Patent Publication Number: US-2023152297-A1

Title: Multi-zone magnetic chip detector

Description:
TECHNICAL FIELD 
     The disclosure relates generally to health monitoring of engines, and more particularly to detecting chips in fluids of aircraft engines. 
     BACKGROUND 
     A magnetic chip detector is commonly found in a lubrication system of an aircraft engine to detect the presence of metallic chips in the lubricating fluid. The chip detector is immersed in the lubricating fluid so as to be exposed to the chips carried by the lubricating fluid. The presence of chips in the lubricating fluid may indicate a developing and/or impending mechanical problem exhibiting excessive wear of one or more components of the aircraft engine interacting with the lubrication system. When chips are collected by the chip detector, a gap between two electric terminals is eventually bridged so as to provide electric continuity and cause an indication (e.g., alarm) to be provided to an operator of the aircraft so that an appropriate action can be taken if necessary. The presence of metal chips in engine fluid can be indicative of a deteriorating engine health condition and it is desirable to improve chip detection in aircraft engines. 
     SUMMARY 
     In one aspect, the disclosure describes a multi-zone magnetic chip detector for detecting chips in lubricating fluid of an engine. The multi-zone magnetic chip detector comprises:
     a first magnetic chip capture zone including a first electrically conductive terminal spaced apart from a second electrically conductive terminal to define a first chip-receiving gap therebetween;   a second magnetic chip capture zone including a third electrically conductive terminal and either the second electrically conductive terminal or a fourth electrically conductive terminal to define a second chip-receiving gap therebetween; and   an electric circuit including both the first chip-receiving gap and the second chip-receiving gap, the electric circuit providing an output indicative of a chip detection by one or both of the first magnetic chip capture zone and the second magnetic capture zone.   

     In another aspect, the disclosure describes an aircraft engine comprising:
     a lubrication system for distributing lubricating fluid to one or more lubrication loads; and   a multi-zone magnetic chip detector immersed in the lubricating fluid, the multi-zone magnetic chip detector including:   a first magnetic chip capture zone including a first electrically conductive terminal spaced apart from a second electrically conductive terminal to define a first chip-receiving gap therebetween;   a second magnetic chip capture zone including a third electrically conductive terminal and either the second electrically conductive terminal or a fourth electrically conductive terminal to define a second chip-receiving gap therebetween; and   an electric circuit including both the first chip-receiving gap and the second chip-receiving gap, the electric circuit providing an output indicative of a chip detection by one or both of the first magnetic chip capture zone and the second magnetic capture zone.   

     In a further aspect, the disclosure describes a method of detecting metallic chips in engine fluid of an engine using a multi-zone magnetic chip detector including: a first magnetic chip capture zone defined between a first electrically conductive terminal and a second electrically conductive terminal; and a second magnetic chip capture zone defined between a third electrically conductive terminal and either the second electrically conductive terminal or a fourth electrically conductive terminal. The method comprises:
     when the multi-zone magnetic chip detector is immersed in engine fluid, receiving one or more metallic chips in one or both of the first magnetic chip capture zone and the second magnetic chip capture zone; and   using an electric circuit including both the first magnetic chip capture zone and the second magnetic chip capture zone, generating an output indicative of a chip detection in the one or both of the first magnetic chip capture zone and the second magnetic capture zone.   

     Further details of these and other aspects of the subject matter of this application will be apparent from the detailed description included below and the drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the accompanying drawings, in which: 
         FIG.  1    is a schematic axial cross-section view of a turbofan gas turbine engine including a multi-zone magnetic chip detector as described herein; 
         FIG.  2 A  is an exemplary schematic representation of the multi-zone magnetic chip detector of the engine of  FIG.  1   ; 
         FIG.  2 B  is a schematic representation of an electric circuit associated with the multi-zone magnetic chip detector of  FIG.  2 A ; 
         FIG.  3 A  is a schematic axial cross-section view of another exemplary multi-zone magnetic chip detector of the engine of  FIG.  1   ; 
         FIG.  3 B  is a schematic representation of an electric circuit associated with the multi-zone magnetic chip detector of  FIG.  3 A ; 
         FIG.  4 A  is a schematic axial cross-section view of another exemplary multi-zone magnetic chip detector of the engine of  FIG.  1   ; 
         FIG.  4 B  is a schematic representation of an electric circuit associated with the multi-zone magnetic chip detector of  FIG.  4 A ; 
         FIG.  5 A  is a schematic axial cross-section view of another exemplary multi-zone magnetic chip detector of the engine of  FIG.  1   ; 
         FIG.  5 B  is a schematic representation of an electric circuit associated with the multi-zone magnetic chip detector of  FIG.  5 A ; 
         FIG.  6 A  is a schematic representation of another exemplary multi-zone magnetic chip detector of the engine of  FIG.  1   ; 
         FIG.  6 B  is a schematic representation of an electric circuit associated with the multi-zone magnetic chip detector of  FIG.  6 A ; 
         FIG.  7 A  is a schematic side view of another exemplary multi-zone magnetic chip detector of the engine of  FIG.  1   ; 
         FIG.  7 B  is a schematic axial end-on view of the multi-zone magnetic chip detector of  FIG.  7 A ; 
