title: Aviation signal light gun: variations in photometric and colorimetric properties among airports.
abstract: OBJECTIVE
  The aviation signal light gun (LG) is believed by some to be the only color-critical task in aviation without redundant coding. However, there are questions regarding its practicality as a test of color vision given that the brightness and colors may vary between airports.
  
  
  METHODS
  The chromaticity coordinates and relative intensities of five LGs were measured with a portable spectroradiometer. Four of the LGs were measured at airports in southern Ontario and compared with a newly purchased LG (ATI Avionics). The air traffic controllers (ATCs) were also surveyed regarding the frequency of LG use.
  
  
  RESULTS
  Only 40% of the LGs at the airports were in good working condition. All working LGs met the ICAO standards for airport signal lights. However, differences did exist between models which were related to the date of manufacture. Older LG lights were dimmer and their green and white lights were more yellow than the newer LGs. ATCs reported that they used the LG primarily for pilot instruction and demonstration. However, in two locations, the LG was used to signal pilots who were flying their aircraft in for radio repair. This occurred about once or twice a month.
  
  
  CONCLUSIONS
  The LG is used primarily for instructional purposes. However, if a radio repair shop is at the airport, then the LG will be used about once to twice a month. There is sufficient variability in the light colors and intensity across airports so that any given LG cannot be used as valid practical test of color vision in aviation.
authors.affiliation: University of Waterloo, School of Optometry, Ontario, Canada. jhovis@uwaterloo.ca
authors.forename: Jeffery K
authors.initials: JK
authors.lastname: Hovis
authors.forename: Evanne
authors.initials: E
authors.lastname: Casson
authors.forename: Walter
authors.initials: W
authors.lastname: Delpero
mesh_terms: D001359:Aviation / Q000295:instrumentation*; D003117:Color Vision Defects; D003124:Colorimetry; D004867:Equipment Design; D006801:Humans; D008029:Lighting; D011874:Radiometry / Q000379:methods; D013053:Spectrophotometry / Q000379:methods