AIRWORTHINESS DIRECTIVE
For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
Bell Helicopter Textron Canada (BHTC) 407 Series Helicopters
AD/BELL 407/24 Tail Rotor Gearbox 11/2003
Applicability: Bell Helicopter Textron Canada Model 407 Helicopters serial number (S/N) 53000 through 53498, 53500 through 53522, 53524 and 53526, equipped with tail rotor gearbox case part number (P/N) 406-040-406-109 or 406-040-406-113.
Requirement: 1. Identify the tail rotor gearbox case installed on the helicopter and, if applicable, check for the presence of oil feed gallery in accordance with the Accomplishment Instructions, Part I of ASB 407-03-57 Rev B.
2. If the oil feed gallery is present, re-identify the case assembly in accordance with the Accomplishment Instructions, Part I of ASB 407-03-57 Rev B.
3. If the oil feed gallery is not present create an oil feed gallery and re-identify the case in accordance with the Accomplishment Instructions, Part II of ASB 407-03- 57 Rev. B.
Note: Transport Canada CF-2003-10 refers.
Compliance: Tail Rotor Gearboxes installed in an aircraft:
For Requirement 1: Within 50 flight hours or 30 days from the effective date of this Directive, whichever occurs first.
For Requirement 2: Within 50 flight hours or 30 days from the effective date of this Directive, whichever occurs first.
For Requirement 3: For tail rotor gearboxes with less than 1800 flight hours time since new; prior to reaching 1800 flight hours time since new.
For tail rotor gearboxes with less than 1800 flight hours since last overhaul; prior to reaching 1800 flight hours since overhaul.
For tail rotor gearboxes with more than 1800 flight hours time since new; within 50 flight hours or 30 days from the effective date of this Directive.
For tail rotor gearboxes with more than 1800 flight hours time since last overhaul; within 50 flight hours or 30 days from the effective date of this Directive.
Bell Helicopter Textron Canada (BHTC) 407 Series Helicopters
AD/BELL 407/24 (continued)
Tail Rotor Gearboxes held as spares:
For Requirements 1, 2 and 3: Prior to installation in a helicopter. This Airworthiness Directive becomes effective on 30 October 2003.
Background: There have been a number of tail rotor gearboxes identified as not having the required oil feed gallery to the duplex bearing. This reduces the oil supply to the bearing that could lead to failure of the duplex bearing. The splash lubrication the bearing receives will be sufficient to maintain the integrity of the bearing before modification of the tail rotor gearbox is required as detailed in this Directive.
Jim Coyne
Delegate of the Civil Aviation Safety Authority 19 September 2003
The above AD is notified in the Commonwealth of Australia Gazette on 8 October 2003.
Overview
The Airworthiness Directive issued under the Civil Aviation Safety Regulations 1998 (CASR 1998) by the Civil Aviation Safety Authority (CASA) on 19 September 2003, addresses an identified safety issue with the tail rotor gearbox of Bell Helicopter Textron Canada Model 407 Helicopters. Specifically, the Airworthiness Directive (AD/BELL 407/24) pertains to aircraft with certain serial numbers and tail rotor gearbox case part numbers. The directive mandates corrective actions to ensure the presence of an oil feed gallery to the duplex bearing, which is crucial for maintaining the bearing's integrity and preventing potential failure. This directive was introduced to address the unsafe condition where some tail rotor gearboxes were not equipped with the required oil feed gallery, which could lead to inadequate oil supply and subsequent bearing failure. The policy objective is to enhance the safety of the affected aircraft by ensuring compliance with these specified modifications within defined timeframes.
Scope and Application
The Airworthiness Directive (AD) F2006B04637 applies to specific serial numbers of Bell Helicopter Textron Canada Model 407 Helicopters, particularly those equipped with certain tail rotor gearbox case part numbers. These helicopters must adhere to the requirements specified in the directive, which is aimed at addressing an unsafe condition related to the tail rotor gearbox that could lead to bearing failure due to inadequate oil supply. The directive applies to helicopters in operation as well as those held as spares, mandating compliance before installation or within specified timeframes based on flight hours or since last overhaul. The AD is effective from 30 October 2003 and was issued under subregulation 39.1(1) of the Civil Aviation Safety Regulations 1998 by the Civil Aviation Safety Authority (CASA). The AD was gazetted on 8 October 2003, providing clear instructions on identifying and rectifying the issue with the tail rotor gearbox to ensure airworthiness.
Key Provisions
The Airworthiness Directive (AD/BELL 407/24) issued by the Civil Aviation Safety Authority (CASA) under subregulation 39.1(1) of the Civil Aviation Safety Regulations 1998, addresses specific safety concerns related to the tail rotor gearboxes of Bell Helicopter Textron Canada (BHTC) 407 Series Helicopters. The directive applies to helicopters with specific serial numbers and equipped with certain tail rotor gearbox case part numbers. The main requirement is to identify the tail rotor gearbox case installed on the helicopter, check for the presence of the oil feed gallery, and take appropriate action based on the findings. If the oil feed gallery is present, the case must be re-identified. If the oil feed gallery is not present, it must be created and the case re-identified.
The directive imposes obligations on the operators of the affected helicopters. These obligations include identifying the tail rotor gearbox case, checking for the oil feed gallery, and taking corrective action as specified in the directive. Operators must ensure compliance within the specified timeframes, which vary based on the flight hours and overhaul status of the tail rotor gearbox. For tail rotor gearboxes installed in aircraft, the actions must be completed within 50 flight hours or 30 days from the effective date of the directive, whichever occurs first. Spare tail rotor gearboxes must be modified prior to installation in a helicopter.
Failure to comply with the requirements of the AD may result in significant safety risks, as the absence of the oil feed gallery can lead to a failure of the duplex bearing, which could compromise the safety of the aircraft. The directive does not explicitly state penalties for non-compliance, but non-compliance with CASA directives generally can result in enforcement actions, including fines and potential grounding of the aircraft until compliance is achieved. The severity of the consequences underscores the importance of adhering to the specified requirements to ensure airworthiness and safety.