         FIG.  7 C  is a schematic representation of an electric circuit associated with the multi-zone magnetic chip detector of  FIG.  7 A ; 
         FIG.  8 A  is a schematic axial end-on view of another exemplary multi-zone magnetic chip detector of the engine of  FIG.  1   ; 
         FIG.  8 B  is a schematic representation of an electric circuit associated with the multi-zone magnetic chip detector of  FIG.  8 A ; 
         FIG.  9 A  is a schematic axial end-on view of another exemplary multi-zone magnetic chip detector of the engine of  FIG.  1   ; 
         FIG.  9 B  is a schematic representation of an electric circuit associated with the multi-zone magnetic chip detector of  FIG.  9 A ; and 
         FIG.  10    is a flow diagram of a method of detecting metallic chips in engine fluid of an engine. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to systems and methods for detecting metallic chips in engine (e.g., lubricating, cooling) fluids. In some embodiments, the systems and methods described herein may help assess a condition of an engine by using one or more multi-zone magnetic chip detectors to reduce the probability of generating nuisance chip detections and associated annunciations or alarms. For example, the systems and methods described herein may reduce the probability of nuisance chip detections associated with the accumulation of acceptable smaller/fine magnetic debris/particles, commonly referred to as “fuzz” at a magnetic chip detector immersed in lubricating fluid. Some fuzz can be generated during the normal operation of an aircraft engine and may not necessarily be indicative of a developing or impending mechanical problem. For example, such fuzz can normally be generated during the initial period (e.g., a few hundred hours) of operation of an aircraft engine following initial entry into service or following extensive maintenance such as an overhaul. This initial period is also known as the engine’s “break-in” period. Chip detections caused by the accumulation of the acceptable and relatively harmless fuzz, during the break-in period for example, oppose the design intent of the magnetic chip detector and are undesirable since they do not provide an accurate indication of a possible developing or impending problem. 
     Metallic chips that are carried by the lubricating fluid may be from metallic engine parts such as gear teeth or bearings for example. Some disc type magnetic chip detectors use one disk-shaped magnet placed in a non-conductive and non-magnetically permeable isolator with two conductive steel end caps which, in combination, create a single chip capture zone. When a metallic chip of a sufficient size is attracted to the capture zone by the magnet, the metallic chip bridges (e.g., short-circuits) the gap between the steel end caps to complete an electric circuit that includes the gap. A controller or other annunciation circuitry connected to the magnetic chip detector may detect this change in resistance caused by the metallic chip and indicate to a pilot of the aircraft via a cockpit indication the presence of one or more magnetic chips having been detected by the magnetic chip detector. 
     Magnetic chip detectors may use rare earth magnets that provide a relatively high capture efficiency. This can result in a high sensitivity of a magnetic chip detector, which may increase the probability of nuisance detections. For example, a magnetic chip detector with a single capture zone may function as an on/off switch and may trigger an annunciation based on a relatively harmless single metallic filament having been captured in the single capture zone. Once the chip detection is triggered by one or more chips, the pilot may be required to abort the mission mid-flight, return to the ground (e.g., base) as soon as possible, and remove (or have maintenance personnel remove) the magnetic chip detector for visual inspection. The visual inspection verifies whether significant debris has been collected by the magnetic chip detector and hence whether maintenance is required before the aircraft can be dispatched again. If the detection is triggered by an insignificant metallic filament or other insignificant metallic particle(s), such detection can be a nuisance to the pilot and/or aircraft operator. 
     In some embodiments, the magnetic chip detectors described herein may reduce the probability of single chip detections and other nuisance detection events. In some embodiments, the magnetic chip detectors described herein may reduce the probability of fuzz-induced nuisance detections. In some embodiments, the magnetic chip detectors described herein may provide an indication of a degree of contamination that allows a system to discriminate between harmless/tolerable contamination and gross contamination indicative of a developing and/or impending mechanical problem. In some embodiments, the magnetic chip detectors described herein may provide an ability to discriminate between small or large chips being detected. 
     In some embodiments, the magnetic chip detectors described herein may provide a more informative indication via a single interface, which may facilitate installation (e.g., retrofitting) into existing engines and associated controllers by not requiring an increased number of inputs to the controller or aircraft. In some embodiments, the magnetic chip detectors described herein may permit the monitoring of different regions of a fluid (e.g., lubrication, cooling) system of an aircraft engine via the single interface. 
     Aspects of various embodiments are described through reference to the drawings. Even though the description below is provided in relation to lubricating fluid, it is understood that some embodiments of the magnetic chip detectors, systems and methods described herein may also be used on other types of engine fluids such as engine coolant for example. 
     The term “connected” may include both direct connection (in which two elements that are connected to each other contact each other) and indirect connection (in which at least one additional element is located between the two elements). 
     The term “substantially” as used herein may be applied to modify any quantitative representation which could permissibly vary without resulting in a change in the basic function to which it is related. 
