Abstract: The speed (54, 56) of the free turbine (40) of a helicopter engine (20) is compared (103) with the speed (105, 106) of the helicopter rotor (10) to indicate (101, 102) autorotation, and the deceleration (108) of the rotor above a threshold magnitude (110) is utilized (81, 68, 69) to increase fuel flow (72) to the engine in anticipation of rotor speed droop which would otherwise occur during recovery from the autorotation maneuver.

Abstract: The prompt starting of a gas turbine engine is achieved, even when utilizing comparatively poor grade fuel with relatively high viscosity, by modulating the fuel flow between high and low flow rates during the ignition portion of a start schedule. The fuel flow modulation is accomplished by delivering a pulse width modulated control signal to a fuel metering device and modulation is terminated when ignition is verified.

Abstract: A fuel metering system for a gas turbine engine with a low pressure drop fuel vaporizing system includes an engine driven centrifugal pump (10) supplied with fuel at a given absolute pressure (Pi) from a tank. The pump discharges fuel to a rapidly pulsed, solenoid operated ball valve (20) which functions as a metering valve in controlling flow to the engine. The solenoid (38) of the metering valve receives periodic voltage pulses of appropriate width from an electronic control which senses selected engine parameters and computes the required fuel flow and the pressure differential (Pr-P.sub.D) across the metering valve. Since the pressure differential across the metering valve increases with engine speed, favorable flow turndown ratios may be achieved without operating the metering valve at high or low values of duty cycle.

Abstract: The failure of a gas turbine engine, particularly flame-out or output drive train breakage, is immediately detected and a warning signal generated. Engine flame-out is defined as an unacceptably fast gas turbine deceleration rate while output shaft failure is determined by sensing a mismatch between the engine output shaft speed and load speed.

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: The difference in the speed (54, 56) of a helicopter gas engine (20), free turbine (40) from a reference speed (62, 64) generates (80) a desired acceleration signal (81). The difference (82) in actual turbine acceleration (84, 86) from desired acceleration is integrated (100) to provide an engine fuel command signal (67-73) whenever (88) the speed error signal exceeds (90) a predetermined threshold magnitude.

Abstract: A shaft seal assembly for an aircraft engine fuel pump has a seal housing (30) mounted upon the pump housing (32). A carbon face seal (42) is in wiping engagement with a seal face (40) on the drive shaft (36) of the pump. The carbon face seal has a recess (46) which receives a projection (44) for preventing face seal rotation. A universal washer (46), which is mounted in the seal housing in front of the carbon face seal, embodies four protuberances (48, 50, 52, 54) having bores (56, 58, 60, 62) which extend completely through the universal washer. Compression springs (64, 66) are contained in the bores and have their rear and front extremities in respective engagement with washers (70, 72) disposed on either side of the universal washer. The spring force, which is transmitted to the carbon face seal by the front washer, is overcome as pump pressure pushes the shaft toward the front of the pump. In the compressed condition, non-axial shaft alignments are accommodated by the universal washer.

Abstract: A combined pressure regulator and jet pump includes a valve member and cooperating nozzle defining member which are coaxial and independently movable. Both members are responsive to the difference in upstream and downstream pressures and each member will move relative to the other in response to a predetermined pressure difference. The relative movement between the nozzle defining and valve members will not interrupt the pumping action resulting from fluid flow through the variable area nozzle formed by these members.

Abstract: A high speed fuel pump for a gas turnbine engine has a positively-driven shroud (28) positioned between a main impeller (14) and the wall of a pumping cavity (12) to reduce impeller drag. The shroud is formed by a first disc (30) having a boost impeller (36) connected to its central hub portion 30a and a second disc (32) having a gear (32b) carried by its central hub portion (32a). The main drive shaft assembly (24), to which the main impeller is connected, carries a gear (64) which meshes with gear (62) mounted upon a shaft (58). The shaft (58) also carries a gear (56) which meshes with the gear 32b. The gears are sized so that the shroud is driven at one-half the speed of the main impeller in order to maximize impeller drag reduction and enhance pumping capability when severe inlet conditions are present at the pump inlet (10).

Abstract: The response time and power consumption of a solenoid-type actuator are minimized through exercising control over a transistor connected in series with the solenoid coil and a current source. Upon receipt of a command signal the series connected transistor is driven into saturation for a period of time commensurate with the current flow through the coil to rise to the level where a magnetic field of sufficient magnitude to pull in the solenoid plunger will be generated. The solenoid current is, once the solenoid armature moves, reduced to that level needed to maintain the field by controlling the transistor such that there is a constant voltage across the solenoid winding.

