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

• 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

• 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)

Specifications (Monospar ST-25 Jubilee)

See also

• General Aircraft ST-18 Croydon

References

Notes

Citations

Bibliography

• Howson, Gerald. 1990. Aircraft of the Spanish Civil War 1936–39. Putnam
• Jackson, A.J. (1973). British Civil Aircraft since 1919, Volume 2. Putnam. pp. 215–220, 519–521
• Ogden, Bob (2009). Aviation Museums and Collections of Mainland Europe. Air-Britain.