Abstract: An engine arrangement (10) comprises propulsion means for propelling the aircraft (12), and drive means to drive the propulsion means. The arrangement (10) further includes mounting means to mount at least the propulsion means in a location spaced above the upper surface of the aircraft (10). In the preferred embodiment, the propulsion means is in the form of tip driven fans (14), and the drive means comprises gas generators (34) mounted within the body of the aircraft (10) fixedly connected by intake ducts (36) to the underside of the aircraft (10).

Abstract: An engine arrangement (10) comprises propulsion means for propelling the aircraft (12), and drive means to drive the propulsion means. The arrangement (10) further includes mounting means to mount at least the propulsion means in a location spaced above the upper surface of the aircraft (10). In the preferred embodiment, the propulsion means is in the form of tip driven fans (14), and the drive means comprises gas generators (34) mounted within the body of the aircraft (10) fixedly connected by intake ducts (36) to the underside of the aircraft (10).

Abstract: An auxiliary gas turbine engine comprises: a load compressor (110); a cabin air supply duct (115) which supplies at least some of the air from the exit of the load compressor to the aircraft cabin; a high pressure compressor (120) which further compresses the remaining air from the exit of the load compressor; a combustor (130); a turbine (140); an electrical generator (150) driven by the turbine; an electric motor (160) driven by the electrical output of the generator, the electric motor in turn driving the load compressor; and at least one air heater/cooler (170A, 170B or 170C) comprising a heat exchanger matrix (172A,172B or 172C) located in the appropriate air duct and a reversible refrigeration plant or heat pump (174A,174B or 174C) which is electrically powered from the generator so that it can either cool or heat the air passing through the matrix. The load compressor and heat exchanger(s) together produce air at the pressure and temperature required for supply to the aircraft cabin.

Abstract: In operation of an engine it is desirable to be able to keep track of engine condition by measuring the values of various engine parameters such as temperatures and pressures and seeing how the relationship between them change. This must be done while the engine is in a steady state condition, generally this requires that the engine be in a cruise condition for some time but this is impractical for military aircraft. It is suggested that each of the sense parameter values be operated on by a trending algorithm which generates a trend estimate which provides a measure of the rate of change of the parameter value. When all of the parameters have trend values are below some pre-set value the engine condition is taken to be at least temporarily steady state condition and parameter values recorded for later analysis.

Abstract: For processing data relating to the performance of an apparatus, the data is analyzed using a Kalman Filter. After a first pass of data through the filter, the results are refined by discarding at least one less significant component performance change and/or sensor bias. The Kalman Filter is then re-run using the modified data. As further runs of the Kalman Filter are performed, as required, the input of each successive run is refined by discarding from the preceding run at least one further component performance change and/or sensor bias. For each run, an objective function is evaluated for the amount of unexplained measurement change and/or the amount of component performance change and sensor bias. The run whose results show an acceptable value for the objective function is selected as the best solution. In this way, the tendency of the Kalman Filter to distribute the cause of any sensed performance change over all the possible sources of that change is avoided.