Pilatus P3 Swiss Airforce Primary Trainer
Pilatus Aircraft Factory was started in 1952 under the direction of Henry ( Heinrich ) Fierz to develop the two seater P3 primary and advanced trainer Aircraft.
Henry Fierz had been on the design staff of the Swiss Comte Aircraft Factory.
After its bankruptcy, he immigrated to England and then to the USA, where he worked for several companies during World War II. He returned to Switzerland to work as Chief Designer for the fledgling Pilatus Aircraft Company.
In conversation with several high-ranking officers, he tried to fathom the future needs of the Flugwaffe. They were eager to simplify their flight training with a modern trainer. At that time, student pilots were initially instructed on the Jungmann, converting to the Bu 131 Jungmeister for aerobatics.
Formation and instrument flying took place in the Pilatus P-2; from there the pilots upgraded to the North American AT 6 Texan and Morane I – 3801 (AE43) for the tactical phase of flight training. The generally agreed principle was to replace all these types with a single design. This new aircraft was used to prepare pilots to fly jets, which in Switzerland meant De Havilland Vampires. A tricycle undercarriage arrangement was mandatory, excellent visibility deemed necessary, an instrument flight rules (IFR) equipped cockpit was needed, and it had to be reasonably priced to acquire and operate.
Fierz realized that he could not hope for a development contract. The design would risk company funding so it would have to be a private venture.
Fierz’s leadership was based on expertise. In his daily routine and his management, he knew how to win his team’s undivided loyalty. His decisions were quick and primarily based on hard evidence. If there were no facts on hand, he based his solutions on intuition, which took the same amount of time as rationally argued theories.
What is surprising is that nobody could ever remember him being seriously wrong. However, he did have a few favorite rules of thumb, one of which was “You don’t fit a new engine to a new design”.
Leo Stofer was responsible for the static design but most important was the participation of Wenzel Landolf, who was in charge of aerodynamics. His calculations led to the excellent handling control. Landolf proposed shortening the fuselage by 20in (50cm) to increase maneuverability and save weight without detrimentally affecting the stability. Fierz accepted Landolf’s proposal. Unknowingly, this was going to cause problems many years later.
Test Pilot Hans Hafliger had to conceal his grin when he met the opposition’s pilot. Not only was the American of large build but also his frame gave away his obvious liking for good food. His Swiss rival was indeed glad for every single extra pound that would reduce the weight difference between the two aircraft. Hafliger had been significantly involved in the flight testing of the Pilatus P3 and had flown the aircraft through its process of certification just a few weeks earlier.
The fact that he had flown the type to its very limits was now providing him with a great advantage. He knew exactly how long and at what angle he would have to dive to reach maximum speed. At the end of his rapid descent, he would be directly over the heads of the Swiss military evaluation committee with a speed of 379mph (609km/h). (Later P3’s would be red-lined at 316mph, (508km/h).) The maneuver with which he intended to complete the display was the “vertical eight”. He knew it was the only aerobatic feat that the Beechcraft T 34 Mentor could not perform – however heavy its crew was!
The Swiss officers assembled on the ground knew the limitations of the latest offering from the Pilatus factory. With an operational weight of 3.100lb (1.406kg) and a Lycoming GO-435 C2 engine, producing 240hp (179kW), the climb rate was a mere 1,200ft/min (365m/min). This figure was well below that of the preceding types such as the Bucker Bu 131 Jungmann and the Pilatus P-2 that the newer type would have to replace.
The point Hafliger tried to prove with his demonstration was that even very rigorous flight regimes could be met, as long as one was sure of one’s energy management. At the pinnacle of his second loop, he knew that he had beaten the Mentor by points. The year was 1955 and the place was the airfield of Altenrhein on the shore of Lake Constance. He could not have known then that his performance had done the trick, with the P3 being ordered by the Swiss Flugwaffe as its standard primary trainer. The plant at Stans would be busy for years to come. Nor would Hafliger have known that the subsequent derivatives of the P3 – the PC-7 and PC-9 – would become major export successes decades later. With the experience of the P3, together with its qualities and its blatant shortcomings, Pilatus established its position as one of the leading manufacturers of propeller-driven trainers.
George Gissler made the first flight on September 3, 1953. It proved Landolf right in most areas. There were a number of minor flaws, which needed to be ironed out, but none were considered too serious. The inherent engine noise had to be reduced for the benefit of pilots and the local population. The controls were very precise and enabled both instructor and trainees to easily follow each other’s actions. This was a very distinct quality for a trainer.
The second prototype was designated P3-02 and registered HB-HOO. It flew in August 1954 and was outfitted for military use. It had two wing hard points that enabled the installation of light armament for gunnery practice (this feature was included in later versions of the P3-03 but was never used by any operator). The second aircraft was used for the certification flights and the aforementioned demonstration at Altenrhein.
The P3’s major setback was the distinct lack of power. The controls enabled a wide range of aerobatic maneuvers to be performed, but by doing so, it would lose altitude constantly which had to be subsequently regained prior to the next stage of the flight. The poor climb quality was in strong contrast to the Swiss expertise in utilizing the vertical dimension.
