Summary
We propose to adopt a new airworthiness directive (AD) for certain Hawker Beechcraft Corporation (Type Certificate previously held by Raytheon Aircraft Company; Beech Aircraft Corporation) Model 400A airplanes. This proposed AD was prompted by a report that the wiring for the 5-volt direct current (DC) system is undersized and does not have adequate circuit protection for the smaller gauge wire. This proposed AD would require installing an in-line fuse in the 5-volt DC system for each of the five instrument lighting control power supplies. We are proposing this AD to prevent failure of the wiring, which could result in smoke in the cockpit, loss of cockpit lighting, and potential damage to surrounding wiring for other cockpit equipment such as the stick shaker function or angle-of-attack indicators.