The RB.203 was a private venture engine built on the core of the Rolls-Royce Turbomeca Adour turbofan used in the SEPECAT Jaguar and the later Hawker Siddeley Hawk.
The thermal efficiency is expressed mathematically as:
where:
- is the thermal efficiency,
- is the thrust produced by the engine,
- is the jet velocity,
- ṁf is the mass flow rate of fuel,
- is the specific enthalpy of the fuel.