Abstract: Records of signals (FIG. 6) derived from probes (1, 2, 3) in a gas turbine engine are captured (FIG. 8) so as to provide digital signal records indicative of waveshapes (FIGS. 57-80) which can be correlated to identify the causal engine event, including history samples which occur before a record-starting threshold crossing (FIGS. 6 and 8).

Abstract: The quality factors (Q) indicative of the likelihood of the waveshape (FIGS. 57-80) of signals produced by electrostatic probes (1, 2, 3, FIG. 1) disposed in the gas stream of a gas turbine engine are combined for certain categories of sets of the probes which will simultaneously sense the same engine event (FIGS. 9, 12a, 12b). The likelihood of signals correlating to particular engine event as a function of positive and negative threshold crossings (FIG. 83) is correlated as between pairs of probes, both digitally (FIGS. 85 and 86) and by analog hardware (FIGS. 87 and 88).

Abstract: A plurality of computer programs (FIGS. 25-56) utilize variable discriminators (Tables 2-9) to classify signals derived from electrostatic probes (1, 2, 3) disposed in the gas stream of a gas turbine engine in accordance with characteristics of the wave shapes (FIGS. 57-80) thereof into categories correlated with causal engine events. The discriminators allow use of programs for more than one category, and even for more than one of the probes, and allow varying the discrimination as necessary to tailor the system to different engines and to accommodate newly-discovered signals.

Abstract: A light-off detector for an afterburner of a gas turbine jet engine comprises an afterburner flameholder (24) electrically insulated (70) from an attached igniter (38) and insulated from other engine parts by means of non-electrically-conductive support rods (30, 45) or by means of electrically conductive rods (30) insulated (50, 52) from the engine case (12) and insulated (70) from an attached igniter (38). An electrical connection (54) brought through the engine case connects the flameholder to a resistor (57) through a bias battery (56). Ionic current flow resulting from flame causes a Schmidt trigger (60) to provide a light-off signal, A/B LIT (62).

Abstract: The waveforms (FIGS. 57-80) of signals produced by electrostatic probes (1, 2, 3, FIG. 1) are established in records (FIGS. 5 and 6) about 80 milliseconds long; if successive records are sensed contiguously (into N, without any break in-between) the first record of a string is provided with a flag indicative thereof (FIG. 8a) and the second and last records in the contiguous string are stored in special buffers (FIGS. 8b and 8c). All of the other records in-between are thrown away. The string of contiguous records are treated specially: the three records have their characteristics combined in identifying acceleration/deceleration (FIG. 80) and peeled off abraidable seals (FIGS. 62 , FIG. 45c); only the first record is utilized to identify the start of an afterburner chop (FIGS. 77 and 54a) and only the last record is utilized to identify the end of a chop (FIGS. 78, 79 and 54a).

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: The categories assigned to waveshapes (FIGS. 57-80) of signals derived from electrostatic probes (1, 2, 3, FIG. 1) disposed in the gas stream of a gas turbine engine are combined over a classification record group of about 20 or 30 records (FIG. 81). The possible causation of signals identified by positive and negative threshold crossings is statistically combined by summation across a group of records (FIGS. 85 and 86). The quality values indicative of the likelihood of a waveform correlating to a catagory of engine event are combined across records, category by category, before decisions are made (FIGS. 87 and 88).

Abstract: Diagnostic apparatus which analyzes the waveforms (FIGS. 57-80) of signals provided by electrostatic probes (1, 2, 3) is declared to have a system fault in the event that signals appear on two out of three probes simultaneously. In one embodiment (FIG. 14) the sample number of the digital value which crosses threshold is compared between two adjacent probes. In another embodiment (FIGS. 15-18) default is declared if the signals appear in an approximate time slot (T=1, T=2, T=3).

Abstract: Engine distress is indicated by ten times a normal count for a healthy engine, of signals derived from electrostatic probes (1, 2, 3) disposed in the gas stream of a gas turbine engine, within a variable time interval which is established (FIG. 7) as the integral of R.M.S. noise on one of the probes (3), thereby providing a variable time intervale indicative of the rate at which the engine is working.

Abstract: A radio frequency, plasma-enhanced, vapor deposition reactor has apparatus (3-7) for providing a flow of silane in an inert gas carrier, a deposition chamber (20) formed between a pair of flow restrictors (18, 27) and an RF coil (22) for providing inductive coupling of RF power (24) for plasma excitation, disposed downstream of a fixture (8) for holding the substrate upon which amorphous silicon is to be disposed. A baffle (30) provides diversion of the gas flow toward a gravity trap chamber (31), thereby collecting some particulates and prolonging the cycle time before plugging of the vacuum pump (7) can occur.

