Abstract: A vapor core centrifugal fuel pumping system (10') has a main flow impeller (72) and a low flow impeller (81) mounted upon the front plate (74) of the main flow impeller. Both of the impellers receive flow from an inlet passage (26') which proceeds past an inlet throttling valve (114). During pumping operation of the low flow impeller, a surface (122) on the inlet throttling valve forms a labyrinth seal with the radially inner lip (120) of the front plate to reduce inlet fuel flow entering the main impeller. A first check valve (124) and a second check valve (126) respectively prevent flow from the low flow impeller from entering the main flow impeller and flow from the main impeller from entering the low flow impeller. The second check valve is associated with conduits (140, 142) to evaculate liquid adjacent the main impeller during operation of the low flow impeller to reduce windage losses.

Abstract: A centrifugal main fuel pump (10') for a gas turbine engine has a housing (18') in which a centrifugal impeller (12') is mounted for rotation. The impeller discharges flow to a collector (20') and diffuser (22'). A low flow diffuser (26) has its inlet opening positioned closely adjacent the outer periphery of the impeller. Proper design and placement of the low flow diffuser ensures that a high percentage of the fluid energy available in the high velocity flow adjacent the impeller outer periphery is recovered as pressure rise. The low flow diffuser produces adequate fuel flow at the pressure necessary for engine light-off while the first mentioned diffuser recovers a lower pressure rise but is adapted to supply higher engine fuel flow demand in the normal range of operation. A check valve (34) prevents flow from the low flow diffuser from returning to the impeller. The check valve opens to allow the first mentioned diffuser to supply fuel when its discharge pressure exceeds that of the low flow diffuser.

Abstract: A mechanical multiplier (25) in a fuel control for a gas turbine engine has a first track member (26) mounted for lateral movement and a first axially movable displacement member (34) connected to the first track member. A second track member (42) is mounted adjacent the first track member for pivoting movement about an axis (52). A follower assembly (54) operatively interconnects the track members and has rollers (120,122) respectively received in the tracks of the first and second track members. A second displacement member (55) is connected to the follower assembly for movement generally perpendicular to the direction of lateral movement of the first track member. The second displacement member is connected to the output piston (65) of a pressure transducer (66) which senses compressor discharge pressure; and the first displacement member is operatively connected to a fuel metering valve (100).

Abstract: A fuel control for a gas turbine engine has an actuator (24) for a fuel metering valve (22) which includes two stepper motors (46 and 48) which selectively drive a differential mechanism operatively connected to the valve. The differential mechanism includes two identical gear assemblies (60, 64) which are mounted for rotation upon a shaft (26) connected to the valve. The gear assemblies include worm gears (58, 62) in engagement with worms (54, 56) driven by the stepper motors and bevel gears (68, 70). A spider bevel gear (66), carried by the shaft, is in meshing engagement with the bevel gears of the gear assemblies such that rotation of one of the gear assemblies with the other at rest causes a circumferential movement of the spider bevel gear which rotates the shaft and positions the valve. Two identical electronic control units (A, B), which each sense selected engine parameters are respectively connected to the stepper motors for controlling their operation.

Abstract: A shaft seal assembly (2) for a fuel pump includes a seal housing (4) attached to the fuel pump housing (6). A drive shaft (10) mounted for rotation in the fuel pump housing has a sealing face (14) which is engaged by a thrust face (42) of a thrust member (40) and by a seal face (18) of a carbon face seal (20). The thrust member and the carbon face seal are positioned with a steel carrier (26) mounted in the seal housing. A universal washer (32) is located between the carrier and the rear wall of the seal housing so that the carrier may undergo universal movement in response to movements of the thrust member. Misalignments between the axis of the shaft and the axis of the seal housing result in corresponding movements of the thrust member and the carrier which enable the axis of the face seal to remain aligned with the axis of the shaft.

Abstract: A fuel control for a gas turbine engine has a positive displacement pump (28) for supplying fuel to the engine. Fuel flow from the pump is metered by a metering valve (30) which has a constant pressure head held across it by a metering head regulator valve (48) adapted to bypass flow around the pump in a conduit (50). An overspeed valve and solenoid assembly (42) is positioned in the control downstream of the metering valve for shutting off fuel flow to the engine in the event of an overspeed of a turbine of the engine. The metering head regulator valve is referenced to a pressure downstream of the overspeed valve and solenoid assembly by a pressure sense line (68). The solenoid (96) is controlled by a dual channel overspeed valve control circuit (102) having proportional plus derivative gains (108, 110). When the overspeed valve (76) of the assembly is operated, the pump is not deadheaded because the metering head regulator valve is referenced to a lower pressure downstream of the overspeed valve.

Abstract: A pumping system has a main pumping unit (14) and a backup pumping unit (16) mounted in a common housing (4) and adapted to be driven by a drive member (44). The main pumping unit is connected to the drive member by a main drive coupling (68) which incorporates a reduced shear section (76) designed to fail upon a jamming or seizure of the main pumping unit. A backup drive coupling (78) connected to the backup pumping unit is adapted to be axially displaced and threadably connected to the drive member after stoppage of the main pumping unit. An actuation device (18) functions to axially displace the backup drive coupling to establish threaded engagement. When the backup drive coupling is engaged with the drive member, the backup pumping unit will provide flow.

Abstract: A fuel control for a gas turbine engine is operable in a training mode in addition to the conventional automatic and manual back-up modes. In the training mode the manual mode is simulated, with signals commensurate with operator action being delivered to the fuel metering valve actuator, while protection against exceeding the safe operating limits of the engine is provided.

