The Australian Transport Safety Bureau recommends that the
Direction Generale de l'Aviation Civile (DGAC) take appropriate
action to ensure the continued airworthiness of aircraft fitted
with Turbomeca Arriel engines incorporating modification TU204.
We acknowledge receipt of the to Air Safety Recommendations
R20010193 and R20010197 from the Australian Transport Safety Bureau
which relate to Arriel engine failure.
These recommendations were carefully analysed and I am pleased to
provide our conclusions which are the following:
R20010197: taking into account the possible occurrence rate
(probability calculation) of a double engine failure on twin engine
helicopters and the fact it is no longer possible to install or
repair blades modified by TU 204, there is no need to take a
specific action for twin engine helicopters.
However, as a conservative approach, DGAC will mandate by
airworthiness directive the replacement of all these blades on
single engine helicopters.
Appendixes attached to this letter describe DGAC's approach in more
details.
