The rocky horror show that left the Queen in a scrape: Brian Cathcart on the inexact science of seafaring that put a hole in the QE2

AT 8.50pm on 7 August 1992 the liner Queen Elizabeth 2, with 1,824 passengers and 1,003 crew on board, weighed anchor off the New England resort island of Martha's Vineyard to begin a voyage to New York.

The night was clear and warm, with a light breeze. The ship was the pride of the British merchant navy, and the two men in charge, Robin Woodall, the ship's master, and John Hadley, a Massachusetts pilot, between them had 70 years' experience at sea. The waters round about, while not without hazards, have been known to seamen for three centuries.

One hour and eight minutes later the QE2 hit an object on the seabed and was holed. In a blaze of embarrassing publicity, all passengers had to be taken off, and the ship spent two months in dry dock. The cost, including lost business, was pounds 20m.

How could it happen? How could such a big, well-equipped ship with a first-class crew simply 'bump into America', as the papers put it? Three investigations have been carried out, two American and one British, and the reports are alarming. They tell of old, incomplete charts, of poor bridge communication, of a narrow channel without speed restrictions and of surprising scientific uncertainty about the behaviour of big ships in shallow water. Above all, they demonstrate that seafaring in the 1990s is far from an exact science. Where the blame lies is disputed, but the investigators identified four factors: course, charts, speed and a phenomenon known as 'squat'. Let us look at them in turn.

After turning his ship that evening, Captain Woodall handed control to the pilot, whose job was to take it out to open sea. Captain Hadley had brought the QE2 in that morning, but before that it had been 18 months since he had piloted any ship in the Vineyard Sound, and the biggest vessel he had handled there was smaller and slower.

An outward course had already been plotted by the QE2 navigator and approved by the master. This led down the sound and on to the point where the pilot would disembark. Captain Hadley ignored this course, as was his right. He said later: 'I had in my own mind my own practice of proceeding out of Vineyard Sound.' This involved using buoys and lights, and occasionally radar to verify his position.

At the northern end of the sound there is little choice about how to proceed. It is straight and narrow and leads to a buoy due east of Cuttyhunk Island, called the NA Buoy, where the channel widens. The QE2 passed this buoy at 9.44pm.

At that moment, though no one realised because no one was monitoring the echo sounders, the ship came very close to grounding. US Coast Guard investigators reported: 'There may have been less than 1ft of clearance between the bottom of the hull and the sea floor.'

The pilot now altered course, turning the ship to the right, so that it would pass closer to Cuttyhunk Island than had been proposed by the QE2 navigator. He planned a further change of course once level with the island, which would point the ship towards his disembarkation point. He had not told the officers on the bridge that this was his plan, but again he was within his rights.

The second officer drew a line on the chart showing where the new course was leading, then noticed that some miles ahead lay a shoal with depths as shallow as 34ft. The QE2's draught was 32ft 4in. He alerted the first officer, who told Captain Woodall.

Unhappy about this, the master suggested taking the QE2 further to the south of Cuttyhunk. Although the pilot had planned a second adjustment before reaching the shoal, he accepted the master's suggestion, and at 9.54pm the change was made. These alterations, of course, are crucial. Had the pilot accepted the navigator's route, or had the master accepted the pilot's route, there would have been no accident. Again the second officer drew a line on the chart to plot the new course, and again it passed through shallow water. This time the depth marked was 39ft; he judged this to be safe and said nothing. Later the pilot said he 'had in his mind' a 39ft depth.

At 9.58pm the QE2 hit rocks, sustaining fractures, gouges and denting along more than one-third of its length. It was never in danger of sinking and no one was injured, but the voyage was over.

The culprits were two rocks, neither marked on the charts. It soon emerged that the charts for Vineyard Sound were based on soundings taken by primitive echo sounders in 1939. This caused surprise, but there is nothing unusual about it, except in the sense that the charts may have been better than average: 60 per cent of US inshore charts are based on data gathered using even more rudimentary methods. (The picture in Britain is not much different; some Isle of Man waters and parts of the north Cornish coast were last surveyed in the 1850s.)

This is known to mariners, who are warned to treat charts with caution. The guidance book for Massachusetts pilots, for example, says: 'It cannot be too strongly emphasised that even charts based on modern surveys may not show all seabed obstructions.' Speed had a part in the accident. Captain Woodall had told the pilot early in the day that he hoped to make good speed on the way out so that he would not have to push the ship too hard in the latter part of its voyage to New York. When the QE2 started down the sound in the evening - 55 minutes late - the master asked the pilot if he objected to a speed of 24 knots, and was told that was acceptable.

This is very fast, but the QE2 is built to be fast, and Captain Woodall testified that it routinely operated at even greater speeds. The US Safety Board criticised master and pilot, saying a slower speed would have meant more time for corrective action.

There is another way in which speed played a part, and this has to do with 'squat'. When a vessel moves through the water, it is subject to curious hydrodynamic effects which, among other things, cause the water level around the hull to fall. The bottom of the vessel thus moves closer to the seabed. This effect is accentuated in shallow water, and by speed.

All this is incompletely understood, but mariners are generally aware of the phenomenon. The master and the pilot on the QE2 said later that they were estimating squat at 2ft. At the same time, they were also estimating the tide as 2ft above the level used in establishing the chart figures. Their mental calculation was that squat and tide cancelled each other out, and that in passing over a 39ft sounding, the QE2, with its draught of 32ft 4in, would have ample clearance.

They were wrong about the tide, which was only about 6in above the chart level, and the US and British authorities say they were also wrong about the squat. There is no scientific certainty on this, but the US view is that, travelling at 24 knots in 40ft of water, they should have allowed at least 4ft 6in for squat, perhaps as much as 8ft.

The British Marine Accident Investigation Branch suggests at least 3ft 3in. Cunard, the ship's owner, suggests 2ft to 3ft 6in.

The differences are important because Cunard insists that the sole cause of the accident was a bad chart. By its measure - and by the MAIB's - even if correct allowances had been made for tide and squat, the QE2 would have passed over the 39ft sounding safely. It was only the uncharted rocks that caused a collision, says Cunard.

The US authorities, by contrast, say that even if there had been no rock shallower than 39ft, the QE2 would still probably have hit bottom; it should not have been where it was, nor travelling so fast.

How big were the rocks? At least 16 were found on the seabed in the area, and at least two were struck. The impact had pushed them downwards, but it is estimated that at the moment they were struck they were between 30ft and 35ft beneath the surface.

The grounding of the QE2 was not the sinking of the Titanic - no lives were lost and the crew were praised for their conduct after the impact - but it highlighted problems at sea in a way that no ordinary shipping accident could have done. US investigators insisted that masters and pilots should always agree on a route before the anchor is weighed, a proposal that Cunard has accepted. All the reports also called for more research into squat.

As for the charts, there is now pressure for sweeping new surveys of American waters. The rocks that did the damage have been clearly marked.

(Photograph omitted)