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Designing CVF

[Note that this article is badly out of date, dating to late 2001,
but is retained for historical interest!]

(Above) This picture shows the contrasting approach to aircraft carrier design adopted by the USN and various European Navy's over the last 20 years

 

Two CVF design from BAE Systems, (above) a STOVL carrier and (below) a CTOL carrier.

 


 

Introduction

The design of CVF will be influenced by a variety of factors, especially advances in subsystems technologies. Two of the most significant aspects of the new carrier will be how aircraft launch and recover, and the overall machinery concept of the ship. 

Aircraft
Launching and recovering aircraft is likely to remain the central function of aircraft carriers and the one that has the greatest influence on their design. 

In the 1970’s the Royal Navy moved from carriers capable of operating large conventional takeoff and landing (CTOL) aircraft such as the Phantom II and Buccaneer, to those capable of operating only short takeoff and vertical landing (STOVL) aircraft, i.e. the Harrier and Sea Harrier. 

Operating conventional takeoff and landing (CTOL) aircraft requires powerful catapults and arresting gear, which have a major impact on the overall machinery concept of the ship and also drive the size and layout of the flight deck. STOVL aircraft do away with catapults and arrestor gear, allowing much simpler, smaller and cheaper aircraft carriers, but at the penalty of more complex aircraft with poorer performance due to the weight penalty of providing their STOVL capabilities. 

In January 2001 the UK Ministry of Defence (MOD) effectively selected the Joint Strike Fighter (JSF) to meet its Future Carrier Borne Aircraft (FCBA) requirement, a programme since renamed the Future Joint Combat Aircraft (FJCA).   In October 2001 the Lockheed Martin F-35 was selected to be JSF, and thus will be the UK's FJCA.  The UK has committed $2 billion to be a full partner in the next JSF System Development and Demonstration (SSD) phase, plus another £600 million to develop a UK compatible variant meeting UK only requirements, overall the MoD now expects to spend up to £10 billion buying up to 150 F-35's.   

The FJCA program provides the Royal Navy UK with an opportunity to review the commitment to STOVL aircraft for the carrier force. The current plan for JSF is to develop separate F-35 aircraft variants tailored to the specific needs of the US Navy, US Marine Corps and US Air Force.  The Marines will get a short takeoff and vertical landing (STOVL F-35) aircraft to support Marine Air-Ground Task Force (MAGTF) operations from amphibious ships and expeditionary airfields. The US Navy would get a Carrier Variant (CV F-35) CTOL aircraft with greater range and payload, and with increased stealthiness to ensure survivability.  In view of the outstanding record of the Harrier aircraft and Invincible Class carriers, sticking with STOVL for FCJA might seem the natural choice, and indeed it has long been assumed to be the way the MOD will go. However recently it become apparent that alternative paths might result in a greater effectiveness and/or lower cost for the overall ship/aircraft system.

The FJCA will enter service with the RAF and RN at roughly the same time as the first CVF, which has created a nearly unique opportunity to re-evaluate how aircraft are launched and recovered from RN aircraft carriers.  The UK has not yet selected between the F-35 CV and STOVL variants for FJCA. The MOD is currently closely exploring the two alternatives and intends to make a decision by September  2002. This is essential because this choice will have a major impact on the design of the CVF and detailed design work cannot proceed until a decision is made.  Once FJCA and CVF (and the FOAEW support aircraft) are decided, it will be a long time (30+ years) before the RN will have another chance to develop new fighter and support aircraft, and design a new aircraft carrier. 

If the RN/RAF adopts STOVL JSF then for compatibility the FOAEW would probably also need to be a STOVL or STOL (short takeoff and landing) design.  A STOVL aircraft would open up a wide design arena for CVF – which could then in size then be as small as 20,000 tonnes, and allow JSF operations from the existing Invincible Class aircraft carriers if CVF was delayed or cancelled. Also experience with the current Harrier’s indicates that STOVL would also lead to increased sortie rates under some conditions and allow greater flexibility in the basing for naval aircraft. The JSF STOVL aircraft will be much more capable than the original Sea Harrier FRS.1 (and Harrier GR.1) or even the current Sea Harrier FA.2 (and Harrier GR.7).  Nonetheless, the STOVL path raises serious issues about performance and risk: 

