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Safety Action

Summary

Local safety action

Operator

Following this occurrence, the operator conducted a one-time borescope inspection of its fleet centrifugal diffusers for cracks. No cracks were discovered.

Engine manufacturer

The engine manufacturer has discontinued the installation of all modification TU204 GG turbine blades at its factory and at repair centres. On 26 November 2001, Turbomeca issued service bulletin (SB) 292 72 0258 with applicability to all Arriel 1B engines (single engine variants), which recommends removal of modules with modification TU204 embodied.

In addition, the manufacturer has implemented dimensional checking on all new Arriel model engine module three assemblies, for turbine blade platform/GG disc interferences and on this operator's engines with more than 1,000 hours time accumulated on a module three.

RECOMMENDATIONS

As a result of the investigation, the Australian Transport Safety Bureau has identified a safety deficiency related to Turbomeca Arriel engine fire propagation following turbine blade failure and rear bearing collapse. The Australian Transport Safety Bureau therefore issued the following recommendations.

R20010192 issued on 18 September 2001

The Australian Transport Safety Bureau recommends that the Australian Civil Aviation Safety Authority assess the adequacy of the Turbomeca Arriel engine module three bearing lubrication installation to determine if it meets the applicable design standard requirements to ensure the continued airworthiness of relevant Australian registered aircraft.

Australian Civil Aviation Safety Authority response received on 25 February 2002:

"CASA advised the Direction Generale de L'Aviation Civile (DGAC) of the ATSB determination that an engine fire occurred as a result of engine failure. CASA notes that the DGAC does not support the ATSB determination. CASA has no evidence of the Turbomeca Arriel Module 3 bearing lubrication system not satisfying turbine engine certification standards. CASA notes that the DGAC, in advice to the ATSB dated 31 December 2001, has determined the Arriel 1 engine complies with the latest requirements of JAR-E-530 "Fire"."

Australian Transport Safety Bureau response classification- CLOSED-NOT ACCEPTED

Physical evidence and pilot reports substantiate the occurrence of fire. The failure mode of oil tube separation has still not been proven to meets the applicable design standard requirements to ensure the continued airworthiness of relevant Australian registered aircraft.

R20010193 issued on 18 September 2001

The Australian Transport Safety Bureau recommends that the Direction Generale de l'Aviation Civile assess the adequacy of the Turbomeca Arriel engine module three bearing lubrication installation to determine if it meets the applicable design standard requirements.

Direction Generale de l'Aviation Civile response received on 15 January 2002:

"In light of the incidents related in your referenced document, DGAC determined that the Arriel 1 engine complies with the latest airworthiness requirement, i.e. JAR-E-530 "Fire" under "Notice for Proposed Amendment "NPA-E-24 and interpretative material NPA-E-37 (note: these requirements result from the harmonisation with FAR 33, but are not significantly different from current JAR-E requirements)."

Australian Transport Safety Bureau response classification- MONITOR

The Direction Generale de l'Aviation Civile response proposes a change to the applicable regulation. The Australian Transport Safety Bureau will monitor that proposed change.

The Australian Transport Safety Bureau has also identified a safety deficiency related to Turbomeca Arriel engine gas generator turbine blade failures. The Australian Transport Safety Bureau therefore issued the following recommendations.

R20010196 issued on 18 September 2001

The Australian Transport Safety Bureau recommends that the Australian Civil Aviation Safety Authority take appropriate action to ensure the continued airworthiness of Australian registered aircraft fitted with Turbomeca Arriel engines incorporating modification TU204.

Australian Civil Aviation Safety Authority response received on 25 February 2002:

"CASA has been advised that the engine manufacturer, Turbomeca, cancelled the incorporation of Modification TU 204 in 1998. The DGAC has advised of action to be taken to address engines in service incorporating TU204. CASA notes that the DGAC, in advice to the ATSB dated 31 December 2001, advises the DGAC will be issuing an Airworthiness Directive to require the mandatory removal of turbine blades incorporating modification TU 204. The Directive is to be limited to single engine helicopters. CASA will review the DGAC Airworthiness Directive on its receipt and advise the ATSB of the results of that review. CASA looks forward to receiving a final briefing on the conclusions of the ATSB investigation of Occurrence No. 200103038."

Australian Transport Safety Bureau response classification- MONITOR

The Civil Aviation Safety Authority response proposes a review of the DGAC airworthiness directive when issued. The Australian Transport Safety Bureau will continue to monitor that proposed action.

R20010197 issued on 18 September 2001

The Australian Transport Safety Bureau recommends that the Direction Generale de l'Aviation Civile take appropriate action to ensure the continued airworthiness of aircraft fitted withTurbomeca Arriel engines incorporating modification TU204.

Direction Generale de l'Aviation Civile response received on 15 January 2002:

"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."

Australian Transport Safety Bureau response classification- MONITOR

The Direction Generale de l'Aviation Civile response proposes an airworthiness directive to address single engine variant helicopter engines only. The Australian Transport Safety Bureau will continue to monitor this proposed action.

 
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