Brditschka HB-3
# Brditschka HB-3

The Brditschka HB-3, HB-21 and HB-23 are a family of motor gliders of unorthodox configuration developed in Austria in the early 1970s.

## Design and development

The unusual design was based on work done by Fritz Raab in Germany in the 1960s. The pilot and passengers sit in a fuselage pod with the engine and propeller behind them. The pod also carries the fixed tricycle undercarriage and the high cantilever wing. The tail is carried on a pair of booms that emerge from the top and bottom of the fuselage pod, the upper of which passes through the propeller hub. The HB-21 has a conventional tail and has two seats in tandem accessed by a sidewards-hinged canopy, while the HB-23 has a T-tail and side-by-side seating accessed via gull-wing doors in the canopy.

The Militky MB-E1 was a modified HB-3 with an 8-10 kW (11-13 hp) Bosch KM77 electric motor. It was the first full-sized, manned aircraft to be solely electrically powered. Flights of 12 minutes duration at up to an altitude of 380 m (1,247 ft) were just within the Ni-Cd battery's capacity. Its first flight was on 23 October 1973.

## Variants

### Brditschka HB-3

    Single seat powered sailplane, powered by 31 kW (42 hp) Rotax 642 engine, 12.00 m (39 ft 4 in) wingspan.

### HB-Flugtechnik HB 21

    Tandem two-seat derivative of HB-3 with longer span (16.24 m (53 ft 3 in)) wings.

### HB-Flugtechnik HB 23/2400 Scanliner

    Observation version of HB-23 with bubble canopy and provision to carry FLIR or LLTV pods under the wings.

### Militky MB-E1

    electrically powered version.

## Specifications (HB-23/2400 Hobbyliner)

Data from Jane's All The World's Aircraft 1990

General characteristics

* Crew: 1
* Capacity: 1 passenger
* Length: 8.00 m (26 ft 3 in)
* Wingspan: 16.40 m (53 ft 10 in)
* Height: 2.45 m (8 ft 0 in)
* Wing area: 19.07 $m^2$ (205.3 sq ft)
* Aspect ratio: 14.1:1
* Airfoil: Wortmann FX-61-184 at root, FX-60-126 at tip
* Empty weight: 560 kg (1,235 lb)
* Max takeoff weight: 760 kg (1,676 lb)
* Fuel capacity: 76 L (17 imp gal; 20 US gal)
* Powerplant: 1 × Volkswagen air-cooled 4-cylinder engine, 73 kW (98 hp)

Performance

* Cruise speed: 180 km/h (110 mph, 97 kn) (max cruise)
* Stall speed: 80 km/h (50 mph, 43 kn) (powered)
* Never exceed speed: 200 km/h (120 mph, 110 kn)
* Range: 800 km (500 mi, 430 nmi)
* Endurance: 6 hours
* Service ceiling: 5,000 m (16,000 ft)
* Maximum glide ratio: 22:1
* Rate of climb: 3.80 m/s (748 ft/min)
* Rate of sink: 1.20 m/s (236 ft/min)
* Takeoff run to 15 m (50 ft): 160 m (525 ft)
