Polyteknisk Flyvegruppe (Flying Group of the Technical University of Denmark) Polyt V
The Polyt V, sometimes written as Polyt 5, was intended from the start as a glider tug. It was designed by six graduates and student members of the Flying Group of the Technical University of Denmark, Copenhagen, (Led by Helge Petersen)a group comprising about 50 students and graduates of that University. As many as 20 other Group members built the aircraft.
It is a low wing, single-seat monoplane with a fixed tricycle undercarriage and a high T-tail, powered by a 200 hp (150 kW) Lycoming IO-360-A2B flat four engine, driving either a Polyteknisk two-blade fixed-pitch wooden propeller or a Hoffmann HO27-HM-205B-105 two-blade propeller.
For cooling the engine during low-speed flight, a 21 in (53 cm) diameter fan with 16 plastic blades is mounted in the circular air intake behind the propeller and is capable of blowing some 3,500 cu.ft (99 cu.m) of air per minute – about four times the normal cooling flow. To prevent excessive cooling the under-nose cooling flap aft of the cowling closes automatically during a dive. Fuel in two aluminum tanks in the wings, total capacity 23.24 gal (88 l). Overwing refueling point in each tank. Oil capacity 1.98 gal (7.5 l).
Its wings are built around a wooden box spar and plywood covered except for fibreglass leading edges. Wing section NACA 63-618 at root, NACA 63-218 at tip. Dihedral 4° from roots. Incidence 2°. No sweepback. They carry wide span ailerons with centrally-located trim tabs; inboard are glider style aluminium spoilers or airbrakes which can be extended to 50° to slow the aircraft after a diving release of the glider. When deployed, the spoiler surfaces extend both below and above the wing, the upper part perforated. These surfaces are carried on a shaft at 80% chord, the portion ahead of this shaft being perforated and the rear portion plain. Of aluminum construction, they have a maximum deflection of 50°; their use has no affect on lift or trim.
The tail surfaces are all wood structurally, with plywood covered fixed surfaces and a fabric covered rudder with a short trim tab. The all moving, fabric covered, constant chord tailplane carries full span anti-tabs. Trim tab in rudder.
The fuselage of the Polyt V is a plywood covered box structure, the pilot sitting over the wing under a single piece, rearward-sliding canopy. An electrically driven winch at the rear retrieves the launch cable, which exits the aircraft at the narrow extreme stern of the fuselage, at a rate of about 1 m/s.
Non-retractable tricycle type landing gear. The main wheels are mounted on a 3 m diameter semi-circular glass fibre gear legs one-third arc of a circle of 6 ft 6.5 in (2.00 m) diameterattached to the fuselage undersideCessna CFP 4097 main wheels. The nose wheel unit (leg, wheel and shock-absorber) is largely that of a Piper Colt, fitted with shimmy damper from a Cessna 172. All tires size 600 x 6, pressure 24 lb/sq.in (1.69 kg/sq.cm).
Accommodation is a single seat for pilot under fully-transparent rearward-sliding canopy. Cockpit heated and ventilated. Electrical system includes AC alternator and 12V battery for engine starting, instruments, lights and towing winch. Vacuum pump for directional gyro. Equipment includes an electrically-operated winch in the rear fuselage, which can reel in over 130 ft (ca. 40 m) of nylon tow line in 40 sec after sailplane is released. Aircraft can make seven or eight launches an hour.
The Polyt V flew for the first time on 12 April 1970, construction having started in 1965. The Polyteknisk Flyvegruppe have used the sole Polyt V to launch their various gliders from 1970 to at least 2006. OY-DHP (c/n 12001) remained on the Danish register in 2010 and was still active as a glider tug. Some modifications have been made: the original Polyteknisk designed propeller, optimised for low speed flight has been replaced by a quieter Hoffmann one and the rudder trim tab has been extended to half rudder height.
Engine: 1 × Lycoming IO-360-A2B, 150 kW (200 hp)
Propeller: 2-bladed Polyteknisk designed wooden fixed pitch
Prop diameter: 2.05 m (6 ft 9 in)
Length: 6.20 m (20 ft 4 in)
Wingspan: 9.60 m (31 ft 6 in)
Wing aspect ratio: 6.35
Wing chord, constant: 4 ft 11 in (1.50 m)
Height: 2.60 m (8 ft 6 in)
Wing area: 14.4 m2 (155 sq ft)
Empty weight: 615 kg (1,356 lb)
Max takeoff weight: 760 kg (1,676 lb)
Wing loading: 10.8 lb/sq.ft (52.8 kg/sq.m)
Power loading: 8.38 lb/hp (3.8 kg/hp)
Tailplane span: 9 ft 10 in (3.00 m)
Ailerons area (total) : 17.87 sq.ft (1.66 sq.m)
Air-brakes/flaps area (total): 10.98 sq.ft (1.02 sq.m)
Fin area: 12.92 sq.ft (1.20 sq.m)
Rudder area, incl. tab: 5.06 sq.ft (0.47 sq.m)
Tailplane area, incl. tab: 29.06 sq.ft (2.70 sq.m)
Wheel track: 7 ft 0.5 in (2.15 m)
Wheel base: 4 ft 9 in (1.5 m)
Propeller ground clearance: 6 in (15 m)
Maximum speed: 200 km/h (124 mph; 108 kn) at sea level
Max dive speed: 144 mph (232 kmh)
Cruising speed: 185 km/h (115 mph; 100 kn) maximumat sea level
Econ cruise speed: 103.5 mph (166 kmh) at sea level
Stall speed: 46 mph (74 kmh)
Endurance: about 2 hrs
Service ceiling: 5,500 m (18,045 ft)
Climb, solo: 1,575 ft (480 m)/min
Climb, with single-seat glider: 1,050 ft (320 m)/min
Climb, with two-seat glider: 820 ft (250 m)/min
Takeoff run, solo: 280 ft (85 m)
Takeoff run, with single-seat glider: 510 ft (155 m)
Takeoff to 50 ft (15 m), solo: 460 ft (140 m)
Takeoff to 50 ft (15 m), with single-seat glider: 900 ft (275 m)
Landing run from 50 ft (15 m): 920 ft (280 m)
Landing run: 460 ft (140 m)