Royal Navy aircraft carrier ski jumps – a history12 Aug 2019 SaveTheRoyalNavy"British inventors have been responsible for many of the innovations that have made carrier aviation possible. The ‘ski jump’ was first developed in the 1970s to enable the Sea Harrier jet to launch more safely and efficiently and is a feature of the new QEC aircraft carriers, helping launch the latest generation of jets. Here we look at the history, design and purpose of the ramp....
...On 5th August the 1977 first ski-ramp trial was conducted at RAE Bedford using a test aircraft (The first Sea Harrier did not fly until 20th August 1978). Within a year, the ramp had been tried at angles between 6.5 – 20º and the tests showed that the aircraft was indeed able to get airborne with much heavier loads. The ramp also added a considerable margin of safety, even if the ship pitched down at the moment of launch, the aircraft would still have enough height above the sea. If the engine failed during launch, the pilot had about three times the amount of time to eject than if launched off a flat deck.
In simple terms, the aircraft does not fly off the ski jump, instead, forward momentum is partially converted into vertical thrust by the ramp. Together with upward thrust generated by the vectored jet nozzles, the aircraft follows a semi-ballistic trajectory for a few hundred yards until it has enough forward speed for the wings to provide all the lift. As the aircraft moves along the ramp, there is additional force applied to the landing gear but both the Sea Harrier and F-35B were designed with heavy vertical landings in mind which often put far greater stress on the undercarriage....
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Lessons learnedThe ski jump is a relatively cheap and simple addition to the carriers, being a straightforward steel construction with no moving parts. However it was discovered, once in service that apparently small differences in the build quality of the ramps of the three ships affected the life of the Sea Harrier undercarriage. The original design work assumed an absolutely smooth ramp but small ruts or imperfections in the surface were enough to cause cracking on some aircraft landing gear. This issue was expensively resolved and the lesson led to higher design tolerances being specified for the QEC ramps. Additionally, the F-35 has a wide tricycle gear which is more affected by small bumps, demanding more careful ramp design than for the Harrier’s tandem main gear. The centre section of the QEC deck is slightly cambered to help water runoff, further complicating the interface with the ramp....
...Detailed work on the ramp design was started but in 2007, once Lockheed Martin had done enough simulator work and had developed mature flight control models. The QEC ramp was designed by BAE Systems with input from LM, rather than the shipbuilders. It is not immediately obvious but the ramp has two very subtle curves. The entry section is a long ‘cubic’ curve that leads to a second let-down or ‘ellipse’ section where the aircraft is launched....
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The next generationWork on ski jump trials with the F-35B began in 2014 in the United States at NAS Patuxent River, initially using offline and manual simulation. Most of the work involved exploring what would happen if problems occur during take-off, such as a sudden drop in wind velocity, loss of engine power, blown tyres or nose wheel failure. A UK company, Williams Fairey Engineering Limited (WFEL) was awarded a £2M contract to construct a test ramp in the Centre Field at Pax River. The design was based on the CVS ramp profile and completed in 2009, although the first F-35B ski-jump STO was not made until June 2015.
By June 2016, 31 test launches had been made testing a variety of approach speeds and internal loads with speeds off the end of the ramp ranging from 65-95 knots. Some issues were discovered during testing but nothing serious and the results informed the minor design changes to flight control software. A second phase of trials numbering around 150 launches was begun in 2017 to understand the characteristics of the aircraft during overspeed or underspeed take-offs and carrying external weapons, including asymmetric loads. When the first jet was successfully launched from HMS Queen Elizabeth’s ski jump on 25th September 2018, years of simulations and preparation ensured it was considered a very low-risk aspect of the programme….
...The US Navy has never adopted ski ramps for its Harrier and F35-B-equipped assault ships, although the benefits of the ramp are fully appreciated and well understood by the Marine Corps aviation community. Unlike other nations, who’s STOVL aircraft are the primary armament of the ship, the Gator Navy’s main purpose is to deliver Marines ashore and the helicopters have priority. With limited flight deck space, a ramp would take up at least two helicopter spots. The USMC concept of operations also sees the fixed-wing aircraft being sent ashore at the earliest opportunity to work in close support of the troops while flying from small airstrips. There is an unspoken political concern within the USN that the addition of a ramp might see the assault ships become perceived as small aircraft carriers, undermining the case for the giant conventional carriers (CVN) that are the centrepiece of the surface fleet. For the Royal Navy, this relatively simple invention will continue to play a key part in enabling fixed-wing operations from its two aircraft carriers for many years to come."
Source: https://www.savetheroyalnavy.org/royal- ... a-history/ 
09 Aug 2017, 19:43
I do not have a subscription to AvWEAK to get more than this about Ski Jump Testing - so I'm sad. 
So is AvWEAK. 
