General Aircraft Monospar ST-25

The General Aircraft Monospar ST-25 was a British 1930s light twin-engined utility aircraft.

Design and development
The Monospar ST-25 was a low-wing cantilever monoplane with a fabric-covered metal structure. The monospar name came from the use of a single spar in the wing structure, that had been developed by H J Stieger. The cabin was enclosed with five seats. It was based on the GAL Monospar ST-10, with the addition of a folding seat for a fifth passenger, extra side windows, and the addition of a radio receiver. On 19 June 1935, the prototype (G-ADIV) made its first flight at Hanworth Air Park. It was designated Monospar ST-25 Jubilee, to honour the 25th anniversary of the reign of King George V.

Operational history

 * The last flying Monospar ST-25 (ZK-AFF), of Piet Van Asch, the owner of New Zealand Aerial Mapping Ltd, was lost in 1986 in a hangar fire.
 * The last surviving Monospar ST-25 (OY-DAZ), an ST-25 Ambulance, was fully restored during 1989–1999, and is now displayed in Egeskov Veteranmuseum at Egeskov Castle, Denmark.

Variants

 * Monospar ST-25 Jubilee
 * (1935-1936) Single fin and rudder. 30 built.


 * Monospar ST-25 De Luxe
 * One Monospar ST-25 Jubilee with a large single fin and two Niagara II engines, later converted to the prototype Monospar ST-25 Universal, with twin fins.


 * Monospar ST-25 Ambulance
 * Variants of both Monospar ST-25 Jubilee and ST-25 Universal, with a large door on the starboard side to allow a stretcher to be loaded.


 * Monospar ST-25 Universal
 * (1936-1939) Twin fin and twin rudder. 29 built, including the conversion of the De Luxe.


 * Monospar ST-25 Freighter
 * A variant of the Monospar ST-25 Universal, with a large freight door but without the passenger seating.


 * GAL.26
 * One modified Monospar ST-25 Jubilee, fitted with two Cirrus Minor I engines in 1936.


 * GAL.41
 * One experimental aircraft based on the Monospar ST-25 Universal. A new fuselage was built containing a pressurized section with two seats. Its purpose was to test possible pressurization systems for a proposed airliner, the GAL.40. The GAL.41 flew for the first time on 11 May 1939, and was grounded in 1941.

Operators

 * Aden
 * Arabian Airways
 * Adelaide Airways/Australian National Airways
 * Airlines WA
 * Eastern Canada Air Lines (five ST-25 Freighters, delivered in 1936)
 * Maritime Airways
 * Zone-Redningskorpset - 1 ambulance version
 * ES-AXY "Vahur", in the service of the Ministry of Transport and Communications
 * Armée de l'Air (2 ST-25 in Indochine (Vietnam) in November 1945)
 * Van Melle's Confectionery Works, Breskens (one Jubilee, PH-IPM "Dubbele Arend", delivered in 1935)
 * New Zealand Aerial Mapping
 * Royal New Zealand Air Force
 * Royal Romanian Air Force
 * 🇪🇸 Spain
 * Spanish Republican Air Force
 * Spanish Air Force
 * General Command of Mapping (Turkey)
 * Turkish Government (two ST-25 Freighters for parachute training delivered in 1937)
 * Crilly Airways
 * Utility Airways
 * Royal Aircraft Establishment (two Jubilees used for radio development)
 * Royal Air Force (impressed civil aircraft used during the second world war)
 * Spanish Republican Air Force
 * Spanish Air Force
 * General Command of Mapping (Turkey)
 * Turkish Government (two ST-25 Freighters for parachute training delivered in 1937)
 * Crilly Airways
 * Utility Airways
 * Royal Aircraft Establishment (two Jubilees used for radio development)
 * Royal Air Force (impressed civil aircraft used during the second world war)
 * Utility Airways
 * Royal Aircraft Establishment (two Jubilees used for radio development)
 * Royal Air Force (impressed civil aircraft used during the second world war)