North Sea crash helicopter's gearbox 'failed'


Operators of a North Sea helicopter had been planning to replace its main rotor gearbox a week before the unit suffered a "catastrophic failure" leading to a crash which killed all 16 aboard, an air accident report said today.

A magnetic particle had been found on the chip detector in the gearbox of the Eurocopter Super Puma, a final report by the Air Accidents Investigation Branch (AAIB) said.

This had led the operator to initiate a plan to remove the main rotor gearbox and replace it with a unit from another helicopter undergoing heavy maintenance, the AAIB said.

But actions taken following the discovery of the particle meant it was not recognised as an indication of the degradation of a part of the gearbox known as the second stage planet gear.

"The gearbox was declared serviceable by the operator and its planned replacement cancelled," said the report.

It was this second stage planet gear that failed as a result of a fatigue crack, causing the failure of the main rotor gearbox.

As the helicopter was flying to Aberdeen from the Miller Platform in the North Sea on the afternoon of April 1 2009, the main rotor separated from the fuselage and the aircraft crashed into the sea.

All 14 offshore workers and the two crewmen died.

The report told how, six seconds after expressing alarm, the captain had transmitted "Mayday Mayday Mayday" followed one second later by the co-pilot transmitting "Mayday Mayday Mayday, this is Bond 85 November, emergency, currently on the 055."

The report went on: "One second later, one of the flight crew uttered an expletive; this was the final radio transmission."

The AAIB said that the particle had been discovered on March 25 2009. The operator's engineers had sought the assistance of the manufacturer, Eurocopter, to deal with with what they considered to be a complex main rotor gearbox problem.

The AAIB added: "The use of verbal and email communication between the operator and manufacturer on March 25 led to a misunderstanding or miscommunication of the issue."

The discovered particle was initially identified as a piece of scale.

But further visual examination led the engineers to misidentify it as silver or cadmium plating which, according to the maintenance task card guiding maintenance staff, was "unimportant" and did not require the gearbox to be removed from service or to be put on "close monitoring".

The AAIB said that after March 25, the existing detection methods did not provide any further indication of the degradation of the second stage planet gear.

It added that the possibility of a material defect in the planet gear or damage due to the presence of foreign object debris "could not be discounted".

The report said that after March 25 the maintenance task to examine the ring of magnets on the helicopter's oil separator plates was not carried out.

It added that the ring of magnets reduced the probability of detecting released debris.

The AAIB also said this helicopter did not provide an alert to the flight crew when the magnetic chip detector detected a particle.

The aircraft was at 2,000ft when the accident happened. The first indication to the crew of a problem was loss of main rotor gearbox (MGB) oil pressure and the triggering of a master warning.

Two and half seconds before this indication, the co-pilot had made a radio transmission stating that the helicopter was serviceable.

Immediately after the loss of MGB oil pressure, the helicopter began to descend and failed to respond to control inputs. The main rotor system separated from the helicopter approximately 20 seconds after the loss of MGB oil pressure.

During separation the main rotor blades struck the helicopter's tail boom in several places, severing it from the fuselage.

"The fuselage fell into the sea at high vertical speed and the impact was non-survivable for all occupants," the AAIB said.

In today's final report, which followed three interim reports, the AAIB listed 17 recommendations that it had made during its investigation.

They included recommendations to Eurocopter, the European Aviation Safety Agency, the UK's Civil Aviation Authority and America's Federal Aviation Administration.

Scotland's Crown Office and Procurator Fiscal Service (COPFS) welcomed the publication of the report on this "tragic incident, following a technically complex and challenging investigation".

It went on: "The findings contained therein will now be fully considered by the health and safety division of COPFS.

"The division and Grampian Police have been engaged in this investigation since the tragedy occurred and will continue to progress lines of inquiry and carry out such investigation as is necessary in order that a decision may be taken in relation to the form of any proceedings.

"The liaison with the nearest relatives of the 16 men who lost their lives will also continue and the division will keep them advised of significant developments."