The Flugwaffe ordered 12 aircraft to undertake a feasibility study within the framework of the existing training regime. Designated P3-03s, these were to have a three-bladed Hartzell constant speed propeller.
Meanwhile, Pilatus was looking for foreign customers, but they were not too forthcoming. Demonstration tours were organized to neighboring countries and while generating interest was easy, firm commitments were much harder to achieve.
The Pilatus Company director Mr. Alioth had six more aircraft produced “off spec” and these were put on the civilian register. These aircraft were designated P3-04 and had civilian instrumentation (the military measured in meters and km/h), civil radios and IFR equipment. Swissair tested one aircraft (HB-HOE) for use at its SLS (Schweizerische Luftverkehrsschule) commercial pilot training center. However, it refused to take up an option to purchase the P3. The six civilian Aircraft, were later sold to the Brazilian Navy and shipped out in crates. This proved to be the first foreign military order for Pilatus.
Meanwhile the Flugwaffe had found the P3 acceptable to such an extent that it began to negotiate for 60 more aircraft, provided that they could be delivered with more power. This was to be the largest order to date for the small company.
Fierz had his staff examine the possibility of installing the larger Lycoming GSO-480s of 340hp (254kW) which were powering the new PC-6 Porters, into the P3 airframe. The lengthening and widening of the forward fuselage section and the shifting of the center of gravity would affect the positive flying characteristics considerably. A fair proportion of the power advantage would be taken up by the weight increase required for the structural strengthening.
Fierz opposed the new engine and its associated anomalies, and the Flugwaffe relented. Bowing to his expertise, the air force ordered the standard model. This act ruled out the P3’s real purpose of standardizing basic training on one type and this was never actually achieved. The Pilatus P-2’s, which were preferred for aerobatics, continued to serve until they were retired in 1981.
The Phantom Dive
During initial flight testing Hans Hafliger had performed stall and spin trials. The second P3 had been equipped with a 66-gallon (300 liters) water tank in place of the rear seat. This ballast could be jettisoned if there were recovery problems. However, no such problems were encountered – Hafliger could enter and recover from normal, flat and inverted spins without any undue difficulty. This again, was a distinct quality for a trainer.
The flat spin itself was especially impressive. The aircraft rotated with a rate of one turn per second and its attitude was upright with the axis of the motion being in the area of the forward pilot’s spine. An instructional film regarding spins was made in 1958. Several instructors ran a contest to see who could perform the most rotations.
The first indication of trouble came with the incident report from a Colonel Meier. Trying to recover from a flat spin, he had gone into a steep spiral dive. He described the motion as having a radius of 40 yards (36.5m) while producing considerable acceleration forces. A steep angle of descent resulted at a very high vertical speed. Meier also recalled a surprising lack of control response during this incident. Since this report was the first describing the symptom, it caused little alarm. However, Meier’s report soon rang true when a similar maneuver was witnessed by the commanding officer of the pilot’s school at Magadino on August 22, 1963.
The instructor, F/L Erwin Stauier, was training P/O Jurg Walser to recover from flat spins. Walser was training to become an instructor and would soon have to relay this flying technique to his pupils. They entered the stall at 7,500ft (2,286M) above ground level. At 4,400ft (1.341m) Staufer realized that control was lost and gave the order to bail out. Walser, being of small build, had considerable trouble climbing out of the rear seat, jamming his seat parachute in the process. He eventually became free at 450ft. (137M). The partially inflated chute decelerated him sufficiently for cooling splashdown into the Ticino River. Stauter, who left the tumbling machine earlier, opened his parachute too late. He was found dead on the riverbank. Collision with the tailplane on exit could have caused a loss of consciousness during the fall.
The investigation came to the conclusion that the spiral dive was closely linked to the flat spin. Consequently flat spins were immediately restricted and most observers were sure that the “phantom” had been defeated.
There was still the occasional report mentioning recovery problems, but by that stage those that had prevailed regarding spinning seemed to have affected the flying procedures, as there were no further accidents for five years.
The spell was broken on October 24,1968. P/O Gaensli and F/S Keller crashed at San Vittore airfield in Canton Graubuenden and from the evidence it became obvious that the “phantom” had struck again. The crew had been tasked with practicing standard stall and spin recoveries. Caught in the vicious spiral dive, they had descended below the safe bail out altitude at 90ft (27m) above the ground. The aircraft was again under control, but impacted the terrain seconds later. Both crew were killed instantly.
Call for the Spindoctor
Test pilot Walter Spywa Spychiger was given the task of investigating the exact causes of the phenomenon. Spinning his head to the point of complete dizziness in the same quarantined aircraft, he attempted to duplicate the spiral dive in six flights. He was not successful. He found, however, that precise aileron handling was essential when spinning. While an aileron adjustment of one-quarter (its entire length of travel) had no effect whatsoever, a move of one third would force the P3 straight into the dreaded flat spin. This would have the effect of more than doubling the rotation speed instantly. It was easy to believe that an ensuing disorientation of the crew had been causing the crashes. Spychiger proposed to prohibit flat spinning with the aid of a newly added ventral fin.
