Since then, the Federal Aviation Administration issued Airworthiness Directive 64 FR 4959 No. 2102/02/99, a portion of a federal program that mandated corrective design and operational measures. The FAA’s AD requires proper management and inspection of fuel tanks, flame arrestor and pressure relief valve installations, and modifications designed to provide shielding and separation of fuel system wiring.
In addition, the Naval Air Warfare Center in NAVAIR 01-1A-35 (wing tank procedure guidelines) states that “personnel shall not enter fuel cells which contain flammable atmospheres above 10% of the LEL or which are Immediately Dangerous to Life and Health (IDLH) except in case of extreme emergency such as a rescue effort.â€