Rolls – Royce Merlin engines: Rocker Arm Inspection

The CAA has issued a Mandatory Permit Directive (MPD 2010/004) regarding Rolls-Royce Merlin engines incorporating Modification 9/223/M2623. These engines are fitted on but not limited to Supermarine Spitfire, Hawker Hurricane and North American P51 Mustang series aircraft.

This follows reports of the separation of a small number of carbide pads fitted under the authority of the above modification.

Once released, the pads drop onto the block and may migrate, potentially causing engine damage and possible engine failure.

Reason: The reason for the loss of bond is still under investigation. This Directive is therefore raised as an interim measure to instruct a regular inspection of the rocker arms for detachment or indication of loss of bonding between the pad and rocker arm, and removal of failing pads from service. Within five flying hours, one month or at the next Permit renewal, whichever is the sooner from the effective date of the MPD:

The full directive and illustrative images can be found via the link at the bottom of the page.

http://www.caa.co.uk/docs/33/20100506MPD2010004.pdf