Royal Navy Wartime Experience and Analysis – Carrier Warfare

On 3 December 1945, Captain.Winkle Brown became the first pilot to land on and (pictured) take-off from an aircraft carrier (HMS Ocean) in a jet aircraft. The aircraft he flew — the de Havilland Sea Vampire LZ551/G — is now preserved at the Fleet Air Arm Museum in Yeovilton, Somerset. Extract from Documentary: Britain’s Greatest Pilot The Extraordinary Story of Captain Winkle Brown.

Until at least 1936, the Royal Navy did not try to interest the British Air Ministry in the development of high-performance fighters for its aircraft carriers, because the RN’s air officers did not think that an effective combat air patrol could be mounted around a carrier. By the time approaching bombers could be sighted and identified, it would be too late. Consequently, the RN carriers that followed Ark Royal, which was laid down in 1935, had armored flight decks so that they could absorb punishment and still operate attack aircraft. The advent of shipboard air-search radar in the first year of World War II, however, changed the situation, and the RN procured Royal Air Force (RAF) and U.S. Navy fighters and experimented with the central control of fighter defenses.

The RN also did not expect before World War II to have to operate its carriers against waves of high-performance land-based bombers—as it would be forced to do first in Norway in 1940 and then, in 1941, in the Mediterranean. The RN’s decision to construct carriers with armored flight decks restricted the number of aircraft such carriers could operate, so it chose to emphasize strike aircraft over fighters. The RN projected the logic of its own decisions about carrier-based strike aircraft upon the Imperial Japanese Navy (IJN). Accordingly, it was surprised by the IJN’s very effective carrier-based attacks in the Pacific and the Bay of Bengal in the spring of 1942.

The leaders of the RN responded to the challenges to the Fleet Air Arm posed by operations against the Germans in the Mediterranean and the Japanese in the Indian Ocean by creating the Future Building Committee (FBC), chaired by the Deputy First Sea Lord, in July 1942. The FBC was “the only organization within the Admiralty charged with the overall review of British naval requirements,” and its deliberations supported those of the Joint (i.e., Royal Air Force/Royal Navy) Technical Committee. At the end of 1942, the Joint Technical Committee had accepted the idea that future strike aircraft would be significantly heavier, and it recommended that all future carrier aircraft therefore be designed to use rocket-assisted takeoff equipment. The committee also approved an increased carrier-landing speed for all aircraft. In February 1943, the FBC specified that “carrier interceptor fighters should be the equals (in performance) of their land counterparts,” which implied significant increases in the size and weight of carrier fighters. In March 1943, the Aircraft Design Subcommittee of the FBC was split off to become a distinct organization—the Naval Aircraft Design Committee. This committee was an “early proponent of the catapult as the primary means of launching aircraft” from carriers.

Also in 1943, the RN’s famous test pilot Eric Brown successfully landed a combat-loaded, twin-engine Sea Mosquito fighter on a carrier, and the Future Building Committee recommended that the Mosquito design be modified to create a long-range carrier fighter equipped with radar. The resulting aircraft, christened Sea Hornet, first flew in April 1945. In September 1944 the First Sea Lord, Adm. Andrew B. Cunningham, asked the chief of the RAF’s Air Staff to provide the RN with Mosquitoes modified for use on carriers. Admiral Cunningham was thinking in early 1945 about long-range attacks from RN carriers against Japanese bases like Singapore. The Admiralty asked for two hundred Sea Mosquitoes “for delivery in 1945 and 250 to follow in 1946.”

That same month (September 1944), the Naval Aircraft Design Committee recommended to the Ministry of Aircraft Production (MAP) that it develop a jet interceptor for use from carriers. The members of the committee were aware that “such a fighter would demand catapult-only launching and that no other aircraft could be within thirty feet of it when its engine opened up to full power,” but they felt that the better air-to-air performance of the jet would more than compensate for the problems created by operating it from existing and planned carriers. By late 1944, the MAP had stopped work on new piston-engine designs and was focused on jet turbines and turboprops. In December 1944, the Naval Aircraft Design Committee “proposed that future naval aircraft be designed without undercarriages, to land on soft (flexible) decks,” and in February 1945 the Royal Aircraft Establishment (RAE) at Farnborough “concluded that any future high-performance naval fighter would have to be a pure jet, and that requirements for takeoff, military load, and landing speed would have to be modified.”

Things were moving fast. By 7 June 1945, the Naval Aircraft Department of the RAE had developed a “Proposed Programme of Experimental Work” for determining whether a carrier could operate jets without undercarriages. The “target for flying trials under seagoing conditions” was May 1946. This project was sent forward to the MAP with an endorsement by the director of the RAE two days later. On 4 July, engineer Lewis Boddington, who headed the Naval Aircraft Department at RAE, completed a paper entitled “Assisted Take-off for Future Naval Aircraft,” which he presented on 17 July to the Naval Aircraft Research Subcommittee of the Naval Aircraft Design Committee. He put his main point right up front: “The large increase in take-off speed which will result from the developments in the aircraft and its power plant, and the resulting necessity to remove the present free-deck take-off restrictions will demand assisted take-off under all conditions.”