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: Orientation and/or position of a first body, such as the inboard end 42 of a helicopter blade 21, with respect to a second body, such as a rotor hub arm 36, is sensed by determining the position of the images 93, 95-97, of light from sources 80, 81 passed through slits 89, 90 on detector arrays 91, 92. Signal processing means (FIG. 5, FIG. 11) provide signals indicative of such image positions, which can be used to determine, from simple trigonometry, the orientation and/or position of the first body.

Abstract: Equipment which analyzes the wave shapes (FIGS. 57-80) of signals derived from electrostatic probes (1, 2, 3, 27) disposed in the gas stream of a gas turbine engine operates differently in dependence upon different engine conditions. When surge is detected (1, 90-93, FIG. 1) the signal records are stored away specially (FIGS. 8 and 8b) and classified specially (FIGS. 8c, 9, 9a and 9b) when a request therefor (93-95, FIG. 1) is made. Acceleration signals (FIG. 80) are looked for (FIG. 12) only when there is significant engine acceleration (FIG. 4). Only nozzle liner erosion (FIG. 69) is looked for (FIG. 12) when the afterburner is lit (89, FIG. 1), in one probe (3, FIG. 1) while at the same time afterburner rumble (FIG. 80) is looked for in a flameholder probe (27, FIG. 1) when the afterburner is lit. When the afterburner fuel is being chopped (FIG. 4a) only afterburner chop signals (FIGS. 77-79) are looked for (FIG. 12). When the engine speed is below idle, no records of signals are made (FIG. 8).

Abstract: A voltage threshold utilized (FIG. 8) to recognize signals of interest provided by probes (1, 2, 3) of a gas turbine engine for analysis of waveshapes (FIGS. 57-80) indicative of the engine event causing the signals, includes an acceleration component (FIGS. 3 and 4), whereby to avoid collecting records of signals related only to normal acceleration and deceleration, without masking abnormal signals which occur with acceleration or deceleration.

Abstract: The classification of signals derived from electrostatic probes (1, 2, 3) disposed in the gas stream of a gas turbine engine in accordance with characteristics (FIGS. 14-23) of wave shapes (FIGS. 57-80) of the signals, employs degradation factors (FIG. 25-FIG. 56) which indicate discrepancy between the signal being classified and exemplary signals (FIGS. 57-FIG. 80) corresponding to a plurality of categories. The degradation factor may be fixed (FIG. 34C) or variable (FIG. 24), based on the deviation of the signal characteristic from the corresponding characteristic of the category. The degradation factors are normalized in each of the routines (e.g. 76, FIG. 34D; 19, FIG. 44; 24, FIG. 45B; etc.). Categories are selected in accordance with the least degradation (FIG. 13).

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 ramp/roller freewheeling clutch (FIG. 2) has a driving member with ramps 19 adapted to wedge rollers 21 against the driving surface 28 of a driven member 29 when the driving member 13 is rotated in the driving direction. The rollers are positioned adjacent the ramps by a primary cage 22, which can be rotated with respect to the driving member 13 so as to force the rollers out of engagement with the ramps 19 and into recesses 20. A secondary cage 39 disposed in fixed relation with the driving member 13 has cam surfaces 37 such that rotation of the primary cage to disengage the rollers forces them up the ramps and locks them in place with the recesses 20 of the driving member 13, thereby to avoid contact with the driven member 29 when the clutch is disengaged.

Abstract: A pair of biased electrostatic probes (27a, 28a) disposed directly within respective dilution air inlets (32) of the combustor (20) in a gas turbine engine (10) provide an indication (62, 68) of surge/stall in response to the outflow of ionic combustion products from the burner can, and block (120, 122, 128) signals (129), indicative of charged engine debris, from reaching wear monitor signal processing apparatus (134).

Abstract: A pair of biased electrostatic probes (27, 28) disposed adjacent respective inlets (32) of the combustor (20) in a gas turbine engine (10) provide an indication of surge (82) if signals, resulting from the outflow of ionic combustion products from the burner can, appear thereon simultaneously, or indications of stall stagnation (97) if signals appear on the two probes out-of-phase with one another, or if either probe senses repetitive signals thereon.

Abstract: A capacitive pressure transducer has a pedestal 25 formed in a silicon layer 14 surrounded by a moat 26 extending through the silicon layer, with borosilicate glass 17, 22 at the edges of the silicon layer forming the walls of the pressure chamber, with a wafer 28 of silicon bonded thereto. The pedestal 25 is joined to the walls of the vacuum chamber by borosilicate glass 16, whereby it is wholly, electrically isolated therefrom. A method of forming a capacitive pressure transducer utilizing the variable etch rates of aluminum, glass and silicon, together with field assisted bonding, is also disclosed.