Description

Description On 27 December 2006, the crew of an SA-365 Dauphin 2 being operated by CHC Scotia on a contract passenger flight from the Millom West platform to the North Morecambe platform and making a night visual approach at destination crashed into the sea from a low altitude within sight of the platform. The aircraft was destroyed by the impact and none of the seven occupants survived.

Investigation

An Investigation was carried out by the UK AAIB. The Combined Voice and Flight Data Recorder (CVFDR) was eventually located and recovered on 16 January 2007. Most of the data from it, which consisted of five hours of flight data derived from the Integrated Health & Usage Monitoring System (IHUMS) and one hour of 3-channel audio, was successfully extracted. However, the magnetic tape recording medium had been exposed to corrosive sea water and it was found that the resultant corrosion had been particularly aggressive where the tape had been in contact with the metal tape heads and so that "in a number of small areas near the end of the tape the data and audio recordings were lost". Other IHUMS data from accelerometers which monitored the operation of rotating components was stored separately from the CVFDR in a Maintenance Data Recorder (MDR) for analysis to detect excessive vibration. However, the MDR was not recovered from the sea after the accident although the operator was able to provide IHUMS data which had already been downloaded from the helicopter. All significant items of wreckage were eventually located and recovered to assist the Investigation.

It was established that the Blackpool-based crew had been rostered to perform eight short flights within the Morecambe Bay Gas Field. Both were familiar with the local operation, the aircraft commander being the Blackpool Base Chief Pilot for the Operator. Five passengers had boarded the helicopter for the first flight from Blackpool to the AP1 platform and left there. There were no passengers for the next flight from AP1 to the Millom West Platform where five passengers destined for the AP1 Platform boarded for the third flight from Millom West to the North Morecambe Platform.There, a sixth passenger and some freight were to be collected before continuing to AP1.

The sequence of flights is depicted on the diagram below. It was noted that it had been "a particularly dark night with the overcast cloud completely obscuring any celestial illumination". The sequence of events immediately prior to the accident was reconstructed from analysis of the recorded data as follows:

• Prior to becoming visual with the North Morecambe platform, the aircraft commander was using the aircraft radar and the Global Positioning System (GPS) to provide range information to the Co-pilot who was PF.
• The Co-pilot visually acquired the North Morecambe platform helideck at a range of approximately 6800 metres and thereafter, the aircraft commander provided no further range information.
• The approach was flown by reference to visual cues but, because of the dark night and prevailing poor weather conditions, these did not provide sufficient information to allow for the normal perception of distance. Although the North Morecambe platform was equipped with a short range NDB to assist aircraft navigation, this was not used by the crew.
• The lack of instrument cross-checks by the commander did not assist the Co-pilot in managing the approach profile and there was no evidence of active monitoring by the Aircraft Commander.
• The Co-pilot became disorientated during the approach and neither pilot made a positive ‘go around’ call.
• The decision to go-around and the transfer of control from the Co-pilot to the Aircraft Commander were "not handled appropriately". The Commander, who "appeared not to be mentally primed to take control", did not respond promptly when asked for help.
• When the Commander took control, the helicopter was "in an extreme and unusual attitude" but he initially succeeded in rolling to a wings level attitude and reducing the pitch angle.
• During the attempted recovery, the Aircraft Commander had no external visual cues and it was considered possible that he was also distracted by concern for the well being of his Co-pilot.
• Some degree of disorientation may have distracted the Commander from his usual instrument scan to the extent that he did not then notice the increasing angle of bank to the right and the continuing descent into the sea.
• The helicopter reached a maximum nose down pitch of 38° coincident with a bank angle of 38° to the right about 8 seconds before impact with the rate of descent approximately 1400 fpm at 170 feet above the sea. The last recorded parameters were a pitch attitude of 12° nose down, a 20° bank to the right and a forward speed of 126 KCAS.
• Impact with the sea occurred approximately 0.25 nm south of the North Morecambe Platform. It was concluded that "the overall impact forces were outside the limits of human tolerance and no additional or alternative safety equipment would have been likely to alter the fatal outcome".

It was established that the aircraft commander had been operating as a helicopter pilot in the Morecambe Bay Gas Field for 20 years and at the time of the accident he was the base Chief Pilot and a Line Training Captain. The Co-pilot had been trained to fly helicopters whilst in the British Army and had left in early 2003 after which he had flown Air Ambulance helicopters for two and a half years before joining CHC Scotia just over a year prior to the accident. It was noted that "although (the accident) flight was with the Chief Pilot it was neither a training flight nor an assessment flight".

The Investigation noted that helideck perimeter lights on the North Morecambe platform had been yellow and that new criteria for such lighting, which would not permit continued use of the installed lighting, was due to become effective on 1 January 2009. The change - to green perimeter lighting - was noted to have been a consequence of research which showed that changing the colour from yellow to green "significantly increased the range at which the pilot could visually locate the helideck amongst other platform lighting" and that green perimeter lighting "also provided a strong colour contrast (with other platform lighting) which enhanced the situational awareness of the pilot and promoted greater confidence in the conduct of the approach".

It was concluded that "the (North Morecambe) helipad at night gave insufficient cues to allow distance to be judged and, without additional information from the weather radar or GPS, the crew...would not have known the distance to run accurately".

