BY ORDER OF THE SECRETARY OF THE AIR FORCE AIR FORCE ...

AFMAN 11-217V1 3 JANUARY 2005 257
11.5.6.1. NOTE: ATC will not assign an altitude that does not provide obstacle
clearance; however, pilots are ultimately responsible for terrain clearance. The
following information will aid you in monitoring assigned altitudes:
11.5.6.2. Low altitude charts may provide several different altitudes that will ensure
obstacle clearance, depending upon aircraft position.
11.5.6.3. If proceeding to an IAF via an airway, the MEA/MOCA will provide
obstacle clearance. If using a published terminal route, the published minimum
altitude along that route ensures obstacle clearance.
11.5.6.4. If not proceeding via a published route, obstacle clearance can be
guaranteed by maintaining the OROCA, ORTCA, minimum sector altitude, or
emergency safe altitude (depending upon aircraft position and altitudes printed on the
approach chart).
11.5.6.5. If you require a lower altitude to start the approach, request it from ATC.
Remember that you may start an approach at a higher than published IAF altitude
provided it is not a mandatory or maximum altitude. If you do this, you must comply
with the remaining altitude restrictions on the approach. If maneuvering is required
to lose excess altitude prior to starting the approach, a clearance from ATC is also
required.
11.6. Radar Vectors. The use of radar vectors is the simplest and most convenient way to
position an aircraft for an approach. Using radar, air traffic controllers can position an
aircraft at almost any desired point, provide obstacle clearance by the use of minimum
vectoring altitudes, and ensure traffic separation. This flexibility allows an aircraft to be
vectored to any segment of a published routing shown on the IAP or to a radar final. Radar
controllers use MVA charts that are prepared by the air traffic facilities at locations where
there are numerous different minimum IFR altitudes. The MVA chart is divided into sectors
that are large enough to accommodate vectoring of aircraft within the sector at the MVA.
Minimum altitudes are established at 1,000 feet or 2,000 feet in designated mountainous
areas (in mountainous areas, MVAs may be authorized at 1,000 feet in order to achieve
compatibility with terminal routes or IAPs). Obstructions may be enclosed in a 3 NM buffer
area (5 NM if the obstruction is beyond 40 NM from the radar antenna); MVAs may be
lower than nonradar MEAs/MOCAs. They may also be below emergency safe, or minimum
sector altitudes. When being radar vectored, IFR altitude assignments will be at or above
MVA.