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Eiri Avion Pik-20

Siren Pik-20




The single-seat high performance Unrestricted Class PIK-20, design work on which, by a team headed by Pekka Tammi, started on 1 May 1971, the first of two prototypes making its first flight on 10 October 1973. Three prototyes were built, followed by 24 of the first series.

The Pik-20 is a 15 m. racing class, all-fiberglass sailplane with water ballast, retractable gear and 90 degrees trailing edge flaps for landing. Finnish certification of the PIK-20 was granted on 20 June 1974, followed by FAA certification exactly a year later.
There is a retractable Tost monowheel with a drum brake as well as a tailwheel. The T-tail is of similar construction to the wings, and the fixed-incidence tailplane has a one-piece elevator.

After over 425 were built, the PIK-20 was soon followed by the PIK-20B in 1975, the main production version, which had an increased gross weight, greater water ballast capacity of 309lb, interconnected flaps and ailerons for improved performance, which could be retrofitted to earlier models, and a pneumatically sealed sideways opening cockpit canopy. From aircraft No 20100 carbon-fibre spars became available as an option, but later became standard, reducing the empty weight to 496 lb. The PIK-20A designation was an unofficial designation used to distinguish the PIK-20 from the PIK-20B.

Ingo Renner won the 15 m. class at the 1976 World Championships at Rayskala, Finland in a B-model, and others finished 2nd, 3rd and 5th.


The PIK-20C designation was not used, but reserved for the JT-6 proof-of-concept prototype for PIK-20E.
The PIK-20D, first flown on 19 April 1976, superseded the B, and this has carbon-fibre spars as standard, and is fitted with Schempp-Hirth air brakes and improved flaps, or 'flaperons', which act as both flaps and ailerons for enhanced performance. The flaperons, operate differentially for roll control and deflect from -12 degrees to +16 degrees for cruise or approach control. The cockpit is enlarged and its layout improved, and carbon-fibre is also used to reinforce the fuselage. The wings and tail surfaces are glass-fiber reinforced plastic (GRP) sandwich with PVC core. The fuselage is a GRP monocoque structure reinforced with ribs of carbon fiber.
The -20D features carbon fiber spar caps and carbon reinforcement strips at critical locations in the fiberglass monocoque fuselage. The PIK-20D-78 production models the nose profile was sharpened, the tail moved 5 inches forward and fuselage fairings recontoured to reduce drag.
PIK-20 production was undertaken by Eiriavion O/Y, and by January 1979 a total of 149 PIK-20Bs and 150 PIK-20Ds had been delivered. The type soon made its mark in competitions, winning the first three places in the Standard class at the 1976 World Gliding Championships in Finland, and also winning several national championships.




The PIK-20E is a -D sailplane with a retractable Rotax two-cylinder two-cycle engine, developed by Jukka Tervamaki, the chief designer of Finland's Eiriavion O/Y, to meet the OSTIV airworthiness regulations for powered sailplanes. A manual crank handle requires about 15 turns to deploy or retract the engine and propeller.
Initial PIK-20E were powered by the Rotax 501 but the PIK-20E II featured a Rotax 505 (two spark plugs per cylinder). The Rotax 503 500cc two-stroke two-cylinder engine produces 43 hp at 6,200 RPM. With double carburetors and resonance exhaust system, the whole snowmobile engine has been redesigned and built to aircraft requirements. The Hoffmann two-blade wooden propeller is belt driven giving a 1:2 reduction. When not in use, the power plant is retracted into the fuselage by a manual crank and lever in the cockpit wall. The glider features fiberglass monocoque construction. Half of the fuselage/wing fairing has been taken to the wing so that the main rib and wing spar are 20 nm higher in order to save weight. The wings, flaps, and complete tail are of sandwich construction with fiberglass skin and PVCfoam core. Wing spars are made of carbon fiber. The PIK boasts a maximum L/D ratio of 40 to 1. With power on, takeoff can be accomplished in less than 1,000 feet if a 50' obstacle has to be cleared and rate of climb is 787 fpm. Cruising speed is 84 mph at 75 percent power, burning 4.4 gph from the 8.7-gallon fuel tank.
The prototype PIK-20E was powered by a 30hp Kohler 440cc engine and first flew on 2 October 1976, making a four hour flight of which two hours were spent soaring with the engine retracted. The production prototype made its first (aero-tow) flight on 16 March 1978, and its first powered flight two days later, and series production began shortly after.
There is an electric starter for the engine, and the fuel tank behind the pilot's seat holds 7.3 Imp gallons. Apart from the engine, the PIK-20E is very similar, structurally and otherwise, to the PIK-20D, with a longer nose, 25% more tailplane area, small fixed wheels at the wing tips and a rubber-sprung tailwheel now mounted on a steel sprung skid
moved behind the fin spar to the base of the rudder so as to make it steerable; the water ballast capacity (an optional feature) is smaller than the D's.
Eiri PIK-20E
The PIK-20F was available as a 15m Class variant (with 308lb of water ballast) or a Club Class variant, the latter having a fixed monowheel. The PIK-20F has carbon-fibre spars, a modified wing profile, a lower drag fuselage, a forward-opening carbon-reinforced cockpit canopy, a carbon-reinforced cockpit area, and a new wing/fuselage epoxy finish.
Production rights for the PIK-20E were sold in 1981 to the French firm Siren SA. Altogether 102 PIK-20Es had been built in Finland when production ceased there in the spring of 1981. By the spring of 1981 a total of 409 PIK-20s of all versions (including the motorised PIK-20E) had been built, of which 85% were for export.






