1983 British Airways Helicopters Sikorsky S-61 crash
The AIB found that the accident was caused by pilot error, in failing to notice and correct an unintentional descent when attempting to fly at low altitude in poor visibility.
Other contributory factors were found to be a failure to monitor flight instruments adequately, and a lack of audio height warning equipment.
On 24 June 1983, Oscar November was assigned to act as a replacement for the British Airways Helicopters commercial passenger service between Penzance and the Isles of Scilly.
[5] Oscar November was one of two flights scheduled to fly from Penzance Heliport to St Mary's Airport on the Isles of Scilly on the morning of 16 July; the other was G-BDDA (Delta Alpha), another S-61 helicopter.
Delta Alpha had been scheduled to depart at 7:50 am (GMT),[a] while Oscar November was due to leave at 8:15 am, but both flights were delayed by poor visibility.
With the possibility of the weather worsening, Lawlor waited for confirmation that Delta Alpha had landed and flown the entire journey according to visual flight rules (VFR).
For his part, Charleton had interpreted the message differently, believing that 300 feet had referred to the height at which Delta Alpha had been when they made the observations, but the pair did not discuss the report.
[8] At roughly 11:35 am, following a string of communication between Charleton and St Mary's, the last message was sent from the aerodrome; "Oscar November is clear to land 300 degrees at 5 knots.
"[9] When Oscar November was roughly 1.5 nautical miles (2.8 km; 1.7 mi) from the coast, the helicopter crashed,[10] hitting the sea three successive times.
[14] In addition to the two pilots, the survivors were Howard Goddard (age 12), Ellen Hanslow (15), Lucille Langley-Williams and Megan Smith (both 60).
Shortly thereafter, they also contacted RNAS Culdrose that Oscar November was overdue, and requested that the search and rescue helicopters be put on stand-by.
The lifeboat, RNLB Robert Edgar, launched around midday, around the same time as the search and rescue helicopter was scrambled from Culdrose.
A second Navy helicopter, a Westland Sea King, arrived around 1:00 pm and was directed to the crash site by flares from the lifeboat, which returned to St Mary's with the survivors not long after.
[21] On the evening of the crash, the MV Seaforth Clansman, a Royal Navy charter in Naval Party 1007, sailed from Falmouth with a crew of divers, arriving at the site that the survivors had been picked up at 10:10 pm.
It took until 6:00 pm that evening to get an accurate position for the helicopter, but sea conditions meant that they could not commence diving until early the following morning.
[23] An article in The Times initial speculated that the helicopter could have flown into a flock of seagulls, after mutilated bird corpses were found near the scene, or suffered a mechanical failure.
[26] These issues were contested by British Airways Helicopters, and along with the theories about the seagulls and a mechanical failure, none were found to have caused the crash or the high loss of life in the Accidents Investigation Branch report.
[b][29] He found that the cause was pilot error, specifically that Lawlor did not notice and remedy an "unintentional descent" while intending to fly at 250 feet (76 m).
[33] The main recommendation from the report was for an audible height warning on passenger helicopters operating off-shore and for the altimeter to be moved nearer to the pilot's 'head-up field of vision'.
[34] The United Kingdom Civil Aviation Authority made it mandatory that audible ground proximity warning systems had to be installed in all passenger helicopters by August 1985.
