To the unsuspecting onlooker the Rolls-Royce ‘thrust-measuring rig’ which was better known as the ‘Flying Bedstead’ must have been an awesome and yet frightening sight when it hovered in the skies for the first time during the late summer of 1954. With pilot perched rather precariously on top, and as it filled the skies with huge noise from two 5,000-lb thrust ‘Nene’ engines mounted with fuel tanks, controls and pilot seat, on a frame that consisted of steel tubes with legs, the ‘Flying Bedstead’ would represent yet another giant leap for Britain in aerospace engineering technology.
Whether in aerospace, maritime, defence or nuclear engineering Rolls-Royce has been breaking technology barriers throughout its very long history. What emerged at Hucknall as the ‘Flying Bedstead’ sixty years ago marked the beginnings of global leadership for Rolls-Royce in short take-off and landing (STOVL) technology and one that remains to this very day.
Given the unrivalled experience and the very high relevance of STOVL technology in the UK’s future carrier strike capability plus that of other air forces around the world; the very first sighting outside of the USA of the ‘B’ variant of the Lockheed Martin F-35 ‘Lightning ll’ aircraft that is due to fly later this week at the UK’s premier military airshow event, the Royal International Air Tattoo at RAF Fairford, will be eagerly awaited.
Having myself already been able to witness STOVL variants of the F-35 Lightning ll aircraft piloted by Royal Air Force and Royal Navy pilots flying the aircraft at Eglin Air Force Base, Florida earlier this year I can say without hesitation that I was extremely impressed with the aircraft performance and in particular, the hovering manoeuvre.
The F-35 Joint Strike Fighter represents a new generation of fast jet military aircraft capability in three variants and is expected, over a thirty plus year production life, to become the largest single fast jet programme in the history of military aviation. F-35 Lightning ll is the future but I believe that we would do as well to stop awhile and remember that without the vast research and development engineering effort, investment, determination and self-belief of Rolls-Royce STOVL technology that is represented in the ‘B’ variant of this very fine military aircraft capability would not be where it is today.
What was to be learned from the thrust measuring ‘Flying Bedstead’ ‘rig’ would lead eventually to development of engines used in the first fixed-wing VTOL (vertical take-off and landing) Short SC.1 aircraft that was specifically designed to study problems associated with transitioning between VTOL and forward flight.
If my records are correct August 9th will mark the sixtieth anniversary of the first ‘untethered’ hovered flight of ‘Flying Bedstead’ in the capable hands of Rolls-Royce test pilot, R T Shepherd. ‘Flying Bedstead’ was not an aircraft in the true sense of the word of course but rather a large research tool that was built and based during it period of use at RR’s Hucknall, Nottinghamshire test facility and that today happens to also produce parts for the STOVL variant of the F-35 Joint Strike Fighter Lightning ll.
VTOL jet engine technology was originally based on having four rotating nozzles to direct thrust over a range of angles. Its development would eventually lead to the Bristol Pegasus engine (Rolls-Royce acquired Bristol Siddeley in 1966) and by Hawker-Siddeley of the P.1127, the later ‘Kestrel’ which would eventually morph into the V/STOL (Vertical Short Take-Off and Landing) Harrier jump jet that we all know so well today. Designed by Hawker Siddeley and further developed by BAE Systems a large number of Harrier aircraft continue to operate with US, Spanish and Indian military forces mainly in the updated AV-8B form that was built in the US by McDonnell Douglas under licence from BAE Systems. Harrier, with its Pegasus radial engine V/STOL technology, remains one of the most successful post war military aircraft developments to have emerged from the UK aerospace industry. If I have any regret, apart of course from its premature withdrawal from the Royal Air Force list, it is that I never flew in Harrier although I am fortunate to know a great many that did!
In its final form the Rolls-Royce Pegasus 11-61/Mk.107 provided 23,800 lbs of thrust allowing Harrier aircraft to return to an aircraft carrier without the prior need to dump weapons. The adage used by experienced Royal Air Force Harrier GR9 pilots ‘thrust is a must, lift is a gift’ springs to mind here when one looks at how Rolls-Royce have further developed Short Take-Off and Vertical Landing (STOVL) technology into what is today incorporated into the ‘B’ STOVL variant of this fifth generation F-35 Joint Strike Fighter fast jet capability.
