AD NUMBER: 2007-10-06
MANUFACTURER: Turbomeca
SUBJECT: Airworthiness Directive 2007-10-06
SUMMARY: We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as: Two cases of flameout have been reported on Arriel 2B1 engines: One when lowering collective pitch on ground at landing and one when switching from Flight Position to idle Position on ground. Both flameout events are explained as follows: In caseof stepper motor loss of steps to a value below the 'level 1 failure' detection threshold, the fuel flow of the anti-flameout limit can be reduced. The reduction can be sufficient to cause engineflameout when decreasing rapidly the demand for power (it can therefore also happen in-flight). This condition may lead to an uncommanded in-flight shutdown. On a single-engine helicopter, the result may be emergency autorotation landing or, at worst, an accident. To prevent this, software version 5.02 (TU 144C) increases the anti-flameout limit in the event of small steppermotor loss of steps (below the 'level 1 failure' detection threshold). This AD requires actions that are intended to address the unsafe condition described in the MCAI.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/