       FIG.  1    is a schematic axial cross-section view of aircraft engine  10  (referred hereinafter as “engine 10”) of a turbofan gas turbine engine preferably provided for use in subsonic flight, generally comprising, in serial flow communication, fan  12  through which ambient air is propelled, multistage compressor  14  for pressurizing the air, combustor  16  in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and turbine section  18  for extracting energy from the combustion gases. Engine  10  may be mounted to an aircraft and used to propel such aircraft. Even though  FIG.  1    shows engine  10  being of the turbofan type, it is understood that aspects of the present disclosure are also applicable to other (e.g., turboshaft, turboprop, internal combustion) types of aircraft engines. 
     Engine  10  may include lubrication (and/or other fluid) system  20  shown schematically and partially in  FIG.  1   . Lubrication system  20  may serve to lubricate, cool and clean one or more lubrication loads  22  such as bearings and gears of engine  10 . Lubrication system  20  may include tank  24  and other components such as one or more pumps, one or more valves, and one or more filters. Tank  24  may be a reservoir containing a supply of lubricating fluid  26  such as oil for use by lubrication system  20 . Lubrication system  20  may include one or more magnetic chip detectors (MCDs)  28 . For example, lubrication system  20  may include a single MCD  28  or a plurality of MCDs  28  disposed at different locations within lubrication system  20 . MCD  28  may be at least partially immersed in lubricating fluid  26  during operation. For example, MCD  28  be disposed inside tank  24 , inside a gearbox, or in a scavenge line. 
     MCD  28  may be part of chip detection system  30  (referred hereinafter as “system 30”) and may be associated with and/or may be part of engine  10 . System  30  may include controller  32  or other detection circuitry operatively connected to MCD  28 . In various embodiments, controller  32  may include or form part of a Full Authority Digital Engine Control (FADEC) which may, for example, include one or more digital computer(s) or other data processors, sometimes referred to as electronic engine controller(s) (EEC) and related accessories that control at least some aspects of performance of engine  10 . Controller  32  may, for example, be configured to make decisions regarding the control of engine  10 . Controller  32  may include one or more data processors and non-transitory machine-readable memory. Controller  32  may receive input(s) from MCD  28 , perform one or more procedures or steps defined by instructions stored in the memory to generate output(s) such as triggering a suitable annunciation to a pilot of the aircraft for example. Various aspects of the present disclosure may be embodied as systems, devices, methods and/or computer program products. 
       FIG.  2 A  is an exemplary schematic representation of MCD  28  shown a as part of chip detection system  30  of engine  10 , and  FIG.  2 B  is a schematic representation of electric circuit  34  associated with MCD  28 . MCD  28  may include two or more magnetic chip capture zones  36 A,  36 B to thereby reduce the probability of single-chip and/or fuzz-induced nuisance detections. MCD  28  may include first capture zone  36 A and second capture zone  36 B. First capture zone  36 A may include first electrically conductive terminal  38 A (referred hereinafter as “first MCD terminal  38 A”) spaced apart from second electrically conductive terminal  38 B (referred hereinafter as “second MCD terminal  38 B”) to define first chip-receiving gap G 1  (referred hereinafter as “first gap G 1 ”) therebetween. Second capture zone  36 B may include third electrically conductive terminal  38 C (referred hereinafter as “third MCD terminal  38 C”) spaced apart from second MCD terminal  38 B to define second chip-receiving gap G 2  (referred hereinafter as “second gap G 2 ”) therebetween. The size(s) of first gap G 1  and of second gap G 2  may be selected based on the chip sizes of interest. In some embodiments, the size(s) of first gap G 1  and second gap G 2  may be between 1/64″ (0.4 mm) and ⅛″ (3.2 mm) for example. 
     MCD  28  may be an axial disk-type magnetic chip detector. However, aspects of the present disclosure are also applicable to other types of magnetic chip detectors such as prong-type magnetic chip detectors as explained further below. For example, MCD  28  may include first magnet  40 A disposed and retained between first MCD terminal  38 A and second MCD terminal  38 B. MCD  28  may include second magnet  40 B disposed and retained between third MCD terminal  38 C and second MCD terminal  40 C. Suitable electrically non-conductive and non-magnetically permeable isolators (not shown) may be disposed between first magnet  40 A and the respective first MCD terminal  38 A and second MCD terminal  38 B. First MCD terminal  38 A and second MCD terminal  38 B may be metallic (e.g., steel) end caps between which first magnet  40 A is retained. Similarly, second magnet  40 B may be disposed and retained between second MCD terminal  38 B and third MCD terminal  38 C. Suitable electrically non-conductive and non-magnetically permeable isolators (not shown) may be disposed between second magnet  40 B and the respective second MCD terminal  38 B and third MCD terminal  38 C. Second MCD terminal  38 B and third MCD terminal  38 C may be metallic (e.g., steel) end caps between which second magnet  40 B is retained. In some embodiments, second MCD terminal  38 B may be common to both first capture zone  36 A and second capture zone  36 B and may be a double-sided end cap that is sandwiched between first magnet  40 A and second magnet  40 B. 
