No. 3043-S-00
SAFETY INFORMATION NOTICE
SUBJECT: GENERAL
UPDATE ON EC225LP ACCIDENT IN NORWAY DATED APR. 29th
For the attention of
ATA : 00
Version(s)
AIRCRAFT
CONCERNED
Civil
EC225
LP
EC725
Military
AP
Airbus Helicopters welcomes the publication on May 27th 2016 by the AIB Norway (AIBN) of the updated
preliminary report. Airbus Helicopters is encouraged by the progress made by the investigation and
continues to provide its full support to the AIBN.
Airbus Helicopters has hosted the official investigation team led by AIBN. The visit was held on 24th, 25th
and 26th May 2016 in Marignane with the participation of AIBN, BEA France, AAIB UK, EASA, CAA UK
and CHC.
As stated in AIBN report:
“The main purpose of this 3 days meeting was to agree on further investigation of the parts that the AIBN
has sealed and sent to Airbus Helicopters, and to discuss a list of possible scenarios that could explain
the detachment of the main rotor.”
The intent of this Safety Information Notice is to complement the AIBN report with technical information
from the on-going analysis at Airbus Helicopters. The views expressed in this document are those of
Airbus Helicopters.
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Based on elements available at the date of this SIN, the in-depth analysis of the fault-tree has led Airbus
Helicopters to retain the seven following possible initial events, whatever the root cause (design,
production, maintenance or combination thereof):
1) Opening of the MGB fixed ring due to fatigue failure;
2) Abnormal loads on the main rotor (possibly due to an event such as impact with FOD, a flight control
issue, blade damage…);
3) Flexible plate (BBQ) loss of attachment;
4) MGB conical housing failure;
5) Jamming (seizing) of the epicyclic module;
6) Opening of the MGB fixed ring following internal epicyclic module damage;
7) Suspension bar attachment failure.
Nota : in the AIBN report dated 27/05/16 the 3 scenarios “under consideration” are
- MGB Conical housing (possible initial event 4 of the above list)
- Failure of the epicyclic module (possible initial event 5 and 6)
- Suspension bar (lift strut) attachment (possible initial event 7)
At this stage of the investigation and in line with the AIBN report, Airbus Helicopters assesses that the
initial events no 1, 2, 3 are not retained because inconsistent with the investigation findings.
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Airbus Helicopters specifically scrutinizes the four possible initial events:
Potential initial event 4): MGB conical housing failure
The pieces of the conical housing retrieved to date show signs of static failures.
At that stage, Airbus Helicopters sees the conical housing rupture as a consequence and not as a cause.
More analysis is needed to reach a conclusion.
Potential initial event 5): Jamming (seizing) of the epicyclic module
Analysis of data from the CVFDR and inspection of parts recovered already (including
indicate significant elements differing with the 2009 AS332 L2 G-REDL accident. Among
technical elements, there is for example evidence that the tail rotor was turning and driven
main module until impact (the engines were running and the MGB main module was
impact).
MGB parts)
the relevant
by the MGB
turning until
As a result of a comprehensive review, Airbus Helicopters observes that the jamming event is
contradicted by available evidence.
Potential initial event 6): Opening of the MGB fixed ring following internal epicyclic module
damage
Recovered parts from the MGB have been transferred by the AIBN to QinetiQ, an independent
laboratory in the UK.
The retrieved parts are undergoing detailed metallurgical examinations at QinetiQ at the date of this SIN.
Results are expected in June 2016.
In parallel, the AIBN investigation team is still searching for missing parts from the MGB at the accident
site.
More analysis is needed to reach a conclusion.
Potential initial event 7): Suspension bar attachment failure
This potential initial event may have two main different origins:
1. Detachment of suspension bar fitting from the airframe: such a detachment could be due to failure of
attachment fitting bolts.
Airbus Helicopters is finalizing additional calculations and fatigue tests. Conclusions are expected in
the beginning of June 2016.
2. Displacement and disengagement of one suspension bar pin due to the absence of safety pins
Dedicated tests are being done to further assess this scenario. Results are expected by end of June
2016.
The AIBN investigation team is still searching for the missing parts from the front suspension bar at the
accident site.
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At this stage of the investigation, Airbus Helicopters considers that this potential initial event is not
contradicted by any available technical evidence.
For all potential initial events, analysis of the helicopter’s maintenance history should support a better
understanding of the most likely causes.
Airbus Helicopters will provide updated information as the investigation progresses.
Additional conservative measures on the fleet:
As a precautionary measure regarding the potential initial event 7): Suspension bar attachment failure,
and based on the feedback from the application of the EASB 53A058 (EC225LP) and 53A055
(EC725AP) issued on the 4th May 2016, Airbus Helicopters has decided to request, by a new EASB, a
set of additional precautionary actions. An EASA AD will be issued in a similar timeframe.
Airbus Helicopters technical representatives will contact the operators in order to provide guidance and
procedure clarification.
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