Thursday, March 29, 2012

Anti-Collision Lights

Whelen® Engineering Company makes the LED position/anti-collision/tail light assemblies at each wing tip. These are comprised of light emitting diode arrays: three emitters are used for the position light, and three are used for the tail light. The anti-collision light is designed with 26 LED’s, and flash at a rate of approximately 45 cycles per minute. The intensity of the light and the flash rate of the anti-collision array prevent inspection for failed elements, so Built-In-Test (BIT) circuitry is employed to assure proper operation.

This BIT circuitry measures the power used during the on cycle, and will automatically shut off the strobe function after 9 or 10 flashes if a failure is detected. This same functionality will turn off the strobes if the system is operated with low voltage, less than 11.3 volts, on the buss. Most operators will not notice this issue once the engine is started since the alternator will be supporting the buss voltage and charging the battery. It is possible, however, for the engine throttle to be reduced to a low idle condition and the voltage to drop below the spec on a cold day. If this occurs, cycling the strobe switch to OFF and then back to ON with the engine above idle RPM will reset the BIT circuitry, and return the anti-collision function of the position lights.

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