A division of Martek Power Group

Ground Bond Testing for Production and Maintenance

Presentation

How Aircraft are protected from Lightning?

Lightning: risk for aircraft

Why measure bonding resistance? Bonding resistance measurement with new

Sefelec Milliohmmeter RCP2A

Lightning:Risk for Aircraft

A commercial aircraft is struck by lightning on an average once every 1500 flight hours

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

The risk of strikes by lightning is increased in rainy zones, at approximately 4000 meters and between -5°C and +5°C

Lightning: Risk for Aircraft

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

Direct effects of lightning Strikes

They are caused by the effect of the discharge or by the conduction of the lightening strike current (up to 200 kA!)

Lightning direct effects damage

To an unprotected aircraft

Composite panel

Direct effects of lightning strikes

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.

This is called “surface metallization“ or “bonding of these surfaces”, which becomes indispensable and thus the control of this bonding and the continuity

In this case the composites are made with an embedded layer of conductive fibers or screens to carry lightning currents.

Today Aircraft are made of advanced composite materials: significantly less conductive than aluminium

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

Why measure bonding resistance? “Bonding” is the electrical interconnection of metallic

aircraft parts for the safe distribution of electrical charges and currents

BONDING TEST = LOW RESISTANCE MEASUREMENT

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

RCP2A: The right solution for bonding resistance measurement

According all current aircraft specifications

Bonding resistance measurement with new Sefelec Milliohmmeter RCP2A

Specifications / Key PointsRange Current Resolution Precision

6 m 1A / 10A 1µ (0,1% rdg+0,1% FS)

60 m 1A / 10A 10µ (0,1% rdg+0,1% FS)

600 m 1A / 10A 100µ (0,1% rdg+0,1% FS)

6000 m 0,1A / 1A 1m (0,1% rdg+0,1% FS)

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

Specifications / Key PointsRange Current Resolution Precision

6 m 1A / 10A 1µ (0,1% rdg+0,1% FS)

60 m 1A / 10A 10µ (0,1% rdg+0,1% FS)

600 m 1A / 10A 100µ (0,1% rdg+0,1% FS)

6000 m 0,1A / 1A 1m (0,1% rdg+0,1% FS)

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

Front panel

Measure terminalsMeasureEnter key

Red / Green light LCD sreen Joystick Batteries

Start/Stop Function keys

Block batteries’s front panelExtraction handle RS232 socket

Charger socket

Locking screw

Measurement press button

Locking screw

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.

Kelvin Method

-I

RLead

RLead

RLead

RxIc

+I

+U

-U

RLead

Ux

Rx = Ux / Ic

RCP2A Accessories (leads etc.)

Bonding resistance

RLead = Lead resistance

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

Software RCP2A / Sequence mode

Software RCP2A / Sequence mode

RCP2A MANUEL SEQU TEST CONF

GAMMES DE MESURE : Bat :100% ABCDD123456789 ABCDE123456789 DEDDE123456789 CBCDE123456789

FIN

ABCDE123456789 S:150.0m at

001: - - - - m POINT ABSENT VALIDE CONF FIN

ABCDE123456789 S:150.0m at

001: 142.3 m POINT ABSENT VALIDE CONF FIN

Software RCP2A / Sequence mode