Wing span: 15m / 49.2ft
Length: 21 ft 10 in
Wing area: 10sq.m / 107.6sq.ft
Aspect ratio: 22.5
Empty Weight: 220kg / 485lb
Payload: 140kg / 308lb
Gross Weight: 450kg / 992lb
Wing Load: 45kg/sq.m / 9.2lb/sq.ft
Water Ballast: 140kg / 308lb
Seats: 1
Lift / drag at 53 kt: 40
L/DMax: 42 @ 110 kph / 63 kt / 73 mph
MinSink: 0.66 m/s / 2.16 fps / 1.28 kt 44 kts
Max airspeed 130 kt
Rough-air speed 130 kt
Stall 31 kts
Airfoil: Wortmann FX 67-K-170/150


Span: 49 ft 2.5 in/ 15.0 m
Length: 21 ft 2 in / 6.45 m
Height: 4 ft 6.75 in / 1.45 m
Wing area: 107.6 sqft / 10.0 sq.m
Aspect ratio: 22.5
Wing section: Wortmann FX-67-K-170/150
Empty weight: 480 lb / 220 kg
Max weight: 992 lb / 450 kg
Water ballast: 309 lb / 140 kg
Max wing loading: 45kg/sq.m / 9.21 lb/sq.ft
Max speed: 181 mph 158 kt / 292 km/h (in smooth air)
Stalling speed: 32 kt / 60 km/h
Max aero-tow speed: 118 mph / 130 kt / 240 km/h
Min sinking speed: 2.17 ft/sec at 53.5 mph
Min sinking speed: 0.56 m/sec / 1.84 ft/sec at 39 kt / 73 km/h
Best glide ratio: 42:1 at 73 mph / 63 kt / 117 km/h
Engine: Rotax 503, 32 kW / 43 bhp
Wing span: 15m / 49 ft 2.5 in
Wing area: 10.0 sq.m / 107.6 sq.ft
Airfoil: Wortmann FX 67-K-170/150
Aspect ratio: 22.5
Length: 6.53 m / 21 ft 5 in
Height: 4 ft 8.75 in
Empty Weight: 310kg / 684 lb
Payload: 160kg / 352 lb
Gross Weight: 470kg / 1036 lb
Wing Load: 47kg/sq.m / 9.6 lb/sq.ft
Water Ballast: 80kg / 176 lb
L/DMax: 40 @ 110 kph / 63 kt / 73 mph
MinSink: 0.66 m/s / 2.16 fps / 1.28 kt at 55 mph / 42 kt / 77 km/h (power off)
Max speed: 177 mph 154 kt / 285 km/h (power off)
Max cruising speed: 84 mph (power on)
Stalling speed: 36 kt / 66 km/h
Rate of climb: 4.0 m/sec / 13 ft/sec
Take-off run: 1,640ft to 50ft
Seats: 1







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