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Britain's decision to change the basic design of its new aircraft carriers, centerpiece of the nation's biggest arms program, for the second time in as many years is raising doubts about the country's defense decision-making at the highest level.

In early May, the British Defense Ministry dumped its late-2010 plan to convert one and possibly both in-build Queen Elizabeth II-class aircraft carriers to operate the F-35C catapult-arrest version (known as the CV) of the Joint Strike Fighter. The U.K. opted instead to revert to the short-takeoff-and-vertical-landing (Stovl) F-35B.

The first decision to switch to the F-35C was based on simple arguments, put forward by Prime Minister David Cameron in late 2010. The F-35C has a larger weapons load than the F-35B, thanks to a larger bomb bay, and longer range than the F-35B because it carries fuel where the latter has its lift fan. The F-35C was said to be less costly to buy and operate than the mechanically complicated F-35B. The F-35B was on probation at the time, so was deemed to be risky by the U.K. The more capable F-35C would also make up for the fact that the U.K. would not be buying 138 JSFs, as originally envisaged.

The switch to the C was contingent on using the U.S.-developed Electromagnetic Aircraft Launch System (Emals). The idea of fitting dedicated steam generators to the turbine-electric carriers never looked attractive, and by late 2010, the once-problematic Emals had started showing success in U.S. testing.

It all seemed logical, which made the decision to revert to the Stovl approach more startling.

What became apparent at a briefing held by the Defense Ministry in early May was that the cost estimates for fitting the ships with Emals and arrester gear had been either slapdash or wildly optimistic. The estimated cost of converting the second-in-class ship, HMS Prince of Wales, had more than doubled, from just under £1 billion ($1.5 billion) to £2 billion. The first-of-class ship, Queen Elizabeth II, which was more advanced in construction, would need £3 billion in modification costs. Modifications for both ships would cost £5 billion, close to what they had been expected to cost in total without them.

A senior ministry official said the conversion schedule had been equally optimistic and that the first modified ship would not have been delivered until 2023, not by 2019-20 as had been planned. This gap in carrier-borne aviation was deemed unacceptable—the current lack of carrier air capability in the U.K. is a politically fraught issue, highlighted by the Libya operation in 2011.

One reason that the cost and time for the conversion had been so badly underestimated was a miscalculation of the impact of the modifications on the ships. At first it was hoped to confine the changes to 80 compartments (out of about 1,200), but real engineering work showed that major modifications to over 290 compartments would be required, with 250 more needing smaller modifications.

On top of this, assumptions about the cost of Emals turned out to be wide of the mark. U.K. planners had assumed that since the Emals used on the Ford-class carriers includes four catapults, and the U.K. would only need two, the cost would be half the U.S. Navy's. But as a senior ministry official said, “the cost of breaking out common systems [from Emals] turned out to be more expensive than had been thought.”

One issue little noticed, but mentioned by senior ministry officials, was the negative influence of the U.S. Defense Department. Their reported insistence that the Emals hardware had to be procured via the Foreign Military Sales system added a 7% surcharge—some £150 million—to the planned costs, which a senior ministry official indicated was not favorable. Further, according to the same official, the U.S. agency wanted to have control over the integration of Emals into HMS Prince of Wales—“they would have had control of the process, not us”—and this was deemed utterly unacceptable, as it could have led to program overruns which the U.K. could not control.

The story gets stranger when it comes to the switch of aircraft variant, as one senior military official said that, “the weapons carried [by the F-35C] would be no different to those carried by the Stovl version.” This suggests that the argument 18 months earlier —that the F-35C's bigger weapons bay would be useful—might not have been as well thought-out as should have been the case. A senior officer with aviation experience added that the shorter range of the F-35B was “a marginal compromise,” and he said that since many—if not most—U.K. operations were conducted with inflight refueling support, this was not really an issue.

