[SystemSafety] 2012 Super Puma Ditchings

From: Peter Bernard Ladkin < >
Date: Fri, 13 Jun 2014 06:43:41 +0200

>From Ian Chard in today's Risks 28.02

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Date: Wed, 11 Jun 2014 08:47:55 +0100
From: Ian Chard <ian_at_xxxxxx
Subject: `Switch incompatibility' leads to two helicopter ditchings

In 2012, two Super Puma helicopters with a total of 33 people on board were forced to ditch in the North Sea when both the primary and emergency main router lubrication systems failed. Everyone survived with only minor injuries.

The main router lubrication system in both aircraft failed due to fatigue cracking in a critical part, and the pilots activated the emergency lubrication system, which sprays glycol into the rotor and gives the aircraft 30 minutes' safe flying time. However, on both helicopters a warning light illuminated indicating that this emergency system failed as well, forcing them to ditch immediately (per their procedures).

It turns out that the emergency lubrication systems were working fine, but the switch that was supposed to detect its failure was wired incorrectly, meaning that the warning light would *always* illuminate shortly after the system's activation. The aircraft manufacturer made an early design change affecting the switch's pin assignments but, when it re-ordered the switches, it used the original specification by mistake. This was compounded by the fact that 'the emergency lubrication sub-systems were tested individually, [but] no test was carried out on the complete system during certification, either on a test rig or installed on a helicopter'.

The full Air Accident Investigation Bureau report is available as a PDF: http://www.aaib.gov.uk/publications/formal_reports/2_2014_g_redw_g_chcn.cfm

Ian Chard <ian_at_xxxxxx

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The significant part is the gearbox failure. This has happened on other Super Puma ditchings with less happy outcomes.

The bit about the switch is deja vu. First, switch parts: recall Air Transat, where the connector between tank lead and fuel pump was replaced with a part for a slightly different model engine, instead of the correct redesigned part which avoided the chafing that later caused the failure. Second, lack of integration tests: recalls Ariane 5.

PBL Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany Tel+msg +49 (0)521 880 7319 www.rvs.uni-bielefeld.de

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systemsafety_at_xxxxxx Received on Fri Jun 13 2014 - 06:43:49 CEST

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