[Code of Federal Regulations]
[Title 14, Volume 2]
[Revised as of January 1, 2005]
From the U.S. Government Printing Office via GPO Access
[CITE: 14CFR91.171]

[Page 223]
 
                     TITLE 14--AERONAUTICS AND SPACE
 
CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION 
                               (CONTINUED)
 
PART 91_GENERAL OPERATING AND FLIGHT RULES--Table of Contents
 
                         Subpart B_Flight Rules
 
Sec. 91.171  VOR equipment check for IFR operations.

    (a) No person may operate a civil aircraft under IFR using the VOR 
system of radio navigation unless the VOR equipment of that aircraft--
    (1) Is maintained, checked, and inspected under an approved 
procedure; or
    (2) Has been operationally checked within the preceding 30 days, and 
was found to be within the limits of the permissible indicated bearing 
error set forth in paragraph (b) or (c) of this section.
    (b) Except as provided in paragraph (c) of this section, each person 
conducting a VOR check under paragraph (a)(2) of this section shall--
    (1) Use, at the airport of intended departure, an FAA-operated or 
approved test signal or a test signal radiated by a certificated and 
appropriately rated radio repair station or, outside the United States, 
a test signal operated or approved by an appropriate authority to check 
the VOR equipment (the maximum permissible indicated bearing error is 
plus or minus 4 degrees); or
    (2) Use, at the airport of intended departure, a point on the 
airport surface designated as a VOR system checkpoint by the 
Administrator, or, outside the United States, by an appropriate 
authority (the maximum permissible bearing error is plus or minus 4 
degrees);
    (3) If neither a test signal nor a designated checkpoint on the 
surface is available, use an airborne checkpoint designated by the 
Administrator or, outside the United States, by an appropriate authority 
(the maximum permissible bearing error is plus or minus 6 degrees); or
    (4) If no check signal or point is available, while in flight--
    (i) Select a VOR radial that lies along the centerline of an 
established VOR airway;
    (ii) Select a prominent ground point along the selected radial 
preferably more than 20 nautical miles from the VOR ground facility and 
maneuver the aircraft directly over the point at a reasonably low 
altitude; and
    (iii) Note the VOR bearing indicated by the receiver when over the 
ground point (the maximum permissible variation between the published 
radial and the indicated bearing is 6 degrees).
    (c) If dual system VOR (units independent of each other except for 
the antenna) is installed in the aircraft, the person checking the 
equipment may check one system against the other in place of the check 
procedures specified in paragraph (b) of this section. Both systems 
shall be tuned to the same VOR ground facility and note the indicated 
bearings to that station. The maximum permissible variation between the 
two indicated bearings is 4 degrees.
    (d) Each person making the VOR operational check, as specified in 
paragraph (b) or (c) of this section, shall enter the date, place, 
bearing error, and sign the aircraft log or other record. In addition, 
if a test signal radiated by a repair station, as specified in paragraph 
(b)(1) of this section, is used, an entry must be made in the aircraft 
log or other record by the repair station certificate holder or the 
certificate holder's representative certifying to the bearing 
transmitted by the repair station for the check and the date of 
transmission.

(Approved by the Office of Management and Budget under control number 
2120-0005)

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