56-20-04 CONVAIR: Applies to All 240, 340 and 440 Aircraft.
Compliance recommended at the next engine change or airplane overhaul but required not later than December 31, 1957.
Several recent accidents involving nacelle fires have indicated certain deficiencies in the construction of the fire seals between zone 1 and zone 2. To correct this condition the following rework of the present cowling and zone seals is required.
1. Incorporate an additional fireproof seal at the zone 1 to zone 2 shroud-to-cowl seal around the periphery of the diaphragm where the bottom and side cowl meet.
2. Improve the present nacelle seals by incorporating a fireproof seal along the longitudinal juncture of the cowl segments and also improve the present cowl hinge point seals.
3. Replace any existing aluminum material in the zone 2 chimney vent with steel material. (Applicable to CV-240 aircraft only.)
The following Convair Service Bulletins cover acceptable methods of compliance with these modifications: Nos. 240-472 and 340-177 cover item No. 1; Nos. 240-474, 240-481A, 340- 209, 340-210A, 440-30 and 440-32A cover item No. 2; Nos. 240-470 and Revision 1 cover item No. 3. (Compliance with Revision 2 to 240-470 is not required.)