Abstract: Damping of a helicopter rotor drive train, the drive train including the free turbines of a gas turbine engine propulsion system, the aircraft main and tail rotors, and associated shafts and gears, is accomplished through active modulation of the fuel flow to the engine gas generator. The fuel flow is varied such that a transient torque will be developed by the free turbines which is opposite in phase to drive train resonances.

Abstract: A vane pump (2), with undervane pumping capability, has a housing (4,14) within which a cam ring (16) is mounted. The cam ring has a cam surface which defines a pumping cavity and which includes two diametrically opposed inlet arcs (48, 50), two diametrically opposed discharge arcs (38, 40) and seal arcs (56, 58, 60, 62) disposed between the inlet arcs and discharge arcs. A rotor (12), mounted for rotation within the housing, carries a plurality of spokes (22). Mounted upon the spokes for radially outward and inward movement are channel-shaped vanes (28) having arcuate tips (46) for engaging the cam surface. Variable volume chambers (94), which provide undervane pumping, are formed between the radially outer ends of the spokes and the vanes. The variable volume chambers communicate with intervane volumes (93) through grooves (86) on the spokes. The vane tips engage seal arcs along a line of contact (76) selected to insure that the vanes are pressure balanced.

Abstract: A buttstock (32) for a rifle with a lower receiver extension (20) has a shell (36) of high impact plastic and a molded foam core (52) which defines a stowage compartment (62). The shell includes a longitudinally extending web (48) of semi-circular cross-section which together with the inner periphery of the upper portion shell defines a cylindrical volume (50) for receiving the receiver extension. The web serves to more evenly distribute impact loads to the lower receiver (12) of the rifle when the rifle is impacted through the buttstock, generally strengthens the buttstock and facilitates the flow of core material during the molding process.

Abstract: A fuel control (23) for an aircraft engine (10) employs super contingency logic (76) in response to low rotor speed of a helicopter (130) engine failure (131) or entry into an avoid region of a flight regime following engine failure (133) to alter (161, 166-169) limits on the gas generator (30) of a free turbine gas engine (10), whereby following engine failure or in periods of extreme power need, risk of stressing an engine to its failure point is undertaken in favor of acquiring enough power to avoid a certain crash.

Abstract: A backup fuel pump (16) has a thermal fuse (40) positioned in a bearing. The fuse is adapted to melt at a predetermined temperature during dry running of the pump. Melting of the fuse causes a spring urged braking member (42) to screw into a shaft journal (26) and terminate operation of the pump.

Abstract: A drive shaft (26) of a gear type fuel pump (2) forms a driving interconnection between an engine gearbox (4) and a shaft (14) which carries the driving gear (10) of the fuel pump. The drive shaft has a slightly diverging lubricant supply passage (65) which receives lubricant from an oil jet (70) in the engine gearbox and directs the lubricant to the engaged splines (44, 46) at the inboard end of the drive shaft. Lubricant from the area of spline engagement is returned to the gearbox via radial passage (78), annular lubricant return passage (68) and radial passage (80). O-ring seals (82, 84) on the drive shaft, which straddle a drain passage (86) prevent the mixing of the lubricant and the fuel which may envelop an intermediate portion of the drive shaft. Wear of the engaged, oil lubricated splines (40, 42) at the outboard end of the drive shaft should provide a general indication of spline wear at the inboard end of the drive shaft because both ends are exposed to similar lubrication.

Abstract: The blade angle controlling pitch beam servo (26) of a helicopter tail rotor (22) is responsive to a signal manifestation (76) indicative of free turbine engine (20) gas generator speed (78) to provide torque compensation so that the helicopter airframe will not counter-rotate under the main rotor (10) of a helicopter as a consequence of the torque provided thereto by the airframe-mounted engine (20), or in the absence thereof. A trimming embodiment (FIG. 2) provides only sufficient blade angle command (82a) to compensate for that provided by fixed, collective/tail mixing (110-114). Torque compensation tail rotor blade angle commands may be applied through existing stability and autopilot actuators (30-32) or through an additional torque servo (120, FIG. 3).

Abstract: An acceleration schedule, from which data is derived for use in calculating fuel flow during acceleration of a gas turbine engine, is modified each time the engine surges so as to avoid future surges.

Abstract: A centrifugal main fuel pump (10') for a gas turbine engine has a housing (12') in which a centrifugal impeller (16') is mounted for rotation. The centrifugal impeller includes a disc (24') which carries starting flow impeller elements (34) which are positioned in a radially outer location on the disc and also carries main flow impeller elements (26') positioned in a radially inner location on the disc. The starting flow impeller elements discharge to a starting flow collector (38) and diffuser (44) and the main flow impeller elements discharge to a separate collector (30') and diffuser (32'). The starting flow impeller elements produce adequate fuel flow at the pressure necessary for engine lightoff while the main flow impeller elements are adapted to supply engine fuel flow demand in the normal range of operation. A check valve (46) prevents starting flow from returning to the centrifugal impeller.

Abstract: A fuel control for a gas turbine engine is operable in a training mode in addition to the conventional automatic and manual back-up modes. In the training mode the manual mode is simulated, with signals commensurate with operator action being delivered to the fuel metering valve actuator, while protection against exceeding the safe operating limits of the engine is provided.

Abstract: The ability of a gas turbine engine to recover from surge is enhanced by implementing a closed loop control mode wherein fuel flow is varied as a function of the ratio of the rate of change of engine gas generator speed to compressor discharge pressure.

Abstract: The power available from a gas turbine engine is accurately determined by correcting predicted torque and gas generator speed for variations from normal of engine performance. The correction function is adaptively updated on-line by comparing actual and predicted values of torque and speed, storing any differences and summing the stored differences with the predicted values during the determination of power available.