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Pilot's Handbook of Aeronautical Knowledge
Airport Operations

Airport Lighting

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Pilot's Handbook of Aeronautical Knowledge



Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making




Approach Light Systems
Approach light systems are primarily intended to provide a
means to transition from instrument flight to visual flight for
landing. The system configuration depends on whether the
runway is a precision or nonprecision instrument runway.
Some systems include sequenced flashing lights, which
appear to the pilot as a ball of light traveling toward the
runway at high speed. Approach lights can also aid pilots
operating under VFR at night.

Visual Glideslope Indicators
Visual glideslope indicators provide the pilot with glidepath
information that can be used for day or night approaches. By
maintaining the proper glidepath as provided by the system,
a pilot should have adequate obstacle clearance and should
touch down within a specified portion of the runway.

Visual Approach Slope Indicator (VASI)
VASI installations are the most common visual glidepath
systems in use. The VASI provides obstruction clearance
within 10° of the runway extended runway centerline, and to
four nautical miles (NM) from the runway threshold.
The VASI consists of light units arranged in bars. There are
2-bar and 3-bar VASIs. The 2-bar VASI has near and far
light bars and the 3-bar VASI has near, middle, and far light
bars. Two-bar VASI installations provide one visual glidepath
which is normally set at 3°. The 3-bar system provides two
glidepaths, the lower glidepath normally set at 3° and the
upper glidepath ¼ degree above the lower glidepath.

The basic principle of the VASI is that of color differentiation
between red and white. Each light unit projects a beam of
light, a white segment in the upper part of the beam and a
red segment in the lower part of the beam. The lights are
arranged so the pilot sees the combination of lights shown in
Figure 13-7 to indicate below, on, or above the glidepath.

Two-bar VASI system.
Figure 13-7. Two-bar VASI system.

Other Glidepath Systems
A precision approach path indicator (PAPI) uses lights similar
to the VASI system except they are installed in a single row,
normally on the left side of the runway. [Figure 13-8]
A tri-color system consists of a single light unit projecting
a three-color visual approach path. Below the glidepath is
indicated by red, on the glidepath is indicated by green, and
above the glidepath is indicated by amber. When descending
below the glidepath, there is a small area of dark amber. Pilots
should not mistake this area for an "above the glidepath"
indication. [Figure 13-9]

Pulsating visual approach slope indicators normally consist of
a single light unit projecting a two-color visual approach path
into the final approach area of the runway upon which the
indicator is installed. The on glidepath indication is a steady
white light. The slightly below glidepath indication is a steady
red light. If the aircraft descends further below the glidepath,
the red light starts to pulsate. The above glidepath indication
is a pulsating white light. The pulsating rate increases as the
aircraft gets further above or below the desired glideslope.