Can a STOVL aircraft fully meet the UK requirements?
JSF will be adopted by the Royal Air Force as replacement for its existing Harrier and Jaguar aircraft, with a focus on air support of the British Army, which involves battlefield support missions at fairly close ranges. Tornado and Typhoon aircraft will provide additional air defence, deep strike, and Suppression of Enemy Air Defence’s (SEAD) capabilities. But support to Royal Marine and the Army forces ashore is only part of the Royal Navy’s interests, which cover the full spectrum of theatre air operations.  To support these missions, the original Royal Navy requirements for the FCBA called for additional range, payload, speed and stealth compared with Sea Harrier, which raises the issue of whether a STOVL aircraft would be good enough for the Navy.  For example, a STOVL aircraft may not provide the same degree of all-aspect stealth that is achievable in a CTOL aircraft.  Would such an aircraft be suitable for strikes against a range of targets on the first day of the war when enemy air defences are at full strength?

Lethality is another concern. The internal weapons bay of a CV variant of JSF will accommodate 2,000-pound weapons, whereas STOVL air-craft may be able to accommodate only 1,000-pound weapons internally.  This might limit their use against certain targets.  How serious is this limitation in view of STOVL’s ability to carry 2,000-pound weapons externally, and possible improvements in warhead technology to increase the lethality of 1,000-pound weapons against hard targets? One idea that might help with the range and payload tradeoffs would be to operate STOVL aircraft in different modes, depending on the operating base.  When operating from amphibious assault ships and perhaps forward land-based operating sites, the aircraft would operate in the basic STOVL mode. When operating from carriers, the aircraft would be catapulted (perhaps in conjunction with a ski jump) and arrested, but at lower energies than existing CTOL aircraft—the “soft-cat, soft-trap” concept.  The powered-lift features of STOVL would reduce launch and recovery speeds and the associated catapult and arresting energies, so that a STOVL aircraft would not require the heavy structure of a CTOL aircraft.  At the same time, the additional energy from the catapult might be sufficient to increase the range and payload of the STOVL aircraft to meet Navy requirements. Similarly, the soft trap would enable the aircraft to recover on carriers at heavier weights (i.e., with additional fuel and stores) than in the vertical landing mode. 

How serious are the technical risks of STOVL?
Controlling weight is a difficult task in the design of high-performance combat aircraft. STOVL aircraft are more sensitive to weight growth than CTOL aircraft because of their need to land vertically.  Achieving the type of capabilities envisioned for a FJCA STOVL aircraft would push the limits of engine technology, creating a technical risk for the program. Understanding the magnitude of these risks and the consequences of failing to achieve performance goals is essential when evaluating the costs and benefits of the STOVL path. 

Is a transition strategy to a CTOL force possible?
Adopting STOVL F-35 will logically lead to a CVF without catapults, or a perhaps new type of low-power catapult.  At the lower energies envisioned for soft-cat operations, alternative catapult technologies might be feasible, including hydraulic and even flywheels.  These technologies would open up the options for the machinery concept of CVF carrier, keep carrier costs down, and build on the existing RN/RAF experience with STOVL aircraft. 

Alternatively, the CV JSF path has exciting possibilities for higher performance aircraft, and cross-decking and co-operation with the US and French Navy’s, but it also entails significant risks. The RN will have to reacquire lost CTOL skills.  Current training and procedures will need to replace. Safety issues will have to be addressed.  It’s also unclear how Joint Force 2000 squadrons not dedicated to carrier ops could be kept carrier qualified.  If the UK went CV JSF for FJCA, clearly there are a lot more issues that will need to be resolved (sometimes expensively) than if it went STOVL.  However the USN has made it clear that it is very keen to see the UK adopt the F-35 CV variant, and it has offered to provide considerable assistance with, for example, training.

Machinery Concept
A second major issue affecting the design of CVF is the overall machinery concept for propulsion, aviation launch and recovery equipment, and other ship systems. 

If money was nearly unlimited than the RN would probably prefer to go nuclear propulsion. The outstanding effectiveness of nuclear power has been thoroughly demonstrated in the US Navy’s Nimitz class; the issue is not performance, but cost. Previous cost estimates predict that the additional cost of a nuclear plant might be as large as 30 to 50 percent in initial procurement cost and, at today’s oil prices, 10 to 20 percent in life-cycle cost.  For this price, the RN would get unlimited high-speed endurance, the ability to respond to distant crises in minimum time, and insurance against future increases in the price of oil.  However the cost has always been considered too high and nuclear propulsion was dropped as an option in the earliest stages of the CVF programme. 

