The International Cessna 170 Association

I see the term PAR36 used in landing light discussions.

Please explain what the term PAR36 means.

Any significance to the number 36?

You know, Google is both a curse and a wonderful thing.

Search PAR light definitiion to find:

• Parabolic aluminized reflector light - Wikipedia
  https://en.wikipedia.org/wiki/Parabolic ... ctor_light
  • A parabolic aluminized reflector lamp (also PARCAN light, PARcan, or simply PAR) is a type of electric lamp that is widely used in commercial, residential, and transportation illumination.
  
  What Does PAR mean? - Lumicrest High CRI LED Lighting
  https://lumicrest.com/par-mean/
  • MR stands for Multi-faceted Reflector. Again, a technique for reflecting the maximum light out the front of a halogen lamp. The term “MR” is usually only used for small lamps, 2 inches in diameter or less. ... The number after PAR or MR indicates the diameter of the face of the lamp, expressed in 1/8ths of an inch.

So a PAR36 is a parabolic aluminized reflector lamp of 36/8" or 4-1/4" diameter.

Note this does not describe color temperature, luminosity or watts used. The method of creating light such as LED, or type of filament and or gas such as halogen or tungsten. It does not describe the bulb base style or any other features of the bulb such as molded in tabs. All PAR36 bulbs are not created equal.

When replacing your 4509 landing light bulb with something described as a PAR36 one should be sure the manufacturer lists it as being a replacement for a 4509 which means you have half a chance the bulb will fit in the mount and connect to the wires you have. It still does not mean the light produced by the bulb is suitable for the purpose you intend ie color, luminosity and electrical load.

Now I Know
Bruce you are amazing.

Thank You

Actually the 4509 number is a GE identifier and any replacement that claims to be an identical replacement for the 4509 refers to the 100 watt output as well as the PAR36 size and terminals and the LENS (such as a clear versus a "fog" or "diffusing" or "Fresnel" type. A Wagner, TungSol, or Sylvania lamp identified with PAR36/4509 is claiming to be an identical, incandescent lamp to the GE 4509.

A lamp with claims to "replace" a 4509 might be referencing only the PAR36 size/terminal/candle-power characteristics and may not be incandescent (for example an L.E.D. replacement for 4509.)

Hope that helps clarify without taking a "dim" view.