With origins coming from World War II, when Finnish forces took control of the Russian occupied city of Äänislinna. There they noticed a glider pilot school with planes called UC-3s’. They were brought back to Finland and used as a display at the Victory fair.

The gliders were then examined and found to be inferior in many ways. One of these UC-3’s was tested and found to be good flier, despite of the inferior build quality and several shortcomings.

This UC-3 inspired the building of a similar type of primary glider. The key idea was to make it extremely simple, light and easy to build in aviation clubs around Finland, the Harakka (“European magpie”). They did not bother to make plans for the prototype, but just sort of design as you build.

When the prototype was built and it was found to be good flier and better than Grunau’s & SG’s, approx 28 were built.

First flown in February 1945, the type was built from plans by Finnish gliding clubs and soon replaced earlier primary gliders such as the Grunau 9, becoming a standard piece of equipment in the clubs. Approximately 50 were built.

In 1946, booming aviation clubs needed more primary gliders, but the Harakka needed further development and some upgrades to strengthen it. The Local FAA ordered this further development from PIK whose key designers were Juhani Heinonen, J. Nurmi and Raimo Häkkinen. The new plane was called Harakka II and given the PIK-serial number of 7. Twenty-seven were built.

In 1948, a single example of a more radically redesigned version designated Harakka III flew. This had the framework that supported the tail replaced by a single boom.

All in all, 57 Harakka’s were built (or started, some were not completed). The last Harakka was a replica built from original plans with designation of H-60.

The Moottori-Harakka was a motor glider development of the PIK-7.

Gallery

Harakka
Span: 10.56 m
Length: 5.60 m
Empty weight: 92kg
Start weight: 182 kg
Normal speed: 45 km / h

PIK-7 Harakka II (H-57)
Wingspan: 10.60 m (34 ft 9 in)
Wing area: 15 sq.m (161 sq.ft)
Length: 5.72 m (18 ft 9 in)
Height: 1.30 m (4 ft 3 in)
Empty weight: 92 kg (200 lb)
Gross weight: 200 kg (440 lb)
Maximum speed: 117 km/h (73 mph)
Maximum glide ratio: 10.5:1
Rate of sink: 1.2 m/s (236 ft/min)
Crew: One pilot

Harakka III

The PIK-5 was a training glider produced in Finland in the 1940s, and 1950s, equipping the country’s gliding clubs with an aircraft greater in performance than primary gliders but less than competition sailplanes. The aircraft had a pod-and-boom configuration, with a high, strut-braced monoplane wing and a cruciform tail carried at the end of a tailboom that extended from a position high on the aft end of the pod.

Designed by Kaarlo J. Temmes, the prototype was built by Polyteknikkojen Ilmailukerho and first flew in September 1946, and testing continued until it was badly damaged in a crash in summer 1948.

Over the subsequent months, the wings were repaired, and a new fuselage constructed to a revised design. This was completed the following winter, and flights recommenced. However, this aircraft, now known as the PIK-5B, was destroyed in a crash in summer 1951.

Again, it was rebuilt with modifications, particularly to the wing structure, resulting in the PIK-5C version. This version first flew on 5 July 1952, and went on to become the pattern for 34 similar machines that would be built over the ensuing years.

Gallery

PIK-5

PIK 5A

PIK-5B

PIK-5C
Wingspan: 12.4 m (40 ft 8 in)
Wing area: 14.7 m2 (158 sq ft)
Airfoil: Göttingen 533
Aspect ratio: 10.4
Length: 6.4 m (21 ft 0 in)
Empty weight: 120 kg (265 lb)
Max takeoff weight: 210 kg (463 lb)
Stall speed: 45 km/h (28 mph, 24 kn)
Never exceed speed: 190 km/h (120 mph, 100 kn)
Rough air speed max: 120 km/h (74.6 mph; 64.8 kn)
Aerotow speed: 20 km/h (12.4 mph; 10.8 kn)
Winch launch speed: 90 km/h (55.9 mph; 48.6 kn)
Terminal velocity: with full air-brakes at max all-up weight 180 km/h (112 mph; 97 kn)
g limits: +4 -2
Maximum glide ratio: 18 at 60 km/h (37.3 mph; 32.4 kn)
Rate of sink: 0.85 m/s (167 ft/min) at 52 km/h (32.3 mph; 28.1 kn)
Wing loading: 14.3 kg/m2 (2.9 lb/sq ft)
Crew: 1

