Simplified Directional Facility or SDF is a localizer

Localizer

In aviation, a localizer is one of the components of an Instrument Landing System , and it provides runway centerline guidance to aircraft. In some cases, a course projected by localizer is at an angle to the runway . It is then called a Localizer Type Directional Aid...

-based instrument non-precision approach to an airport, which provides final approach course similar to Instrument Landing System

Instrument Landing System

An instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...

 (ILS) and Localizer Type Directional Aid

Localizer Type Directional Aid

A Localizer Type Directional Aid 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 the runway it serves. In these cases, the localizer antenna array may be offset A Localizer...

 (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. Unlike an ILS, an SDF does not provide vertical guidance in the form of a glideslope. 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

The following SDF approaches are published in the United States (as of June 2011):

1. KAAS, SDF RWY 23, Taylor County Airport
   Taylor County Airport (Kentucky)
   Taylor County Airport is a county-owned public-use airport located two nautical miles northeast of the central business district of Campbellsville, a city in Taylor County, Kentucky, United States.Although most U.S...
   
   , Campbellsville, KY (out of service)
2. KGLW, SDF RWY 07, Glasgow Municipal Airport
   Glasgow Municipal Airport
   Glasgow Municipal Airport is a public use airport located two nautical miles northwest of the central business district of Glasgow, a city in Barren County, Kentucky, United States. It is owned by the Glasgow Airport Board.- Facilities and aircraft :...
   
   , Glasgow, KY (out of service)
3. KLBO, SDF RWY 36, Floyd W. Jones Lebanon Airport, Lebanon, MO
4. KPOF, SDF RWY 36, Poplar Bluff Municipal Airport, Poplar Bluff, MO
5. KFYM, SDF RWY 20, Fayetteville Municipal Airport, Fayetteville, TN
6. KMOR, SDF RWY 05, Moore-Murrell Airport
   Moore-Murrell Airport
   Moore-Murrell Airport is a city-owned public-use airport located four nautical miles southwest of the central business district of Morristown, a city in Hamblen County, Tennessee, United States. It was opened in 1953...
   
   , Morristown, TN
7. KSCX, SDF RWY 23, Scott Municipal Airport
   Scott Municipal Airport
   Scott Municipal Airport is a public-use airport located four nautical miles southwest of the central business district of Oneida, a city in Scott County, Tennessee, United States. The airport is owned by Scott County. It located adjacent to the Big South Fork Airpark, a gated community and...
   
   , Oneida, TN (out of service)
8. KTHA, SDF RWY 18, Tullahoma Regional Airport/William Northern Field
   Tullahoma Regional Airport
   Tullahoma Regional Airport aka William Northern Field is an airport located 2 miles northwest of the central business district of Tullahoma, Tennessee.-References:*, also available as a...
   
   , Tullahoma, TN
9. KMFI, SDF RWY 34, Marshfield Municipal Airport
   Marshfield Municipal Airport (Wisconsin)
   Marshfield Municipal Airport is a public airport located in Marshfield, Wisconsin.-Facilities:*Runway 16/34 5,000 x 100 ft. , asphalt, SDF equipped*Runway 4/22 3,600 x 100 ft. , asphalt...
   
   , Marshfield, WI
10. KSUE, SDF RWY 02, Door County Cherryland Airport
    Door County Cherryland Airport
    Door County Cherryland Airport is a public airport located in Sturgeon Bay, Wisconsin, 2 miles west of the city. It has two runways and is used for corporate and general aviation.- Facilities :...
    
    , Sturgeon Bay, WI
11. KISW, SDF RWY 02, Alexander Field–South Wood County Airport
    South Wood County Airport
    South Wood County Airport , also known as Alexander Field, is a public use airport located one nautical mile south of the central business district of Wisconsin Rapids, a city in Wood County, Wisconsin, United States....
    
    , Wisconsin Rapids, WI

See also

• Instrument approach
  Instrument approach
  For aircraft operating under instrument flight rules , an instrument approach or instrument approach procedure is a series of predetermined maneuvers for the orderly transfer of an aircraft under instrument flight conditions from the beginning of the initial approach to a landing, or to a point...
  
  
• Instrument landing system
  Instrument Landing System
  An instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...
  
  
• Localizer Type Directional Aid
  Localizer Type Directional Aid
  A Localizer Type Directional Aid 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 the runway it serves. In these cases, the localizer antenna array may be offset A Localizer...