the NDB to be considered an on-airport facility, the facility  must be located within one mile of any portion of the  landing runway for straight-in approaches and within one  mile of any portion of usable landing surface for circling  approaches. The final approach segment of the approach  is designed with a final approach area that is 2.5 NM wide  at the facility and increases to 8 NM wide at 10 NM from  the facility. Additionally, the final approach course and  the extended runway centerline angle of convergence  cannot exceed 30° for straight-in approaches. This type of  NDB approach is afforded a minimum of 350 feet obstacle  clearance.  approach, the final approach course is typically aligned  to intersect the extended runway centerline 3,000 feet  from the runway threshold, and the angle of convergence  between the two does not exceed 30°. This type of VOR  approach also includes a minimum of 300 feet of obstacle  clearance in the final approach area. The final approach  area criteria include a 2 NM wide primary area at the facility  that expands to 6 NM wide at a distance of 10 NM from  the facility. Additional approach criteria are established  for courses that require a high altitude teardrop approach  penetration.  When DME is included in the title of the VOR approach,  operable DME must be installed in the aircraft in order to  fly the approach from the FAF. The use of DME allows for an  accurate determination of position without timing, which  greatly increases situational awareness throughout the  approach. Alexandria, Louisiana, is an excellent example  of a VOR/DME approach in which the VOR is off the airport  and a FAF is depicted. [Figure 4-53] In this case, the final  approach course is a radial or straight-in final approach and  is designed to intersect the runway centerline at the runway  threshold with the angle of convergence not exceeding 30°.  When a FAF is established for an NDB approach, the  approach design criteria changes. It also takes into account  whether or not the NDB is located on or off the airport.  Additionally, this type of approach can be made both  moving toward or away from the NDB facility. The Tuscon  Ryan Field, NDB/DME RWY 6 is an approach with a FAF  using an on-airport NDB facility that also incorporates the  use of DME. [Figure 4-55] In this case, the NDB has DME  capabilities from the LOC approach system installed on the  airport. While the alignment criteria and obstacle clearance  remain the same as an NDB approach without a FAF, the  final approach segment area criteria changes to an area that  is 2.5 NM wide at the facility and increases to 5 NM wide,  15 NM from the NDB.  The criteria for an arc final approach segment associated  with a VOR/DME approach is based on the arc being  beyond 7 NM and no farther than 30 NM from the VOR  and depends on the angle of convergence between the  runway centerline and the tangent of the arc. Obstacle  clearance in the primary area, which is considered the area  4 NM on either side of the arc centerline, is guaranteed by  at least 500 feet.  The two types of radar approaches available to pilots when  operating in the NAS are precision approach radar (PAR) and  airport surveillance radar (ASR). Radar approaches may be  given to any aircraft at the pilot’s request. ATC may also offer  radar approach options to aircraft in distress regardless of  the weather conditions or as necessary to expedite traffic.  Despite the control exercised by ATC in a radar approach  environment, it remains the pilot’s responsibility to ensure  the approach and landing minimums listed for the approach  are appropriate for the existing weather conditions  considering personal approach criteria certification and  company OpSpecs.  Perhaps the greatest benefit of either type of radar approach  is the ability to use radar to execute a no gyro approach.  Assuming standard rate turns, ATC can indicate when to  begin and end turns. If available, pilots should make use of  this approach when the heading indicator has failed and  partial panel instrument flying is required.  Like the VOR approach, an NDB approach can be designed  using facilities both on and off the airport, with or without  a FAF, and with or without DME availability. At one time,  it was commonplace for an instrument student to learn  how to fly an NDB approach, but with the growing use of  GPS, many pilots no longer use the NDB for instrument  approaches. New RNAV approaches are also rapidly being  constructed into airports that are served only by NDB. The  long-term plan includes the gradual phase out of NDB  facilities, and eventually, the NDB approach becomes  nonexistent. Until that time, the NDB provides additional  availability for instrument pilots into many smaller, remotely  located airports.  Information about radar approaches is published in tabular  form in the front of the TPP booklet. PAR, ASR, and circling  approach information including runway, DA, DH, or MDA,  height above airport (HAA), HAT, ceiling, and visibility criteria  The NDB Runway 35 approach at Carthage/Panola County  Sharpe Field is an example of an NDB approach established  with an on-airport NDB that does not incorporate a FAF.  [Figure 4-54] In this case, a procedure turn or penetration  turn is required to be a part of the approach design. For  4-69 NDB Approach  Radar Approaches 