Precise and powerful
Lead STOVL Test Pilot, Peter ‘Wizzer’ Wilson, says the F-35B Lightning II is an ‘absolute pleasure to fly,’ thanks to its advanced propulsion technology.
The F-35B Lightning II is one of the most complex fighter aircraft ever designed, capable of stealthy, supersonic flight – or merely parking in mid-air and slowly lowering itself to the ground vertically, via the Rolls-Royce LiftSystem®.
Through this unique Rolls-Royce technology, driven by the F135 turbofan from Pratt & Whitney, the F-35B can perch aloft on 40,000lbs of thrust, in a precise and powerful balancing act.
In the fighter aircraft world, this capability is known as Short Take-Off and Vertical Landing (STOVL), and it is prized for allowing aircraft to operate from short-deck ships or austere, forward-operating bases devoid of lengthy, permanent runways.
Rolls-Royce is the only company in the world to produce the advanced technology that enables the F-35B aircraft to perform with STOVL capability. In May 2012, the company received a US$315 million contract to supply the LiftSystem for 17 F-35B Lightning II aircraft. Last month, the UK also confirmed its decision to go ahead with the acquisition of the F-35B variant.
The stunning complexity and remarkable technology required for STOVL capability is belied by the ease in which the system is initiated – a single button on the left side of the F-35 cockpit.
Peter ‘Wizzer’ Wilson, the Lead STOVL Test Pilot for the F-35 Lightning II programme, describes the mid-flight operation this way: ‘I press the button and all this magic stuff starts happening behind me.’
That’s when the STOVL doors on the fuselage open, then the Rolls-Royce clutch engages, connecting the LiftFan™ just behind the cockpit via a shaft to the 40,000lb thrust Pratt & Whitney F135 engine. The 3-Bearing Swivel Module at the rear of the aircraft twists downward, and Roll Posts on the wingtips provide stabilising air thrust. The LiftFan spools up in about five seconds, which Wilson says sounds like ‘a big humming mosquito kind of noise.
‘Fifteen seconds after pressing the button, I’m in STOVL mode. Fantastic – it is so simple and reliable. Every single time, we come back with a smile on our faces.
‘We’re talking about a massive amount of thrust through that LiftFan. It’s one of the most transformational aircraft that’s ever been.’
Lockheed Martin is the lead integrator on the F-35 programme, with an industry team that includes Northrop Grumman, BAE Systems and Pratt & Whitney. Rolls-Royce provides the LiftSystem as a subcontractor to Pratt & Whitney.
Wilson, who works for BAE Systems, is a former fighter pilot for the Royal Air Force, and flew Sea Harriers for the Royal Navy. Since his flying career began in 1982, he has amassed more than 1,200 hours of flight time, and logged 500 landings at sea.
‘The difference between flying Harriers and the F-35B is remarkable,’ he says. ‘They are worlds apart. It’s like night and day.’
The Harrier, powered by a Rolls-Royce Pegasus engine, is also a STOVL aircraft, but provides all its downward thrust via heated exhaust from the engine, requiring full power as well as absolute full attention from the pilot.
‘The workload of the pilot is high on the Harrier, especially at slow speeds,’ he explains. In the F-35B aircraft, the LiftFan provides approximately half of the vertical thrust. It uses ambient air drawn in and blown downward through a separate ducting system from the engine. The operation is guided almost entirely by computer software and monitored by the pilot.
‘The aeroplane is designed to be a low workload for the pilot. The aeroplane does all the hard work,’ Wilson says.
The pilot, therefore, can concentrate on the mission, while the aircraft and its onboard computers, literally, do all the heavy lifting in STOVL mode. A slight nudge to the control stick is all that’s required from the pilot. ‘It makes it an absolute pleasure to fly. If I want to move forward 12 inches, I can do that. I can go right 12 inches, and stop there. That’s how “inch-perfect” you can fly the jet. It’s phenomenal.’
Wilson says that means ease of operation and enhanced safety. ‘There will be no unpredictability like we had in the legacy plane. There’s nothing difficult about it.’
The current test flight efforts are designed to expand the operational envelope for the aircraft, focusing particularly on integration of the propulsion system and the flight controls.
‘We really do try to push the propulsion system right to its limits. We’d like it to be a carefree aeroplane. We’re close to carefree.’
That ease of operation was reinforced during the ship-board trials involving the USS Wasp last October. ‘The ship trials were a huge success, by anyone’s standards. The very first landing went like clockwork, with the wind directly into the bow of the ship. Gradually, we expanded the wind envelope to stronger and weaker headwinds, then crosswinds. The propulsion system performed flawlessly throughout.’ Wilson and three US Marine Corps pilots flew a total of 72 take-offs and 72 landings aboard the Wasp.
‘By the end of three weeks at sea, we had opened up a flight envelope that was bigger than the Harrier ever achieved, despite its years in service.’
Wilson praises the overall Pratt & Whitney and Rolls-Royce propulsion system, calling it ‘robust and reliable and bringing a level of capability to the aeroplane we haven’t been able to do before.’
‘It’s very smooth when the LiftFan kicks in. It’s well-designed and well-balanced. Safety is absolutely paramount to the system, and it’s in there. You guys have put it in there,’ he concludes.