Start your day with The Independent, sign up for daily news emails
A survey carried out by Sainsbury's Finance found 20% of new university students have never washed their own clothes, while 14% cannot even boil an egg
science...and the results are not as pointless as that sounds
Dominique Alderweireld, also known as Dodo de Saumure, is the owner of a string of brothels in Belgium
newsPhilip Sweeney gets the inside track on France's trial of the year
Cumberbatch was speaking on US television when he made the comment (Getty)
Have you tried new the Independent Digital Edition apps?
ebooksA year of political gossip, levity and intrigue from the sharpest pen in Westminster
Life and Style
Arts and Entertainment
Tom DeLonge, Travis Barker and Mark Hoppus of Blink-182 pictured in 2011.
musicBassist Mark Hoppus and drummer Travis Barker say Tom Delonge is 'disrespectful and ungrateful'
Arts and Entertainment
Olivia Colman and David Tennant star in 'Broadchurch'
tvBroadchurch series 2, episode 4, review - contains spoilers
cyclingDisgraced cycling star says people will soon forgive his actions
Britain's Prince Philip attends a Garden Party at Buckingham Palace in London
Arts and Entertainment
Ed Sheeran will play three sell-out gigs at Wembley Stadium in July
Lena Dunham posing for an official portrait at Sundance 2015
Arts and Entertainment
Under the skin: Sarah Kane in May 1998
theatreThe story behind a new season of Sarah Kane plays
Arts and Entertainment
Preening: Johnny Depp in 'Mortdecai'
filmMortdecai becomes actor's fifth consecutive box office bomb
Bradford City's reward for their memorable win over Chelsea is a trip to face either Sunderland or Fulham (Getty)
Lars Andersen took up archery in his mid thirties
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: International Customer Service Administrators

Negotiable: Recruitment Genius: This is an exciting opportunity to join an awa...

Recruitment Genius: Warehouse Operations & Logistics Manager

£38000 - £42000 per annum: Recruitment Genius: One of the UK's best performing...

Recruitment Genius: GeoDatabase Specialist - Hazard Modelling

£35000 - £43000 per annum: Recruitment Genius: Our award-winning client is one...

Recruitment Genius: Compressed Air Pipework Installation Engineer

£15000 - £21000 per annum: Recruitment Genius: This leading provider of Atlas ...

Day In a Page

Woman who was sent to three Nazi death camps describes how she escaped the gas chamber

Auschwitz liberation 70th anniversary

Woman sent to three Nazi death camps describes surviving gas chamber
DSK, Dodo the Pimp, and the Carlton Hotel

The inside track on France's trial of the year

Dominique Strauss-Kahn, Dodo the Pimp, and the Carlton Hotel:
As provocative now as they ever were

Sarah Kane season

Why her plays are as provocative now as when they were written
Murder of Japanese hostage has grim echoes of a killing in Iraq 11 years ago

Murder of Japanese hostage has grim echoes of another killing

Japanese mood was against what was seen as irresponsible trips to a vicious war zone
Syria crisis: Celebrities call on David Cameron to take more refugees as one young mother tells of torture by Assad regime

Celebrities call on David Cameron to take more Syrian refugees

One young mother tells of torture by Assad regime
The enemy within: People who hear voices in their heads are being encouraged to talk back – with promising results

The enemy within

People who hear voices in their heads are being encouraged to talk back
'In Auschwitz you got used to anything'

'In Auschwitz you got used to anything'

Survivors of the Nazi concentration camp remember its horror, 70 years on
Autumn/winter menswear 2015: The uniforms that make up modern life come to the fore

Autumn/winter menswear 2015

The uniforms that make up modern life come to the fore
'I'm gay, and plan to fight military homophobia'

'I'm gay, and plan to fight military homophobia'

Army general planning to come out
Iraq invasion 2003: The bloody warnings six wise men gave to Tony Blair as he prepared to launch poorly planned campaign

What the six wise men told Tony Blair

Months before the invasion of Iraq in 2003, experts sought to warn the PM about his plans. Here, four of them recall that day
25 years of The Independent on Sunday: The stories, the writers and the changes over the last quarter of a century

25 years of The Independent on Sunday

The stories, the writers and the changes over the last quarter of a century
Homeless Veterans appeal: 'Really caring is a dangerous emotion in this kind of work'

Homeless Veterans appeal

As head of The Soldiers' Charity, Martin Rutledge has to temper compassion with realism. He tells Chris Green how his Army career prepared him
Wu-Tang Clan and The Sexual Objects offer fans a chance to own the only copies of their latest albums

Smash hit go under the hammer

It's nice to pick up a new record once in a while, but the purchasers of two latest releases can go a step further - by buying the only copy
Geeks who rocked the world: Documentary looks back at origins of the computer-games industry

The geeks who rocked the world

A new documentary looks back at origins of the computer-games industry
Belle & Sebastian interview: Stuart Murdoch reveals how the band is taking a new direction

Belle & Sebastian is taking a new direction

Twenty years ago, Belle & Sebastian was a fey indie band from Glasgow. It still is – except today, as prime mover Stuart Murdoch admits, it has a global cult following, from Hollywood to South Korea