Document ID: chunk:federal_register_of_legislation:F2008L02876:body:0:p2
Version: federal_register_of_legislation:F2008L02876
Segment Type: other
Provision Reference: 
Character Range: 2834–4865

2008 refers.
Compliance:     1. Within 30 days after the effective date of this AD, unless previously accomplished.

                2. Before the next such mission after the effective date of this AD.

                3. Within 600 Flight Hours (FH) after the effective date of this AD and thereafter at intervals not to exceed 600 FH.

                4. From the effective date of this AD.

                5. When, after failing to reach the OEI rating, and either the engine, the FCU, engine module 2 and/or engine module 3 is replaced.

                6. After modification of both FCUs in accordance with Turboméca modification TU358.

                7. After 10 April 2009.
             This Airworthiness Directive becomes effective on 28 August 2008.
Background:  Prior to delivery of each helicopter, Eurocopter Deutschland performs the "MAX N1 Check" at a pressure altitude (PA) of about 10,000 feet.  During supplementary testing the "MAX N1 CHECK" at maximum certification altitude, a few MBB-BK 117 C-2 helicopters could not reach the specified N1 power threshold value.  The cause was identified as an engine acceleration limitation due to a delivered fuel flow lower than the engine fuel flow demand to achieve the OEI rating at high altitude.  The fuel flow is limited by the FCU acceleration law in those cases.  This limitation could potentially occur at altitudes exceeding 10,000 feet, depending on the engine and FCU characteristics.  As a conservative measure, TURBOMECA and EUROCOPTER decided that take-off, landing and HIGE (Hover In Ground Effect) and/or HOGE (Hover Out of Ground Effect) operations above 10,000 feet or level flight above 13,000 feet require a dedicated mandatory check.

             Turboméca has now developed a modification (TU358) that will, when accomplished on both engines installed on the helicopter, cancel the required checks and allow the removal of the placard and flight manual changes.

James Coyne
Delegate of the Civil Aviation Safety Authority

17 July 2008