(a) Instrument approaches to civil airports.
    Unless otherwise authorized by the Administrator, when an instrument
  letdown to a civil airport is necessary, each person operating an aircraft,
  except a military aircraft of the United States, shall use a standard
  instrument approach procedure prescribed for the airport in part 97 of this
  chapter.
    (b) Authorized DH or MDA. For the purpose of this section, when the
  approach procedure being used provides for and requires the use of a DH or
  MDA, the authorized DH or MDA is the highest of the following:
    (1) The DH or MDA prescribed by the approach procedure.
    (2) The DH or MDA prescribed for the pilot in command.
    (3) The DH or MDA for which the aircraft is equipped.
    (c) Operation below DH or MDA. Where a DH or MDA is applicable, no pilot
  may operate an aircraft, except a military aircraft of the United States, at
  any airport below the authorized MDA or continue an approach below the
  authorized DH unless--
    (1) The aircraft is continuously in a position from which a descent to a
  landing on the intended runway can be made at a normal rate of descent using
  normal maneuvers, and for operations conducted under part 121 or part 135
  unless that descent rate will allow touchdown to occur within the touchdown
  zone of the runway of intended landing;
    (2) The flight visibility is not less than the visibility prescribed in the
  standard instrument approach being used; and
    (3) Except for a Category II or Category III approach where any necessary
  visual reference requirements are specified by the Administrator, at least
  one of the following visual references for the intended runway is distinctly
  visible and identifiable to the pilot:
    (i) The approach light system, except that the pilot may not descend below
  100 feet above the touchdown zone elevation using the approach lights as a
  reference unless the red terminating bars or the red side row bars are also
  distinctly visible and identifiable.
    (ii) The threshold.
    (iii) The threshold markings.
    (iv) The threshold lights.
    (v) The runway end identifier lights.
    (vi) The visual approach slope indicator.
    (vii) The touchdown zone or touchdown zone markings.
    (viii) The touchdown zone lights.
    (ix) The runway or runway markings.
    (x) The runway lights.
    (d) Landing. No pilot operating an aircraft, except a military aircraft of
  the United States, may land that aircraft when the flight visibility is less
  than the visibility prescribed in the standard instrument approach procedure
  being used.
    (e) Missed approach procedures. Each pilot operating an aircraft, except a
  military aircraft of the United States, shall immediately execute an
  appropriate missed approach procedure when either of the following conditions
  exist:
    (1) Whenever the requirements of paragraph (c) of this section are not met
  at either of the following times:
    (i) When the aircraft is being operated below MDA; or
    (ii) Upon arrival at the missed approach point, including a DH where a DH
  is specified and its use is required, and at any time after that until
  touchdown.
    (2) Whenever an identifiable part of the airport is not distinctly visible
  to the pilot during a circling maneuver at or above MDA, unless the inability
  to see an identifiable part of the airport results only from a normal bank of
  the aircraft during the circling approach.
    (f) Civil airport takeoff minimums. Unless otherwise authorized by the
  Administrator, no pilot operating an aircraft under parts 121, 125, 127, 129,
  or 135 of this chapter may take off from a civil airport under IFR unless
  weather conditions are at or above the weather minimum for IFR takeoff
  prescribed for that airport under part 97 of this chapter. If takeoff
  minimums are not prescribed under part 97 of this chapter for a particular
  airport, the following minimums apply to takeoffs under IFR for aircraft
  operating under those parts:
    (1) For aircraft, other than helicopters, having two engines or less--1
  statute mile visibility.
    (2) For aircraft having more than two engines-- «  statute mile
  visibility.
    (3) For helicopters--1/2 statute mile visibility.
    (g) Military airports. Unless otherwise prescribed by the Administrator,
  each person operating a civil aircraft under IFR into or out of a military
  airport shall comply with the instrument approach procedures and the takeoff
  and landing minimum prescribed by the military authority having jurisdiction
  of that airport.
    (h) Comparable values of RVR and ground visibility. (1) Except for Category
  II or Category III minimums, if RVR minimums for takeoff or landing are
  prescribed in an instrument approach procedure, but RVR is not reported for
  the runway of intended operation, the RVR minimum shall be converted to
  ground visibility in accordance with the table in paragraph (h)(2) of this
  section and shall be the visibility minimum for takeoff or landing on that
  runway.

                                                           Visibility
                                                            (statute
                             RVR (feet)                      miles)

            1,600 . . . . . . . . . . . . . . . . . . . .         1/4
            2,400 . . . . . . . . . . . . . . . . . . . .         «
            3,200 . . . . . . . . . . . . . . . . . . . .         5/8
            4,000 . . . . . . . . . . . . . . . . . . . .         3/4
            4,500 . . . . . . . . . . . . . . . . . . . .         7/8
            5,000 . . . . . . . . . . . . . . . . . . . .           1
            6,000 . . . . . . . . . . . . . . . . . . . .       1 1/4

    (i) Operations on unpublished routes and use of radar in instrument
  approach procedures. When radar is approved at certain locations for ATC
  purposes, it may be used not only for surveillance and precision radar
  approaches, as applicable, but also may be used in conjunction with
  instrument approach procedures predicated on other types of radio
  navigational aids. Radar vectors may be authorized to provide course guidance
  through the segments of an approach to the final course or fix. When
  operating on an unpublished route or while being radar vectored, the pilot,
  when an approach clearance is received, shall, in addition to complying with
  Sec. 91.177, maintain the last altitude assigned to that pilot until the
  aircraft is established on a segment of a published route or instrument
  approach procedure unless a different altitude is assigned by ATC. After the
  aircraft is so established, published altitudes apply to descent within each
  succeeding route or approach segment unless a different altitude is assigned
  by ATC. Upon reaching the final approach course or fix, the pilot may either
  complete the instrument approach in accordance with a procedure approved for
  the facility or continue a surveillance or precision radar approach to a
  landing.
    (j) Limitation on procedure turns. In the case of a radar vector to a final
  approach course or fix, a timed approach from a holding fix, or an approach
  for which the procedure specifies "No PT," no pilot may make a procedure turn
  unless cleared to do so by ATC.
    (k) ILS components. The basic ground components of an ILS are the
  localizer, glide slope, outer marker, middle marker, and, when installed for
  use with Category II or Category III instrument approach procedures, an inner
  marker. A compass locator or precision radar may be substituted for the outer
  or middle marker. DME, VOR, or nondirectional beacon fixes authorized in the
  standard instrument approach procedure or surveillance radar may be
  substituted for the outer marker. Applicability of, and substitution for, the
  inner marker for Category II or III approaches is determined by the
  appropriate part 97 approach procedure, letter of authorization, or
  operations specification pertinent to the operations.