Search Results

A comparison was done of the prediction capabilities for lightning indirect effects of two two-dimensional (2-D) computer codes using two graphite structural test fixtures. The two codes evaluated were an internal Boeing Method-of-Moments code and a commercially available Boundary Element method code. The codes were compared against each other and against test data. The purpose was to evaluate the prediction capabilities of both codes for use in predicting lightning indirect effects on internal components of graphite structure. Since 2-D codes are much easier to use than 3-D codes, they could be widely used in trade studies and design evaluations for lightning indirect effects protection of composite aircraft. The first code, REDIST, is a Method-of-Moments code developed in the 1980’s for use on the B-2. The REDIST code has short run times and is somewhat easier to use than the second code that was investigated.

This paper reports some of the results of a NASA-prototype composite wingbox direct drive test, performed in the Boeing Lightning Lab from October 23, 2000 to June 8, 2001. The test data is being used to support computer analysis program and modeling efforts that are researching issues concerned with composite fuel tank designs.

Lightning testing performed on fuel tank components or structure utilizes photographic techniques or an explosion test cell to determine tendencies of the hardware to produce sparks. The photographic technique utilizes the no-light-on-film pass/fail criteria with a Polaroid camera at an f-stop of 4.7 and a film speed of 3000 ISO, or a 35 mm camera equivalent (reference 1 and 2). There is speculation that although, per the test specifications, the requirements of the test are met if these film and camera settings are as specified, the various film types would not produce equivalent results. It is common for faster speed films to be grainier which could affect the ability of the film to detect small sparks. There are also color films which, depending on their manufacturer, can have different sensitivities to various light frequencies. The processing of the film can also affect the ability to discern small sparks.