Bartel BM 6
# Bartel BM 6

The Bartel BM 6 was a Polish biplane trainer fighter aircraft of 1930. It did not advance beyond the prototype stage.

## Design and development

The aircraft was designed by Ryszard Bartel in the Samolot factory in Poznań, as a trainer-fighter plane. The BM-6 prototype, designated BM 6a, was flown on 8 April 1930 in Poznań. Its advantage was an easy construction and maintenance, according to Bartel's design philosophy. A distinguishing feature of all Bartels was an upper wing of a shorter span, because lower and upper wing halves were interchangeable (i.e. the lower wingspan included the fuselage width). It first introduced a mixed construction to Bartel's designs.

After trials, the prototype was modified in July 1930. The prototype was later redesignated BM 6a/II after it was substantially modified. It offered quite good flight characteristics and was capable of aerobatic flight. It was demonstrated in a fighter-plane competition in Bucharest in 1930, along with the similar PZL P.1.

The second prototype BM 6b, with a Wright Whirlwind 220 hp radial engine, was ordered, but work upon it ceased with closure of the Samolot factory in mid-1930. The PWS works, which inherited many of Samolot's projects, did not continue the project, for it had its own similar design, the PWS-11.

### Description

Mixed construction biplane. Steel framed fuselage, rectangular in cross-section, canvas covered (engine and upper sections - aluminum covered). Rectangular two-spar wings with rounded ends, plywood and canvas covered. Upper wing span: 7.36 m, lower wing span: 8.10 m. Lower and upper wing halves were interchangeable. Single pilot, sitting in open cockpit, with a windshield. The V8 engine Hispano-Suiza 8Be was modified to lower power output (from 220 hp to 180 hp). Radiator below the fuselage. Fixed landing gear, with a rear skid. Two-blade wooden propeller of fixed pitch. Fuel tank in fuselage: 168 L capacity.

## Operational history

After state trials in 1931, the prototype was used in an advanced training school in Grudziądz, then in an aviation training center in Dęblin.

## Operators

### Poland

* Polish Air Force (single prototype)

## Specifications (BM 6a)

Data from Polish Aircraft 1893–1939

General characteristics

* Crew: 1
* Length: 6.35 m (20 ft 10 in)
* Wingspan: 8.09 m (26 ft 7 in)
* Height: 2.8 m (9 ft 2 in)
* Wing area: 17.6 $m^2$ (189 sq ft)
* Empty weight: 697 kg (1,537 lb)
* Gross weight: 985 kg (2,172 lb)
* Fuel capacity: 170 L (45 US gal; 37 imp gal)
* Powerplant: 1 × Hispano-Suiza 8Be V-8 water-cooled piston engine, 130 kW (180 hp)
* Propellers: 2-bladed Heine fixed pitch propeller

Performance

* Maximum speed: 194 km/h (121 mph, 105 kn) atsea level
* Never exceed speed: 420 km/h (260 mph, 230 kn)
* Service ceiling: 3,800 m (12,500 ft)
* Time to altitude: 4 minutes 24 seconds to 1,000 m (3,300 ft); 18 minutes 57 seconds to 3,000 m (9,800 ft)
* Wing loading: 56 $kg/m^2$ (11 lb/sq ft)
* Power/mass: 0.138 kW/kg (0.084 hp/lb)

Armament

* Guns: 0.303 in (7.7 mm) Vickers machine gun in a fuselage, with a synchronising gear
