| Bi-mono | |
|---|---|
 | |
| 3-way drawing | |
| Role | Experimental aircraft Type of aircraft |
| National origin | United Kingdom |
| Manufacturer | F Hills & Sons |
| First flight | 1941 |
| Number built | 1 |
TheHillson Bi-mono was a Britishexperimental aircraft of the 1940s. It was designed to test the idea of "slip-wings", where the aircraft could take off as abiplane,jettison the upper, disposable wing, and continue flying as amonoplane. A single example was built, which successfully demonstrated jettisoning of the slip wing in flight.
In the 1930s, as take-off weights of aircraft continued to increase, designers grew increasingly concerned about the effects that these weights would have on take-off runs, and several designers investigated the concept of a "slip-wing", which could be jettisoned after take-off. Amongst the proponents of the "slip-wing" wasNoel Pemberton Billing, the founder ofSupermarine, who wrote several articles in the aviation press promoting the idea, either with a manned, reusable auxiliary wing, or a disposable or "scrap-wing".[1][2]Blackburn Aircraft also investigated "slip-wings".[3]
Following the outbreak of theSecond World War,F Hills and Son, a light aircraft manufacturer based atTrafford Park,Manchester offered a design for a light fighter aircraft to the BritishAir Ministry. The fighter would be cheap to build and could be operated from small fields or open roads. To give the required take-off performance, the design was to be fitted with a disposable "slip-wing". While the proposal was not accepted by the Air Ministry, Hills and Sons decided to continue with the project as a private venture, and so built a scale test-bed, to prove the slip-wing process.[1][3]
The test bed, known as the Bi-mono, was a smalltractormonoplane with a fabric-covered steel-tube construction fuselage and a wooden wing. It had a fixedtailwheel undercarriage while an enclosed cockpit was provided for the pilot. The auxiliary wing was attached to the top of the cockpit canopy and to the lower wing byinterplane struts. Two different upper wings were flown. The one used initially had a wingspan of 32 ft (9.8 m) but the later, shorter wing's span of 20 ft (6.1 m) was the same as that of the lower one. The aircraft was powered by a singlede Havilland Gipsy Six engine.[4][5]
The Bi-mono was not the only slip-wing project built by Hills and Sons, as they were also contracted by Pemberton Billing to build his PB.37 design for a slip-wing dive-bomber, with apusher monoplane lower component powered by a 290 hp (216 kW) engine, while the manned slip-wing upper component was a tractor monoplane powered by a 40 hp (30 kW) engine. Construction work started on the PB.37 early in 1940, but work was abandoned in July 1940 when construction was almost finished but the aircraft was unflown.[6][7]
The Bi-mono, which carried noserial number orcivil registration, made its maiden flight fromBarton Aerodrome during 1941.[8] Test flights were made both as a monoplane and as a biplane, with the shorter upper wing being chosen.[4] In order to avoid the potential hazards to people on the ground of dropping the wing, wing jettisoning tests were carried out fromSquires Gate Airport,Blackpool, with the upper wing being successfully dropped over theIrish Sea on 16 July 1941.[5] The test proved successful, with no great change intrim and a few hundred feet in altitude being lost when the upper wing was jettisoned.[9]
The Bi-mono was subject to further testing by theAeroplane and Armament Experimental Establishment atBoscombe Down from October 1941. The A&AEE found that the maximum speed of the biplane configuration was slower than the stalling speed of the monoplane configuration. Its landing characteristics were likened to akangaroo.[10]
Hills and Sons went on to further develop the slip-wing concept, flying the Hillson FH.40, aHawker Hurricane fitted with a slip-wing.[11]
Data from Nothing Ventured...Part 1"[12]
General characteristics
