Simplified directional facility (SDF) is a
localizer
An instrument landing system localizer, or simply localizer (LOC), is a system of horizontal guidance in the instrument landing system, which is used to guide aircraft along the axis of the runway.
Principle of operation
In aviation, a localiz ...
-based instrument
non-precision approach
In aviation, an instrument approach or instrument approach procedure (IAP) is a series of predetermined maneuvers for the orderly transfer of an aircraft operating under instrument flight rules from the beginning of the initial approach to a landi ...
to an airport, which provides final approach course similar to
instrument landing system
In aviation, the instrument landing system (ILS) is a precision radio navigation system that provides short-range guidance to aircraft to allow them to approach a runway at night or in bad weather. In its original form, it allows an aircraft to ...
(ILS) and
localizer type directional aid
A localizer type directional aid (LDA) or Instrument Guidance System (IGS) is a type of localizer-based instrument approach to an airport. It is used in places where, due to terrain and other factors, the localizer antenna array is not aligned with ...
(LDA) approaches, although not as precise.
The SDF signal is fixed at either 6 or 12 degrees, as necessary to provide maximum flyability and optimum course quality.
[AIM 1-1-10 (March 7, 2013 Revision), accessed 2013-07-06] Unlike an ILS, an SDF does not provide vertical guidance in the form of a
glideslope
Instrument landing system glide path, commonly referred to as a glide path (G/P) or glide slope (G/S), is "a system of vertical guidance embodied in the instrument landing system which indicates the vertical deviation of the aircraft from its o ...
.
The SDF course may or may not be aligned with the runway because its antenna may be offset from the runway centerline. Usable off-course indications are limited to 35 degrees either side of the course centerline.
Current SDF approaches in the United States
On January 01, 2018, the SDF approach at KMFI was permanently decommissioned leaving only one remaining operational SDF approach in the United States.
# KMOR, SDF RWY 05,
Moore–Murrell Airport
Morristown Regional Airport (formerly called Moore–Murrell Airport) is a city-owned public-use airport located four nautical miles (7 km) southwest of the central business district of Morristown, a city in Hamblen County, Tennessee, United ...
, Morristown, TN
See also
*
Instrument approach
In aviation, an instrument approach or instrument approach procedure (IAP) is a series of predetermined maneuvers for the orderly transfer of an aircraft operating under instrument flight rules from the beginning of the initial approach to a landi ...
*
Instrument landing system
In aviation, the instrument landing system (ILS) is a precision radio navigation system that provides short-range guidance to aircraft to allow them to approach a runway at night or in bad weather. In its original form, it allows an aircraft to ...
*
Localizer type directional aid
A localizer type directional aid (LDA) or Instrument Guidance System (IGS) is a type of localizer-based instrument approach to an airport. It is used in places where, due to terrain and other factors, the localizer antenna array is not aligned with ...
References
External links
Aeronautical Information Manual (AIM) published in US by
Federal Aviation Administration
The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...
FAA NOTAM website
Aircraft landing systems
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