PRODUCT: Eurocopter Deutschland GMBH (ECD) Model MBB-BK 117 C-1 and C-2 helicopters. SUBJECT: Airworthiness Directive 2012-09-11 ACTION: Final Rule
SUMMARY: This AD requires installing a placard that corresponds to the maximum permissible flight altitude, amending the Rotorcraft Flight Manual (RFM) to revise the maximum permissible operating altitude, and inserting revised performance charts into the RFM. This AD also requires a repetitive maintenance 'MAX N1 CHECK' to determine the appropriate maximum altitudes. This AD also requires, if the engine or a Fuel Control Unit (FCU) or module 2 or 3 is replaced, repeating the maintenance "MAX N1 CHECK." Finally, this AD specifies that modifying both engines would provide terminating action for the AD requirements.
This AD was prompted by the failure of a "few" engines to reach the specified one-engine-inoperative (OEI) rating at altitudes above 10,000 feet. The actions of this AD are intended to prevent flights at altitudes where the full OEI engine power cannot be reached and subsequent loss of control of the helicopter if an OEI operation is required.