54-04-01 AC SPARK PLUG: Applies to All Engines Equipped With AC LA-87 Spark Plugs, Except Pratt and Whitney R-1830 Engines of 1,200 HP or Less and Wright R-1820 Engines of 1,200 HP or Less.
Compliance required prior to March 1, 1954.
A. In order to preclude possibilities of engine failure, when using AC LS-87 spark plugs in engines for which they are not approved, these spark plugs must be removed from all engines with the exceptions of the R-1820 having a T.O. rating of 1,200 h.p. or less and the R-1830 having a T.O. rating of 1,200 h.p. or less.
B. On R-1820 and R-1830 engines of 1,200 h.p. or less, the LS-87 plug is limited to a maximum of 120 hours of service with no reconditioning permitted. Plugs having over 120 hours must be removed from service.
This supersedes AD 49-26-02.