Original URL: http://www.theregister.co.uk/2010/03/18/f35b_hover_flight/

Supersonic stealth jumpjet achieves its first mid-air hover

Brit test pilot balances on roaring columns of hot air

By Lewis Page

Posted in Science, 18th March 2010 11:56 GMT

Vids The F-35B supersonic stealth jumpjet has achieved its first hover in flight testing. British test pilot Graham Tomlinson held aircraft BF-1 stationary in midair 150 feet above the runway yesterday before executing a slow 70-knot rolling landing.

The F-35B is now in flight testing at the Patuxent River naval air station in Maryland. The radical hover-jet also achieved another first yesterday, making its first short-roll takeoff assisted by its vertical-thrust equipment:

The F-35B has a vertical-thrust fan, driven by a shaft from the engine, mounted in a shaft behind the cockpit. The big fliptop lid seen in the videos covers the top of the shaft in normal flight, while the smaller dorsal doors just behind it allow extra air into the engine for high-power hovering operations. Simultaneously, the jet's exhaust swivels downward in hover mode. There are also two small outlets for engine gas under the wings, to stop the jet rolling over.

The F-35B is intended for service with the US Marine Corps, Royal Navy and RAF, replacing existing fleets of Harrier jumpjets. There is also a normal runway-only version of the jet (F-35A) which will go to the US air force and many international customers, and a version designed for carrier catapult launch and arrested landing (F-35C) for the US Navy.

F-35 - It's flying, but will it ever get off the ground?

The whole F-35 programme has been dogged by delays and cost increases which have led to the recent dismissal of the project chief by US Defence secretary Robert Gates. It remains highly uncertain just how many jets will be bought and by whom, and this affects the likely cost of each plane.

Though the F-35 had been planned to be bought in thousands by the US forces alone, suggesting good economies of scale and affordable prices for export customers down the road, critics of the programme are now alleging that costs are so far out of control that the well-known military procurement "death spiral" process has set in: higher price, fewer planes bought, unit cost driven up even higher, even fewer planes bought and so on.

However it's important to note that if the F-35 is successful it has the potential to destroy large amounts of the present global military aerospace industry. If it does get made in large enough numbers to be offered cheaply in time, it will be more sophisticated and yet cheaper than any other combat jet on the market, in all likelihood putting several of its competitors out of business in decades to come. This is probably a major reason why so many aerospace people are desperate for it to fail.

But there are others who feel that the Western fighter jet industry is overlarge, bloated, has no real threat to confront any more and is consuming funds which might be better spent on simpler things such as infantrymen or helicopters. They might be hoping that the F-35 can resolve its problems.

Others such as the Royal Navy feel they simply must have the F-35B in particular, as the new British carriers will have no catapults and so will require jumpjets - and the F-35B is the only one on offer.

The F-35B hover-jet also has other issues apart from cost, however. Its hellishly hot and violent exhaust downwash is expected to warp and buckle a ship's flight deck, for one - Brit carrier designers take note. British engineers and test pilots are also sceptical of its ability to make a hovering deck landing with weapons still aboard, a vital capability for a patrol fighter (which will be a major role for the jet with the Royal Navy, unlike the US Marines where it will mainly be a strike plane).

To deal with this, Brit test pilots and boffins have developed a "Shipboard Rolling Vertical Landing" (SRVL) technique, where a jumpjet sets down still going fast enough to get lift from its wings as well as its engine - but slow enough that it can stop within the confines of a carrier deck without arrester wires. SRVL, in addition to letting an F-35B land in a heavier condition, should also mitigate the deck-buckling issue. It will avoid the need to run engines at maximum redline power during landing, too, which causes a lot of wear and tear.

But none of this will be any use if Blighty can't afford any F-35s, so the Royal Navy will be watching the situation in America anxiously. ®

Bootnote

No F-35Bs needn't mean no carriers, however. It would be possible to alter the ships' design to include catapults. This would be easiest using electric mass-driver ones of the sort now under development for the next US Navy supercarrier - alternatively ordinary steam cats could be used. The latter option would mean installing auxiliary steam boilers alongside the ship's gas-turbine engines, or changing them to nuclear propulsion. Nuclear would cost a bit more, but would offer extra benefits: the ships wouldn't need to be refuelled, and the absence of exhaust funnels and intake trunks for gas plant would significantly enlarge the hangars and flight decks.

With catapult carriers, the UK could buy much cheaper F-18 tailhook jets - or perhaps F-35Cs later on, if Stealth were truly deemed necessary. It would also be possible to buy Hawkeye tailhook radar planes as used by the US and France, rather than having to develop a custom chopper or tiltrotor radarcraft, which would cost more and not be as good.