Airworthiness Directive · Amendment 39-11509 · Eurocopter Deutschland GMBH Model MBB- BK 117 Helicopters
Eurocopter Deutschland GMBH Model MBB- BK 117 Helicopters
Superseded. A later AD replaced this one: AD 2000-26-06. Comply with the one in force.
Model MBB-BK 117 A-1, A-3, A-4, B-1, B-2, and C-1 helicopters, certificated in any category.
eliminated, the request should include specific proposed actions to address it.
This amendment supersedes an existing emergency priority letter airworthiness directive (AD), applicable to Eurocopter Deutschland GMBH (ECD) Model MBB-BK 117 helicopters, that currently requires, before further flight, creating a component log card or equivalent record and determining the age and number of flights on the tension-torsion (TT) strap. The AD also requires inspecting and removing, as necessary, certain unairworthy TT straps. This amendment requires the same actions as the emergency priority letter AD but clarifies the compliance requirements specified in the emergency priority letter AD. This amendment is prompted by an accident in which a main rotor blade (blade) separated from a helicopter due to fatigue failure of a TT strap. The actions specified by this AD are intended to prevent failure of a TT strap, loss of a blade, and subsequent loss of control of the helicopter.
Required as indicated, unless accomplished previously.
To prevent main rotor blade (blade) separation due to failure of a tension-torsion (TT) strap, accomplish the following:
(a) Before further flight,
(1) Create a component log card or equivalent record for each TT strap.
(2) Review the history of the helicopter and each TT strap. Determine the age since initial installation on any helicopter (age) and the number of flights on each TT strap. Enter both the age and the number of flights for each TT strap on the component log card or equivalent record. Where the number of flights is unknown, multiply the number of hours time-in-service (TIS) by 5 to determine the number of flights.
(3) If the number of flights and age cannot be determined, remove the TT strap from service.
(4) Remove any TT strap from service that has either accumulated 25,000 or more flights or is equal to or greater than 180 months of age.
(b) When a TT strap age is equal to or greater than 120 months and less than 180 months and the number of flights on the TT straps are less than 25,000, inspect the TT strap in accordance with paragraph 2.B.2 of the ``Accomplishment Instructions,'' Eurocopter Deutschland GMBH Alert Service Bulletin MBB-BK 117 No. ASB-MBB-BK 117-10-120 (ASB), Revision 1, dated August 31, 1999, according to the following:
(1) If the age is greater than or equal to 120 months but less than 132 months and has less than 22,000 flights, inspect the TT strap within the next 6 weeks. If the number of flights equals or exceeds 22,000, inspect the TT strap before further flight.
(2) If the age is greater than or equal to 132 months but less than 144 months and has less than 19,000 flights, inspect the TT strap within the next 5 weeks. If the number of flights equals or exceeds 19,000, inspect the TT strap before further flight.
(3) If the age is greater than or equal to 144 months but less than 156 months and has less than 16,000 flights, inspect the TT strap within the next 4 weeks. If the number of flights equals or exceeds 16,000, inspect the TT strap before further flight.
(4) If the age is greater than or equal to 156 months but less than 168 months and has less than 13,000 flights, inspect the TT strap within the next 3 weeks. If the number of flights equals or exceeds 13,000, inspect the TT strap before further flight.
(5) If the age is greater than or equal to 168 months but less than 180 months and has less than 10,000 flights, inspect the TT strap within the next 2 weeks. If the number of flights equals or exceeds 10,000, inspect the TT strap before further flight.
Remove any TT strap from service before exceeding the allowable number of flights or 180 months, whichever occurs first.
(c) If a defect is found as a result of the inspection, remove the TT strap from service prior to further flight.
(d) If no defect is found as a result of the inspection in paragraph (b), a maximum of 500 flights is permitted on a one-time basis before the TT strap must be replaced, provided the limits of paragraphs (a)(4) and (b) are not exceeded.
(e) TT straps, part number (P/N) 2604067 or J17322-1, are not eligible for installation. Prior to installation, P/N 2604067 or J17322-1 must be re-identified according to paragraph 2.B.1 of the ``Accomplishment Instructions'' of the ASB, Revision 1, dated August 31, 1999.
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.
