A gas turbine engine installation is provided that has a plurality of flexible printed circuit board (FPCB) harnesses to transfer electrical signals, including electrical power, around a gas turbine engine. The plurality of FPCB harnesses is held to the gas turbine engine installation using generally U-shaped clips that have a base from which first and second sidewalls extend. The FPCB harness is held between the tips of base-teeth extending from the base, and side-teeth extending from the first and second sidewalls. In this way, the FPCB harness can be held securely in position by the clip.