Icore TTH plating

 

Lightning Strike Test Report

 

 
 

01-DTR-868A
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


WRITTEN BY: ____________________                   DATE: ____________________

Jon White

 

 

 

AUTHORIZED BY: __________________                DATE: ____________________

Jon White

(Product Development Team Leader)

 

 

 

 

Circulation:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

           

1.     Introduction

Icore’s TTH protective plating can be used with brass and aluminium hardware as a nickel and/or cadmium replacement. It offers superior corrosion performance and equal conductivity to nickel and/or cadmium. This report details a lightning test conducted on an TTH plated aluminium backshell. The testing was carried out at ITS Laboratories (formerly ERA), Leatherhead, England.

2.     Objectives

To prove a TTH-plated aluminium backshell passes an indirect lightning strike effect type test without damage or performance degradation.

3.     Conclusions

The Icore TTH plated 38999 shell size 13 aluminium backshell passed a 10kA single strike test to waveform 5B from RTCA/DO-160C section 22.  The Icore backshell was tested with a standard 38999 connector.  The sample showed no significant change in measured resistance before and after the test and no damage was evident during a post test inspection. 

4.     Technical Background

Direct effects of a lightning strike are rapid localised heating and mechanical damage caused by the current at the points of entry and exit of the strike.

 

More widespread heating, mechanical damage and induced electrical interference then follow, throughout the whole aircraft.  These are the indirect effects that arise as the current from the lightning strike is dissipated throughout the aircraft.  The current that an individual backshell or connector is exposed to during a lightning strike is dependent upon the distribution of conductive component’s throughout the aircraft. During a lightning strike on an aircraft, a backshell could be exposed to indirect lightning strike effects.

 

A number of test waveforms are stipulated by the avionics industry for different pieces of equipment. These are detailed in RTCA/DO-160C, section 22. In the case of indirect effects the differing severity of the test waveforms represent the different magnitude and duration possible from a lightning strike.

5.     Experimental Sample

Icore MIL-C-38999 Series III shell size 13 TTH plated Icore Terminator backshell (ATT0M40-1306-CT) with Icore Ni-Cu braid (type B2405-45) clamped to the TTH plated Misty yoke with a 1/8” Band-It strap. The backshell was screwed onto an aerospace female connector that was fixed to an earthed aluminium plate. The braid was clamped to a copper tube that was used to inject the current.

 

 

 

Figure 1          TTH plated Terminator backshell with TTH plated Misty yoke

6.     Experimental Method

The test assembly was exposed to waveform 5B of RTCA/DO-160C.  To meet the standard the peak current must be reached after 50 ms ±20%, and decay to the half maximum after 500ms ±20%, shown in figure 2.  The peak current, which is dependent upon the charge voltage, must be within ±10% of the specified test level.  The current level, IT, is the specified peak current.

Figure 2          Waveform 5b from RTCA/DO-160C

 

Pass criteria - To pass the test there must be no visible damage to the plated component and no variation in bond resistance after testing.

 

 


Figure 3          Circuit diagram and equipment layout for lightning strike testing.  The current oscillograms were recorded at the location indicated. 

 

The assembly was connected into the test circuit as shown in figure 3 and during testing each waveform was recorded along with its peak current value.  The duration and shape of each waveform was monitored to ensure the tests were within specification.  A typical test waveform is shown in figure 4 for both the applied current and voltage.

 

 

Figure 4          Test waveform at 5kA.  The voltage waveform is much shorter than the current waveform because as the current flows through the assembly the voltage drops in proportion with the rate of change of current.

 

The sample received a preliminary low-level strike of 2.2 kA.  This strike was necessary to set the voltage required to generate currents at the required levels.

7.     Results

 

Resistance mW

 

Sample

Pre-test

Post-test

Amps

TTH

 

0.16

0.11

2.2kA, 5kA, 10kA

 

Damage

No visible damage was observed on the connector or braid upon inspection following the strike.

 

Resistance

The resistance, as measured from the braid sock to the connector, was lower following the strike. A typically specified value might be in the range of 1 to 2.5 mW.

8.     Conclusions

The Icore TTH plated shell size 13 terminator backshell passed the indirect lightning strike test detailed in this report exhibiting no damage and no change in resistance.

 

Icore TTH plating provides lightning strike performance, without deterioration.