Polyt V

The Polyt V, sometimes written as Polyt 5, was intended from the start as a glider tug. It was designed by six members of the Flying Group of the Technical University of Denmark, Copenhagen, a group comprising about 50 students and graduates of that University. As many as 20 other Group members built the aircraft. The Polyt V flew for the first time on 12 April 1970.[2][3][4]

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 flat four engine. Its wings are built around a wooden box spar and plywood covered except for fibreglass leading edges. They carry wide span ailerons with 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. 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.[1][2]

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. The engine installation is unusual in having a 16 blade adjustable intake cooling fan in the cowling immediately behind the propeller, for low speed high power flight.[5] This additional cooling is automatically blanked off during a dive.[2]

The main wheels are mounted on a 3 m diameter semi-circular glass fibre arc attached to the fuselage underside; the nose wheel unit is largely that of a Piper Colt.[2]

The Polyteknisk Flyvegruppe have used the sole Polyt V to launch their various gliders from 1970 to at least 2006.[4] OY-DHP remains on the Danish register in 2010[6] and is 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 Some modifications have been made: the original Polyteknisk designed propeller, optimised for low speed flight has been replaced by a quieter Hoffmann one[4] and the rudder trim tab has been extended to half rudder height.[7]

Data from Jane's All the World's Aircraft 1972-73[1]

General characteristics

• Crew: 1
• Length: 6.20 m (20 ft 4 in)
• Wingspan: 9.60 m (31 ft 6 in)
• 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)
• Powerplant: 1 × Lycoming IO-360-A2B 4-cylinder horizontally opposed air cooled piston, 150 kW (200 hp)
• Propellers: 2-bladed Polyteknisk designed wooden fixed pitch, 2.05 m (6 ft 9 in) diameter

Performance

• Maximum speed: 200 km/h (120 mph, 110 kn) at sea level
• Cruise speed: 185 km/h (115 mph, 100 kn) maximum
• Endurance: about 2 hrs
• Service ceiling: 5,500 m (18,000 ft)
• Rate of climb: 5.3 m/s (1,040 ft/min) towing single-seat glider, 8 m/s (1,575 ft/min) solo

Related development

• Polyt I sailplane
• Polyt II primary glider
• Polyt III two seat sailplane
• Polyt IV honeycomb sailplane

• An image of the Polyt Five
• Polyteknisk Flyvegruppe homepage
• Polyteknisk Flyvegruppe on Facebook