     In some embodiments, first magnet  40 A, second magnet  40 B, first MCD terminal  38 A, second MCD terminal  38 B, and third MCD terminal  38 C may be disk-shaped and may be disposed in a coaxial manner along axis A. In some embodiments, first magnet  40 A, second magnet  40 B, first MCD terminal  38 A, second MCD terminal  38 B, and third MCD terminal  38 C may be integrated/assembled into a single metallic chip detector that may be disposed in a single region of lubrication system  20  (shown in  FIG.  1   ) of engine  10 . For example, both first capture zone  36 A and second capture zone  36 B may be in fluid communication with each other during use when MCD  28  is immersed in lubricating fluid  26 . MCD  28  could also be configured to define one or more additional capture zones by adding additional magnet(s) and end cap(s). 
       FIG.  2 A  also illustrates a situation where: first metallic chip  42 A has been captured by first capture zone  36 A and electrically bridges first gap G 1 ; and second metallic chip  42 B has been captured by second capture zone  36 B and electrically bridges second gap G 2 . 
     Electric circuit  34  may include first output terminal  44 A and second output terminal  44 B together defining a single interface between MCD  28  and controller  32 . As shown in  FIG.  2 B , electric circuit  34  may include both first gap G 1  and second gap G 2 . Electric resistance value RV across first output terminal  44 A and second output terminal  44 B may serve as a single output communicated to controller  32  as an indication of whether or not a chip detection has occurred at MCD  28  and annunciation  46  is warranted. In various embodiments, first gap G 1  and second gap G 2  may be disposed in series as shown in  FIG.  2 B , or may be disposed in parallel in electric circuit  34 . In some embodiments, first gap G 1  and second gap G 2  may be of substantially the same size. However, in other embodiments, first gap G 1  and second gap G 2  may be of different sizes depending on the sizes of first chip  42 A and of second chip  42 B that are of interest. 
     During operation of MCD  28  shown in  FIGS.  2 A and  2 B  when MCD  28  is immersed in lubricating fluid  26 , resistance value RV may be high (e.g., open circuit) when neither or only one of first gap G 1  and second gap G 2  is electrically bridged by first chip  42 A or second chip  42 B. On the other hand, resistance value RV may be low (e.g., short circuit, near 0 ohm) when first gap G 1  is electrically bridged by first chip  42 A, and second gap G 2  is electrically bridged by second chip  42 B. Accordingly, the chip detection at MCD  28  may be detected by way of a change in resistance value RV which may be determined at controller  32 . Upon detection of the change in resistance value RV that is indicative of a legitimate chip detection, controller  32  may initiate annunciation  46  which may alert a pilot of the aircraft and/or another interested party. Annunciation  46  may be visual (e.g., indicator light or message) or aural (e.g., tone or spoken message). It is understood that in some embodiments, controller  32  may be replaced by suitable analog circuitry that causes annunciation  46  upon first MCD terminal  38 A and third MCD terminal  38 C becoming electrically bridged by the presence of both first chip  42 A and second chip  42 B. 
       FIG.  3 A  is a schematic axial cross-section view of another exemplary multi-zone MCD  128  which may be part of chip detection system  30  of engine  10 , and  FIG.  3 B  is a schematic representation of electric circuit  134  associated with MCD  128 . MCD  128  may have elements in common with MCD  28  described above and like elements are identified using like reference numerals. In contrast with MCD  28 , MCD  128  may include shunt resistor R 1  disposed in parallel with both first gap G 1  and second gap G 2 . MCD  128  may also include first capture zone  36 A, second capture zone  36 B, and optionally one or more additional capture zones to thereby reduce the probability of single-chip and/or fuzz-induced nuisance detections. First capture zone  36 A may include first MCD terminal  38 A spaced apart from second MCD terminal  38 B to define first gap G 1  therebetween. Second capture zone  36 B may include third MCD terminal  38 C spaced apart from second MCD terminal  38 B to define second gap G 2  therebetween. MCD  128  may be an axial disk-type magnetic chip detector. In some embodiments, first gap G 1  and second gap G 2  may be of substantially the same size. However, in other embodiments, first gap G 1  and second gap G 2  may be of different sizes depending on the size of first chip  42 A and of second chip  42 B that are of interest. In various embodiments, first gap G 1  and second gap G 2  may be disposed in series as shown in  FIG.  3 B , or may be disposed in parallel in electric circuit  134 . 
     During operation of MCD  128  shown in  FIGS.  3 A and  3 B  when MCD  128  is immersed in lubricating fluid  26 , resistance value RV may the value of R 1  (e.g., 2k Ohm) when neither or only one of first gap G 1  and second gap G 2  is electrically bridged by first chip  42 A or second chip  42 B (shown in  FIG.  2 A ). On the other hand, resistance value RV may be low (e.g., short circuit, near 0 ohm) when first gap G 1  is electrically bridged by first chip  42 A, and second gap G 2  is electrically bridged by second chip  42 B. Accordingly, the chip detection at MCD  128  may be detected by way of a change in resistance value RV which may be determined at controller  32 . Upon detection of the change in resistance value RV that is indicative of a legitimate chip detection, controller  32  may initiate annunciation  46  which may alert a pilot of the aircraft and/or another interested party. 
