Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
  • G01M3/24—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using infrasonic, sonic or ultrasonic vibrations

Definitions

• This invention relates to the acoustic testing of aircraft components
• the method is particularly, but not exclusively, applicable in relation to
• Aircraft fuel wing tanks are designed and built as an integral part of
• wingwet the surface of the wing creating what is termed in the industry as "wingwet”.
• a vacuum is
• breach can last a number of days.
• a second and less preferred method is to apply a vacuum to the fuel
• a helium detector is used to attempt to identify first of
• the method proposed includes receiving acoustic signals
• acoustic sensing is unsuitable for identifying the course of a leakage path
• apparatus for locating fluid leakage, said apparatus comprising a device to be
• said device comprising two acoustic transducers arranged to
• This aspect of the invention provides apparatus suitable for following
• sensing apparatus comprising a rigid rod member held by a
• an acoustic transducer attached within a cavity inside said rod member
• transducer being arranged in said cavity to sense acoustic vibrations
• This aspect of the invention provides a sensitive and accurate method
• an acoustic sensing device for detecting a defective or failing component in the aircraft by contacting an acoustic sensing device, adapted to focus on sounds emanating from the
• Figure 1 is a cross-section of an aircraft wing which leaks fuel
• Figure 2 is a schematic illustration of components of a test kit used in
• FIG. 3 is a schematic illustration of further components of the test kit
• Figure 4 is a cross-section of an embodiment of acoustic sensor which
• Figure 5 is a cross-section of a further embodiment of acoustic sensor
• a common structure of aircraft wing 2 includes
• the wing is divided into several fuel tank compartments 8, by a series of
• baffles 10 which include connecting passages 12 to allow the transfer of fuel
• baffles The purpose of the baffles is to
• Figure 1 shows an example of a typical leakage path which has
• the leakage path 18 lies between the resin lining 6 and the
• Figure 2 shows components of a test kit according to this embodiment
• a control case 70 houses a vacuum pump 24, connected to
• the inlet port 40 is connected to a manually-operable three
• the selector valve 42 connects the inlet port 40 to the pressure regulator 40.
• manually-operable two position selector valve 44 connects an outlet port 46
• the pressure gauge 32 is connected to the outlet port 46.
• One of the pressure transducers 34 is connected to a first pressure
• the other pressure transducer 36 is connected to a
• selector valve 56 depending on its position.
• the pressure transducers 34, 36 are electronic pressure transducers
• Model No DPI 700 A coil of neoprene tubing 58, 60,
• this tubing coil is to provide a damping action in relation
• the coils move, i.e. expand and contract, to
• transducers 34, 36 for example liquid mercury, which would damp such
• test that it is preferably carried out with a tank containing its normal liquid
• the tank(s) being tested are preferably filled to
• pressure return port 48 are sealingly connected, via a T-junction and flexible
• vent box located centrally in the fuselage, via a vent
• vent port is used to alter the vent port
• the specially-adapted connector is similar to a standard
• control case 20 is set. using the
• selector switch 42 the pressure regulator 30 and two-way selector switch 44,
• the fuel storage tank is next sealed for a monitoring period, to
• the gas pressure within the storage tank is
• the pressure monitored on the second pressure transducer 36 is the sum of the
• control case 20 to a negative pressure in the region of -20 to -200 Mb
• the leak path may be
• the initial leakage rate under vacuum consists of a combination of the leakages into each of the internal breaches 16.
• test pressures and above the liquid surface and below the liquid surface may be used by a test operator, using the indications referred to above, to identify
• the next stage of the testing procedure concerns identifying the course
• control case 20 is set to produce a constant negative pressure
• the fuel storage tank is not
• test kit used in this stage of the test
• a sensing rod 84 and/or a sensing rod 84, a two channel signal receiver and processor 64, a pair
• the dual-microphone acoustic sensor 62 As shown in Figure 4, the dual-microphone acoustic sensor 62
• the microphones are spaced apart on two sides of a
• a circular rubber flange 78 surrounds the space in front of each
• each microphone 72, 74 is filled with a
• silicone gel 80 which also tends to block atmospheric sounds reaching each
• Both microphones 72, 74 are connected to a two channel
• radio transmitter 82 The radio transmitter 82.
• the receiver 64 contains a two channel amplifier and a variable
• breach 16 has a characteristic frequency which is relatively high (between 10-
• the acoustic sensor 62 is first placed adjacent to the known external
• the acoustic sensor 62 is moved to track the course of the internal leakage path 18. The course of the
• the signals shown on the oscilloscope display has a greater amplitude than the
• the acoustic sensor 62 to maintain balance between the two signals.
• test operator can readily identify
• the receiver 64 may also be
• the microphones 72. 74 are spaced by approximately 20
• a sensing rod 84 having a microphone which is also be connected to the
• microphone acoustic sensor 62 In this case, only one channel is required as
• This sensing rod 84 includes a cylindrical body 86 having a solid end
• portion 88 with a rounded base 90 and constructed from a material being non ⁇
• the rounded base 90 is designed to pick up acoustic
• the body has a length of approximately 30 cm and an outer
• the microphone is threaded into the body 86, such that vibrations
• the transmitted along the cavity 94 are transmitted directly to and picked up by the microphone. Furthermore, the microphone 92 is directed towards the
• the sensing rod 84 provides a means of increased sensitivity for
• receiver 64 tuned to select a frequency range spanning the characteristic
• sensing rod 84 over the outer surface of the wing skin 4, preferably starting
• the dual-microphone sensor 62 is used to coarsely plot
• sensitivity is used to diagonally criss-cross in a zig-zag fashion across the
• leakage path 18 will have been repaired along its whole length, and that then
• the sensing rod described may be used to test the condition of
• Condition testing may be
• the components identified which are testable in such manner include the aviation fuel systems (fuel tanks, fuel transfer lines, fuel pumps

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Examining Or Testing Airtightness (AREA)

Applications Claiming Priority (3)

Publications (1)

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Country Status (4)

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Family Cites Families (11)

• 1997
  • 1997-10-29 GB GB9722871A patent/GB2331152A/en not_active Withdrawn
• 1998
  • 1998-10-29 AU AU96371/98A patent/AU9637198A/en not_active Abandoned
  • 1998-10-29 EP EP98950215A patent/EP1027584A2/de not_active Withdrawn
  • 1998-10-29 WO PCT/GB1998/003231 patent/WO1999022214A2/en not_active Ceased

Non-Patent Citations (1)

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