitors, the Wamira may have succeeded.

The Pilatus PC-9 was instead chosen from a final shortlist of three; apart from the A-1OB, the other competitor was the PC-7 (a lesser-powered stablemate of the PC-9). With what is arguably the highest performance of the current generation of turboprop trainers, the PC-9 also had one of the highest price tags.

History

The Pilatus PC-9 developed from the earlier PC-7, which first flew in April 1966. The PC-7 was, in turn, a development of the 1950s advanced piston trainer, the Pilatus P-3.

To trace the development of the PC-9, it is necessary to trace the progress of the PC-7. In the mid-1960s, Pilatus Flugzeugwerke commenced work on a company-funded project – the design of an aircraft to replace the post-war military trainers such as the Harvard (T-6/SNJ) and the T-28 Trojan when finally they retired. Pilatus had designed and built the Lycoming-powered P-3, 80 of which were, at that time, in the Swiss Air Force inventory. Pilatus seized upon the idea of developing and re-engining the P-3, and thus the PC-7 Turbo Trainer was born.

Pilatus actually converted the prototype P-3, HB-HON, to become the prototype for the PC-7. In this new guise, HB-HON flew on its ‘second’ maiden flight on 12th April 1966. The Lycoming GO-435-C2A2 had been replaced with the Pratt & Whitney PT6A-20 turboprop of 550 shaft horsepower. The entire project floundered when it became apparent that the Swiss Air Force were happy to keep their P-3s in service until the 1980s. This in turn deflated a proposal to have the aircraft built under licence in the US by Fairchild Hiller. As the Australian Government learnt with its attempt to sell the Wamira to the RAF, no one wants to buy an aircraft when the country of origin has no orders on the books. The future of the PC-7 seemed sealed when HON was almost symbolically written off in a wheels up landing.

Oddly enough it was the fuel crisis of 1973 that lead to the resurrection of the Turbo Trainer. The end of cheap fuel made air forces re-examine their training methods, and a new philosophy of broadening the capabilities of the basic training aircraft to reduce the amount of expensive jet training was to emerge. It was in such a climate that the Beech Turbine Mentor (a turboprop version of the T-34) emerged in late 1973. A second P-3 was converted to become the second PC-7 prototype and this aircraft, HB-HOZ, took to the air on 12th May 1975. In July 1976, the PT6A-25 finally became available, and was fitted to HOZ. This engine, offering improved fuel consumption and a 30-second inverted capability; was to become the production standard.

Production was launched in 1976 to an initial production run of 35 aircraft, with the first customers being Burma (12) and Bolivia (8). The first production aircraft flew in August 1978. In June 1979, the Swiss parliament approved the purchase of 40 aircraft. With the Turbine Mentor its only competitor, more customers were added with sales to Angola, Abu Dhabi, Austria, Chile, Guatemala, Iran, Iraq, Malaysia, and Mexico. Production is still continuing.

In May 1982, Pilatus began work on an advanced version of the PC-7 with the aim of increasing further the portion of the training syllabus shared with the pure jet trainers. In the Swiss Air Force, the syllabus with the PC-7 and DH Vampire Trainer was broken into 120 PC-7 hours and 180 Vampire hours. The PC-9 aimed to change the ratio to 150 turboprop and 150 Vampire.

The importance of modern high-powered turboprop trainers and their beneficial effects on pilot training are borne out by an examination of the re-orientation they have caused within the following three air arms. When Switzerland used only the aged P-3 and Vampire combination they used to fly typically 60 hours on the piston-engined P-3 and some 240 hours on the jet Vampire. This then changed to 120 hours on the PC-7 and only 180 hours on the Vampire and will eventually be 150 hours on the PC-9 and 150 on the Vampire which ultimately will be replaced by the BAe Hawk.