       FIG.  4 A  is a schematic axial cross-section view of another exemplary multi-zone MCD  228  which may be part of chip detection system  30  of engine  10 , and  FIG.  4 B  is a schematic representation of electric circuit  234  associated with MCD  228 . MCD  228  may have elements in common with other MCDs described above and like elements are identified using like reference numerals. In contrast with MCD  128 , MCD  228  may include shunt resistor R 1  disposed in parallel with first gap G 1 , and shunt resistor R 2  disposed in parallel with second gap G 2 . Resistor R 1  and resistor R 2  may have different or substantially identical resistance values. Resistor R 1  and resistor R 2  may be disposed in series with each other in electric circuit  234 . 
     MCD  228  may also include first capture zone  36 A, second capture zone  36 B, and optionally one or more additional capture zones. First capture zone  36 A may include first MCD terminal  38 A spaced apart from second MCD terminal  38 B to define first gap G 1  therebetween. Second capture zone  36 B may include third MCD terminal  38 C spaced apart from second MCD terminal  38 B to define second gap G 2  therebetween. MCD  228  may be an axial disk-type magnetic chip detector. In some embodiments, first gap G 1  and second gap G 2  may be of substantially the same size. However, as shown in  FIGS.  4 A and  4 B , first gap G 1  may be larger than second gap G 2  so that G 1 &gt; G 2 . First gap G 1  and second gap G 2  may be sized based on the size of first chip  42 A and second chip  42 B that are of interest. In various embodiments, first gap G 1  and second gap G 2  may be disposed in series as shown in  FIG.  4 B , or may be disposed in parallel in electric circuit  234 . 
     During operation, the use of MCD  228  when MCD  228  is immersed in lubricating fluid  26  may allow to discriminate whether one or both of first capture zone  36 A and second capture zone  36 B is/are contaminated by metallic chips. For example, if resistor R 1  and resistor R 2  each have a resistance value of 2k Ohms and none of first gap G 1  and second gap G 2  are electrically bridged by first chip  42 A or second chip  42 B (shown in  FIG.  2 A ), resistance value RV between first output terminal  44 A and second output terminal  44 B will be about 4k Ohms. However, if one of first gap G 1  and second gap G 2  is electrically bridged by first chip  42 A or second chip  42 B, resistance value RV between first output terminal  44 A and second output terminal  44 B will be about 2k Ohms. If both first gap G 1  and second gap G 2  are electrically bridged by first chip  42 A and second chip  42 B respectively, resistance value RV between first output terminal  44 A and second output terminal  44 B will be about 0 Ohms (i.e., short circuit). 
     The configuration of MCD  228  may also be used to identify which one(s) of first capture zone  36 A and second capture zone  36 B is/are contaminated by metallic chips by using different resistance values of first resistor R 1  and second resistor R 2 . This may be particularly useful if first gap G 1  and second gap G 2  are of different sizes and/or first capture zone  36 A and second capture zone  36 B are in different locations of lubrication system  20 . For example, if first resistor R 1  has a resistance value of 4k Ohm and second resistor R 2  has a resistance value of 2k Ohm, and none of first gap G 1  and second gap G 2  are electrically bridged by first chip  42 A or by second chip  42 B (shown in  FIG.  2 A ), resistance value RV between first output terminal  44 A and second output terminal  44 B will be about 6k Ohms. However, if first gap G 1  is electrically bridged by first chip  42 A and second gap G 2  is not electrically bridged by second chip  42 B, resistance value RV between first output terminal  44 A and second output terminal  44 B will be about 2k Ohms. If first gap G 1  is not electrically bridged by first chip  42 A and second gap G 2  is electrically bridged by second chip  42 B, resistance value RV between first output terminal  44 A and second output terminal  44 B will be about 4k Ohms. If both first gap G 1  and second gap G 2  are electrically bridged by first chip  42 A and second chip  42 B respectively, resistance value RV between first output terminal  44 A and second output terminal  44 B will be about 0 Ohms (i.e., short circuit). 
     Controller  32  can then use the single resistance value RV to assess whether a small chip has been detected, a large chip has been detected, or if both first gap G 1  and second gap G 2  are electrically bridged by first chip  42 A and second chip  42 B respectively. This approach of discriminating between which capture zone(s) is causing the detection may be extended to MCDs of three or more detection zones. 
     In various embodiments disclosed herein, the single resistance value RV may provide a single and informative input to controller  32  and allow controller  32  to determine the state of MCD  228 . For example, resistance value RV may be the sole piece of information transferred from MCD  228  to controller  32 . Controller  32  may then use resistance value RV with one or more rules available to controller  32  to determine whether annunciation  46  is warranted. The rules may include actions associated with predetermined values for resistance value RV or predetermined ranges of values for resistance value RV. The rules and the multiple capture zones may be selected to provide a sensitivity suitable for providing legitimate chip detections and annunciations  46 . 
