Federal Aviation Administration, DOT § 91.175

a certificated and appropriately rated in paragraph (b)(1) of this section, is radio repair station or, outside the used, an entry must be made in the air- United States, a test signal operated or craft log or other record by the repair approved by an appropriate authority station certificate holder or the certifi- to check the VOR equipment (the max- cate holder’s representative certifying imum permissible indicated bearing to the bearing transmitted by the re- error is plus or minus 4 degrees); or pair station for the check and the date (2) Use, at the airport of intended de- of transmission. parture, a point on the airport surface designated as a VOR system check- (Approved by the Office of Management and point by the Administrator, or, outside Budget under control number 2120–0005) the United States, by an appropriate authority (the maximum permissible § 91.173 ATC clearance and flight plan bearing error is plus or minus 4 de- required. grees); No person may operate an aircraft in (3) If neither a test signal nor a des- controlled airspace under IFR unless ignated checkpoint on the surface is that person has— available, use an airborne checkpoint (a) Filed an IFR flight plan; and designated by the Adninistrator or, (b) Received an appropriate ATC outside the United States, by an appro- clearance. priate authority (the maximum per- missible bearing error is plus or minus § 91.175 Takeoff and landing under 6 degrees); or IFR. (4) If no check signal or point is (a) Instrument approaches to civil air- available, while in flight— ports. (i) Select a VOR radial that lies along the centerline of an established Unless otherwise authorized by the VOR airway; Administrator, when an instrument (ii) Select a prominent ground point letdown to a civil airport is necessary, along the selected radial preferably each person operating an aircraft, ex- more than 20 nautical miles from the cept a military aircraft of the United VOR ground facility and maneuver the States, shall use a standard instrument aircraft directly over the point at a approach procedure prescribed for the reasonably low altitude; and airport in part 97 of this chapter. (iii) Note the VOR bearing indicated (b) Authorized DH or MDA. For the by the receiver when over the ground purpose of this section, when the ap- point (the maximum permissible vari- proach procedure being used provides ation between the published radial and for and requires the use of a DH or the indicated bearing is 6 degrees). MDA, the authorized DH or MDA is the (c) If dual system VOR (units inde- highest of the following: pendent of each other except for the (1) The DH or MDA prescribed by the antenna) is installed in the aircraft, approach procedure. the person checking the equipment (2) The DH or MDA prescribed for the may check one system against the pilot in command. other in place of the check procedures (3) The DH or MDA for which the air- specified in paragraph (b) of this sec- craft is equipped. tion. Both systems shall be tuned to the same VOR ground facility and note (c) Operation below DH or MDA. the indicated bearings to that station. Where a DH or MDA is applicable, no The maximum permissible variation pilot may operate an aircraft, except a between the two indicated bearings is 4 military aircraft of the United States, degrees. at any airport below the authorized (d) Each person making the VOR MDA or continue an approach below operational check, as specified in para- the authorized DH unless— graph (b) or (c) of this section, shall (1) The aircraft is continuously in a enter the date, place, bearing error, position from which a descent to a and sign the aircraft log or other landing on the intended runway can be record. In addition, if a test signal ra- made at a normal rate of descent using diated by a repair station, as specified normal maneuvers, and for operations

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conducted under part 121 or part 135 un- or above MDA, unless the inability to less that descent rate will allow touch- see an identifiable part of the airport down to occur within the touchdown results only from a normal bank of the zone of the runway of intended landing; aircraft during the circling approach. (2) The flight visibility is not less (f) Civil airport takeoff minimums. Un- than the visibility prescribed in the less otherwise authorized by the Ad- standard instrument approach being ministrator, no pilot operating an air- used; and craft under parts 121, 125, 127, 129, or 135 (3) Except for a Category II or Cat- of this chapter may take off from a egory III approach where any necessary civil airport under IFR unless weather visual reference requirements are spec- conditions are at or above the weather ified by the Administrator, at least one minimum for IFR takeoff prescribed of the following visual references for for that airport under part 97 of this the intended runway is distinctly visi- chapter. If takeoff minimums are not ble and identifiable to the pilot: prescribed under part 97 of this chapter (i) The approach light system, except for a particular airport, the following that the pilot may not descend below minimums apply to takeoffs under IFR 100 feet above the touchdown zone ele- for aircraft operating under those vation using the approach lights as a parts: reference unless the red terminating (1) For aircraft, other than heli- bars or the red side row bars are also copters, having two engines or less—1 distinctly visible and identifiable. statute mile visibility. (ii) The threshold. (2) For aircraft having more than two (iii) The threshold markings. engines—1⁄2 statute mile visibility. (iv) The threshold lights. (3) For helicopters—1⁄2 statute mile (v) The runway end identifier lights. visibility. (vi) The visual approach slope indica- (g) Military airports. Unless otherwise tor. prescribed by the Administrator, each (vii) The touchdown zone or touch- person operating a civil aircraft under down zone markings. IFR into or out of a military airport (viii) The touchdown zone lights. shall comply with the instrument ap- (ix) The runway or runway markings. proach procedures and the takeoff and (x) The runway lights. landing minimum prescribed by the (d) Landing. No pilot operating an military authority having jurisdiction aircraft, except a military aircraft of of that airport. the United States, may land that air- (h) Comparable values of RVR and craft when the flight visibility is less ground visibility. (1) Except for Category than the visibility prescribed in the II or Category III minimums, if RVR standard instrument approach proce- minimums for takeoff or landing are dure being used. prescribed in an instrument approach (e) Missed approach procedures. Each procedure, but RVR is not reported for pilot operating an aircraft, except a the runway of intended operation, the military aircraft of the United States, RVR minimum shall be converted to shall immediately execute an appro- ground visibility in accordance with priate missed approach procedure when the table in paragraph (h)(2) of this sec- either of the following conditions exist: tion and shall be the visibility mini- (1) Whenever the requirements of mum for takeoff or landing on that paragraph (c) of this section are not runway. met at either of the following times: (2) (i) When the aircraft is being oper- ated below MDA; or Visibility RVR (feet) (statute (ii) Upon arrival at the missed ap- miles) proach point, including a DH where a DH is specified and its use is required, 1,600 ...... 1¤4 1 and at any time after that until touch- 2,400 ...... ¤2 3,200 ...... 5¤8 down. 4,000 ...... 3¤4 (2) Whenever an identifiable part of 4,500 ...... 7¤8 the airport is not distinctly visible to 5,000 ...... 1 1 the pilot during a circling maneuver at 6,000 ...... 1 ¤4

