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6/17/21 

AIM 

2. 

When the aircraft descends from green to red, the pilot may see a dark amber color during the transition from green to 

red. 

FIG 2

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Pulsating Visual Approach Slope Indicator 

NOTE

 

Since the PVASI consists of a single light source which could possibly be confused with other light sources, pilots should 
exercise care to properly locate and identify the light signal. 

FIG 2

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Alignment of Elements 

Above Glide Path 

On Glide Path 

Below Glide Path 

d.  Pulsating Systems. 

Pulsating visual ap-

proach 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 glide path 
indication may be a steady white light or alternating 
RED and WHITE light. The slightly below glide path 
indication is a steady red light. If the aircraft descends 
further below the glide path, the red light starts to 
pulsate. The above glide path indication is a pulsating 
white light. The pulsating rate increases as the aircraft 

gets further above or below the desired glide slope. 
The useful range of the system is about four miles 
during the day and up to ten miles at night. (See 
FIG 2

1

7.) 

e.  Alignment of Elements Systems. 

Alignment 

of elements systems are installed on some small 
general aviation airports and are a low

cost system 

consisting of painted plywood panels, normally black 
and white or fluorescent orange. Some of these 
systems are lighted for night use. The useful range of 

Airport Lighting Aids 

2

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