The Bartel M.6 was a fighter trainer that had reached the prototype stage when the Samolot company went into insolvency, so never entered production.
Samolot’s first trainer was the Bartel M.2 of 1926. This only reached the prototype stage, but the company then began work on modified versions in response to official requests for primary and intermediate trainers for the Polish Air Force. The M.4 primary trainer was judged to be a success, and was ordered into production. The original design for the intermediate trainer, the M.3, was soon abandoned in favour of a modified version of the M4, which entered production as the M.5
In February 1929 the M.5 was tested as a possible fighter trainer. The first prototype was given skies instead of wheels, but it proved to be too stable, and couldn’t be spinned, making it useless as a fighter trainer. Instead Samolot was ordered to produce a dedicated fighter trainer, which became the M.6
The M.6 had the same basic layout as the earlier aircraft, with staggered biplane wings that had four identical wing panels. As with the earlier versions the upper wing panels met above the fuselage, the lower wings were carried on the lower longerons, so the lower wing had a longer span than the upper wing.
The biggest change was the move from the wooden structures of the earlier aircraft to one built around a welded steel tube framework with a wooden superstructure to give it shape. The front was covered with detachable aluminium panels, the rear with fabric. It was also the first version to be armed, carrying a single fixed forward firing machine gun mounted on the port side of the fuselage. The M.6 was significantly smaller than the M.5, with 10ft less wingspan and almost 5ft shorter. It was also lighter. Unsurprisingly it was also faster, climbed faster and had a higher service ceiling.
The aircraft was originally designed to use a 220hp Wright/ Skoda radial engine, but the Department of Aeronautics wanted it to be powered by war surplus 180hp Hispano-Suiza engines instead. Late in 1929 a contract was placed for one static test airframe and two flying prototypes, one using each engine.
The Hispano-Suiza powered BM 6a made its maiden flight on 8 April 1930. After its manufacturers trials it went to Warsaw for airworthiness and service trials, where it performed very well, reaching 260mph in a dive. A series of minor changes were made, and the modified prototype flew on 23 July 1930. This version was approved for service, and ended up being used at the training school at Deblin.
By this point the Samolot company had decided to go into voluntary liquidation, and in the summer of 1930 it was finally wound up. As a result work on the half completed prototype of the BM 6b was cancelled.
M.6/ BM 6a
Engine: Hispano-Suiza eight-cylinder v water cooled engine
Span: 26ft 6.75in
Length: 20ft 10.25in
Empty Weight: 1,537lb
Loaded Weight: 2,171lb
Maximum Speed: 120.6mph at sea level
Climb rate: 4m 24s to 3,280ft; 18min 57sec to 9,842ft
Guns: One fixed forward firing machine gun