Abstract: A ducted fan gas turbine engine is provided with a fan which is carried by a shaft. A frangible fuse ring maintains the shaft carrying the fan coaxial with the engine longitudinal axis. In the event of severe fan damage, the fuse ring (28) fractures and the fan shaft orbits about the engine longitudinal axis. A pair of threaded members (39, 41), one of which is of generally frusto-conical configuration, cooperate as a result of the orbiting motion to restore the coaxial relationship between the fan shaft and the engine longitudinal axis.

Abstract: A flexible coupling and torque monitoring device includes a hub having two sets of flexible spokes extending radially outwardly from a common hub to respective separate rims; the rims are each provided with fingers attached at one end to one rim and with the opposite end extending over the other rim with the fingers of one rim interspersed with the fingers of the other rim; the rims are each attachable respectively to the end of a drive and driven shaft; a sensing member is located radially outwardly of the rims to detect deviations in the spacing between the fingers.

Abstract: An abradable seal comprises a plurality of hollow aluminosilicate spheres in a matrix of aluminium phosphate. The matrix of aluminium phosphate also has an aluminosilicate filler. The hollow aluminosilicate spheres have a diameter in the range of 400 to 1800 microns, preferably a diameter in the range of 800 to 1400 microns. The weight proportion of hollow aluminosilicate spheres in the abradable seal is 30% to 50%. The density of the abradable seal is 1.5 grams per cubic centimeter. The hollow aluminosilicate spheres in the aluminium phosphate matrix have a relatively high temperature capability of approximately 1300.degree. C. maximum. This makes the abradable seal better able to withstand the environment in the turbine of a turbofan gas turbine engine.