AD NUMBER: 2008-08-16
SUBJECT: Airworthiness Directive 2008-08-16
SUMMARY: The FAA is superseding an existing
airworthiness directive (AD) for Turbomeca Makila 1A, 1A1,and 1A2
turboshaft engines. That AD currently requires replacing certain
digital electronic control units (DECUs) and electronic control
units (ECUs) with modified DECUs and ECUs.
This AD applies only to Makila 1A and 1A1 turboshaft engines,
and requires replacing the selector comparator board in the ECU
with a board incorporating Turbomeca modification TU 250. This AD
results from recent unexplained reversions of the ECU to the 65% N1
We are issuing this AD to prevent dual-engine continued
operation at 65% N1 after reversion of the ECU to the 65% N1
back-up mode due to temporary loss of N2 speed signal, which could
lead toinability to continue safe flight, emergency autorotation
landing, or an accident.