AIM 

4/20/23 

23.  Transponder set on radio failure Code 7600 (RDOF flashes) 

24.  Computer ID #228, CST indicates target is in coast status 

25.  Assigned altitude FL 290, transponder code (these two items constitute a “limited data block”) 

Note: numbers 10, 11, and 12 constitute a “full data block” 

Other symbols: 

26.  Navigational aid 

27.  Airway or jet route 

28.  Outline of weather returns based on primary radar. “H” represents areas of high density precipitation which might be 

thunderstorms. Radial lines indicated lower density precipitation. 

29.  Obstruction 

30.  Airports 

Major: 
Small: 

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3.  Surveillance Radar 

a. 

Surveillance radars are divided into two general categories: Airport Surveillance Radar (ASR) and Air 

Route Surveillance Radar (ARSR). 

1. 

ASR is designed to provide relatively short

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range coverage in the general vicinity of an airport and to 

serve as an expeditious means of handling terminal area traffic through observation of precise aircraft locations 

on a radarscope. The ASR can also be used as an instrument approach aid. 

2. 

ARSR is a long

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range radar system designed primarily to provide a display of aircraft locations over 

large areas. 

b. 

Surveillance radars scan through 360 degrees of azimuth and present target information on a radar display 

located in a tower or center. This information is used independently or in conjunction with other navigational 

aids in the control of air traffic. 

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5

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4.  Precision Approach Radar (PAR) 

a. 

PAR is designed for use as a landing aid rather than an aid for sequencing and spacing aircraft. PAR 

equipment may be used as a primary landing aid (See Chapter 5, Air Traffic Procedures, for additional 

information), or it may be used to monitor other types of approaches. It is designed to display range, azimuth, 

and elevation information. 

b. 

Two antennas are used in the PAR array, one scanning a vertical plane, and the other scanning horizontally. 

Since the range is limited to 10 miles, azimuth to 20 degrees, and elevation to 7 degrees, only the final approach 

area is covered. Each scope is divided into two parts. The upper half presents altitude and distance information, 

and the lower half presents azimuth and distance. 

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5.  Airport Surface Detection Equipment (ASDE

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X)/Airport Surface Surveillance 

Capability (ASSC) 

a. 

ASDE

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X/ASSC is a multi

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sensor surface surveillance system the FAA is acquiring for airports in the 

United States. This system provides high resolution, short

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range, clutter free surveillance information about 

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5

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10 

Surveillance Systems