Original URL: http://www.theregister.co.uk/2010/03/19/f35b_vertical_landing/

And now - new stealth jumpjet makes first hover landing

'Cobblestones' effect reduced, says Brit test pilot

By Lewis Page

Posted in Science, 19th March 2010 09:49 GMT

Vid Following yesterday's initial hover, the new F-35B Lightning II - world's first supersonic stealth jumpjet - has now made a vertical landing. British test pilot Graham Tomlinson said the aircraft is much easier to set down than today's Harrier.

“Today’s vertical landing onto a 95-foot square pad showed that we have the thrust and the control to maneuver accurately both in free air and in the descent through ground effect,” said Tomlinson, a former RAF Harrier jockey and now lead test pilot for the F-35B. The first three jumpjets are in flight tests at Naval Air Station Patuxent River in Maryland.

The vertical landing was a venture into the unknown for the F-35B, as its design is radically different from the Harrier and it had not previously hovered low enough for surface effects to come into play.

Tomlinson has previously said that the F-35B is easier to handle in the hover than a Harrier: apart from more sophisticated control systems, he says that the forward lift fan, driven by a shaft from the engine and mounted in a vertical tunnel behind the cockpit*, blasts cool air downward as the swivelling jetpipe nozzle at the back of the plane blows fiercely hot jet exhaust.

In the Harrier, hot exhaust roiling up from the ground can get sucked into the jet's engine intakes, causing unpredictable power blips, but Tomlinson has said that the F-35B's fanshaft air acts as a "dam", causing the hot exhaust to stay to the rear and letting the engine operate more consistently. He told reporters that the "cobblestones" felt during a hover landing were "very light" compared to his days flying Harriers.

“The low workload in the cockpit contrasted sharply with legacy short takeoff/vertical landing (STOVL) platforms,” he added.

Tomlinson also gave it as his assessment that data from the landing yesterday indicated the F-35B will be able to make vertical landings still carrying 5,000lb of fuel and weapons. This will mean that it can come in to a hover landing on ships at sea still armed with air-to-air missiles, a vital requirement if the plane is being used as a patrol fighter to protect a fleet.

Royal Navy's running-jump-jet landing technique may not be required after all

The US Marines, the main planned buyer of the F-35, will be using it primarily as a strike plane - but the Royal Navy, which will have no other jets, will also use it as air cover for the fleet and will need it to get back on deck without dumping weapons. The Sea Harrier's inability to do this in hot climates** was the reason the legendary fighter was taken out of service some years back, limiting the Royal Navy today to Harrier GR9s that have no fighter radar and carry only short-range Sidewinder missiles as opposed to the Sea Harrier's arse-kicking beyond-visual-range AMRAAMs.

The Royal Navy have even gone so far as to develop a new landing profile for jumpjets which they call Shipboard Rolling Vertical Landing (SRVL), where a Harrier or F-35B can come down still going forward fast enough to use wing lift as well as engine/fan thrust - and yet slowly enough to halt before falling off the side of the ship, even without use of arrester wires.

Senior naval aviators have told The Reg that the Royal Navy will probably use SRVL regardless of the F-35B's vertical landing performance, as it will allow still more load to be carried and will mean that engines don't have to be run at maximum redline power in the hover so much.

That said, rolling SRVL landings will take up a lot more room on a carrier's deck than hovering ones, and jumpjets have had to land on other ships than carriers in the past, so the RN may yet be glad to have the full vertical-landing option.

Despite yesterday's success, however, serious question marks still hang over the F-35B and indeed over the whole F-35 programme (there are also A and C versions of the jet, intended for runway and catapult-carrier operations).

Today, though, worried Pentagon project bureaucrats and manufacturers in the US and UK*** will simply be happy to have some good news to tell us for once. ®

Bootnotes

*The big fliptop lid covers the top of the fan tunnel; the small dorsal doors behind it let extra air into the engine for high-thrust hover operations. There are more doors on the underside to let the jet exhaust twist downward and to cover the bottom of the fan tunnel when not in use.

**Jet engines lose thrust when sucking hotter air.

***The F-35's lead maker is Lockheed of the US, but quite a lot of work - especially on the F-35B - is being done in Blighty. BAE Systems' UK operations make significant parts of the plane (Tomlinson is a BAE employee, too) and Rolls-Royce make the thrust fan, swivelling exhaust pipe and the under-wing minijets which stop the plane rolling over in the hover. Rolls is also working on an a new engine, the F136, which is meant to be offered to F-35 buyers in future as an alternative to the current F135 from Pratt & Whitney.