AD/GBK 117/25 Amdt 1 Tail Rotor Gearbox Bevel Gear (Cth)
AIRWORTHINESS DIRECTIVE
On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/GBK 117/25 and issues the following AD under subregulation 39.001(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.
Eurocopter BK 117 Series Helicopters
| AD/GBK 117/25 Amdt 1 | Tail Rotor Gearbox Bevel Gear | 9/2009 TX |
Applicability: | Eurocopter Deutschland (ECD) GmbH MBB-BK117 C-2 helicopters. |
Requirement: | 1. Determine the serial number (S/N) of the bevel gear part number (P/N) 2. If, as a result of the inspection detailed in Requirement 1 of this AD, no bevel gear with one of the S/Ns listed in Table 1 of ECD ASB MBB BK117 3. If, as a result of the inspection detailed in Requirement 1 of this AD, a bevel gear with one of the S/Ns listed in Table 1 of ECD ASB MBB BK117 C-2-04A-005 Revision 01 is installed, the associated reduced life limit must be entered into the list of life-limited parts and in the log card of the IGB in accordance with ECD ASB MBB BK117 C-2-04A-005 Revision 01. 4. Replace bevel gears before exceeding their reduced life limit with a serviceable part in accordance with ECD ASB MBB BK117 C-2-04A-005 Revision 01. If the bevel gear reduced life limit has already been exceeded at the effective date of this AD a ferry flight up to a maximum of 20 Flight Hours (FH) to a maintenance facility is allowed. Note: Helicopters in compliance with AD/GBK 117/25 might not be compliant with the present AD and need to be re-inspected due to the newly identified bevel gear S/Ns. The use of later approved revisions of the referenced ASB is acceptable for compliance with the requirements of this AD. |
| Note: EASA Emergency AD 2009-0158-E dated 16 July 2009 refers. |
Compliance: | For Requirements 1 and 3 - Before further flight after the effective date of this AD, unless previously accomplished. For Requirement 4 - From the effective date of this AD. |
| This Amendment becomes effective on 21 July 2009. | |
Background: | During a recent review of the production documents for the bevel gears of the IGB for the ECD MBB BK117 C-2 helicopter, it was discovered that certain production batch numbers have tooth foot fillets below the required minimum values that would ensure the approved life limits for this part. This condition, if not corrected, could lead to a significant reduction of the lifetime of IGB bevel gears, potentially resulting in failure of the IGB and consequent loss of control of the helicopter. This AD requires a one-time inspection to determine if one of the affected bevel gears is installed. If an affected bevel gear is installed, this AD also requires the revision of the life limit in the aircraft maintenance program, in accordance with ECD ASB MBB BK117 C-2-04A-005 Revision 01. |
| The original issue of this Directive became effective on 13 June 2009. |
James Coyne
Delegate of the Civil Aviation Safety Authority
17 July 2009
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