Lightning Travels with NTS Pittsfield Full Vehicle TestingJune 24, 2014
The most widely traveled equipment at NTS Pittsfield is our Full Vehicle Test Sets. This equipment travels to customers’ facilities for use, supporting customers over much of the continental United States but also South America, Europe, the Middle East, and Asia. Full Vehicle Tests are used to verify induced lightning threat levels on cable bundles and individual wires in aircraft, partial aircraft structures and engines. The test technique was developed through the late 60s and entered its present form in the early 70s in Pittsfield. The test first entered guidance material in the SAE AE4 Committee Special Task F ‘Red Book” in 1976 followed by the Committee AE4L “Blue Book’ (AE4L-78-1); both of which committees were co-chaired by J. A. Plumer of Lightning Technologies. The present form of the test technique is described in Section 6.1 of SAE Aerospace Recommended Practice (ARP) 5416A released in 2013.
Testing typically involves development of a return structure that surrounds the test vehicle with an array of conductors. The return structure reduces the inductance of the test circuit to permit delivery of the lightning test waveforms and provides for a somewhat uniform current distribution over the test vehicle surfaces. At NTS Pittsfield, this return structure involves an array of wires stretched over a non-conducting support structure of wood, foam, and/or PVC. Currents up to several thousand amperes are delivered into the test vehicle from lightning impulse generators while voltages and currents are monitored at the equipment connector interface as well as on cable bundles. Connections to the aircraft and the return array are adjusted to provide maximum coupling to cable bundles based on expected lightning attachment locations.
The measured induced transients are extrapolated to a full threat equivalent for a 200 kA lightning strike to define the Actual Transient Level (ATL) for the electrical/electronic equipment on the vehicle. Excessive levels can often be mitigated during the course of the vehicle testing with improved electrical bonding or shielding and occasional rerouting of cable bundles. With a 2-to-1 margin, these levels define the Equipment Transient Design Level (ETDL) that are used to verify the waveform and levels used during equipment tests to Section 22 of RTCA DO-160 or, if the full vehicle tests are performed early enough, are used to specify the Section 22 test waveforms and levels.
If you are interested in Full Vehicle Testing or would like more information please contact NTS Pittsfield at 413.499.2135 or view our brochure.