The Rolls-Royce LiftSystem which is at the heart of F-35 Lightning ll STOVL variant technology capability represents the culmination of 60 years sustained innovation and technical excellence. The company has creating what we may well regard as potentially the ultimate in manned fast jet powered lift solutions and will be engaged not only in the manufacturing programme but within through life programme support across what is likely to be the largest ever international military aircraft programme.
Aircraft weight is an important component of efficient STOVL capability. Using technology developed by Rolls-Royce Commercial Engine division the use of hollow blade technology in LiftFan together with bladed disk (blisk) and linear friction welding (the latter developed on other Rolls-Royce defence programmes) has enabled considerable weight savings to be made on the F-35 ‘B’ STOVL variant.
In terms of the defined engineering technology capability LiftSystem consists of three modules, a LiftFan to provide vertical thrust at the forward end of the aircraft; a three-bearing swivel module for redirecting main engine thrust from axial to vertical plus two roll posts to provide for roll stability. The technology itself is all contained within the airframe during conventional flight thus improving aerodynamic profile and stealth capabilities of the aircraft.
Having some time ago visited the purpose built facilities at Rolls-Royce Bristol plant to look the technology behind the design and the required level of manufacturing excellence I can say that I was enormously impressed at the level of engineering excellence achieved.
For Rolls-Royce, involvement with LiftSystem and in what will likely be the world’s largest ever combat aircraft programme has enabled the company to not only retain but considerably extend its long standing record of excellence and global leadership in STOVL based technology.
Supporting 900 jobs at several UK based Rolls-Royce plants including Bristol (where the 3 Bearing Swivel Module is manufactured and assembled) Hucknall, Nottinghamshire (blisk manufacturing) and Barnoldswick (hollow blade manufacture) together with other Rolls-Royce jobs located at Indianapolis in the US (assembly, test together with maintenance, repair and overhaul activity) my understanding is that the current value of LiftSystem contracts secured by the company covering F-35 through life programme manufacture is approximately $2bn. In addition it should be noted that over twenty UK companies are involved in the supply chain.
Powered solely by the main aircraft engine which provides a significant improvement in thrust efficiency capability the F-35B STOVL variant is reputed to have almost twice the lift capability of its Harrier predecessor whilst at the same time being able to travel faster and further. The Rolls-Royce LiftFan is capable of delivering 20,000lbf cold thrust and delivers 29,000 shaft horsepower from the main engine to the Rolls-Royce LiftFan. The Roll posts direct 1,950 lbf of bypass thrust from the main engine and hydraulically actuated nozzles during STOVL operation and I am told by Royal Air Force and Royal Navy pilots that this provides excellent roll control and stability. The 3 Bearing Swivel Module directs 18,000 lbf thrust from the main engine and is designed to rotate 95 degrees in 2.5 seconds.
(Note that as the largest single defence programme in the world with an expectation of over 3,000 aircraft of all three variants likely to be built, the F-35 Joint Strike Fighter programme is not only of crucial important to the UK military in terms of future air power capability but also of tremendous importance to UK industry as well. Led by BAE Systems as the primary tier-one partner on the Lockheed Martin led programme 15% of each F-35 aircraft will be built by UK based companies. Apart from BAE Systems and Rolls-Royce the list of some 500 UK companies involved on the F-35 manufacturing programme includes Cobham, Martin Baker, MBDA, Selex, Survitec, Ultra Electronics, GE Aviation ((formally Smiths Aviation division) and Honeywell. In the years ahead not only will all these companies enjoy involvement in original manufacturing they will also enjoy maintenance repair and overhaul (MRO) activity along with follow-on development and sustainment. The importance of the F-35 programme to the UK economy cannot be understated.)
CHW (London 7th July 2014)
Howard Wheeldon FRAeS