Section 27.1327 - Magnetic direction indicator(a) Except as provided in paragraph (b) of this section-(1) Each magnetic direction indicator must be installed so that its accuracy is not excessively affected by the rotorcraft's vibration or magnetic fields; and(2) The compensated installation may not have a deviation, in level flight, greater than 10 degrees on any heading.(b) A magnetic nonstabilized direction indicator may deviate more than 10 degrees due to the operation of electrically powered systems such as electrically heated windshields if either a magnetic stabilized direction indicator, which does not have a deviation in level flight greater than 10 degrees on any heading, or a gyroscopic direction indicator, is installed. Deviations of a magnetic nonstabilized direction indicator of more than 10 degrees must be placarded in accordance with § 27.1547(e) .Amdt. 27-13, 42 FR 36972, July 18, 1977 Secs. 313(a), 601, 603, 604, and 605 of the Federal Aviation Act of 1958 (49 U.S.C. 1354(a) , 1421 , 1423 , 1424 , and 1425 ) ; and sec. 6(c) of the Dept. of Transportation Act (49 U.S.C. 1655(c)