In vehicle applications, such as aviation and boating, vehicle-to-vehicle collisions are prevented by mounting navigation lights on the exterior of the vehicle. The lights function by alerting approaching vehicles of the presence and orientation of the first vehicle. The success navigation lights have in preventing collisions is partly due to an industry standard that dictates the color of light a navigation light must emit depending on the light's position on the body of the vehicle. Based on the color pattern of navigation lights visible to an approaching vehicle, the approaching vehicle can quickly deduce the direction, and therefore heading, of the vehicle it is approaching. For example green, red or white are often used to indicate the starboard, port or rear positions of a vehicle, respectively.
Several types of lighting are used in navigation light applications. One lighting type is the light emitting diode (LED). One problem with LED lighting in navigation lighting applications is that LED lights degrade gradually over time, compared with the catastrophic failure of incandescent lights. As a consequence of their gradual failure, LED lights carry the risk of being left in use after their level of intensity has degraded below that required for industry compliance. The airline industry imposes minimum standards for intensity level, as shown in the following table. According to industry guidelines, an aircraft should not be allowed to dispatch without navigation lights that are compliant with the following minimum standards:
Degrees from longitudinal axis0-1010-20.20-110110-180Minimum intensity (cd)4030520
To prevent LED lights from being inadvertently left in operation after their intensity has fallen below an accepted intensity threshold, a number of systems have been developed. One system is a timer system that disables LED light operation after a certain period of time. Another is a manual maintenance log system. The timer system does provide a level of assurance that the lights will comply with requirements, however disablement can occur unexpectedly, leading to the need for unexpected delays in vehicle operation for maintenance. The manual maintenance log system suffers from the requirement for human diligence. An ideal maintenance system would provide an indication a certain period of time in advance that an LED lighting system is approaching the time when it needs to be replaced.