01/02/1999 Ask Mike! Archive
What's the skinny on proper use of lights?

Dear Mike:

As a recent private pilot and aircraft owner, I've heard many stories around the 'ol coffee pot about proper use of lights on the airplane.  What's the skinny?

Ralph

Ralph,

I'll answer that question in three parts, as I am a pilot, aircraft owner, and technician.
 
As a pilot, ALWAYS follow the FAR's concerning use of position, landing, and anti-collision lighting (strobes and or beacon).  91.205(c) and 91.209 are good sources of reference.  Additionally, if equipped with a beacon(red or white, but notice I didn't say 'strobe'), it's not a bad idea to have it on all the time (except engine start-up and shutdown).  Strobes are better turned on at the end of a run-up, like when you switch the transponder to "alt" from "standby".  It's more neighborly.  Landing lights should be used as required (I personally don't use them at night; it throws off my depth perception...) like in a two-way high-traffic corridor.
 
As an aircraft owner, nothing is more bothersome than having to replace the lights.  Common position light bulbs can cost between $15 to $25 each. Landing lights retail for $30 to over $60 each, and strobe lamps are around $100 (let alone the power supplies...) BUT, in the name of safety...
 
As a technician, let's look at systems.  Average current draw for position (navigation) lights are about 5 or 6 amps total.  Not much load, not much to worry about.  Generally speaking, modern aircraft are over-wired for this load.  Same goes for strobes.  Landing lights, however, draw a much higher current.  This can have detrimental effects on battery life at low engine speed operations (unless you have one heck of an alternator!)  You didn't say what kind of aircraft you own, but if it's a later Cessna with the plastic rocker switches, you better have your technician check the switches and terminals for servicability.  These switches are NOT rated for the loads they are asked to carry, and WILL melt, corrode or cause other problems.  (Why this was ever approved by the FAA is amazing!)  This is especially true with Cessna 150, 152, and 172 models that have the single cowl-mounted landing light.  If you need more info on an approved (STC'd) modification to help with this problem, e-mail me!
 
Lastly, don't forget about your instrument lights.  If you're not using them, turn them off!  ALL dimmer circuits heat up, whether it basic rheostat or transistorized.  Save them for when you need them; it's really easy to leave them on after a night flight, and not realize they are on until several day flights later.
 
Gear-Green,
Mike