Time leaving the holding fix must be known to ATC before  succeeding aircraft can be cleared to the vacated airspace.  Leave the holding fix: The same entry and holding procedures apply to DME  holding, but distances (nautical miles) are used instead of  time values. The length of the outbound leg is specified by  the controller, and the end of this leg is determined by the  DME readout. Compliance with the approach procedures shown on the  approach charts provides necessary navigation guidance  information for alignment with the final approach courses,  as well as obstruction clearance. Under certain conditions,  a course reversal maneuver or procedure turn may be  necessary. However, this procedure is not authorized when: Unless otherwise authorized, when an instrument letdown to  an airport is necessary, the pilot should use a standard IAP  prescribed for that airport. IAPs are depicted on IAP charts  and are found in the TPP. ATC approach procedures depend upon the facilities available  at the terminal area, the type of instrument approach executed,  and the existing weather conditions. The ATC facilities,  NAVAIDs, and associated frequencies appropriate to each  standard instrument approach are given on the approach  chart. Individual charts are published for standard approach  procedures associated with the following types of facilities: If an approach clearance is required, ATC authorizes the pilots  to execute his or her choice of standard instrument approach  (if more than one is published for the airport) with the  Figure 10-8 shows an approach procedure at an airport  without an operating control tower. When approaching  such a facility, the pilot should monitor the AWOS/ASOS  if available for the latest weather conditions. When direct  communication between the pilot and controller is no  longer required, the ARTCC or approach controller issues a  clearance for an instrument approach and advises “change to  advisory frequency approved.” When the aircraft arrives on  a “cruise” clearance, ATC does not issue further clearance  for approach and landing. When an approach is flown with the assistance of radar  vectors, ATC provides guidance in the form of headings and  altitudes, which position the aircraft to intercept the final  approach. From this point, the pilot resumes navigation,  intercepts the final approach course, and completes the  approach using the IAP chart. This is often a more expedient  method of flying the approach, as opposed to the full  approach, and allows ATC to sequence arriving traffic. A  pilot operating in radar contact can generally expect the  assistance of radar vectors to the final approach course. An IAP can be flown in one of two ways: as a full approach  or with the assistance of radar vectors. When the IAP is flown  as a full approach, pilots conduct their own navigation using  the routes and altitudes depicted on the instrument approach  chart. A full approach allows the pilot to transition from  the en route phase, to the instrument approach, and then to  a landing with minimal assistance from ATC. This type of  procedure may be requested by the pilot but is most often  used in areas without radar coverage. A full approach also  provides the pilot with a means of completing an instrument  approach in the event of a communications failure. 1.  When ATC issues either further clearance en route or  approach clearance; 2.  As prescribed in 14 CFR part 91 (for IFR operations;  two-way radio communications failure, and  responsibility and authority of the pilot-in-command);  or 3.  After the IFR flight plan has been cancelled, if the  aircraft is holding in VFR conditions. 1.  Nondirectional beacon (NDB) 2.  Very-high frequency omnirange (VOR) 3.  Very-high frequency omnirange with distance  measuring equipment (VORTAC or VOR/DME) 4.  Localizer (LOC) 5.  Instrument landing system (ILS) 6.  Localizer-type directional aid (LDA) 7.  Simplified directional facility (SDF) 8.  Area navigation (RNAV) 9.  Global positioning system (GPS) 1.  The symbol “NoPT” appears on the approach course  on the plan view of the approach chart. 2.  Radar vectoring is provided to the final approach  course. 3.  A holding pattern is published in lieu of a procedure  turn. 4.  Executing a timed approach from a holding fix. 5.  Otherwise directed by ATC. DME Holding Approaches Compliance With Published Standard Instrument  Approach Procedures Instrument Approaches to Civil Airports Approach to Airport Without an Operating Control  Tower 10-13