Hillson Bi-Mono
F. Hills and Sons · United Kingdom · first flew 1941 · light aircraft
The Hillson Bi-Mono was a British experimental aircraft designed to test the slip-wing concept, in which an additional upper wing provides extra lift for take-off and is then jettisoned once the aircraft is airborne, leaving a cleaner monoplane configuration.
Recognition (WEFT)
| W — Wings | Low-mounted, tapered |
|---|---|
| E — Engines | 1 × piston, nose-mounted |
| F — Fuselage | 5.94 m fuselage |
| T — Tail | Conventional |
WEFT is AircraftIQ's four-point recognition method — how it works.
Spot it by:
- Jettisoning upper wing converts biplane to monoplane in flight
- de Havilland Gypsy Queen engine; only one built
- Take off as biplane, cruise as monoplane — slip-wing concept
On the ground, an unconventional biplane with an upper wing supported on a simple pylon structure above the main fuselage. After wing release, it presented as a conventional low-wing monoplane — the only visual clue being the release attachment points on the fuselage spine.
Specifications
- The Hillson Bi-Mono has a length of 5.94 m (19 ft).
- It has a wingspan of 6.1 m (20 ft).
- Typical crew: 1.
Figures are for the representative variant described above; marks differ. See how AircraftIQ sources figures.
History
Built by F. Hills and Sons of Manchester and first flown in 1941, the aircraft achieved its first successful wing-drop on 16 July 1941. A&AEE evaluation found a fundamental flaw: the biplane maximum speed was lower than the monoplane stall speed, making the conversion transition hazardous. No further development followed.
Variants
One aircraft only; the concept was not pursued.
Where you'll see it
Research and evaluation only; never proposed for operational service.
Related aircraft
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