The leading candidate for a new non-nuclear plant is an integrated full electric propulsion (IFEP) system powered by Rolls Royce-Northrop Grumman WR-21 gas turbines. Electric drive is essential to this concept because the existing geared mechanical drive requires location of the gas turbines deep within the ship. But the turbines’ intake manifolds and exhaust stacks require a large amount of shipboard space. Electric drive permits placement of the gas turbines closer to the skin of the ship, minimizing the intake/exhaust problem. Electric drive would also enhance ship survivability (because of redundant routing of electricity), and it would enable the Navy to eliminate maintenance- intensive steam auxiliaries. Although gas-turbine IFEP drive is an exciting concept, it has not been proven for the scale of an aircraft carrier. 

Another problem will be if the MOD decides to adopt the CV JSF, which would imply that CVF must be a CTOL carrier with catapults.  This would make critical the development of a new, non-steam catapult because generating sufficient steam for existing catapults is not practical in a non-steam propulsion system. Options include using an electromagnetic catapult or liquid propellants instead of steam. Although the MoD has already awarded some contracts to investigate these options, significant development will be required before either concept is ready for a new carrier.  If the technology proves out, the gas-turbine IFEP drive would offer (compared with existing machinery plants) reduced manning and lower procurement and maintenance costs.

Operations
Exploring innovative concepts of operations forms an integral part of the development process for CVF aircraft carrier. At the level of individual platforms, the central issue concerns which functions the carrier and its air wing should perform.  Improvements in the capabilities of off board and unmanned systems and the increasing capacity and reliability of communication links to the carrier imply an opportunity to re-examine whether some current functions could be performed more efficiently by off board systems. Various intelligence, surveillance and administrative functions are candidates to move off board. A related change in concepts of operations concerns the size of the crew. Moving some functions off board and automating others has promise for major reductions in manpower, which accounts for more than one-third of the life-cycle costs of existing carriers.  Truly significant reductions are feasible only by combining new technology with new concepts for operating the ship. New technology and concepts of operations may create opportunities for sea-basing platforms to assume new tasks that are important in the joint littoral warfare environment of the future.  For example, perhaps Tomahawk Land Attack Missiles (TLAMs) and Uninhabited Air Vehicles (UAVs) could be added to the aviation systems of CVF. Changes in concepts of operations could apply to the battle group or the force as a whole, as well as to the individual platforms. One possibility is to rethink the assignment of functions among platforms.  The current division of labour among carriers, surface combatants and amphibious ships is the product of long experience, and it has worked well. But now is an appropriate time to consider out-of-the-box ideas, because the concurrent development of the Future Surface Combatant (FSC) and CVF provides a once-in-a-generation opportunity to consider a major change of course.  One radical change would be to incorporate certain functions of surface combatants or amphibious ships into the design of a new carrier. For example, CVF could include multifunctional phased-array radar, improved helicopter support for Royal Marines and special warfare forces, and perhaps even some form of well deck to support future surface craft. Another area that deserves serious thought concerns options for getting increased operational availability out of the carrier force. There is a strong incentive to come up with new concepts that can enable a CVF carrier to spend more of its time in operational deployments around the world, including new schemes for rotating ships, aircraft and crews.  Some of these ideas represent a significant departure from current systems and operational practices.  But the RN is likely to improve upon current capabilities within a constrained budget only by combining new concepts of operations with new technology and design. 

Affordability
A major focus in the development of the carrier of the future is the need to reduce costs. The problem is not that the cost of aircraft carriers has gone up. When adjusted for inflation, the intention is that the CVF’s will cost no more than the current Invincible’s to build and operations, although far more capable.  The problem is that the RN’s budget has declined significantly and unless the budget increases or MOD realizes huge savings in infrastructure, the RN must reduce the cost of buying and operating future warships or face the inevitability of smaller force levels (it already has been announced that only 2 CVF’s will replace 3 Invincible’s).  Because an increase in the Defence Budget is unlikely, reducing the cost of the next-generation CVF carrier is absolutely essential in order to prevent any possibility of cancellation of CVF and total elimination of the RN’s carrier force, as undoubtedly advocated by some senior officers in the RAF and Army. Putting affordability near the top of the priority list forces the Royal Navy to contemplate significant changes but reducing costs must be given high priority. The RN must be willing to consider selected tradeoffs in capabilities and new ways of doing business to reduce costs. Such changes will not occur without some risk. But given the continuing squeeze on resources, either we will find new ways to perform the essential tasks more efficiently or the fleet of the future will be even smaller than we now imagine. 
 

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 © 2004-13 Richard Beedall unless otherwise indicated.