# 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

### Australia

* Adelaide Airways/Australian National Airways
* Airlines WA

### Canada

* Eastern Canada Air Lines (five ST-25 Freighters, delivered in 1936)
* Maritime Airways

### Denmark

* Zone-Redningskorpset - 1 ambulance version

### Estonia

* ES-AXY "Vahur", in the service of the Ministry of Transport and Communications

### France

* Armée de l'Air (2 ST-25 in Indochine (Vietnam) in November 1945)

### Netherlands

* Van Melle's Confectionery Works, Breskens (one Jubilee, PH-IPM "Dubbele Arend", delivered in 1935)

### New Zealand

* New Zealand Aerial Mapping
* Royal New Zealand Air Force

### Romania

* Royal Romanian Air Force

### Spain

* Spanish Republican Air Force

### Spain

* Spanish Air Force

### Turkey

* General Command of Mapping (Turkey)
* Turkish Government (two ST-25 Freighters for parachute training delivered in 1937)

### United Kingdom

* 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)

Data from Jackson, 1973
General characteristics
* Crew: one
* Length: 26 ft 4 in (8.03 m)
* Wingspan: 40 ft 2 in (12.24 m)
* Height: 7 ft 10 in (2.39 m)
* Wing area: 217 sq ft (20.2 m$^2$)
* Empty weight: 1,680 lb (762 kg)
* Gross weight: 2,875 lb (1,304 kg)
* Powerplant: 2 × Pobjoy Niagara II 7-cyl. air-cooled radial piston engine, 90 hp (67 kW) each
Performance
* Maximum speed: 142 mph (229 km/h, 123 kn)
* Range: 585 mi (941 km, 508 nmi)
* Service ceiling: 16,000 ft (4,900 m)
* Rate of climb: 800 ft/min (4.1 m/s)