Introduction
An Aerospatiale SA365N Dauphin 2 helicopter, registration G-BLUN, was destroyed when it crashed into the Irish Sea near the North Morecambe platform on 27 December 2006. The helicopter was conducting a commercial air transport flight with two crew and five passengers. All seven occupants received fatal injuries or were missing; six bodies were recovered, and the search for the seventh continued for two days without success. The UK Air Accidents Investigation Branch (AAIB) commenced a field investigation the day after the accident.
Flight History
The helicopter operated from its base at Blackpool in support of offshore gas operations in the Morecambe Bay gas field. On the night of the accident, it departed Blackpool for a scheduled flight of eight sectors. The first two sectors were completed without incident. At 1826 hrs, the helicopter took off from the Millom West platform and began a transit to the North Morecambe platform at a height of 500 ft.
The three-man helideck team on the North Morecambe platform observed the helicopter making its approach. They reported the approach appeared normal until the helicopter turned to the right and flew close to the platform without slowing. It then straightened briefly before banking slightly and descending at a steady rate. The team lost sight of the helicopter and seconds later heard it crash into the sea. The alarm was raised and the coastguard contacted at 1835 hrs.
Weather Conditions
A weather observation from the Central platform at 1700 hrs reported surface wind from 150° at 22 kt, visibility 4 km in rain, sky obscured, temperature +5°C, dew point +4°C, and mean sea level pressure 1020 hPa. This information was passed to the helicopter operator for flight planning. A standby vessel near the North Morecambe platform recorded at 1810 hrs a surface wind from 130° at 20 kt with visibility between 3 and 5 nm. Minimum weather conditions for night flights between helidecks required a cloud base allowing flight at 500 ft to remain clear of cloud and visibility of 5 km.
Search and Rescue
Liverpool Maritime Rescue Co-ordination Centre coordinated the search and rescue operation. A rescue helicopter arrived at the scene within 35 minutes. The standby vessel’s rescue craft, already searching, recovered six bodies that evening. The search for the seventh occupant continued for a further two days without success.
Wreckage Recovery
The fuselage disintegrated on impact and most of the structure sank. The tail boom and fenestron were found floating on the surface and recovered within the first few hours. Recovery of remaining wreckage and the flight data recorder was delayed by persistent storms in the Irish Sea throughout early January. The flight data recorder was located on 5 January, and main wreckage elements, including the main rotor head, main gearbox, and both engines, were recovered on 10 January. The remaining major items and the flight data recorder were recovered on 16 January. More than 90% of the helicopter was eventually recovered.
Preliminary Engineering Findings
Representatives of the airframe and engine manufacturers completed an initial appraisal of the wreckage under AAIB supervision. The preliminary examination found no signs of pre-impact malfunction of any major mechanical components, including the tail rotor and its drive shaft. Indications of torque delivery were observed on both engines, and damage to the main rotor blades was consistent with normal operating rpm at impact. A detailed strip inspection of the transmission, engines, flying control actuators, and instruments was to commence.
Flight Data Recorder Analysis
The helicopter was fitted with a combined cockpit voice and flight data recorder. Initial analysis indicated that the first two sectors, flown by the co-pilot, were completed without incident. The helicopter departed Millom West with the co-pilot as handling pilot. During the approach to North Morecambe, the helicopter slowly pitched nose down and commenced a slow roll to the right. The collective lever was raised, increasing engine power, and indicated airspeed and altitude began to increase. The crew became unhappy with the approach and decided to abort the landing.
During the go-around, the helicopter continued to roll to the right and pitch nose down. The co-pilot asked for assistance, and the commander took control. Data showed that one second later, the helicopter reached a maximum nose-down pitch attitude of 38°, coincident with a bank angle of 38° to the right. Indicated airspeed was increasing through 80 kt, radio altitude decreasing through 300 ft with a rate of descent of approximately 1,400 ft per minute. Over the next 2.5 seconds, the helicopter rolled level and pitch attitude reduced to 13° nose down. Radio altitude indicated 170 ft, airspeed over 100 kt, and rate of descent about 1,400 ft per minute. During the following 5.5 seconds, pitch attitude remained stable, airspeed continued to increase, and the helicopter commenced a slow roll to the right. The last recorded parameters showed radio altitude 30 ft, pitch attitude 12° nose down, indicated airspeed 126 kt, and bank angle 20° to the right.
A review of the recorded data to date indicated no problems of a technical nature, and no helicopter manoeuvres were identified that were not in response to flight control inputs.
Ongoing Investigation
The AAIB continued a detailed investigation of the wreckage, further analysis of recorded data, and a thorough assessment of operational aspects of the accident. No safety recommendations were considered appropriate at the time of the special bulletin.