JAR-OPS 1 Subpart L SECTION 1
JAR-OPS 1.865(b)(1)
(c) Navigation equipment. An operator shall ensure that navigation equipment
(1) Comprises not less than:
(i) One VOR receiving system, one ADF system, one DME [except that an ADF system need not be installed provided that the use of ADF is not required in any phase of the planned flight]
....
(vii) An additional ADF system on any route, or part thereof, where navigation is based only on NDB signals, or
(2) Complies with the Required Navigation Performance (RNP) Type for operation in the airspace concerned.