     The use of the single input may also facilitate integration of MCD  228  and other magnetic chip detectors disclosed herein with new or existing aircraft engines. For example, the retrofitting of MCD  228  into engine  10  may require little to no hardware modifications, but may require software modifications to apply rules and carry out desired actions based on resistance value RV. 
       FIG.  5 A  is a schematic axial cross-section view of another exemplary multi-zone MCD  328  which may be part of chip detection system  30  of engine  10 , and  FIG.  5 B  is a schematic representation of electric circuit  334  associated with MCD  328 . MCD  328  may have elements in common with other MCDs described above and like elements are identified using like reference numerals. First capture zone  36 A of MCD  328  may include first MCD terminal  38 A spaced apart from second MCD terminal  38 B to define first gap G 1  therebetween. Second capture zone  36 B may include third MCD terminal  38 C spaced apart from second MCD terminal  38 B to define second gap G 2  therebetween. In various embodiments, first gap G 1  and second gap G 2  may be disposed in parallel as shown in  FIGS.  5 A,  5 B , or may be disposed in series in electric circuit  334 . MCD  328  may be an axial disk-type magnetic chip detector. In some embodiments, first gap G 1  and second gap G 2  may be of substantially the same size. However, in other embodiments, first gap G 1  and second gap G 2  may be of different sizes depending on the size(s) of first chip  42 A and of second chip  42 B that are of interest. MCD  328  may include three or more capture zones defining respective gaps disposed in parallel or in series. 
     In contrast with MCD  228 , MCD  328  may include first shunt resistor R 1  disposed in series with first gap G 1 , second shunt resistor R 2  disposed in series with second gap G 2 , and third shunt resistor R 3  disposed in parallel with both first gap G 1  and second gap G 2 . 
     During operation of MCD  328  when MCD  328  is immersed in lubricating fluid  26 , the resultant resistance value RV may be indicative of which one(s) of first gap G 1  and second gap G 2  is/are electrically bridged by first chip  42 A and/or second chip  42 B based on which combination of first resistor R 1 , second resistor R 2 , third resistor R 3 , electrically bridged first gap G 1 , and electrically bridged second gap G 2  are reflected in resistance value RV. Accordingly, the chip detection at MCD  328  may be detected by way of a change in resistance value RV which may be determined at controller  32 . Upon detection of the change in resistance value RV that is indicative of a legitimate chip detection, controller  32  may initiate annunciation  46  which may alert a pilot of the aircraft and/or another interested party. 
     In various embodiments first capture zone  36 A and second capture zone  36 B may be in fluid communication with each other during operation. Alternatively, first capture zone  36 A and second capture zone  36 B may be fluidly sealed from each other and disposed in different fluid streams or in different fluid systems of engine  10 . 
       FIG.  6 A  is a schematic representation of another exemplary multi-zone MCD  428  of which may be part of chip detection system  30  of engine  10 , and  FIG.  6 B  is a schematic representation of electric circuit  434  associated with MCD  428 . MCD  428  may have elements in common with other MCDs described above and like elements are identified using like reference numerals. First capture zone  36 A of MCD  428  may include first MCD terminal  38 A spaced apart from second MCD terminal  38 B to define first gap G 1  therebetween. Second capture zone  36 B may include third MCD terminal  38 C spaced apart from fourth MCD terminal  38 D to define second gap G 2  therebetween. In various embodiments, first gap G 1  and second gap G 2  may be disposed in series as shown in  FIGS.  6 A,  6 B , or may be disposed in parallel in electric circuit  434 . In some embodiments, first gap G 1  and second gap G 2  may be of substantially the same size. However, in other embodiments, first gap G 1  and second gap G 2  may be of different sizes depending on the size(s) of first chip  42 A and of second chip  42 B that are of interest. 
     MCD  428  may be a combination of two or more single-zone axial disk-type magnetic chip detectors that are daisy chained together. For example, first capture zone  36 A may be provided by a first magnetic chip detector electrically integrated into electric circuit  434  via first connector C 1 , and second capture zone  36 B may be provided by a second magnetic chip detector electrically integrated into electric circuit  434  via second connector C 2 . In some installations, first capture zone  36 A and second capture zone  36 B may be in fluid communication with each other during operation. Alternatively, first capture zone  36 A and second capture zone  36 B may be fluidly sealed from each other and disposed in different fluid streams or in different fluid systems of engine  10 . The configuration of MCD  428  may permit the monitoring of different regions of lubrication system  20  using the single interface providing resistance value RV. The configuration of MCD  428  may permit a combination of different types of single-zone and/or multi-zone MCDs to be daisy chained together and provide a single output. For example, MCDs of different configurations (e.g., axial disk-type and prong type) and/or of different gap sizes may be combined together to meet requirements of the specific application. 
     MCD  428  may include first shunt resistor R 1  disposed in parallel with first gap G 1 , and second shunt resistor R 2  disposed in parallel with second gap G 2 . 
