GOLF BRAVO ZULU................
Don't the AAIB lads use blown bulbs as a clue to which were lit when an aircraft piled in? A blown bulb was a lit bulb.
Not strictly correct.
The various factors to be taken into account in analyzing aircraft light bulbs are listed below; each is discussed in some detail with appropriate illustrations on subsequent
pages:
1. type and manufacturer of bulb;
2. orientation of the bulb relative to the flight path at impact;
3. applied voltage during the accident sequence;
4. nature and severity of impact;
5. degree of aging.
See:
http://www.tc.gc.ca/tdc/publication/pdf/6255e.pdf