In cases where the IAF is part of the en route structure and feeder routes are not required, a transition or terminal route is still needed for aircraft to proceed from the IAF to the intermediate fix (IF). These routes are initial approach segments because they begin at the IAF. Like feeder routes, they are depicted with course, minimum altitude, and distance to the IF. Essentially, these routes accomplish the same thing as feeder routes but they originate at an IAF, whereas feeder routes terminate at an IAF.

DME ARCS DME arcs also provide transitions to the approach course, but DME arcs are actually approach segments while feeder routes, by definition, are not. When established on a DME arc, the aircraft has departed the en route phase and has begun the approach and is maneuvering to enter an intermediate or final segment of the approach. DME arcs may also be used as an intermediate or a final segment, although they are extremely rare as final approach segments.

An arc may join a course at or before the IF. When joining a course at or before the IF, the angle of intersection of the arc and the course is designed so it does not exceed 120°. When the angle exceeds 90°, a radial that provides at least 2 NM of lead shall be identified to assist in leading the turn on to the intermediate course. DME arcs are predicated on DME collocated with a facility providing omnidirectional course information, such as a VOR. A DME arc cannot be based on an ILS or LOC DME source because omnidirectional course information is not provided.

Required obstruction clearance (ROC) along the arc depends on the approach segment. For an initial approach segment, a ROC of 1,000 feet is required in the primary area, which extends to 4 NM on either side of the arc. For an intermediate segment primary area the ROC is 500 feet. The initial and intermediate segment secondary areas extend 2 NM from the primary boundary area edge. The ROC starts at the primary area boundary edge at 500 feet and tapers to zero feet at the secondary area outer edge. [Figure 5-28]


Some approach procedures do not permit straight-in approaches unless pilots are being radar vectored. In these situations, pilots will be required to complete a procedure turn (PT) or other course reversal, generally within 10 NM of the PT fix, to establish the aircraft inbound on the intermediate or final approach segment.

If Category E airplanes are using the PT or there is a descent gradient problem, the PT distance available can be as much as 15 NM. During a procedure turn, a maximum speed of 200 knots indicated airspeed

Figure 5-28. DME Arc Obstruction Clearance.

(KIAS) should be observed from first crossing the course reversal IAF through the procedure turn maneuver to ensure containment within the obstruction clearance area. Unless a holding pattern or teardrop procedure is published, the point where pilots begin the turn and the type and rate of turn are optional. If above the procedure turn minimum altitude, pilots may begin descent as soon as they cross the IAF outbound.

The 45° procedure turn, the racetrack pattern (holding pattern), the teardrop procedure turn, or the 80°/260° course reversal are mentioned in the AIM as acceptable variations for course reversal. When a holding pattern is published in place of a procedure turn, pilots must make the standard entry and follow the depicted pattern to establish the aircraft on the inbound course. Additional circuits in the holding pattern are not necessary or expected by ATC if pilots are cleared for the approach prior to returning to the fix. In the event additional time is needed to lose altitude or become better established on course, pilots should advise ATC and obtain approval for any additional turns. When a teardrop is depicted and a course reversal is required, pilots also must fly the procedural track as published.

A procedure turn is the maneuver prescribed to perform a course reversal to establish the aircraft inbound on an intermediate or final approach course. The procedure turn or hold- in lieu- of- procedure turn (PT) is a required maneuver when it is depicted on the approach chart. However, the procedure turn or the hold-in-lieu-of-PT is not permitted when the symbol "No PT" is depicted on the initial segment being flown, when a RADAR VECTOR to the final approach course is provided, or when conducting a timed approach from a holding fix. The altitude prescribed for the procedure turn is a minimum altitude until the aircraft is established on the inbound course. The maneuver must be completed within the distance specified in the profile view. The pilot may elect to use the procedure turn or hold-in-lieu-of-PT when it is not required by the procedure, but must first receive an amended clearance from ATC. When ATC is Radar vectoring to the final approach course, or to the Intermediate Fix as may occur with RNAV standard instrument approach procedures, ATC may specify in the approach clearance “CLEARED STRAIGHT-IN (type) APPROACH” to ensure that the pilot understands that the procedure turn or holdin- lieu-of-PT is not to be flown. If the pilot is uncertain whether ATC intends for a procedure turn or a straight-in approach to be flown, the pilot shall immediately request clarification from ATC (14 CFR Part 91.123).

Approach charts provide headings, altitudes, and distances for a course reversal. Published altitudes are “minimum” altitudes, and pilots must complete the maneuver within the distance specified on the profile view (typically within 10 NM). Pilots also are required to maneuver the aircraft on the procedure turn side of the final approach course. These requirements are necessary to stay within the protected airspace and maintain adequate obstacle clearance. [Figure 5-29]

Figure 5-29. Course Reversal Methods.

A minimum of 1,000 feet of obstacle clearance is provided in the procedure turn primary area. [Figure 5-30] In the secondary area, 500 feet of obstacle clearance is provided at the inner edge, tapering uniformly to zero feet at the outer edge. The primary and secondary areas determine obstacle clearance in both the entry and maneuvering zones. The use of entry and maneuvering zones provides further relief from obstacles. The entry zone is established to control the obstacle clearance prior to proceeding outbound from the procedure turn fix. The maneuvering zone is established to control obstacle clearance after proceeding outbound from the procedure turn fix.