Abstract: The capability of compensating automatically for a failure in an actuator and the associated drive circuit is enhanced by providing a dual channel actuator, each channel having a drive coil and a position sensor tracking the position of the actuator output shaft. A separate circuit is provided for each actuator channel to detect drive loop failures and hydraulic failures. When the drive loop of one channel fails, it is disengaged, and the gain in the remaining drive loop is doubled to maintain authority. In an embodiment, the remaining drive loop cannot disengage when certain criteria, relating to the failure of associated actuators, are met. The invention is particularly useful for aerospace applications.

Abstract: In a dual actuator system, runaways are identified by comparing the position and rate of one actuator to another. When there is a threshold position discrepancy and a sustained rate discrepancy, a fault is indicated. The faster actuator is identified as the runaway.

Abstract: The sense (direction) of outer-loop commands is compared with the sense (direction) of inner-loop signals in an aircraft AFCS. A disparity in sense indicates an outer-loop failure. To reduce nuisance failures the comparison is made only when inner-loop signal thresholds are exceeded and, in the context of outer-loop commands which are pulses, only at the onset of an outer-loop command and for a limited time thereafter.

Abstract: An electrostatic probe (27) includes seals (47, 54) adapted to engage sealing surfaces of a borescope access hole provided in the inner and outer walls (24, 25) of the fan duct (22) of a gas turbine engine. The probe includes a center conductor (60), the exposed proximal end of which (31) forms an electrode tip, insulated (35, 36) from an outer metallic wall structure (38, 66), the conductor and wall structure terminating in a coaxial connector 64. A latch means (34, 58) cooperates with a lock pin (76) in one of the fan duct walls.

Abstract: A high pressure vessel (19), having a curved end piece (22) and an access plug (20) threaded into a recessed hole (26) in the end piece and sealed therein by a weld (46) disposed around the periphery of the plug, is provided with an annular lip (28) around the access hole. The flask lip has a sloped surface (34) that cooperates with the lip (38) of a cap (36) that is clamped to the vessel so that the clamping force on the cap is directed by the sloped surface through the weld to precompress the weld, thereby relieving the tensile stresses on the weld which result from pressure inside the vessel acting inside the hemispherical end piece of the vessel.

Abstract: Machine operations are performed by a robot at a plurality of locations on a workpiece based on off-line data. The off-line data is corrected based on two levels of workpiece/robot alignment. First the robot determines the orientation of a fixture to which the workpiece is mounted by "touching-off" on known reference points (touchblocks) on the fixture. Coordinate data for the location of local features on the workpiece is corrected based on the first level of alignment and the positions of the local features are then sensed to provide a coordinate transformation for subsequent application to nominal machine operation location coordinates. The local features may be preassembly rivets and provide for individualized robot response on a workpiece-by-workpiece basis.

Abstract: Centering and stabilizing against rotation of a helicopter swashplate stationary ring are provided by spokes that are attached between the airframe and the stationary ring. When the swashplate tilts for cyclic control, the spokes bend and twist. When the swashplate translates for collective control, the spokes are required to lengthen and skew with respect to the swashplate. An elastomeric bearing having a cylindrical component to allow for skew and a shear pad to allow for lengthening attaches each spoke to the swashplate. The invention eliminates the need for the ball joint, standpipe and scissors associated with traditional swashplate centering techniques.

Abstract: A short-circuited loop of conductor 10, 32, 44, 54 comprises an electromagnetic short-circuit hoop probe which is electrically insulated from a gas stream passing therethrough either by spatial isolation (FIG. 2) or by a coating of electrical insulation (FIGS. 3-5), whereby to reduce noise and DC current levels which could otherwise pollute signals of interest therein. A large hoop version of the non-contact probe permits electrostatic diagnostics of gas streams downstream of flame (FIG. 2).

Abstract: Rotor tilt is permitted by two spherical elastomeric bearings, one above a hub member and one below, that have coincident centers at a tilt point (P) on the rotorshaft axis which is below the rotor plane. Positive rotor thrust is reacted by the upper bearing and negative rotor thrust is reacted by the lower bearing. Techniques for assembling the rotor system, precompressing the bearings, and limiting tilt are also disclosed.

Abstract: An aircraft automatic flight control system (AFCS) includes a pair of fast, limited authority inner loop actuators responsive to signals indicative of aircraft attitude or other flight parameters such as airspeed, the inner loop being recentered by an outer loop actuator responsive to attitude or other aircraft parameter-indicating signals (54,55). Commands applied to the outer loop are applied in a lagged fashion in opposite direction so as to drive the inner loop actuators back toward the center of their authority. The rate of response of the outer loop is adaptive in response to magnitude of inner loop input (101, FIG. 2). A pitch bias command is provided to the inner loop as a function of airspeed multiplied inversely with collective pitch, and as a function of the rate of change of collective stick position, so as to provide a positive static pitch trim gradient and decouple collective pitch from the longitudinal cyclic pitch channel.

