Behaviour of a Fibre Optic ARINC629 Data Bus System in an Extreme Lightning Environment of a Carbon Fibre Test Wing 1999-01-2341
The paper presents the results of a lightning test performed on a fibre optic ARINC629 data bus system installed on the front spar of a Carbon Fibre test wing. The data bus electronics were located at the front spar near the wing tip of a 6.3m long test wing, just some 20cm apart from the entry point of the test current pulses. 115V/400Hz power supply was provided to the electronic box via a usual twisted shielded pair of wires. The electrical power was fed across a specially arranged transformer which provided separation of the unit’s local potential from the potential of the aircraft’s power supply system by interrupting the common mode current path from the data bus circuits to other aircraft systems. Grounding of the data bus electronics was done on the local wing structure. There was no excessive additional shielding of the wires nor internal pulse suppression inside the electronic box, except one small low power suppressor diode across the power input terminals. Data communication to and from the system was established and monitored during test across optical fibres.
The primary intention of the test was not to demonstrate the capabilities of an ARINC629 system but, more general, to show how effective lightning protection can be provided when combining fibre optic technology together with potential separation of the power supply system. The ARINC629 system was chosen because it was already available, it comprises quite complex electronics and was therefore suitable for this test, and it is easy to monitor it’s proper functioning.
The test result was amazing. Lightning threat of more than 200kA did not cause any signs of disturbance in the data transfer.