Cats, traps and claptrap. Why the Royal Navy’s new aircraft carriers operate VSTOL aircraft

There is a consistently held view that the Royal Navy was mistaken when it chose to adopt Vertical/Short Take-Off and Landing (VSTOL) aircraft carriers. In this long read we look at the convoluted history of the issue and review the arguments both for and against.


During the development of the QEC aircraft carriers, various configurations and aircraft options were considered (see previous article) but the STOVL B variant of the Joint Strike Fighter was formally recommended by the navy in September 2002 and approved in July 2006. From the outset the design was specified as ‘adaptable’, should it be decided to reconfigure the ship as a conventional carrier in future. Work on STVOL carriers proceeded until 2010 when the coalition government made the announcement that the QEC would instead be configured for Catapult Assisted Take-Off and Barrier Arrested Recovery (CATOBAR colloquially known as ‘cats and traps’). The C variant of the F-35 would be purchased and the UK would be back in the conventional carrier business (which they had effectively pioneered but were shut out of in 1966 with the decision not to build the CVA-01 carriers).

The Prime Minister saw the main advantage of the change as cementing relations with the US and France as the RN’s carriers would be fully ‘interoperable’ with the conventional carriers of our key allies. Most in the navy and many commentators (including this writer) initially backed the decision as it offered a significant uplift in capability and was an apparent bright spot amongst the carnage of the 2010 defence review. Both carriers would be completed (The ACA sensibly locked the MoD into a contract for the 2 ships that was too expensive to cancel on the whims of political or financial expediency) but one would be ‘held in extended readiness’. In practice, this meant one would be put into mothballs and possibly sold, but there were hopes this decision could be overturned in time as finances improved.

An 18-month study into converting HMS Prince of Wales to CATOBAR began but it rapidly uncovered serious cost implications and delays that the changes would entail. Alterations and new equipment required were estimated at £886 Million per ship in November 2010 but by February 2012 the figure was £2 Billion and rising. Perhaps even more intolerable was the realisation that the conversion work would have added another 3 years to the construction time. Purchasing the F-35C would leave HMS Queen Elizabeth unable to operate any fixed-wing aircraft until she was replaced by the second carrier around 2023. Something had to be done.

One of the possible configurations for the CATOBAR QEC aircraft carriers featured twin catapults launching over the bow.

The U-turn on the U-turn

On 10 May 2012, the Defence Secretary Philip Hammond announced that the government had decided “not to proceed with the cats and traps conversion, but to complete both carriers in the STOVL configuration.” This was painfully embarrassing for the Tories who had loudly blamed Labour for making the wrong initial choice. During the whole episode no one had covered themselves in glory, the navy, the civil servants and politicians had been deceived by a conspiracy of optimism as they over-reached for a capability that in reality was beyond the means of the inadequate defence budget. To be fair to Hammond, although part of a government responsible for brutal cuts to defence, at least he had faced up to a thorny problem that he could easily have left to fester, only to be faced by one of his successors.

Research by the National Audit Office reveals an exceptionally lax assessment had been done of the true cost of CATOBAR conversion in 2010. Part of the problem was the ‘adaptable carrier’ just had some empty spaces that could theoretically be used to take CATOBAR equipment but no detailed design work had ever been done. The specifics of the commercial contract are not public but it is unclear just how mature the CATOBAR elements were supposed be. There is some suggestion the MoD had effectively paid for a ‘feature’ that the ACA had ignored, once STVOL configuration had be decided on.

The head of the MoD at the time, Sir Bernard Gray said that General Atomics had significantly raised the price of the Electromagnetic Aircraft Launch System (EMALS) , Advanced Arresting Gear (AAG) and related equipment by more than £200M to £577M between 2010-12 and the costs of technical assistance had added another £150M. This is at odds with the fact that US Assistant Secretary of the Navy for Research, Development and Acquisition, Sean J Stackley wrote to Defence Procurement Minister, Peter Luff pricing equipment at £458 million and promising the US would underwrite any further cost risk. The USN was keen to help the RN rejoin the CATOBAR club.

The cost of conversion work quoted by the Aircraft Carrier Alliance had also risen by over £100M. Original estimates did not make any allowance for UK industry testing and commissioning It was also ‘discovered’ that as a Foreign Military Sale, the purchase of EMALS would be subject to absurd Treasury rules that added VAT amounting to around £130M.

It was not really in BAE Systems’ commercial interest to fit cats and traps as it could potentially allow a much wider choice of carrier aircraft than just the F35B in which they had a significant stake. Some have speculated that the ACA, of which BAES was a major shareholder, was quite happy to see the quotes inflated. This is pure speculation and either way, it is clear the project was subject to genuine significant cost rises.