The phantoms only appear when they are not expected. At the end of his investigation, spychiger’s boss told him to take Berny (test pilot Dr. Bernhard Alder) airborne and show him the otherwise restricted flat spin. Both were excellent pilots and they were entering the spin deliberately; yet afterwards, having also descended far below safe altitude, they were both unable to relay exactly how they induced the spiral dive. There was an immediate ban on all spins and other aerobatic maneuvers in the proximity of the stall envelope. As a result, pilot training became severely restricted and the fleet of 70 aircraft appeared to have little use left in the training role.
In order to make the P3 safe again; the Federal Aircraft Factory at Emmen studied a wide range of possible modifications. To evaluate their effect, some time was “purchased” in the vertical wind tunnel at Lille in France. The results confirmed the selection of a ventral keel that ruined whatever elegance the aircraft could still claim but eventually reinstated the type’s reputation.
In the rear cockpit of A-807 an extensive range of telemetry equipment was installed. For the first time in Switzerland, these black boxes transmitted all control movements in real-time to a ground station. The trial spins were also recorded with a cine camera – its large telephoto lens aimed via modified Fledermaus fire control radar. As an extra precaution, a “drag and yank” escape system was purchased from the USA. The system was ground tested at Emmen in February 1972, when a 190 lbs. (86kg) dummy was fired through the Perspex canopy, resulting in a smooth parachute descent.
It was down to Walter Spycliger, who had already made the phantom’s unholy acquaintance, to prove that the aircraft was now 100% ready. His dedication to the task soon earned him the nickname Spindoctor. The new tin fitted its purpose extremely well by prohibiting both the dive and flatspin. The programmed modification was given clearance, and all restrictions were lifted on retrofitted aircraft.
Fiertz had refused to install a larger and heavier piston engine to the P3, but as early as 1958 he authorized Emil Siengenberger, present day Chief Designer for Pilatus, to study the use of the French Turbemeca Astazou XII turbine rated at 573 hp (427kw). Customer response was, however, less than enthusiastic and the whole project was shelved. With hindsight, this was a wise decision as those PC-6 Turbo-Porters, that were to use this engine, were plagued with problems arising from the turbine/propeller combination.
It was Pratt & Whitney Canada PT6A that once again sparked off the new engine initiative. As a private venture, Pilatus purchased a P3. It was the first prototype, which had been sold to arms manufacturer Contraves for target flights with that company’s air defense programs. This airframe was fitted with – 20 series turbine of 650 shp 9484kW), flat rated to 550shp (410kW) for torque limitations and lower time between overhaul. Very few changes were required to transform the ‘lame duck’ into an elegant and powerful swan. Work included lengthening the fuselage by 12 in. (30cm) and moving the control surfaces further aft. This rendered the ventral fin superfluous. The rear section of the aircraft now closely resembled Fiertz’s original design.
This modified HB-HON was initially designated P3-06 or P3B, and it was not until the Paris Salon of 1967 that the term PC-7 was used. The design had one major flaw – it was ten years too early. The market place did not respond to the potential that the PC-7 offered. Avgas was still cheap and a multitude of piston-powered trainers fulfilled their tasks to everyone’s apparent satisfaction. The prototype was handed back to Contraves and was written off in a forced-landing soon after.
By 1975 the situation had changed enough for Pilatus to make a second attempt. Under considerable time pressure, the A-871, whose hours were the lowest in the Flugwaffe’s fleet, was borrowed and registered HB-HOZ. Undergoing many modifications, this aircraft became the first of the new generation of PC-7’s and the further much-retired PC-9, producing the market success that Pilatus now basks in.
After the introduction of the PC-7 into the Swiss Air Force, the P3’s were used for liaison work. In three auctions – the last of which occurred on April 22, 1995 – the fleet of 65 aircraft was sold to the public. The hammer went down at prices ranging from 50,000 – 60,000 Swiss Francs . The amount of airframe hours varied from 1,700 to 3,300 total. Many examples ended up abroad.
In an effort to save a few jobs, the Air Force Depot at Lodrino maintains a large stock of spares, the intention being that the new owners will be able to acquire their spare parts for realistic prices in the years to come. Equally, the Farner Company at Grenchen, which maintained a lengthy overhaul contract with the Flagwaffe for most of the type’s military career, is offering its services to the new operators. At least one of the examples that have been shipped to the USA will shortly be equipped with a 350hp Lycoming engine. One cannot help but wonder if Henry Fiertz’s reluctance over re-engineering was indeed justified.
Experience is the sum of vital lessons gained from the total number of mistakes made along the way. Historically, the P3 proved to be a cornerstone in the evolution of the Pilatus range of trainers. The company managed to preserve its qualities in the follow-on PC-7 and PC-9 models, without having to accept its shortcomings. In consideration of the P3’s primary purpose – the training of pilots – it can be determined to have been a moderate success. The P3 taught a few very important lessons to its manufacturer. But it also passed on countless lessons to the students who honed their skills flying at the controls of the Pilatus product. What more can a trainer really do?