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History

In 1972 hopes for hovercraft were still high. Considerable importance was attached to the future of military hovercraft designs since the Vosper Thornycroft board recognised that, whereas they had once enjoyed a significant technical lead, which almost amounted to a monopoly, in the design of the fast gas-turbine powered torpedo boats, there was much more competition in the patrol boat markets now being addressed. Investing in hovercraft development was seen as one way of re-establishing a niche. Although hovercraft eventually turned out to be a dead end, it is hard to see how this could have been foreseen at the time.

Just before Christmas 1972, therefore, the Vosper board agreed on expenditure to convert the prototype VT1-001 to a fully amphibious craft, which was to be known as "VT2". The new craft was a VT1 with the skegs and water screws removed, and above-water propulsion substituted. The latter was novel, a good deal of thought having gone into its design.

Firstly, two ducted fans, rather than conventional airscrews were used. They had a relatively low rotational speed and were mounted above the stern, enclosed in annular ducts, which also housed pitch and yaw control surfaces. Drive shafts for these fans emerged direct from the gearboxes in the hull, each of which also drove lift fans: no additional gearing was included to make the thrust line horizontal.

The fans therefore were mounted at a slight angle to the horizontal, but the loss due to this was more than compensated for by the lack of an additional expensive and power consuming gear train, to turn the fan thrust line horizontal. The fans themselves were specially designed and built by Dowty Rotol, and had variable pitch control. This meant that the thrust could be varied without changing the speed of rotation, or, therefore, the speed of the lift fans. Also, at low forward speeds, the craft could be steered by differential thrust alone. This made it, for an air-propelled craft, very quiet and very manoeuvrable.

To drive each of the two propulsion fan/lift fan units, a Proteus gas turbine was fitted in place of the smaller Lycoming. The resulting craft was fully amphibious, with a slightly better payload capability than VT1, and capable of 60 knots, which speed it could maintain comfortably in a sea state which would have been most uncomfortable, to say the least, in a Brave class FPB at full speed.

The hovercraft also compared well with conventional boats in its ability to withstand damage; this fact was perhaps not widely appreciated, the uninitiated tending to regard the flexible skirt as akin to a tyre, or even a balloon, to which one bullet hole might prove disastrous. In fact, quite large portions of the skirt and its peripheral fingers could be shot away without haying any serious effect upon performance, and damage (arising in practice from wear and tear rather than battle damage!) was quick and easy to repair, without any special facilities.

The VT2 was another technical success, in that it performed well up to expectations. It was at that time the largest naval hovercraft in the world, with a payload of up to 33 tonnes. It proved popular with the Interservices Hovercraft Unit (IHU), who first hired the prototype for evaluation. Some exciting exercises were carried out with the army, on exercises in the Hebrides, when troops and vehicles were delivered rapidly to some most unexpected places.

With this encouragement, Vosper Thornycroft designed various different configurations for the export market. The Logistic Support Hovercraft was basically the prototype configuration. In this role, it could carry 130 fully equipped troops, together with transport. The latter could comprise four Land Rovers with trailers, or a couple of 4 tonne Bedford trucks, or even three Scorpion light tanks. The Fast Missile Hovercraft was the same raft and propulsion system, but fitted with a 57mm or 76mm gun and two surface to surface missiles.

There was also a great deal of interest in the application of hovercraft to mine countermeasures, largely because, sitting on a big bubble of air, the craft proved almost invulnerable to underwater explosions unless detonated immediately beneath it. A considerable amount of study work was performed on this role, and after a refit, MOD(N) eventually bought the VT2 prototype for extended evaluation as an MCMV support vehicle.

However, the world remained suspicious of hovercraft, unnerved, perhaps, by the unusual operating characteristics. Most small navies (and some large ones) tend to be very conservative and wary of adopting new ideas unless given a strong lead by major armed forces elsewhere. There are few rewards for initiative, especially in peacetime, promotion being dependent mainly upon time and a "clean" record. Association with an unsuccessful project or incident are however quite enough to eliminate, permanently, all chances of promotion for the individual deemed responsible.

Despite the spectacular top speed of the hovercraft, some were put off by the low endurance, (typically about 300 miles) compared with a conventional patrol boat. It was not always clear why this endurance was necessary: when patrolling a stretch of coastline a boat has little choice but to keep moving up and down over the same area at a slow cruising speed; stopping usually results in most unpleasant rolling. On, say, an anti-smuggling patrol lasting several days, sufficient fuel is required to keep under way, and this translates into quite a substantial number of nautical miles. A hovercraft is quite unable to carry enough fuel to cover the same distance at a slow cruise, and yet might be at least as effective since it can stop and drift for a while, without suffering such uncomfortable motion, thanks to its broad beam. It can also go ashore easily on almost any beach, and thus be relatively well concealed, more comfortable for the crew, but ready to move at high speed at short notice.

There were other roles, as well as mine hunting, where the unique capabilities of the hovercraft appeared to offer advantages to those with sufficient imagination, but even today there has been only limited acceptance of such craft. Despite the success of the IHU trials, the British Armed Forces never showed much interest in hovercraft, and IHU was eventually axed in around of budget cuts. VT2 finally followed her sisters to the scrap yard.

Without a lead by the RN or the British Army, the chances of overseas sales were further diminished, and despite some determined efforts at marketing both the VT2 and other hovercraft designs abroad, the hovercraft department was eventually run down. and most of the staff absorbed into the shipbuilding departments. VT1 and VT2 were splendid solutions which never found the right problems to solve.

 (Quote from book Warships for the World)

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