The Royal Air Force also enjoyed a similar saving in expensive jet time. Formerly, a student flew the Bulldog for 15 hours, then the Jet Provost for 160 hours and finally the Hawk for 80 hours. In future the curriculum will cover 100 hours aboard the new Shorts/ Embraer Tucano and 180 hours on the Hawk. Australia meanwhile logs 60 hours on the CT-4 Airtrainer and 160 hours on the Aermacchi MB-326H. This was to change to 100 hours aboard the AFSR-5044 aircraft (PC-7 or Wamira) and 80 hours on the Macchi. Thanks to the extra power of the PC-9 the new schedule calls for 120 hours on the PC-9 and only 60 hours on the Macchi.

Though it is still not fully decided at this stage it appears that the CT-4s will be retained for perhaps the first two dozen hours of ab initio pilot training where typically a 50% washout rate is experienced. Pilot training streaming is also under review which would further cut down on Macchi time for pilots not requiring fast jet training.

Not only are there direct savings in using turboprops for the majority of training instead of jets, but there are also added benefits such as extended life for the Macchi. With less training hours being flown in the Macchi, i. e. lower utilisation, the type’s end-of-life will be extended significantly. Operating costs of the CT-4 are quoted at around $300 per hour, the PC-9 $900 and the Macchi $1,500. Savings achieved by replacing the CT-4 with the PC-9 are estimated to be $30,000 per student, or 15%.

With financial logic on its side, the next hurdle for Pilatus was to make the aircraft capable of taking some of the jet trainer’s traditional domain.

Performance

Pilatus aimed to improve the performance of the PC-7 while retaining much of its impressive handling characteristics. The best trainer is not necessarily the easiest to fly; it must be kind enough to allow a person to learn to fly, but must be capable and demanding enough to teach the pilot to fly well. The required increase in performance was achieved by replacing the 550shp PT6A-25A with the new PT6A-62 of 950shp. The result was a speed improvement of 40% and a rate of climb improvement of 100%; stall speed increased from 60 knots up to 70 knots – a very reasonable trade-off.

The high performance of the PC-9 necessitated the installation of ejection seats; the lightweight Martin Baker Mk CH11A was chosen, giving a 60 to 400-knot speed capability between zero and 40,000 feet. Ejection seats are now considered compulsory for all trainer aircraft with a stalling speed above 70 knots.

In the aerobatic category (maximum take-off weight of 2250kg), most aerobatic manoeuvres are possible, with up to 60 seconds of inverted flight permissible. Aerobatic ‘g’ limits are + 7 to – 3. 5. Even in the utility category (maximum take-off weight of 3200kg), loops and Cuban Eights are permitted. Utility category ‘g’ limits are + 4. 5 to – 2. 25.

Limiting speeds include a maximum diving speed of 360 knots or 0. 73 Mach, a manoeuvring speed of 210 knots and a maximum speed with flaps or landing gear extended of 150 knots.

To satisfy the perceived need for a weapons training capability, three hardpoints are provided under each wing.

External Configuration

The aircraft is constructed primarily of 2024 aluminium alloy, with stainless steel used for the firewall. The targeted fatigue life of the structure is 10,000 hours or 20,000 ‘training’ landings. The 16. 29m2 (175sq ft) area wing is a one-piece structure with a main spar, a rear auxiliary spar, and two inboard diagonal auxiliary spars, along with interspar ribs. The wingspan is 10. 12m (33ft 2in), length is 10. 18m (33 ft 4 in) and height is 3. 76m (1Oft Bin).

The cockpit is of a ‘stepped tandem’ configuration, each being fully instrumented. For solo flight, the aircraft must be flown from the front position. A generously sized baggage compartment is located aft of the cockpit.

Systems

The landing gear is hydraulically operated, with single main wheels and nose wheel. Part of the Australian purchase agreement was that the undercarriage be modified to enable the aircraft to operate from grass runways: a capability the stock PC-9 did not have. This modification is expected to result in some 11,000 hours of Australian design work.

