Visual Approach Slope Indicators (VASI)

VASI systems with remote on-off switching must be operated when they serve the runway in use and where intensities are controlled in accordance with TBL 3-4-2 and TBL 3-4-3 except:

1. As required by facility directives to meet local conditions.
2. As required by the pilot.

   TBL 3-4-2 VASI Intensity Setting-Two Step System

   Step	Period/Condition
   High	Day-Sunrise to sunset.
   Low	Night-Sunset to sunrise.

   TBL 3-4-3 VASI Intensity Setting-Three Step System

   Step	Period/Condition
   High	Day-Sunrise to sunset.
   Medium	Twilight-From sunset to 30 minutes after sunset and from 30 minutes before sunrise to sunrise,* and during twilight in Alaska.
   Low	Night-Sunset to sunrise.
   *During a 1 year period, twilight may vary 26 to 43 minutes between 25 and 49N latitude.