Improvements in or relating to exhaust units for jet propulsion units

1,135,377. Jet propulsion nozzles. SOC. NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. Nov. 21, 1966 [Nov. 22, 1965], No.52092/66. Heading F1J. A jet propulsion engine nozzle assembly comprises a main nozzle having a fixed convergent portion 19 and flaps 20 movable between convergent and divergent positions 20', 20" respectively, and a variable area auxiliary nozzle 12 branched from the main jet pipe to provide fine control of the exhaust area. A convergent-divergent member 22 having adjustable flaps 23 is mounted downstream of the flaps 20, secondary air 10 being supplied to the throat 22 defined thereby. A similar member 13 downstream of nozzle 12 is also supplied with secondary air 10'. In modifications, Figs. 1 to 6 (not shown), the main nozzle is non-adjustable and all control is by the variable area auxiliary nozzle. Two main and two auxiliary nozzles may be provided to eliminate couple effects. Reheat combustion may occur in the main jet pipe and the nozzle thereof may be fitted with a silencer. The area of a non-circular auxiliary nozzle is controlled by an axially slidable ramp (17), Fig. 6 (not shown), rather than by the flaps shown. Guide vanes (7), Fig. 3 (not shown), may direct gases from the main into the auxiliary jet pipe.