Eclipse is the name given to an Olympus engine powered UAV which is being produced for a MSc in Aircraft Engineering Group Design Project (GDP).  Cranfield University runs the course, with students from various engineering disciplines within BAE SYSTEMS.

The initial specification for the vehicle, provided by the College of Aeronautics, was (intentionally) vague.  The key design drivers were: the aircraft shall be powered by a small scale jet propulsion system, minimum flight duration shall be 10 minutes, with 5 minutes reserves (originally 15 minutes with 15 minutes reserves, however this was leading to a vehicle with too high a fuel load for comfort), the aircraft shall take off and land on its own conventional landing gear, the span of the vehicle shall be less than 2.5 m, the aircraft all up mass shall be such that two persons can safely carry it and finally, the vehicle shall be of a novel configuration to allow investigation of its aerodynamic characteristics.

The initial parametric studies predicted the aircraft size and performance.  Based on the results of the study a number of novel configurations were proposed.  The selection process eventually resulted in a configuration with a diamond platform wing.
The parametric analysis estimated that the aircraft would need an engine producing between 100N and 150N thrust in order to achieve the required performance.  The engines were assessed based on the following criteria; thrust available, the specific fuel consumption (sfc), requirements for separate oil supplies, fuel type, physical size and weight and ease of operation.  The selection process showed the Olympus engine, produced by AMT Netherlands to be the preferred choice.  This decision was based on the superior thrust, good sfc compared with the other liquid fuel engines, no requirement for a separate oil supply, the ability to use standard jet fuel (opposed to Propane) and relatively straight forward starting (especially with the use of the automatic start unit).

The Olympus engine was chosen even though it provided more thrust than the predicted thrust requirement.  This was to allow for installation losses which will reduce the net thrust available.  The extra thrust also provided a margin for any errors in the initial estimates of the UAV's drag and mass.

The fuel system that was recommended by the engine supplier was not suitable for the requirements of the UAV, due to the endurance requirements in the specification.  As a result a new fuel system has been designed based on a similar concept to a motorbike's fuel system, which guarantees a reliable fuel supply as the aircraft attitude varies.  This design does, however, restrict the aircraft to positive 'g' manoeuvres.

The design of the Eclipse airframe uses standard 'home built' composite aircraft construction techniques.  The airframe is based around a solid foam core wing with carbon skins to provide the structural strength.

The Aircraft Systems are based around an Avionics crate originally designed by Cranfield and DERA for a previous UAV.  The Avionics crate contains all the sensors required for sensing the aircraft's attitude, flight direction and location.  The flight control software is resident in this equipment and provides the interface between the operator on the ground demanding an attitude, altitude or heading and the required control surface deflection.  The Avionics crate also includes a telemetry link to the ground station transmitting key flight parameters to allow system health monitoring and provide feedback to the operator for manual landing and take off phases of flight.

The manufacture of the airframe is now complete with first flight scheduled for August 2000.  The completion of the simulation model and flight control system software is now seen as the critical path to achieving the first flight.