By the latter half of the 1930s fighter aircraft had advanced so much that a "fighter trainer" was needed to fill the gap between a basic trainer and a fighter, and in 1937 the Finnish Air Force ordered a trainer/fighter hybrid from VL. Pyry was designed by Arvo Ylinen, Torsti Verkkola and Martti Vainio. it was to be equipped with a 365 hp Wright R-975 Whirlwind engine, but eventually a more powerful 420 hp version of the Whirlwind was chosen.
Pyry's prototype, PY-1, made its maiden flight on 29 March 1939, but significant shortcomings were detected in it, and 66 modifications were made. Because of the start of the Second World War in September 1939, some parts bought from abroad never arrived, and VL had to make substitutes in spring 1940. This, the shortage of some materials and the order to disperse the production in fall 1939 in case of Soviet bombings delayed Pyry's production. The first of the 40 series production aircraft (Pyry II) entered service in early 1941 and the final two were delivered in June 1941, about half a year behind schedule.
Operational service Edit
Pyry played a key role in Finnish fighter pilot training during the Second World War, training about 700 pilots and flying for 56,600 hours.
However, Pyry proved to be tricky and difficult to fly. It was unstable and prone to wingtip stalls, which sometimes had disastrous results, especially in the hands of rookies.
Four Pyrys (PY-1, -24, -32 and -37) were equipped with trapezoidal wings to get rid of the wingtip stall problem, and also to test the structure for the VL Myrsky project, but although the new wings did reduce the risk of wingtip stalls, they made the Pyry even more unstable. PY-37 crashed on 7 March 1943, killing the pilot and the passenger. PY-1 retained the trapezoidal wings, the others were re-equipped with the original wings.
In 1942 Pyrys were grounded due to broken horizontal stabiliser struts, and the original struts were replaced with V struts, but it made the aircraft more tail-heavy. In 1944 the engine mount was lengthened by 16,5 cm and the battery was moved to the front from behind the cockpit. This improved Pyry's stability, but it remained a difficult aircraft to the end. However, in experienced hands the Pyry was a capable aerobatic aircraft thanks to the light controls. During their service, Pyrys suffered 28 hull-loss accidents that killed 27 pilots. PY-1 and PY-27 flew the type's final flights on 6 September 1962.
- Prototype PY-1 is at the Kauhava Aircraft Park.
- PY-35 is at the Finnish Air Force Museum in Tikkakoski. The museum also has the remains of PY-5.
- PY-27 is at the Finnish Aviation Museum in Vantaa.
- The remains of PY-26 are at the Päijänne Tavastia Aviation Museum in Asikkala.
Pyry has a steel tube fuselage covered with fabric and duraluminium. The wings are wooden and covered with plywood.
Specifications (Pyry II) Edit
- Crew: 2
- Length: 7.7 m (25 ft 3 in)
- Wingspan: 9.8 m (32 ft 2 in)
- Height: 2.55 m (8 ft 4 in)
- Wing area: 12.7 m2 (137 sq ft)
- Empty weight: 1,045 kg (2,304 lb)
- Gross weight: 1,535 kg (3,384 lb)
- Powerplant: 1 × Wright R-975-E3 Whirlwind nine-cylinder air-cooled radial piston engine, 340 kW (450 hp) at 2,250 rpm for take-off
- Propellers: 2-bladed variable-pitch propeller
- Maximum speed: 330 km/h (210 mph, 180 kn)
- Cruise speed: 286 km/h (178 mph, 154 kn)
- Range: 1,050 km (650 mi, 570 nmi)
- Service ceiling: 5,600 m (18,400 ft)
- Rate of climb: 5 m/s (980 ft/min)
- Time to altitude: 1,000 m (3,300 ft) - 2 minutes 28 seconds
- 2,000 m (6,600 ft) - 5 minutes 7 seconds
- 3,000 m (9,800 ft) - 8 minutes 27 seconds
- 4,000 m (13,000 ft) - 12 minutes 43 seconds
- 5,000 m (16,000 ft) - 20 minutes 10 seconds
- Wing loading: 120.87 kg/m2 (24.76 lb/sq ft)
- Power/mass: 0.201 kW/kg (0.068 hp/lb)
- Armament: 1x 7.7 mm (0.303 in) Browning machine gun in the nose, 480 rounds