72-12-04 CESSNA: Amdt. 39-1459. Applies to Models 401 and 402 series airplanes.
Compliance: Required within 50 hours' time in service after the effective date of this AD, unless already accomplished.
To assure proper support of fuel lines and to eliminate chafing of fuel lines with possible fire hazard due to fuel leakage in the wing leading edge, accomplish the following:
A) On airplanes (Serial Numbers 401-0001 thru 401-0225 and 402-0001 thru 402-0225, except 402-0171, 402-0172, 401-0189, 402-0191, 401-0197, 402-0209, 402-0210, 402-0212, 401-0214 thru 401-0225, and 402-0214 thru 402-0225), remove the engine cowling, turbo supercharger and the firewall access opening for both engines. Visually inspect the fuel crossfeed lines for chafing at the firewall vertical stiffeners. Replace chafed fuel lines with a serviceable part and install fuel line support clamps in accordance with Cessna Service Letter ME68-6, dated April 16, 1968, or later revision, or any equivalent method approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region. Maintain a minimum of .50 inch clearance between the fuel crossfeed lines and the firewall vertical stiffener. Replace firewall access plate using AN515-8R5 or equivalent screws or screws removed from firewall that do not exceed 5/16 inches in length.
B) On airplanes (Serial Numbers 401-0001 thru 401A0010 and 402-0001 thru 402-0319 except 401A0001, 401A0003, 402-0218, 402-0298 and 402-0317), remove all inspection access plates in wing leading edge outboard of the engine nacelle and visually inspect main fuel supply and vapor return lines for chafing. Replace chafed fuel lines with a serviceable part and install fuel line support clamps in accordance with Cessna Service Letter ME68-27, dated December 27, 1968, or later revision, or any equivalent method approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region.
C) On airplanes (Serial Numbers 401-0226 thru 401B0216 and 402-0226 thru 402B0220:
(1) Remove the engine cowling and screws from the firewall vertical stiffener as shown in Cessna Service Letter ME72-11, dated May 26, 1972, or later revision.
(2) If screws removed are more than .312 inches in length, remove firewall inspection plate and inspect fuel crossfeed lines for chafing and replace any chafed fuel line with a serviceable part.
(3) Replace screws removed from firewall vertical stiffener with MS35266-60 screws.
Cessna Service Letter ME72-11, dated May 26, 1972, or later revision, pertains to the subject matter of this paragraph.
This amendment becomes effective June 16, 1972.