UFC 3-535-01
17 November 2005
Chapter 3: STANDARDS FOR LIGHTED APPROACH AIDS
3-1
APPROACH LIGHT SYSTEM WITH SEQUENCED FLASHING LIGHTS,
(ALSF-1)
3-1.1
Purpose
The ALSF-1 is a high intensity approach lighting system with sequenced flashing lights
where operations under Category I conditions are required. This system provides the
visual guidance to pilots for alignment of the approaching aircraft with the runway and
for final corrections before landing at night and during low visibility weather conditions.
3-1.2
Associated Systems
In addition to electronic aids such as ILS, PAR, or Microwave Landing System (MLS),
the ALSF-1 should include the following:
3-1.2.1
The runway should be paved and not less than 50 meters (150 feet) wide.
The length should not be less than 2,000 meters (6,000 feet), but shorter lengths may
be approved for special operating conditions.
3-1.2.2
The runway must be equipped with the following:
3-1.2.2.1
Precision approach runway markings.
3-1.2.2.2
High-intensity runway edge lights.
3-1.2.2.3
High-intensity threshold lights.
3-1.2.2.4
Runway end lights.
3-1.2.3
The approach should have a paved or stabilized end zone area extending
300 meters (1,000 feet) into the approach area and not less than the runway width. The
first 100 meters (300 feet) of this paved or stabilized area should have the same slope
as the first 300 meters (1,000 feet) of the runway. The remainder of the paved or
stabilized area may have a slope of not more than 1.5 percent. This criteria and further
details are provided in UFC 3-260-01, Airfield and Heliport Planning and Design.
3-1.2.4
The runway should have a Runway Visual Range (RVR) system.
3-1.2.5
Air traffic control should be provided during normal operating hours.
3-1.3
Configuration
The ALSF-1 consists of a pre-threshold light bar, a terminating bar, a 300 meter (1,000
foot) crossbar, centerline lights, sequenced flashing lights, and threshold lights. Figure
3-1 shows the typical layout. The system centerline coincides with the extended runway
centerline. The overall system length is 900 meters (3,000 feet) extending from the
runway threshold into the approach zone. For the Air Force only, if terrain or other local
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