58-01-01: Fuel Vent Line Replacement

58-01-01 AERO COMMANDER: Applies to All Models 520, 560, 560A, 560E and 680 Aircraft With Serial Numbers 231 Through 580 except 315, 466, 471, 485, 492, 509, 523, 547, 568, 570, 572, 574, 576, 579. Compliance required as soon as possible but not later than July 1, 1958. A number of failures of the vent lines located above the nacelle upper fire shield have resulted in the release of fuel and/or fuel vapor in the engine compartment creating a dangerous fire hazard. These failures are a result of interference or chafing between wing structure and the carburetor return and the fuel tank vent lines. Also, failures have occurred at the carburetor vapor return elbow located in the upper fire shield. Replace the portions of the carburetor vapor vent and fuel tank vent lines located above the upper fire shield with flexible hose assemblies, P/N 6630086-237, 6630086-223, and 6630086-229, or equivalent. Securely fasten the hose assemblies to the wing structure with hose clamps to prevent interference or chafing. Replace the existing carburetor vapor return line elbows located at the upper fire shield with antirotation fittings, P/N 5630085-21 and 5630085-29, and install upper fire shield channels, P/N 5630086-25 and 5630086-23. (Additional details relative to this rework are included in Aero Design Service Bulletin No. 45 dated September 20, 1957.)