§ 91.187 – Operation under IFR in controlled airspace: Malfunction reports.
(a) The pilot in command of each aircraft operated in controlled airspace under IFR shall report as soon as practical to ATC any malfunctions of navigational, approach, or communication equipment occurring in flight.
(b) In each report required by paragraph (a) of this section, the pilot in command shall include the—
(1) Aircraft identification;
(2) Equipment affected;
(3) Degree to which the capability of the pilot to operate under IFR in the ATC system is impaired; and
(4) Nature and extent of assistance desired from ATC.