Supersonic stealth jumpjet in first hover-system flight test

Brit pilot fires up Rolls-Royce lift kit

Vid The world's first supersonic stealth jumpjet, the F-35B, has belatedly begun flight tests of its vertical-thrust technology - much of which is from Blighty. The radical plane is intended to replace the famous Harrier in the services of many nations, including the UK.

Here's a vid of the test aircraft trying out its downward-swivelling jet exhaust and central lift fan in the skies near Patuxent River Naval Air Station in the US, with British test pilot Graham Tomlinson at the controls:

The big dorsal fliptop lid covers the shaft containing the Rolls Royce engine-driven lift fan: you can also see the bottom shaft doors opening. The smaller dorsal doors allow more air into the engine for vertical-thrust ops, and another pair of ventral doors is provided below the swivelling exhaust to allow it to point all the way down.

Lockheed, lead maker of the F-35, says that the test aircraft stayed at 180 knots (207 mph) or faster throughout the initial test. Further flights will see it going slower and slower until it is actually hovering, before Tomlinson and his colleagues begin to carry out actual landings and vertical-thrust-assisted takeoffs.

The F-35B is intended for service with the US Marines, with other US armed services purchasing more conventional runway and catapult-carrier versions. The F-35B is also planned to replace the Harrier in the Royal Navy and RAF: the navy requires it for operations from Blighty's new carriers, which on current plans will not offer catapult launch.

The RAF by contrast has cooled right off on jumpjets in recent times, and it has been suggested that the air marshals would rather close the entire joint Harrier force down now - quite likely torpedoing the carriers, which wouldn't upset the RAF in the slightest - and not bother with F-35Bs; instead spending the cash on upgrading the Eurofighter into a modern deep-strike bomber.

At the moment the navy appears to be resisting these moves, but cuts to the present RAF Harrier force have lately been announced as part of a push intended to give more support to troops in Afghanistan.

Meanwhile the F-35B is now well behind schedule, having been supposed to start these lift-system tests months ago (and that deadline was already later than had been hoped). Then there are other issues to be confronted, not least the fact that the plane is thought likely to melt and buckle carrier flight decks with its superhot exhaust - its F135 engine is "the most powerful ever flown in a fighter", according to Lockheed.

The Royal Navy is pretty much wedded to the F-35B, and barring a sudden upset will surely wind up getting some: but it remains to be seen whether any serious number of the jumpjets will ever be bought by the RAF. This could be an issue, as it isn't thought that the navy can afford to have two carrier groups' worth of F-35Bs on its own - especially with British government finances in such straitened conditions just now. ®