It was found that the CHC Scotia Operations Manual stated that:

• the absolute minima for night VFR operations were 5000 metres visibility with a cloud base of 1,200 feet.
• for visual flights between helidecks less than 10nm apart at night, the minimum forward visibility was 5000 metres and the cloud base must be such as to allow flight at 500 feet whilst clear of cloud.
• Flying between helidecks at night when the cloud base was lower than 500 feet was only permissible if it was above the Airborne Radar Approach (ARA) limit of 300 feet and the crew are flying the ARA procedure.

It was noted that an ARA could be flown to ¾ nm from a platform as measured on the helicopter’s radar but that the accident helicopter crew "were not conducting an ARA during the flight to the North Morecambe platform and their previous approaches, to the AP1 and the Millom West platforms, were conducted visually".

The Findings of the Investigation included the following:

• There was no evidence that any loss of airworthiness had contributed directly or indirectly to the loss of control which occurred.
• Although the prevailing weather conditions were poor, they were above the required minima and not unusual for operations of the type being undertaken.
• Both pilots were familiar with operations onto the North Morecambe platform and the lighting on the platform was serviceable - although it was of a type due to be upgraded from a colour regime which had been found to add difficulty to visual acquisition of helidecks at night in poor visibility.
• The impact of the helicopter’s fuselage with the sea surface was not survivable.

The Investigation identified the following three Contributory Factors:

1. The co-pilot was flying an approach to the North Morecambe platform at night, in poor weather conditions, when he lost control of the helicopter and requested assistance from the commander. The transfer of control was not precise and the commander did not take control until approximately four seconds after the initial request for help. The commander’s initial actions to recover the helicopter were correct but the helicopter subsequently descended into the sea.
2. The approach profile flown by the co-pilot suggests a problem in assessing the correct approach descent angle, probably, as identified in trials by the CAA, because of the limited visual cues available to him.
3. An appropriate synthetic training device for the SA365N was available but it was not used; the extensive benefits of conducting training and checking in such an environment were therefore missed.

Safety Action taken by CHC Scotia as a result of the accident findings was noted to have included the following:

• By the spring of 2008, all SA365 pilots had received simulator training.
• More specific guidance has been provided to crews on the actions to be taken following disorientation or incapacitation.
• Go around procedures which included guidance on the use of the AP coupler had been developed
• A night circuit pattern had been developed and published.

The following six Safety Recommendations were made as a result of the Investigation.

1. that CHC (Scotia) review their Standard Operating Procedures related to helideck approaches, to ensure that the non-handling pilot actively monitors the approach and announces range to touchdown and height information to assist the flying pilot with his execution of the approach profile. This is especially important on the SA365N helicopter when the co-pilot is flying approaches in poor visual conditions and cannot easily monitor a poorly positioned radio altimeter. [2008-032]
2. that the European Aviation Safety Agency ensure that research into instrument landing systems that would assist helicopter crews to monitor their approaches to oil and gas platforms in poor visual flying conditions and at night is completed without delay. [2008-033]
3. that CHC (Scotia) conduct a thorough review of their Standard Operating Procedures related to helideck approaches, for all helicopter types operated by the company, with the aim of ensuring safe operations. [2008-034]
4. that the Civil Aviation Authority should ensure that the recurrent training and checking of JAR-OPS, Part 3 approved operators should be carried out in an approved Synthetic Training Device. [2008-035]
5. that the European Aviation Safety Agency (EASA) investigate methods to increase the conspicuity of immersion suits worn by the flight crew, in order to improve the location of incapacitated survivors of a helicopter ditching. [2008-036]
6. that the Civil Aviation Authority ensure that personnel who are required to conduct weather observations from offshore installations are suitably trained, qualified and provided with equipment that can accurately measure the cloud base and visibility. [2008-037]

The Final Report was published on 17 October 2008.

Related Articles

• Loss of Control
• Night Visual Approaches
• Health and Usage Monitoring System (HUMS)
• Situational Awareness
• Offshore Helicopter Safety Review 2014 UK CAA
• Ditching: Rotary Wing Aircraft
• Emergency Breathing Systems (EBS) for Offshore Helicopter Occupants
• Helicopter Emergency Floatation Systems (EFS)

Further Reading

UK CAA

• CAP 1077: Specification for an Offshore Helideck Lighting System
• CAP 437: Standards for Offshore Helicopter Landing Areas, 7th ed.

NTSB Safety Alerts on General Aviation risks

• Safety Alert 19 - Prevent Aerodynamic Stalls at Low Altitude
• Safety Alert 20 - Reduced Visual References Require Vigilance
• Safety Alert 23 - Pilots: Manage Risks to Ensure Safety
• CAP 1145: Civil Aviation Authority – Safety review of offshore public transport helicopter operations in support of the exploitation of oil and gas, February 2014
• UK CAA CAP 437 Standards for Offshore Helicopter LandingAreas, February 2013
• UK CAA CAP 1077 Specification for an offshore helideck lighting system, July 2013
• Analysis of Offshore Helicopter Reportable Accidents 1976 - 2012 an internal UK CAA review of all UK offshore public transport helicopter reportable accidents during the period 1976 to 2012