Operator’s Route Guide for Blacksod. Photo courtesy of the the Air Accident Investigation Unit Ireland
Neither the pilot nor co-pilot of the Irish Coast Guard S-92 that crashed in mid-May had recently flown the approach that ended in their deaths and those of two crewmembers, according to the accident investigators’ preliminary report.
The flight crew also was using a route guide developed by the aircraft operator, CHC, that the Irish Air Accident Investigation Unit is recommending be reviewed to ensure such documents provide adequate information on obstacle and terrain heights positions.
CHC Ireland should review and re-evaluate all route guides in use by its search-and-rescue helicopters in Ireland, the Irish investigators recommended in the preliminary report, “with a view to enhancing the information provided on obstacle heights and positions, terrain clearance, vertical profile, the positions of waypoints in relation to obstacles” and Enhanced Ground Proximity Warning System database terrain and obstacle limitations.”
The Sikorsky helicopter crashed before 1 a.m. local time, apparently after its tail struck terrain on Black Rock, a small island a few miles off northwest of the Irish coast near Blacksod Bay. The Irish unit’s preliminary report, issued April 13, noted that Black Rock Island and the lighthouse on it were not included in the terrain database of Honeywell Mark XXII EGPWS installed on the S-92.
The aircraft, designated Rescue 116, had been dispatched from Dublin to fly “top cover” for another Coast Guard S-92 sent to retrieve ill crewmen from the fishing vessel more than 150 nautical miles off the northwest Irish coast. Rescue 116 was flying the CHC-specific approach to Blacksod Bay for refueling when the crash occurred. According to an "aftercast” provided to investigators by the Irish Meteorological Service, visibility at Black Rock was about 1 to 2 miles in mist and drizzle at the time of the crash, with an overcast layer of clouds whose base was at 300 to 400 feet.
The preliminary report states that, based on analysis of the aircraft's cockpit voice recorder (CVR), the pilot briefed the crew on the approach to Blacksod and also commented to the other crewmembers “on a number of occasions that it had been a substantial period of time since she had previously landed in Blacksod.”
The report states: “On one occasion, the commander asked the co-pilot when he had last been into Blacksod, and he indicated that he had not been there recently.”
According to the report, CHC’s guide for the APBSS, or Blacksod South Route, includes a separate page of text setting out waypoint designations and coordinates, hazards and obstacles and other general comments. “This page identified a lighthouse at Black Rock with an associated height of 310 feet,” the report says. The Irish Aviation Authority Aeronautical Chart West, which covers the accident area, “shows an elevation of 282 feet for the lighthouse,” the report notes, adding that the lighthouse, which is painted white and stands 50 feet tall, was operating at the time of the crash.
The CVR indicates that during the approach the co-pilot was using the S-92’s Honeywell Primus 701A airborne, ground and sea mapping weather radar system to identify terrain features. The report, citing Honeywell’s manual, says, “This mode provides the best sensitivity for ground mapping of targets” and “disables all ground-clutter and sea-clutter reduction modes.”
The aircraft was flying at 200 feet above msl and 75 kt during the final moments of approach. About 26 seconds prior to the initial impact, the radar altimeter made an “ALTITUDE, ALTITUDE” callout, an aural alert the report says the pilot attributed to a small island below the helicopter, stating it was actually a waypoint on the approach. At that time, the report says, it indicated the aircraft was 0.65 nm west of Black Rock.
About 13 seconds prior to the initial impact, the report says, the winchman or winch operator in the rear of the aircraft identified an island head of the aircraft, “probably through the use” of the aircraft’s Wescam MX-15i EO/IR camera system.
“Looking at an island just in, directly ahead of us now guys,” the rear crewmember said. “You want to come right.”
The pilot initiated a heading change. “Then the rear crewmember then interjected, with increasing urgency, ‘Come right, now come right, COME RIGHT,’” the report states.
Wreckage from the S-92’s tail and intermediate gearbox were found close by the Black Rock lighthouse. The bulk of the aircraft remains three crewmembers were found in the ocean just east of that island. The pilot was rescued from the sea shortly after the crash, but died of her injuries.