Realistic simulations reveal weaknesses in preparation
- Predicted recovery times by an open fast rescue craft speeding through the water at 29 mph, from a stand-of distance of 2.5 nautical miles, for 12 personnel ditched from a helicopter in the North Sea in 2.5 meter waves. (Source: Conoco UK) [33,268 bytes].
Narrowly averted disasters provide the best test of safety suits, escape routines, and emergency response measures, it transpired. Few emerged with flying colors in a UK operater's report on a ditched North Sea helicopter. However, the lessons are being absorbed in the form of more realistic preparatory training by Conoco, among others.
The helicopter concerned was a Bristow Super Puma enroute to Marathon's Brae Field complex, carrying 16 passengers and two crew members on January 19, 1995. All were wearing Gortex-type immersion suits and a harness-type life-jacket, containing a strobe light (introduced following an earlier Cormorant Alpha Field accident).
Weather for the flight was gusty, but not unusually so. However, a lightning strike when the aircraft was still some way off from the Brae A platform could not be anticipated. This damaged the tail and one of the rotor blades, which subsequently detached, along with the gearbox. But the First Officer still managed a safe, controlled landing in the water.
Attempts to launch the helicopter's port life raft on the windward side failed as it blew up on its edge against the door. To speed up the evacuation, all 16 passengers were transferred to the starboard raft (normal carrying capacity for 14 people) which had inflated successfully. However, this raft was then punctured in the scramble to get away, causing one buoyancy ring to be lost.
Survival training procedures did pay off, although preparations for operating the raft after boarding, such as erecting the canopy, were not up to expectations. On the plus side, the passengers had been part of a close working team offshore and this helped to raise morale during the ordeal.
Response from local rescue sources was excessive. This proved a problem also for the director of the rescue effort - to be performed by fast rescue craft.
From his review of the incident, Mack concluded that immersion suits do not provide good thermal protection and ingress of water reduces their thermal properties. Actions adopted following the incident included:
- Mandatory use of thermal liners in suits on all flights when sea temperatures dip below 10!C
- Improved lightning observation for North Sea flights
- Clearer guidelines on management of rescue resources
- Extra video briefings for personnel on lifecraft equipment location.
Poor definitionJeremy Daniel of the Standby Ship Operators Association is a long-time campaigner against corner cutting in emergency response. He alluded to a table from the UK's Health & Safety Executive concerning the time scale during which the "standard man" will likely succumb to drowning.
Daniel insisted that planning should cater for people less fit than the standard man, which means a large segment of the offshore workforce. He also advocated increased use of personal location devices (which aided the Brae A search effort), and a more sensible analysis of sea conditions when dealing with injured passengers.
He claimed that there was still widespread evidence in the North Sea of pressures on offshore managers causing critical elements of emergency response programs to be discarded.
David Foster of Britain's HM Coastguard Agency complained that some evacuation training exercises were not realistic, too tightly scripted, and too rigid in setting rescue time scales.
Conoco has tried to step up realism in its southern North Sea Loggs/Viking area installation rescue arrangements. It launched a study in late 1994 which had to satisfy upcoming legislation in the UK concerning prevention of fire and explosion and emergency response.
Risk analysis was performed to determine the most effective sharing arrangements for standby vessels, evaluating the risks to personnel against Conoco's 1995 workscope in the southern sector.
Among the conclusions were that introduction of PLBs would turn a search and rescue operation into one of rescue alone, in turn cutting rescue times, especially in rough weather. PLBs would also allow a standby vessel equipped with a daughter craft to rescue an individual within 30 minutes, with a 50% probability of doing so when operating at a range of 10 nautical miles from the installation.
Following talks with Viking and Loggs safety representatives, Conoco tightened its perfromance criteria for rescue craft in attendance during helicopter landing and take-off and periods of overside working Conoco then developed a concept of sharing circles, or 10 nautical mile "guard zones," employing the mother vessel at the center. The vessel master positions additional standby vessels within the radius of this zone, depending on how the emergency situation unfurled. A radar receiver allows him to accept information broadcast from the Loggs complex radar systems onshore in Lincolnshire.
To aid effective use of its standby fleet, Conoco integrated its southern sector work planning Primavera systems with new software for managing vessel movements. These were simulated off the Viking platform in 1996. These trials included use of dummies in moderate seas to simulate a ditched helicopter - all dummies were recovered by the master vessel within 35 minutes (starting from a point four nautical miles from the incident).
Rescue vessel procedures were then implemented by Conoco in September 1996. Performance standards have been under continual review ever since.
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