Abstract: Signals which exceed a threshold magnitude (FIGS. 8, 15 and 17) produced by the upstream-most one of a plurality of electrostatic probes (1, 2, 27, 3, FIG. 1) are utilized (FIGS. 14, 16 and 18) the section of the engine most likely to have produced the signal. This provides a diagnostic aid in determining the section of the engine which is most likely to have a component exhibiting abnormal wear, or other engine event.

Abstract: When the number of signals derived from electrostatic probes (1, 2, 3) disposed in the gas stream of an engine reaches a certain value (M, FIG. 8) an additional, N, number of records are acquired (FIGS. 5 and 8) to provide a classification group of records for classification (FIG. 9) into categories indicative of the engine event likely to have caused the excessive number of signals.

Abstract: The wave shapes of signals derived from electrostatic probes (1, 2, 3) disposed in the gas stream of a gas turbine engine are utilized to correlate the signals (FIGS. 57-59; FIGS. 62-80) with causal engine events, and also to correlate some of such signals (FIGS. 60 and 61) to faults in the diagnostic system, utilizing a special routine (FIG. 44) and also utilizing a routine that can discriminate between fault and engine event (FIG. 45).

Abstract: The wave shapes (FIGS. 57-80) of signals derived from electrostatic probes (1, 2, 3) disposed in the gas stream of a gas turbine engine are classified (FIG. 9) into categories relating to engine and other events, and are further correlated or discriminated by other conditions of the engine. Engine acceleration and the sign thereof (FIG. 4) are utilized to correlate and discriminate acceleration and deceleration (FIG. 81). Power lever angle (68, FIG. 1) is utilized (FIG. 4A) to provide an indication of afterburner being lighted, a flameholder probe (27, FIG. 1) becomes biased (82, 83, 85, FIG. 1) to sense when the afterburner is lit, for correlation with afterburner nozzle liner erosion (FIG. 69, FIG. 81). Chopping the fuel to the afterburner is correlated (FIG. 4A, FIG. 81) with signals indicative of the character of the afterburner chop (FIGS. 77-79).

Abstract: Signals provided by probes (1, 2, 3) disposed in the gas stream of a gas turbine engine are classified in accordance with discriminators (Tables 2-9) utilized in various routines (FIGS. 25-56), including some discriminators which are not currently used, but may allow further discrimination of additional signals, when recognized. The categories of waveshapes (FIGS. 57-80) which are classified includes categories (FIGS. 70 and 71) which are readily distinguishable but have not as yet been correlated to engine events, thereby providing a data history base in the event they become correlated and aiding in the discrimination of these signals from other, correlated signals.

Abstract: The waveforms (FIGS. 57-80) of signals derived from electrostatic probes (1, 2, 3) are classified (FIG. 9) in terms of width (FIG. 14), presence or absence of following peaks (FIG. 15), presence of multiple peaks (FIG. 21), frequency content (FIG. 22), and noise content of a portion thereof (FIG. 23) as well as polarity utilizing routines related to the various probes (FIGS. 10-12).

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 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 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: 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: 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: An ion/electrostatic probe for an afterburning gas turbine jet engine comprises an afterburner flameholder (24) electrically 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). An electrical connection (54) may be brought through the engine case. The flameholder (24) may be insulated (70) from an attached igniter.