Abstract: An improved flight director go-around mode adjusts the collective stick position in a closed loop to increase lift to a desired value. If the engagement airspeed is below the maximum rate of climb airspeed, the airspeed is increased towards the maximum rate of climb airspeed at a moderate rate. When the maximum rate of climb airspeed is attained, or if the engagement airspeed is at least the maximum rate of climb airspeed, and the rate of climb is satisfactory, the airspeed is maintained. If the engagement airspeed is greater than the maximum rate of climb airspeed and the desired rate of climb is not achieved within ten seconds, the airspeed is decreased towards the maximum rate of climb airspeed. Heading or course is automatically maintained when go-around is engaged.

Abstract: A robot "touches off" on the orthagonal touchblock faces of a workpiece holding fixture and the coordinate of the touches along axes nominally normal to the faces provide significant data from which a coordinate transformation indicative of the orientation and location of the touchblocks in the robot frame of reference can be determined. The coordinate transformation is subsequently applied to workpiece coordinates indicative of the location and orientation of the workpiece and/or points thereon.

Abstract: The axial load-carrying ability of an axially-lobed, nearly-spherical elastomeric joint is enhanced by offsetting the elastomer layers so that there is more elastomer to react the load in compression. The improvement is useful in the application of the joint to a gimbal-like rotor system.

Abstract: Squared-ends are provided in an overrunning clutch spring by notching the end of the tube stock; cutting the endmost coil on a lead equal to the cutter diameter (D) so that it varies in thickness from W/2 at its end to 3W/2, where (W) is its desired thickness; and cutting subsequent coils on a lead equal to cutter diameter plus desired coil thickness; and compressing the spring. Notches (70, 72) resulting from the process are advantageously positioned for enhancing the centrifugal balance of the spring.

Abstract: Hub moment and driving torque is provided for a helicopter gimbal rotor by two-part flat springs that are in-plane with the rotor tilt point (P). The inboard end of an outward part of each spring is connected to the rotorshaft and the inboard end of an inward part of the spring is connected to the tiltable hub member. The outboard ends of the two spring parts are journaled together by an eccentric elastomeric joint that allows for spring foreshortening that accompanies rotor tilt.

Abstract: Hub moment for a tilt rotor is provided by U-shaped springs that extend outwardly from the rotorshaft and in-plane with the tilt point (P) and inwardly to the tiltable hub member in the rotor plane, which is above the tilt point (P). Driving torque is supplied to the rotor via a torque disc that has a resilient diaphragm portion attached to the rotorshaft in-plane with the tilt point (P) and a rigid rim attached to the tiltable hub member in the rotor plane. The torque disc comprises the lower half of an aerodynamic fairing which encases the hub.

Abstract: An oscillatory-failure monitor (101) compares a parameter of a plurality of signals (A, B) within a tolerance (TOL) to determine agreement or disparity among the signals. Each discrete miscompare occurrence (i.e., singular disparity following full agreement) is counted by incrementing (27; 54) a counter (OSCCT; CNTR). The counter is decremented (32; 62) whenever the signals compare for a predetermined time interval (29; 47). An oscillatory-failure is declared when the counter increments to a threshold (28, 21; 57, 58, 60). Both digital (FIG. 1) and dedicated hardware (FIG. 4) embodiments are disclosed.

Abstract: A torque limiting altitude hold system for a helicopter engages torque limiting (56, 203) when excessive torque is anticipated (138, 202) as determined by the summation of present torque and torque rate times a reference value (126, 194) exceeds maximum torque with torque limiting engaged, altitude commands are faded out (42, 189) and torque commands are faded in (44, 190) and the collective command integrator is switched from altitude to torque (48, 54; 181, 185), torque limiting is ended in response to negative altitude commands or anticipated desired altitude signal (96, 150, 152; 205, 206); the anticipated desired altitude is determined by subtracting from the altitude error a time function of the altitude rate (84, 90; 193), torque limiting is not allowed to reengage for two seconds after disengaging (144, 204) nor within three seconds after reaching desired altitude during an automatic descent (146, 207), the system provides smooth transitions from altitude control to torque control, without oscillation

Abstract: A maneuver force gradient system causes a helicopter, that otherwise tends to pitch up in a banked turn, to pitch nose-down. A command signal (25) is provided as a function of the roll angle to operate the longitudinal trim actuator (27) which automatically moves the cyclic control (50) resiliently (28) forward to push the nose down. The pilot must consequently pull back on the cyclic control (50) to achieve a desired pitch attitude, thereby establishing a longitudinal positive maneuver-force gradient. The system is operable only when the pilot initiates a roll (33, 38, 50, 51) and the roll angle equals or exceeds 30.degree. (30, 33, 36, 37). Both analog (FIG. 1) and digital (FIG. 2) embodiments are disclosed, and the invention may be practiced in association with an AFCS (101) having the longitudinal trim actuator (27) and resilient linkage (28).

Abstract: A driver circuit for an actuator senses the phase difference between a position request signal to the actuator and a feedback signal from the actuator. A first error signal is indicative of the phase difference when the feedback signal lags the position request signal, and a second error signal is indicative of the phase difference when the feedback signal leads the position request signal. The error signals are amplified in time to provide output drive signals that control four switches which are arranged so that when certain combinations of switches are closed, the actuator will increase or decrease its position, thereby driving the error signal to ZERO. The output drive signals are limited in time so that the loss of an input (position request signal or feedback signal) does not cause an output drive signal hardover and, consequently, does not cause an actuator hardover.