59-12-01: Combustion Heater Inspection

59-12-01 FAIRCHILD: Applies to all F-27 Series aircraft equipped with the heater system. Compliance required by July 15, 1959, and every 100 hours thereafter until forthcoming permanent fix is incorporated. (1) An incident has been reported in which a loose "B" nut on the fuel line connection to the combustion heater fuel control unit caused fuel to leak out around the shroud. In order to preclude possibilities of leakage at the heater fuel system fittings, remove and retain shroud assemblies, P/N 27-774575-1, attached to tube assemblies, P/N's 27-683051-151 or -251 and 27-774512-11, connected to fuel control assembly, P/N 43C80. Also remove and retain shroud assembly, P/N 27-774575-1, attached to opposite end of tube assembly, P/N 27-774512-11, connected to heater assembly, P/N 49C65. (2) At locations where shrouds were removed, inspect and determine that fittings of tube assemblies are torqued to proper values and no evidenceof fuel leakage exists. Torque fittings of tube assembly, P/N 27-774512-11 to 135 in. lbs. min. - 150 in. lbs. max., and tube assembly P/N 27-683051-151 or -251 to 40 in. lbs. min. - 65 in. lbs. max. (3) Operate heater to determine that no evidence of fuel leakage exists at tube assembly connections to fuel control and heater assemblies and reinstall shroud assemblies. (Fairchild F-27 Service Bulletin No. 21-48 dated April 22, 1959, covers this same subject.)