The hydraulic system is a 3000psi high pressure system, with a single pump running off the engine. In addition to the landing gear, hydraulics power the airbrakes, flaps and nosewheel steering. An emergency backup is provided by a nitrogen-charged accumulator system to lower the landing gear and an emergency electrical flap extension system.

The wheel brake system is a sealed hydraulic unit operated by the pedals. The instructor’s cockpit is also fitted with heel pedals to allow over-heavy brake actuation by the student to be countered.

The flight control system is entirely mechanical, with ailerons operated by control rods and rudder and elevators operated by cables. Trim tabs are provided for all three axes. As mentioned previously, the belly-mounted airbrake and flaps are hydraulically operated.

The electrical system is surprisingly complex, consisting of a primary 28v DC system, a secondary 24v DC system, a dual output (26v and 115v) AC system, and 24v/40 amp hour nickel-cadmium battery. External power can also be used. DC power is used for all systems indicators and warnings, trim systems, emergency flap extension, most flight instruments, pitot heaters, lighting, seat adjustment and aural warning systems. AC power is used for the attitude indicator, avionics and gyro compass.

Anti-icing equipment provided on the PC-9 consists of pitot and static port heaters and an angle-of-attack transmitter heater. Pilatus offers an optional propeller de-icing system, but the RAAF aircraft will not have this fitted. Flight into forecast icing conditions is not approved.

Cockpit

The tandem cockpits are entered through a single side-opening canopy hinged on the right side. The aircraft can only be flown solo from the front seat; the rear control stick can be removed and stowed while the front seat has electric vertical adjustment. Instrumentation for the PC-9 is available in conventional analog form or with a dual-screen EFIS system. The RAAF is likely to request a few small instrumentation modifications for its machines. A ‘Head-Up Display’ (HUD) system is also available, although this would be more applicable to weapons training than the ‘ab initio’ role. The engine is controlled by a single Power Control Lever (PCL) on the left side of each cockpit. The PCL has a ‘soft’ detent at the maximum cruise/climb power position, but the lever can be pushed through this detent to the maximum continuous power position. Use of this MAX position is restricted to 10% of the engine operating time. In the fully aft position, the fuel supply is cut and the propeller is moved to the feather position. The propeller has an independent control system comprising a constant speed unit (CSU) and an overspeed governor. In normal operation, the CSU varies the propeller pitch to maintain a prop speed of 2000rpm. If the CSU’s normal governor fails, the overspeed governor will limit propeller speed to a little over 2000rpm. Engine instruments include torque pressure, inter turbine temperature, engine gas generator speed, propeller speed, oil temperature and pressure, fuel flow and fuel used as well as air inlet temperature.

The ejection system is activated by seat pan handles. If a command function is selected (through a switch in the rear cockpit), both seats will be fired by activation of the instructor’s handle, with the front seat following the rear by 1. 25 seconds. If the command function is not selected, both seats operate independently. The canopy is not jettisoned during ejection, the seats smash through the canopy with the help of canopy breakers on the top of the seat itself.

A diluter/demand type oxygen system is provided with the oxygen cylinder located behind the cockpit. The cylinder can be topped up on the ground through a replenishment point under the fuselage. An optional anti-g system is available, using pressure air from the environmental control system.

Summary

Like the F-111 and F-18 before it, the PC-9 is destined to a controversial future, regardless of its eventual service history or production run. One of the overwhelming points in favour of the selection of the PC-9 was the fact that Australian industry would benefit more from offset work from the PC-9 than it would have from full-scale production of the A-1OB. In fact, part of the PC-9 deal was that Australia would be involved in future light transport and helicopter projects on the Pilatus drawing boards. Additionally, Australia would be able to market the PC-9 in its region and already hopes are high that a sale may be made to New Zealand.

In the long run, the PC-9 will be judged by the proficiency of the new pilots that it produces and not by the politics and bickering surrounding its purchase.