     During operation of MCD  428  when MCD  428  is immersed in lubricating fluid  26 , the resultant resistance value RV may be indicative of which one(s) of first gap G 1  and second gap G 2  is/are electrically bridged by first chip  42 A and/or second chip  42 B based on which combination of first resistor R 1 , second resistor R 2 , electrically bridged first gap G 1 , and electrically bridged second gap G 2  are reflected in resistance value RV. 
       FIG.  7 A  is a schematic representation of another exemplary multi-zone MCD  528  of which may be part of chip detection system  30  of engine  10 . MCD  528  may be a prong-type magnetic chip detector.  FIG.  7 B  is a schematic axial end-on view of MCD  528  looking at MCD  528  along axis A in  FIG.  7 A .  FIG.  7 C  is a schematic representation of electric circuit  534  associated with MCD  528  of  FIG.  7 A . First capture zone  536 A of MCD  528  may include first MCD terminal  538 A spaced apart from second MCD terminal  538 B to define first gap G 1  therebetween. First MCD terminal  538 A may be a magnetic prong having properties of a magnet and having a north (N) polarity. Second MCD terminal  538 B may be a magnetic prong having properties of a magnet and having a south (S) polarity. Second capture zone  536 B may include third MCD terminal  538 C spaced apart from first MCD terminal  538 A to define second gap G 2  therebetween. Third MCD terminal  538 C may be a magnetic prong having properties of a magnet and having a south (S) polarity. As shown in  FIG.  7 B , first MCD terminal  538 A, second MCD terminal  538 B, and third MCD terminal  538 C may be disposed in a triangular formation. A gap between two neighboring prongs of the same polarity such as between second MCD terminal  538 B and third MCD terminal  538 C, which are both south pole prongs, will not be a capture zone since the magnetic chips on prongs of the same polarity will repel each other. 
     In various embodiments, first gap G 1  and second gap G 2  may be disposed in series as shown in  FIG.  7 C  or may be disposed in parallel in electric circuit  534 . In some embodiments, first gap G 1  and second gap G 2  may be of substantially the same size. However, in other embodiments, first gap G 1  and second gap G 2  may be of different sizes depending on the size(s) of first chip  42 A and of second chip  42 B that are of interest. MCD  528  may include first shunt resistor R 1  disposed in parallel with first gap G 1 , and second shunt resistor R 2  disposed in parallel with second gap G 2 . 
     During operation of MCD  528  when MCD  528  is immersed in lubricating fluid  26 , the resultant resistance value RV may be indicative of which one(s) of first gap G 1  and second gap G 2  is/are electrically bridged by first chip  42 A and/or second chip  42 B based on which combination of first resistor R 1 , second resistor R 2 , electrically bridged first gap G 1 , and electrically bridged second gap G 2  are reflected in resistance value RV between first output terminal  544 A and second output terminal  544 B. 
       FIG.  8 A  is a schematic axial end-on view of another exemplary multi-zone MCD  628  which may be part of chip detection system  30  of engine  10 .  FIG.  8 B  is a schematic representation of electric circuit  634  associated with MCD  628  of  FIG.  8 A . First capture zone  636 A of MCD  628  may include first MCD terminal  638 A spaced apart from second MCD terminal  638 B to define first gap G 1  therebetween. First MCD terminal  638 A may be a magnetic prong having properties of a magnet and having a south (S) polarity. Second MCD terminal  638 B may be a magnetic prong having properties of a magnet and having a north (N) polarity. Second capture zone  636 B may include third MCD terminal  638 C spaced apart from first MCD terminal  638 A to define second gap G 2  therebetween. Third MCD terminal  638 C may be a magnetic prong having properties of a magnet and having a north (N) polarity. Third capture zone  636 C may include third MCD terminal  638 C spaced apart from fourth MCD terminal  638 D to define third gap G 3  therebetween. Fourth MCD terminal  638 D may be a magnetic prong having properties of a magnet and having a south (S) polarity. As shown in  FIG.  8 A , first MCD terminal  638 A, second MCD terminal  638 B, third MCD terminal  638 C, and fourth MCD terminal  638 D may be disposed in a rectangular or square formation. A gap between two neighboring prongs of the same polarity will not be a capture zone since the magnetic chips on prongs of the same polarity will repel each other. 
     In various embodiments, first gap G 1 , second gap G 2 , and third gap G 3  may be disposed in series as shown in  FIG.  8 B , or may be disposed in parallel in electric circuit  634 . In some embodiments, first gap G 1 , second gap G 2 , and third gap G 3  may be of substantially the same size. However, in other embodiments, first gap G 1 , second gap G 2 , and third gap G 3  may be of different sizes depending on the size(s) of chips that are of interest. For example, second gap G 2  may be larger than first gap G 1  and also larger than third gap G 3  as shown in  FIG.  8 B . MCD  628  may include first shunt resistor R 1  disposed in parallel with first gap G 1 , second shunt resistor R 2  disposed in parallel with second gap G 2 , and third shunt resistor R 3  disposed in parallel with third gap G 3 . 
