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A division of Martek Power Group

Ground Bond Testing for Production and Maintenance. A division of Martek Power Group. Presentation. Lightning: risk for aircraft. How Aircraft are protected from Lightning?. Why measure bonding resistance?. Bonding resistance measurement with new Sefelec Milliohmmeter RCP2A.

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A division of Martek Power Group

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  1. Ground Bond Testing for Production and Maintenance A division of Martek Power Group

  2. Presentation • Lightning: risk for aircraft • How Aircraft are protected from Lightning? • Why measure bonding resistance? • Bonding resistance measurement with new Sefelec Milliohmmeter RCP2A

  3. Lightning:Risk for Aircraft • A commercial aircraft is struck by lightning on an average once every 1500 flight hours • The risk of strikes by lightning is increased in rainy zones, at approximately 4000 meters and between -5°C and +5°C • During a strike by lightning, the lightning does not stop on the plane but sweeps it to continue its way in the atmosphere with a point of initial entrance and a point of final exit

  4. Lightning: Risk for Aircraft

  5. Direct effects of lightning Strikes Types of the damage: • Thermic with perforation of walls by fusion • Dynamic with rise of pressure which generates a destructive shock wave for the cabling and the dissimilar and composite materiels. • Electromagnetic which perturbs the on board equipment • They are caused by the effect of the discharge or by the conduction of the lightening strike current (up to 200 kA!)

  6. Direct effects of lightning strikes Lightning direct effects damage To an unprotected aircraft Composite panel

  7. How Aircraft are protected from Lightning ? • Most Aircraft Skins are made primarily of aluminium which is a very good conductor of electricity. This constitutes an excellent protection against lightning strikes. • Today Aircraft are made of advanced composite materials: significantly less conductive than aluminium • In this case the composites are made with an embedded layer of conductive fibers or screens to carry lightning currents. • This is called “surface metallization“ or “bonding of these surfaces”, which becomes indispensable and thus the control of this bonding and the continuity

  8. How Aircraft are protected from Lightning ? • Lightning indirect effects - transients, protection by careful shielding and grounding • Protection of fuel system where even a tiny spark could be disastrous

  9. Why measure bonding resistance? • “Bonding” is the electrical interconnection of metallic aircraft parts for the safe distribution of electrical charges and currents • GOOD ELECTRICAL BONDING provides a means of protection against lightning strikes: • Minimise damage to the aircraft structure or components • Prevent the passage of such electrical currents as would cause dangerous malfunctioning of the aircraft or its equipment and • Prevent the occurrence of high potential differences within the aircraft BONDING TEST = LOW RESISTANCE MEASUREMENT

  10. Bonding resistance measurement with new Sefelec Milliohmmeter RCP2A RCP2A: The right solution for bonding resistance measurement According all current aircraft specifications

  11. Specifications / Key Points • True 4-wire measurement / Measurement specifications • Automatic measurement trigger when leads are connected to DUT • Hi-Lo limits with audible and visual warning • Data Logging with up to 1000 readings stored with date/time • Wide range of accessories, especially designed for Bonding test • Rechargeable NiMh batteries / charge indicator / easily replacable • 1000 measures with 10A • Special remote control to enable operation at distance • RS232 interface / windows application software RCP2APRO

  12. Specifications / Key Points • Long cable up to 100 m • Confidence test with built-in resistor of 5 mOhm • Complete calibration kit • Suitcase for instrument and accessories • ERGONOMY: SMALL SIZE AND LIGHT WEIGHT < 4 kg

  13. Red / Green light LCD sreen Joystick Batteries Start/Stop Function keys Enter key Measure Measure terminals Front panel

  14. Extraction handle RS232 socket Locking screw Measurement press button Charger socket Locking screw Block batteries’s front panel

  15. Method of measurement In order to make low resistance measurement with a high precision, the RCP2A uses the 4 wire Kelvin method. • 2 wires are used to connect a constant current source to the resistance to be measured • 2 additional wires are used to measure the difference of potential directly to the terminals of the device under test. • With this method, the resistance of the measuring leads does not introduce any error.

  16. RCP2A Accessories (leads etc.) Bonding resistance +I RLead +U Ux Ic Rx -U Rx = Ux / Ic Kelvin Method RLead RLead RLead -I RLead = Lead resistance

  17. Software RCP2A / Sequence mode • The Software RCP2Apro allows to program test sequences using excel, according Ground Test Instructions. A sequence describes the points of bonding with test parameters (current and max. R) • This SEQUENCE is loaded into the RCP2A • The user sees clearly on the LCD Display which points he has to measure • Measurements are stored into the RCP2A in combination with the corresponding test points • With the Software RCP2Apro, all measurements are uploaded in the PC • THIS MODE ALLOWS DIRECT SAVING AND TRACEABILITY OF THE MEASUREMENTS

  18. Software RCP2A / Sequence mode

  19. Software RCP2A / Sequence mode

  20. Software RCP2A / Sequence mode

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