The PIK series of sailplanes designed and produced in Finland gets its name from the Polyteknikkojen llmailukerho, the flying club of the Student Union formed at Helsinki University of Technology in 1931; this series started in 1945 and the PIK-3 singleseater, intended for use by and for construction by gliding clubs, was the first to go into series production. It was followed by the PIK-5A, B and C intermediate training sailplanes and the PIK-7 primary glider which, together with the PIK-3, became standard types in the Finnish clubs, and the first two-seater in the series, the PIK-12 trainer.

The PIK-3 was 1942 designed by Lars H ‘Pappa’ Norrmen and Ilkka Lounama, originaly designated LHN-3, the first prototype making its maiden flight in the summer of 1950, and was of conventional wooden construction.

It was followed by 20 PIK-3A and PIK-3B variants, the 3B, developed by Aush Koskinen, featuring air brakes instead of the 3A’s wing flaps, and both these versions had a 13m (42 ft 7.25 in) span wing.

The PIK-3C Kajava is a high performance version of the 3B incorporating modifications, in particular a wing span increased to 15m (49 ft 2.5 in), to comply with Standard Class rules. The wing structure was completely redesigned and a new cockpit canopy fitted, the fuselage remaining otherwise unchanged from the 3B’s. The prototype PIK-3C first flew on 20 May 1958 and the 3C was modified for series production by Tuomo Tervo at the Suomen llmailuliito (the Finnish Aeronautical Association); 20 had been built by the beginning of 1970. Resembling the EoN Olympia, but with a more angular fin and rudder, the PIK-3C has high-set single-spar wooden wings and an oval-section wooden fuselage with diagonal ply covering, the fin and tailplane also being ply covered.

The PIK-3c combine features of PIK-3b and the PIK-13, and the PIK-3c Kajava (Kittiwake) was a revised high-performance version of the PIK-3Bwith a span of 15 m and a new cockpit canopy.

Gallery

PIK-3C Kajava
Span: 15.0 m / 49 ft 2.5 in
Length: 6.6 m / 21 ft 7.75 in
Height: 1.0 m / 3 ft 3 in
Wing area: 13.1 sq.m / 141 sq ft
Aspect ratio: 17.1
Wing section: Gottingen 549/693
Empty weight: 165 kg / 364 lb
Max weight: 280 kg / 617 lb
Water ballast: None
Max speed: 155 mph / 135 kt / 250 km/h
Stalling speed: 30 kt / 55 km/h
Max rough air speed: 78 kt / 145 km/h
Min sinking speed: 0.61 m/sec / 2 ft/sec at 40.5 mph / 35 kt / 65 km/h
Best glide ratio: 30:1 at 46.5 mph / 40.5 kt / 75 km/h

Between 1947 and 1948, the test pilot and aeronautical constructor Alexei Ivanovich Pietsuj developed two new projects at the MAI that were called PAI-5 and PAI-6 (Russian: Пьецух ПАИ-6).

The PAI-6 was designed as a single-seater training glider to take advantage of thermal flight and had full aerobatic capabilities. It was generally similar to the previous PAI-5, but was notable for its increased wingspan.

The PAI-6 was a high-cantilever glider with a large trapezoidal high-wing.

The glider was built entirely of wood. The fuselage had a simple construction made up of 24 frames joined by three stringers and a set of stringers. The exterior coating was made with plywood between 1.5 and 2 mm thick. The cross section was oval, with downward elongation. In the upper part of the fuselage, a slit was made, crossed by the force elements of the wing. An aluminium cover was placed over this slit.