     During operation of MCD  628  when MCD  628  is immersed in lubricating fluid  26 , the resultant resistance value RV may be indicative of which one(s) of first gap G 1 , second gap G 2 , and third gap G 3  is/are electrically bridged by chips based on which combination of first resistor R 1 , second resistor R 2 , third resistor R 3 , electrically bridged first gap G 1 , electrically bridged second gap G 2 , and electrically bridged third gap G 3  are reflected in resistance value RV between first output terminal  644 A and second output terminal  644 B. 
       FIG.  9 A  is a schematic axial end-on view of another exemplary multi-zone MCD  728  which may be part of chip detection system  30  of engine  10 .  FIG.  9 B  is a schematic representation of electric circuit  734  associated with MCD  728  of  FIG.  9 A . First capture zone  736 A of MCD  728  may include first MCD terminal  738 A spaced apart from second MCD terminal  738 B to define first gap G 1  therebetween. First MCD terminal  738 A may be a magnetic prong having properties of a magnet and having a north (N) polarity. Second MCD terminal  738 B may be a magnetic prong having properties of a magnet and having a south (S) polarity. Second capture zone  736 B may include third MCD terminal  738 C spaced apart from second MCD terminal  738 B to define second gap G 2  therebetween. Third MCD terminal  738 C may be a magnetic prong having properties of a magnet and having a north (N) polarity. Third capture zone  736 C may include third MCD terminal  738 C spaced apart from fourth MCD terminal  738 D to define third gap G 3  therebetween. Fourth MCD terminal  738 D may be a magnetic prong having properties of a magnet and having a south (S) polarity. Fourth capture zone  736 D may include first MCD terminal  738 A spaced apart from fourth MCD terminal  738 D to define fourth gap G 4  therebetween. As shown in  FIG.  9 A , first MCD terminal  738 A, second MCD terminal  738 B, third MCD terminal  738 C, and fourth MCD terminal  738 D may be disposed in a rectangular or square formation. 
     In some embodiments, first gap G 1  and fourth gap G 4  may be disposed in series, and second gap G 2  and third gap G 3  may be disposed in series in electric circuit  734 . A first branch including first gap G 1  and fourth gap G 4  may be disposed in parallel with a second branch including second gap G 2  and third gap G 3 . In some embodiments, first gap G 1 , second gap G 2 , third gap G 3  and fourth gap G 4  may be of substantially the same size. However, in other embodiments, first gap G 1 , second gap G 2 , third gap G 3 , and fourth gap G 4  may be of different sizes depending on the size(s) of chips that are of interest. MCD  728  may include first shunt resistor R 1  disposed in parallel with first gap G 1 , second shunt resistor R 2  disposed in parallel with second gap G 2 , third shunt resistor R 3  disposed in parallel with third gap G 3 , and fourth shunt resistor R 4  disposed in parallel with fourth gap G 4 . In some embodiments, first resistor R 1 , second resistor R 2 , third resistor R 3 , and fourth resistor R 4  may be connected in a Wheatstone bridge configuration. 
     During operation of MCD  728  when MCD  728  is immersed in lubricating fluid  26 , the resultant resistance value RV between first output terminal  744 A and second output terminal  744 B may be near 0 Ohms (i.e., short circuit) when two or three of first gap G 1 , second gap G 2 , third gap G 3 , and fourth gap G 4  are electrically bridged by metallic chips. 
       FIG.  10    is a flow diagram of method  100  of detecting metallic chips in engine fluid of an engine. Method  100  may be performed using MCD  28 ,  128 ,  228 ,  328 ,  428 ,  528 ,  628 ,  728  described herein or using another MCD. Aspects of method  100  may be combined with other methods or steps described herein. Method  100  may also include aspects of system  30  and of MCD  28 ,  128 ,  228 ,  328 ,  428 ,  528 ,  628 ,  728 . In various embodiments, method  100  may include:
     when the magnetic chip detector (e.g., MCD  28 ,  128 ,  228 ,  328 ,  428 ,  528 ,  628 ,  728 ) is immersed in engine fluid (e.g., lubricating fluid  26 ), receiving one or more metallic chips (e.g.,  42 A,  42 B) in one or both of the first magnetic chip capture zone and the second magnetic chip capture zone (block  102 ); and   using an electric circuit (e.g., electric circuit  34 ,  134 ,  234 ,  334 ,  434 ,  534 ,  634 ,  734 ) including both the first magnetic chip capture zone and the second magnetic chip capture zone, generating an output indicative of a chip detection in the one or both of the first magnetic chip capture zone and the second magnetic capture zone (block  104 ).   

     In some embodiments of method  100 , the output may be indicative of which of the first magnetic chip capture zone, the second magnetic capture zone, or optionally one or more additional magnetic chip capture zones is/are associated with the chip detection. In some embodiments of method  100 , the first magnetic chip capture zone and the second magnetic chip capture zone may be in fluid communication with each other when receiving one or more metallic chips in one or both of the first magnetic chip capture zone and the second magnetic chip capture zone. 
     The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology.