Airworthiness Directive · Amendment 39-22758 · Fuel system wiring
Bell Textron Canada Limited Helicopters
This AD applies to Bell Textron Canada Limited Model 407 helicopters, serial numbers 54832 through 54931 inclusive, 54933 through 54939 inclusive, and 54942 through 54954 inclusive, certificated in any category, with a fuel system standpipe assembly (standpipe) part number 407-062-032-103 installed.
The FAA is adopting a new airworthiness directive (AD) for certain Bell Textron Canada Limited Model 407 helicopters. This AD was prompted by a report that a certain part-numbered fuel system standpipe assembly (standpipe) may have sharp edges at the interval weld joints due to a quality escape during the manufacturing process. This AD requires inspecting certain fuel system parts and, depending on the inspection results, taking corrective actions and performing a fuel quantity gauging system calibration. Depending on the results of the fuel quantity gauging system calibration, this AD requires performing additional corrective actions and repeating the fuel quantity gauging system calibration. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Within 300 hours time-in-service (TIS) or 6 months after the effective date of this AD, whichever occurs first, accomplish the actions required by paragraphs (g)(1)(i) and (ii) of this AD.
(i) With the standpipe removed from the aft fuel cell, inspect the interior of the standpipe for any sharp edges on each internal weld joint, as shown in Figure 1 of Bell Alert Service Bulletin 407-21-124, dated February 1, 2022. If there is a sharp edge on any internal weld joint, before further flight, deburr the edges of each affected weld joint using an aluminum oxide abrasive cloth or paper, or equivalent, ensuring not to exceed 0.015 in (0.38 mm) depth into the tube material at a 45-degree angle to the weld joint. Then, using a clean cloth dampened with isopropyl alcohol or equivalent, remove all sanding residue from the weld joint and apply a chemical film material to any bare metal surfaces.
(ii) With the fuel quantity harness assembly (harness assembly) removed, inspect the harness assembly connectors for any mechanical damage and corrosion to the electrical pins and inspect the insulation tubing and wires for any cracks and chafing. For the purposes of this AD, mechanical damage is indicated by deterioration of the connections or pins.
(A) If there is any corrosion or mechanical damage, before further flight, remove the harness assembly from service and replace it with an airworthy harness assembly.
(B) If there is a crack or any chafing, before further flight, remove the harness assembly from service and replace it with an airworthy harness assembly.
(2) If the harness assembly was required to be replaced as a result of the inspection required by paragraph (g)(1)(ii) of this AD or by this paragraph, before further flight, with the standpipe and harness assembly installed, perform a fuel quantity gauging system calibration in accordance with paragraphs 4 through 18 of Fuel Quantity Gauging System, DMC-407-A-95-65-10-01A-273A-A, dated June 2, 2022, of Chapter 95—Instruments, of Bell Model 407 Maintenance Manual, BHT-407-MM, Issue No. 014, dated December 12, 2023. As a result of the fuel quantity gauging system calibration, if a fuel level does not indicate the correct reading or displays no reading, before further flight, remove the harness assembly from service and replace it with an airworthy harness assembly; and repeat the actions required by this paragraph for the newly installed harness assembly.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
