Helicopter Fuel System Inspection Requirements

Summary

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.

Compliance Requirements

1. #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.; 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.; 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.; 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.; 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.; 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.; You must use this service information as applicable to do the actions required by this AD, unless the AD specifies otherwise.

   Deadline: 2024-08-22(300 hours TIS or 6 months after effective date (35 days after publication in Federal Register))

Market Impacts

• Mandatory airworthiness directive requiring specific inspections and potential replacements for Bell Model 407 helicopters with affected fuel system standpipe assemblies, restricting operations until compliance is achieved; Creates new training and certification requirements for maintenance personnel to perform specific fuel system inspections, deburring procedures, and fuel quantity gauging system calibrations as specified in the AD; Creates compliance barrier for transfer/sale of affected helicopters - aircraft cannot be operated until AD compliance is verified and documented

Validated Company Impacts