# Caudron R.11

The Caudron R.11 (or R.XI in contemporary usage), was a French three-seat twin-engine long range escort fighter biplane developed and produced by Caudron during the First World War.

## Development

The R.XI was intended to fulfill a French Corps d'Armee requirement for a long range three-seat escort fighter. Its design was similar to the Caudron R.4, but without a nose-wheel, and with longer wings and fuselage, with two bracing bays outboard the engines rather than three, along with a much larger tail. Hispano-Suiza 8Ba liquid-cooled V-8 engines were housed in streamlined nacelles just above the lower wing, fitted with frontal radiators, which replaced the air-cooled Renault engines used in the R.4.

## Operational history

Production of the 1000 R.XIs ordered by the French Army began in 1917, with the first aircraft completed late in that year.
The first escadrille, R 46, was equipped with the type in February 1918 and the last escadrille to form was R 246, before the Armistice resulted in an abrupt end to production, at which point approximately 370 aircraft had been completed by Caudron, Régy Frères and Gremont.

## Variants
### Caudron R.XI C.3

    Heavy escort fighter with 160 kW (215 hp) Hispano-Suiza 8Bda engines.

### Caudron R.XII C.3

    R.XI with the more powerful 220 kW (300 hp) Hispano-Suiza 8Fb engines that were expected to boost performance. Sources differ, but it may have had a slightly increased wing area, to 60 m$^2$ (650 sq ft) and an extra wing bay was added outboard of the engines. It first flew in November 1918 but was still undergoing testing in mid-1919 and no production followed despite plans to equip 12 escadrilles.

### Caudron R.XIV Ca.3

    Similar to the R.XII, but armed with a 37 mm (1.5 in) Hotchkiss cannon in addition to the normal complement of 5 machine guns, and with further increased wing area, to 63 m$^2$ (680 sq ft), and a larger, unbalanced rudder. A single example was built following the conversion of an R.XI to carry the cannon in August 1918.

## Operators
### France

* French Air Force
** Escadrille R 46
** Escadrille R 239
** Escadrille R 240
** Escadrille R 241
** Escadrille R 242
** Escadrille R 246

### United Kingdom

* Royal Air Force received two examples for evaluation as a bomber.

### United States

* American Expeditionary Force received two examples for evaluation, and two others were detached to US units.

## Specifications (Caudron R.XI C.3)

Data from Davilla, 1997, p.168
General characteristics
* Crew: 3
* Length: 11.22 m (36 ft 10 in)
* Upper wingspan: 17.92 m (58 ft 10 in)
* Lower wingspan: 16.97 m (55 ft 8 in)
* Height: 2.8 m (9 ft 2 in)
* Wing area: 54.25 m$^2$ (583.9 sq ft)
* Empty weight: 1,422 kg (3,135 lb)
* Gross weight: 2,165 kg (4,773 lb)
* Fuel capacity: 220 L (48 imp gal; 58 US gal)
* Powerplant: 2 × Hispano-Suiza 8Bda V-8 water-cooled piston engines, 160 kW (215 hp) each
* Propellers: 2-bladed wooden fixed pitch propellers
Performance
* Maximum speed: 190 km/h (120 mph, 100 kn) at sea level
   * 183 km/h (114 mph) at 2,000 m (6,600 ft)
   * 178 km/h (111 mph) at 3,000 m (9,800 ft)
   * 173 km/h (107 mph) at 4,000 m (13,000 ft)
   * 164 km/h (102 mph) at 5,000 m (16,000 ft)
* Range: 600 km (370 mi, 320 nmi)
* Endurance: 3 hours
* Service ceiling: 5,950 m (19,520 ft)
* Time to altitude:
   * 2,000 m (6,600 ft) in 8 minutes 10 seconds
   * 3,000 m (9,800 ft) in 14 minutes 30 seconds
   * 4,000 m (13,000 ft) in 22 minutes 30 seconds
   * 5,000 m (16,000 ft) in 39 minutes
* Wing loading: 39.9 kg/m$^2$ (8.18 lb/sq ft)
* Power/mass: 18.08 kW/kg (11.00 hp/lb) This power to weight is wrong.
Armament
* Guns: 5 x 7.7 mm (0.303 in) Lewis machine guns
Related development
* Caudron R.6
Aircraft of comparable role, configuration, and era
* SPAD SA.3
* Ponnier P.1