At the time there were serious doubts about the technical viability of the F-35B and US budget sequestration threating its cancellation. Subsequently, the engineering problems were largely overcome and the USMC was actually first to declare F35 IOC with the B variant. The political viability and long term effectiveness of buying 4th generation alternatives to F35 such as the Super Hornet or Rafale M, in which UK industry had no share, would also have been doubtful.

F-35Cs preparing for steam catapult launch from USS George Washington, August 2016. Many more skilled personnel are needed to work on the flight deck to support CATOBAR operations than is the case with the VSTOL F-35B. Note the raised Jet Blast deflectors also absent from the QEC carriers. (US Navy photo)

Perhaps more significant than the cost of fitting EMALS and changes to the ship are the long term costs of maintaining conventional carrier aircraft capability. CATOBAR operations require a lot more trained personnel on the flight deck who have skills that can perish quickly. For F-35C pilots, making safe arrested landings is far more demanding than the highly automated, push-button vertical landing of the F-35B. The skill to effect a ‘controlled crash’ of carrier deck landing requires constant practice and training. UK has a constrained number of both fast jet pilots and aircraft, with just one carrier likely to available most of the time, there would be a struggle to generate and maintain sufficient qualified personnel. The French Navy has managed to pull this off and typically deploys up to 24 Rafale M on its single carrier. The Marine Nationale, however, owns its jets and its aircrew are entirely focussed on carrier operations, whereas the UK Lighting Force has a dual role and must also conduct land-based operations.

The case for CATOBAR

What is not in dispute is that ultimately a CATOBAR carrier is more capable in most aspects than the VSTOL alternative, although there are some notable exceptions. The F-35C broadly speaking has better range, payload and performance than its F-35B sibling. The larger wings of the C allow it to land more slowly and at low-mid transonic speeds has a better sustained rate of turn than the B. However the large wing reduces its roll and acceleration rates but it can pull slightly higher G than the B. Overall the performance differences are minimal and both can achieve a (software-limited) top speed of Mach 1.6.

The C variant can fly around 1,200nm (depending on weapon load) using internal fuel whereas the B can manage about 25% less, at 900nm. GE Aviation and Pratt & Witney are working on the Adaptive Engine Transition Programme (AETP) examining the possibility of re-engining the F-35 with a more fuel-efficient alternative to the current F135 engine but this is a long-term aspiration. As the reach and speed of modern missiles increase ways to extend the range of carrier aircraft are becoming more important. Land-based in-flight refuelling is the only current option for the QEC carrier aircraft. A V-22 Osprey-based tanking solution would be an expensive and very slim possibility.

The weapons payload of the F-35 C variant is also superior by some margin, able to carry over 8 tonnes compared to the 6.8 tonnes of the B. The arrested landing allows the C to return to the carrier with a full load if weapons have not been released so no expensive ordnance is dumped into the sea. Theoretically, the B can achieve this using Short Rolling Vertical Landing (SRVL) which uses some forward momentum to generate lift from the wings instead of reliance only on vectored thrust to support the aircraft as it descends. The first tentative F-35B SRVL trials were successfully conducted last year but there are still questions about the safety of the manoeuvre in anything but the most benign weather conditions.

CATOBAR would increase the options for fixed-wing aircraft types that the QEC could have embarked. In particular, the E2-D Hawkeye airborne early warning aircraft would be of interest, having vastly superior performance to the Merlin helicopter-based Crowsnest solution the RN is adopting. Hawkeye has a range greater than 400 miles which is probably about double that of the Crowsnest Merlin which cannot achieve anything like the same altitude, speed or endurance. Detection ranges may seem rather abstract but for example, if faced with a volley of Hypersonic (cMach 5) missiles that can cover a mile in a single second, early warning times could really start to matter. Unfortunately, it would probably cost about £1Bn to purchase just five E2-Ds and spares. Then comes the overheads implicit in introducing a new aircraft type to the UK military with the through-life training, maintenance and logistics costs that come with it. Crowsnest is simply the only affordable compromise.

Another argument for CATOBAR is that the F-35C is cheaper to purchase and maintain than the F-35B with its complex lift fan and vectored thrust mechanisms. Supposedly the cheaper aircraft would offset the cost of fitting EMALS. In fact, the cost differential between the variants has reduced considerably over time because the C version is being built in the smallest numbers and has also required some expensive technical fixes. In 2019 the ‘fly away’ price being paid by the MoD for each F-35B has fallen to around £89M, while the C would cost about £82M. The B variant has many more moving parts than the other variants and will need more demanding maintenance. It is impossible to quantify and find figures, but the extra aircraft ownership costs associated with the B will probably still be slightly less than the cost of fitting EMALS, its maintenance and the extra personnel for a single carrier over their lifetime.