Abstract: A fuel control for a gas turbine engine has a positive displacement pump (10) which directs fuel to a constant flow regulator (14) which generates a constant or fixed rate flow of fuel. A flow diverter (16) includes a dividing device which divides the constant flow of fuel between a discharge conduit (18) connected to the burner nozzles of the engine and a bypass conduit (20) connected to the inlet side of the pump. A computer (22) which is adapted to sense various engine parameters; and calculate fuel flow controls the flow dividing device in order to apportion the flow so that the calculated fuel flow is delivered to the engine.

Abstract: Fluid operated time modulated position control mechanisms are operated with a sub-critical carrier frequency. The carrier frequency is selected to be within a band lying between the minimum critical or natural frequency of an actuator system including the control mechanism and the maximum control signal frequency as determined by the system dynamics. The carrier signal is also selected to provide a dither amplitude sufficient to overcome the coulomb friction of the control mechanism and load.

Abstract: A fluid displacement vane pump with undervane pumping has a rotor assembly incorporating a plurality of T-shaped vanes. The outboard undervane surfaces are subjected to the pressure adjacent one side of the vane and the inboard undervane surface is subjected to the pressure adjacent the other side of the vane so that the vanes are hydraulically balanced in the seal arcs as well as in the inlet and discharged arcs. End caps mounted on the rotor function to isolate the undervane cavities and provide uninterrupted bearing surfaces capable of supporting a lubricating hydrodynamic film.

Abstract: A method of controlling fuel flow to a gas turbine engine includes computing the compressor discharge pressure from signals indicative of engine inlet temperature, engine speed and the computed scheduled fuel flow. The method permits accurate scheduling of fuel flow without employing a compressor discharge pressure sensor or continued engine operation in the event of sensor failure.

Abstract: A loading tool for a cartridge magazine embodies a channel for positioning a cartridge to be inserted in the magazine and a rear wall inclined at a preselected angle for orientating the feed mouth of the magazine over the cartridge at the proper angle and relative position such that vertical movement of the magazine causes the rear portion of the cartridge to enter the cartridge opening of the feed mouth. Longitudinal guide surfaces, disposed on either side of the channel and extending from the rear wall, respectively engage the slider lips of the magazine for terminating downward travel of the magazine and guiding subsequent forward movement of the magazine to permit complete insertion of the cartridge.

Abstract: A gear pump suitable for pumping contaminated fuel has a lubrication passage in a pump bearing which receives fuel from the clearance volume between the bearing and the housing in the pump discharge arc. The clearance entrance between the bearing and the housing, which functions as a filter, is smaller than the passage so that contaminants traversing the clearance will not obstruct the passage. Since only contaminants smaller than the clearance entrance can enter the passage, the passage may be made sufficiently small so as not to adversely affect pump performance.

Abstract: A fuel pump assembly for supplying fuel to a gas turbine engine has a centrifugal pump, including an impeller, that furnishes the necessary pressure for engine operation at high engine speeds. A vane pump, attached to the back side of the impeller of the centrifugal pump, supplies fuel to the engine for starting and acceleration to idle. The vane pump is of the type having a stationary centrally disposed cam and an annular rotor with radially inwardly directed vanes which ride over the surface of the cam. Before idle speed is attained, the vanes which are substantially hydraulically balanced and made of a light plastic material are adapted to lift off the surface of the cam without the need of pressure relief behind the vanes.

Abstract: A high pressure centrifugal pump has an impeller assembly including two mating impeller sections which are each constituted by a shroud with fixed geometry blades. The impeller sections are fixedly mounted upon a rotatable shaft and are of a construction which permits the pressure between the impeller sections to engender flexure of the sections away from each other so as to vary the breadth of the impeller assembly. A servo control device is adapted to control the pressure behind the shrouds such that the pump delivers a constant flow at varying back pressures.

Abstract: An axial inducer, which charges the inlet of a centrifugal impeller has a bypass loop connecting its inlet and outlet. A valve member for controlling bypass flow is positioned in the bypass loop. At low flows, the bypass loop permits the inducer to run closer to design flow conditions than would otherwise be possible and, consequently, generate less pressure rise, consume minimum power, and cause minimal heating of the fluid being pumped. An extension of the bypass valve member functions to restrict the centrifugal pump discharge area when the valve member is positioned to bypass flow to reduce recirculating flow in the centrifugal impeller and increase its efficiency.

Abstract: A manual positioning system for the metering valve and variable geometry actuator of a fuel control has a pair of drive shafts which have engagement structures mounted respectively on their ends for drivingly engaging the metering valve and the cam of the variable geometry actuator. The drive shafts carry gears which are in meshing engagement with a gear carried by a speed setting lever member. Upon the application of a manual control signal, the engagement structures respectively engage the metering valve and the cam such that the lever member may subsequently position these elements.