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(i) Operations on unpublished routes specification pertinent to the oper- and use of radar in instrument approach ations. procedures. When radar is approved at certain locations for ATC purposes, it § 91.177 Minimum altitudes for IFR op- may be used not only for surveillance erations. and precision radar approaches, as ap- (a) Operation of aircraft at minimum al- plicable, but also may be used in con- titudes. Except when necessary for junction with instrument approach takeoff or landing, no person may oper- procedures predicated on other types of ate an aircraft under IFR below— radio navigational aids. Radar vectors (1) The applicable minimum altitudes may be authorized to provide course prescribed in parts 95 and 97 of this guidance through the segments of an chapter; or approach to the final course or fix. (2) If no applicable minimum altitude When operating on an unpublished is prescribed in those parts— route or while being radar vectored, (i) In the case of operations over an the pilot, when an approach clearance area designated as a mountainous area is received, shall, in addition to com- in part 95, an altitude of 2,000 feet plying with § 91.177, maintain the last above the highest obstacle within a altitude assigned to that pilot until the horizontal distance of 4 nautical miles aircraft is established on a segment of from the course to be flown; or a published route or instrument ap- (ii) In any other case, an altitude of proach procedure unless a different al- 1,000 feet above the highest obstacle titude is assigned by ATC. After the within a horizontal distance of 4 nau- aircraft is so established, published al- tical miles from the course to be flown. titudes apply to descent within each succeeding route or approach segment However, if both a MEA and a MOCA unless a different altitude is assigned are prescribed for a particular route or by ATC. Upon reaching the final ap- route segment, a person may operate proach course or fix, the pilot may ei- an aircraft below the MEA down to, ther complete the instrument approach but not below, the MOCA, when within in accordance with a procedure ap- 22 nautical miles of the VOR concerned proved for the facility or continue a (based on the pilot’s reasonable esti- surveillance or precision radar ap- mate of that distance). proach to a landing. (b) Climb. Climb to a higher minimum (j) Limitation on procedure turns. In IFR altitude shall begin immediately the case of a radar vector to a final ap- after passing the point beyond which proach course or fix, a timed approach that minimum altitude applies, except from a holding fix, or an approach for that when ground obstructions inter- which the procedure specifies ‘‘No PT,’’ vene, the point beyond which that no pilot may make a procedure turn higher minimum altitude applies shall unless cleared to do so by ATC. be crossed at or above the applicable (k) ILS components. The basic ground MCA. components of an ILS are the localizer, glide slope, outer marker, middle § 91.179 IFR cruising altitude or flight marker, and, when installed for use level. with Category II or Category III instru- (a) In controlled airspace. Each person ment approach procedures, an inner operating an aircraft under IFR in marker. A compass locator or precision level cruising flight in controlled air- radar may be substituted for the outer space shall maintain the altitude or or middle marker. DME, VOR, or non- flight level assigned that aircraft by directional beacon fixes authorized in ATC. However, if the ATC clearance as- the standard instrument approach pro- signs ‘‘VFR conditions on-top,’’ that cedure or surveillance radar may be person shall maintain an altitude or substituted for the outer marker. Ap- flight level as prescribed by § 91.159. plicability of, and substitution for, the (b) In uncontrolled airspace. Except inner marker for Category II or III ap- while in a holding pattern of 2 minutes proaches is determined by the appro- or less or while turning, each person priate part 97 approach procedure, let- operating an aircraft under IFR in ter of authorization, or operations level cruising flight in uncontrolled

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