The newer estimates show that the cost of building, equipping and supporting even one CV-equipped ship would have been high enough to outweigh the costs of running the more expensive F-35B. The costs of keeping F-35C pilots trained and carrier-capable were deemed to be higher than for the F-35B, which is easier to land.

Another key justification for the 2010 decision to opt for the F-35C had changed by 2012. It had been argued that it would make the U.K. force more interoperable with the U.S. and French navies, both of which use CV aircraft. But in May, a senior ministry officer said that, “there are some issues about the physical cross-decking [of the F-35C] with France,” and went on to explain that the F-35C is too heavy to operate from the carrier Charles de Gaulle. This in itself is not surprising —the F-35C's empty weight is almost 60% more than that of France's Rafale M. What is surprising is that nobody saw the problem in 2010.

The late-2010 argument that the F-35C posed less risk than the F-35B had changed if not been reversed by the end of 2011. While by no means out of the woods, the F-35B did complete a series of Stovl tests on the USS Wasp in October 2011. It was the F-35C that flunked one of its first carrier-qualification tests when its tailhook missed the wire on “roll-in” engagement. A new hook tip and hook damper are being tried, but if they don't fix the problem, the next solution will cost a lot more.

Overall, studies and research undertaken in 2011 and 2012 overturned practically every justification for the F-35C. This has been deeply embarrassing for Cameron, who can now expect House of Commons committees and external audit bodies to investigate whether the decision-making process was sound.

Even with the new direction for the JSF and the aircraft carriers nominally settled, there are other expensive decisions ahead. Perhaps the most crucial concerns airborne early warning (AEW) which the Royal Navy lost in the 1970s with the retirement of its last catapult-arrest carriers, and hastily recreated after its absence cost several ship losses in the Falklands war.

The navy's AEW capability is provided by its Sea King ASaC7 (Airborne Surveillance and Control) fleet but will disappear with the retirement of the Sea Kings, scheduled for 2016.

The U.K. Defense Ministry's Planning Round 12, announced to Parliament in May, confirmed funding for a follow-on AEW system, formerly known as MASC (Maritime Airborne Surveillance Capability) but now designated Crow's Nest. The precise budget, timescale and requirement have not yet been settled, but both industry and the ministry expect to see two rival bids for the AEW capability, likely to be deployed on a Merlin helicopter.

Thales UK will offer a development of the existing Sea King's Cerberus mission system, while Lockheed Martin may pitch Vigilance, based on the F-35's Northrop Grumman radar. Both teams are expected to offer palletized systems. With in-service dates for the other elements of the carrier program still in flux, a palletized AEW system enables the ministry to avoid buying, staffing and operating the complete capability before the carrier and jets are ready.

Some people have suggested that the F-35 itself could perform the AEW role. “There is an awful lot of talk about whether the F-35 will be able to do everything, and how many you would need for it to be able to do everything,” says Lt. Cmdr. Simon Flynn, executive officer of the frontline SKASaC unit, 854 Naval Air Sqdn., who has also worked in the carrier strike team at navy command. “I've not seen all the data from F-35, but I know how carrier strike works and how the jets are integrated, and I know that the Americans firmly believe that they still need all the supporting assets, specifically the E-2D.”

As for inflight refueling, the current plan to use RAF assets will keep the carriers close to friendly host base— but the point of an aircraft carrier is that it is not tied to land bases. The U.S. Navy will use F/A-18s as tankers well into the 2030s, and there no plans for a “buddy store” refueling pod for the F-35. In any case, the jet's capability as a tanker (with only two “wet” stores stations) is limited.

The whole process hardly looks well-managed—too many decisions seem to have been made in 2010 that were not based on robust evidence. The about-face has cost close to £150 million as work undertaken to aid the conversion process has had to be scrapped. It now remains to be seen whether the “simpler” carrier can be delivered, as planned, to an earlier than planned timescale that will see the U.K. delivering naval fixed-wing aviation by 2019.