EMALS maladies

At the centre of the CATOBAR, controversy is the issue of the EMALS. This is a new method of launching aircraft that uses a linear induction motor instead of the steam piston used by conventional carriers until now. EMALS offers many supposed advantages – smoother acceleration that places less stress on aircraft and the ability to easily vary the energy delivery depending on the weight of the aircraft. This is especially important as future carrier launched UAVs might weigh just a tonne while the all-up weight of an F-35C is around 27 tonnes. The EMALS installation is lighter and takes up less space in the ship than the steam system. For the QEC carriers than do not have nuclear reactors to generate steam, opting for EMALS was the obvious choice.

By 2010 EMALS had been successfully demonstrated launching aircraft from shore-based test rigs and the USN was confident to specify it for the USS Gerald R Ford, the lead ship of a revolutionary new aircraft carrier design. Unfortunately, although many EMALS launches have been conducted, it is fatally unreliable and in 2017 the USN admitted the system was failing every 400 launches. (The original specification was for a maximum of one failure per 4,100 launches.) The Ford would only have a 7% chance of successfully completing a typical four-day operational period. To compound the problem, when the system fails, all four catapults are out of action, unlike in a steam system where the other 3 cats usually remain working and the carrier can continue operations.

The USN says EMALS reliability is improving but will not provide details as the Ford is increasingly mired in technical problems and is a very long way from being able to sustain combat operations. Hindsight is a wonderful thing but the UK has clearly dodged a bullet by not becoming dependent on EMALS. The Ford’s ongoing woes should be cause for concern to all US allies but does serve to highlight UK success in delivering its carriers.

  • The key elements of the EMALS installation on USS Gerald R Ford. (Image: General Atomics)

  • Advanced Arrestor Gear (AAG) on USS Gerald R Ford. (Image: General Atomics)

Plan B makes sense

Nearly a decade on from the U-turn the first UK aircraft are flying from HMS Queen Elizabeth for the first time. QEC-based Carrier-Enabled Power Projection (CEPP) capability is a vast step up from the CVS/Harrier and QE is going to be ready to deploy operationally in less than two years. Even having selected the ‘budget’ VSTOL carrier option, generating CEPP is still a major overhead for the defence budget. There are still questions about whether the UK will able to afford to maximise the ship’s potential, particularly in terms of aircraft numbers. Conventional carrier/s would be pushing the budget to breaking point and creating more complex manning and training headaches.

Cameron made another U-turn in 2014 and announced that both aircraft carriers would enter service after all and HMS Prince of Wales is currently on sea trials beginning her journey towards becoming operational. Two carriers offer almost continuous carrier availability whereas the CATOBAR carrier would have been be a part-time capability. The officially stated cost of running the STVOL second carrier is just £70M per year (although this seems like a highly optimistic estimate).

From an operational perspective the F-35B does have a few advantages over the C. As their launch and recovery requires less preparation on the ship, the B can sustain higher sortie rates than the C, especially important when aircraft numbers are limited. Aircraft can be launched and recovered in higher sea states and wind conditions and do not need long smooth runways to land ashore. Theoretically, the B could be dispersed to austere landing sites or could land on other ships in an emergency if the carrier was damaged.

British F-35B operating from HMS Queen Elizabeth, October 2019. Without the decision to select the B variant, we would be waiting another 2-3 years to see this.

Those that causally disparage the RNs carriers, bemoan the ski ramp and argue for CATOBAR need to bear in mind the limitations of the defence budget and especially the manpower struggles of the armed forces. Without the 2012 U-turn, where would we be right now? Assuming the project had not been canned in SDSR 2015 having wasted even more money, HMS Queen Elizabeth might be operating as a helicopter-only carrier but due to be mothballed. HMS Prince of Wales would still be about two years away from going to sea and dependent on the US to resolve the ongoing problems with EMALS. The RN would also have to cope with a £2Bn hole in its budget which would have resulted in more cuts elsewhere. Even if there was a major uplift in defence funding, retrofitting the carriers with cats and traps would be some way down the list of priorities. Investing in more F-35Bs, in further weapons integrations and more protection for the carriers would be a better use of resources. In the long term the development of VSTOL UAVs, perhaps sharing the costs with the USMC, would seem sensible.

In an ideal world where defence spending was north of 3% of GDP and manpower was abundant the RN would be commissioning two CATOBAR carriers that would routinely carry 36 F-35Cs. We cannot indulge champagne tastes on a beer budget – the VSTOL Queen Elizabeth Class aircraft carriers are still enormously powerful while more in keeping with the limited resources available. Whether we may come to regret their slightly lesser capabilities in a future conflict should be discussed in the wider context of how Britain prioritises its defence spending.

Main image: US Navy F-35C catches the wire while landing on USS George Washington, Aug 2016. (Photo: Lockheed Martin)