The wing composition comprised two trapezoidal-shaped consoles in plane joined at their bases on the longitudinal axis of the apparatus. The consoles had a TsAGI R-Sh profile of constant relative thickness (15.5%) and were fixed to the fuselage by means of four points of two reinforced frames located in the upper part. The two consoles were joined together by screws and conical fixings. The fixing points to the frames were located on the spar and on the last wing spar.

The wing featured a single spar structure with ends working by twisting. The stringer was made up of two faces with plywood partitions. The wingtips and the frontal region of the wing were covered with plywood and the rest with fabric covered with paint.

The ailerons were attached to an auxiliary spar at three points and featured a single spar structure with diagonal ribs. The front part was covered with plywood and the rest with fabric. The wing-end interceptors were conceived as smooth pine frames with fabric covering on both sides. Each interceptor was attached to the wing spar by three points.

The horizontal tail plane was raised to the top line of the fuselage and positioned in front of the vertical tail. The stabilizer featured a single spar construction with plywood overlay. The elevators also used a single spar and coating similar to that of the ailerons.

The keel was an integral part of the fuselage construction and ended in a rudder with aerodynamic compensation. This rudder featured a two-stringer structure. From the leading edge to the second spar the covering was plywood and from there on fabric. All rudders featured three-point fixation. The landing was made on a wooden ski, with a trunk structure, located in the lower part of the fuselage.

The cockpit, located in front of the wing, was closed by a cover that protruded from the upper line of the aircraft. The flight control was mixed with control of the ailerons by means of ropes and bars for the control of the tail planes.

The control of the interceptors and the tow hook was also carried out by cables, with actuators located on the sides of the cockpit.

Once the tests were completed from the GK NII VVS Experimental Factory, improvements were made to the original design and the entire set of plans and technical diagrams was created to launch production. In Ryazan, Moscow, a small series was built in 1949. Its main destination was the flying clubs of the country. PAI-6 participated in several air parades for Aviation Day in Túshino.

An improved version of this glider known as PAI-6M was built in the early 1950s at the MAI. This aircraft was never flown and was destroyed as a result of the cooling towards the gliders that occurred in the USSR in those years.

PAI-6
Wingspan: 12.4 m
Wing area: 11.8 m²
Aspect ratio: 13
Length: 5.41 m
Height. 1.35 m
Glider weight: 193 kg
Wing loading: 24 kg / m²
Stabilizer surface: 0.9 m²
Elevator area: 0.75 m²
Keel surface: 0.17 m²
Rudder surface area: 0.85 m²
Spoiler area: 1.58 m²
Minimum descent speed: 0.82 m / s
Cruising speed: 85 km / h
Landing speed: 60 km / h
Max glide ratio: 24
Accommodation: 1

Between 1947 and 1948, the test pilot and aeronautical constructor Alexei Ivanovich Pietsuj developed two new projects at the MAI that were called PAI-5 and PAI-6. The Pietsuj PAI-5 (Russian: Пьецух ПАИ-5) was designed as a single-seater competition glider and was built at the GK NII VVS experimental factory in 1947.

The PAI-5 was designed as a high cantilever glider with a small trapezoidal wing.

The glider was built entirely of wood. The fuselage had a simple construction made up of a series of frames joined by four stringers. The outer covering was made with plywood. The wings had an R-Sh profile. The wingtips were covered with plywood and the rest with paint coated fabric.

The horizontal tail plane was raised to the top line of the fuselage and positioned in front of the vertical empennage.

The landing was made on a wooden ski, with a trunk structure, located in the lower part of the fuselage.

The cockpit, located in front of the wing, was closed by a cover that protruded from the upper line of the aircraft.

The PAI-5 glider was tested in February 1948. Pietsuj himself flew the model in front of a group of renowned test pilots, most notably Air Marshal Ye. During the test flight the complete set of high school aerobatics was executed and an overload of 8g was achieved at speeds of 220 km / h.

During the celebration of Air Fleet Day in 1948 Pietsuj made a demonstration of high school piloting. For the design and construction of this glider AI Pietsuj received the Order of the Red Star.