title: Rolls-Royce RB401
text: # Rolls-Royce RB401
  
  The Rolls-Royce RB.401 was a British two-spool business jet engine which Rolls-Royce started to develop in the mid-1970s as a replacement for the Viper. RB.401-06 prototype engines were already being manufactured when a decision to develop the higher thrust RB.401-07 was taken.
  
  Although ground testing of both the -06 and -07 continued into the early 1980s, a lack of funds caused the project to be cancelled.
  
  ## Design and development
  
  Although the basic configuration of both engines was almost identical, the -07 variant had a larger fan diameter. The -06 version HP compressor was based on the eight-stage version of the RC34B research compressor, unscaled, whereas the -07 was a scaled-up unit. A single stage fan, driven by a two-stage LP turbine, supercharged the HP compressor which was driven by the single stage transonic HP turbine. The combustor was annular and the co-annular exhaust featured a lightweight target type thrust reverser.
  
  ## Specifications (RB.401-07)
  
  Data from Jane's.
  
  **General characteristics**
  
  * Type: High-bypass two-spool turbofan
  * Length: 60.8 in (1,545 mm)
  * Diameter: 32.4 in (823 mm) (fan casing)
  * Dry weight: 985 lb (447 kg)
  
  **Components**
  
  * Compressor: Fan:Single-stage axial, HP:8-stage axial, variable inlet guide vanes
  * Combustors: Annular
  * Turbine: Two-stage LP, single-stage HP with air-cooled blades
  * Fuel type: Hydromechanical with provision for electronic monitoring
  * Oil system: Self-contained (tank, pumps,filters and cooler)
  
  **Performance**
  
  * Maximum thrust: Take-off thrust: 5,540 lbf (24.7 kN)
  * Overall pressure ratio: 11.5:1 (HP compressor)
  * Bypass ratio: 4.2:1
  * Air mass flow: 182 lb/s (82.5 kg)
  * Thrust-to-weight ratio: 5.6:1
  