Transcript REUNION COMMERCIALE

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

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
Lightning: Risk for Aircraft
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!)
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
Lightning direct effects damage
To an unprotected aircraft
Composite panel
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
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

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
Bonding resistance measurement with
new Sefelec Milliohmmeter RCP2A
RCP2A: The right solution for bonding resistance measurement
According all current aircraft specifications
Specifications / Key Points
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Range
Current
Resolution
Precision
6 mW
1A / 10A
1µW
(0,1% rdg+0,1% FS)
60 mW
1A / 10A
10µW
(0,1% rdg+0,1% FS)
600 mW
1A / 10A
100µW
(0,1% rdg+0,1% FS)
6000 mW
0,1A / 1A
1mW
(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 Points




Range
Current
Resolution
Precision
6 mW
1A / 10A
1µW
(0,1% rdg+0,1% FS)
60 mW
1A / 10A
10µW
(0,1% rdg+0,1% FS)
600 mW
1A / 10A
100µW
(0,1% rdg+0,1% FS)
6000 mW
0,1A / 1A
1mW
(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
Red / Green light
LCD sreen
Start/Stop Function keys
Joystick
Enter key Measure
Batteries
Measure terminals
Block batteries’s front panel
Extraction handle
Charger socket
Locking screw
RS232 socket
Locking screw
Measurement
press button
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
RCP2A
Accessories
(leads etc.)
+I
+U
Ic
RLead
RLead
Ux
Rx
-U
-I
Rx = Ux / Ic
Bonding
resistance
RLead
RLead
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)
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This SEQUENCE is loaded into the RCP2A
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The user sees clearly on the LCD Display which points he has to measure
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Measurements are stored into the RCP2A in combination with the
corresponding test points
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With the Software RCP2Apro, all measurements are uploaded in the PC
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THIS MODE ALLOWS DIRECT SAVING AND TRACEABILITY OF
THE MEASUREMENTS
Software RCP2A / Sequence mode
Software RCP2A / Sequence mode
 


MANUEL
SEQU




RCP2A 
TEST

CONF
GAMMES DE MESURE :
ABCDD123456789
ABCDE123456789
DEDDE123456789
CBCDE123456789
Bat :100%
FIN
ABCDE123456789
S:150.0mW
at
001:
----
mW
POINT
VALIDE
ABSENT
ABCDE123456789
CONF
FIN
S:150.0mW
001: 142.3
POINT
ABSENT
VALIDE
CONF
at
mW
FIN
Software RCP2A / Sequence mode