Boddington’s paper laid out many of the engineering problems entailed by operating jets from carriers, especially the need for catapult launchings that would not be so violent as to damage an aircraft’s structure and the need safely to recover planes landing with their engines running. He argued, first, that “future aircraft will have no undercarriage and will land on flexible decks,” and, second, that “the solution of the problem giving the best handling and deck operating conditions will be a landing deck immediately under which will be the take-off deck. Ranged aircraft for take-off will not obstruct any landing operations.” By 12 July, the deputy director of RAE’s Panel on Flexible Landing Decks had reviewed the feasibility of an approach technique for a carrier with an (as yet only conceptual) flexible deck and had decided to recommend trials of actual landings using jet aircraft.

On 18 September 1945, Boddington presented a second paper for the Naval Aircraft Research Subcommittee, “Landing of Future Naval Aircraft.” As he observed, “The object of this note is to briefly present the problems of landing on a carrier deck in the future and discuss the effects on the equipment and carrier design.” His argument was that the development of jet aircraft “will result in a new approach technique ending in flight parallel to the deck and engaging the mechanical arresting gear under ‘flying’ conditions.” His paper provided the conceptual justification for the angled flight deck. As he noted, “To cover for the baulked landing, the jet engine will be running at 90% full revs….Non-engagement of the wire will allow the pilot to take-off [sic]again depending on the deck arrangements (barriers, parks, etc.) and the carrier design.” To allow a plane that had missed the arresting gear to get back in the air safely, the flexible deck that Boddington advocated would have to be located away from the deck park. His solution—already proposed—was to have “separate landing and take-off decks.”

Boddington also understood that jet aircraft would require more powerful catapults. In Britain, catapult development was shared between the Royal Aircraft Establishment at Farnborough and the Engineer-in-Chief Department of the Royal Navy. About 1943 Farnborough began experimenting with a new kind of catapult (Type K) using a flywheel to store energy. In 1946, the catapult engineers supervised by Boddington also explored the potential of gas turbines as power sources for carrier catapults.

As the Allied armies had surged across northern France in the fall of 1944, they had encountered the fixed sites built by the Germans to launch V-1 missiles against London. The missile’s pulse-jet engine could not function until it reached a set speed, about 150 mph. Thus the catapults built by the Germans were not too different from what a streamlined jet, with a similar takeoff speed, might require. Unlike the explosive-driven catapults then in use in the U.S. Navy for launching scout planes from cruisers and battleships, the German catapult applied its force directly to the airplane. It was a tube with a slot running along its upper side. A reaction in the tube pushed a piston along it, and the piston was hooked through the slot to the airplane. In the German case, the reaction was the decomposition of concentrated (“high-test”) hydrogen peroxide, which the British called HTP. This was one of several German applications of HTP, others being as an oxidant in the Me-163 rocket fighter and as an oxidant in the Walter closed-cycle U-boat. In each case, HTP showed lethal properties that more or less disqualified it if any alternative could be found.

The British report on the V-1 catapult was written by C. C. Mitchell, at that time a Royal Navy reservist but in peacetime a catapult designer in an Edinburgh engineering firm that produced what the RN referred to as “accelerators” for use on carriers. He had patented a slotted-tube catapult, which he called a “popgun” catapult, in 1938, but the RN had not adopted it. After the war, while working for Brown Brothers (also in Edinburgh), he realized that steam from a ship’s propulsion plant could substitute for the dangerous HTP. He formally proposed such a catapult (it is not clear exactly when) when trials of the Type K showed that the weight of existing hydro-pneumatic catapults was growing faster than their capacity to launch aircraft at high speeds. After 1947 the British formally chose the slotted-tube steam catapult as the sole direction for future development. By 1950, the prototype, christened BXS.1, was ready for testing on HMS Perseus, a war-built light carrier now used for experiments.

The Royal Navy used low-temperature, low-pressure steam on all of its existing carriers, as well as those under construction. Low steam pressure made it easier to build a gasket that would hold the steam inside a slotted-cylinder catapult as the steam drove the piston—attached to the airplane—forward. However, low steam temperature and pressure made for poor efficiency in ship propulsion. The U.S. Navy used much higher steam temperature and pressure in its carriers’ boilers, which made them more efficient thermodynamically and therefore increased the carriers’ endurance—a valuable capability in the Pacific War against Japan. Wartime contact with the U.S. Navy convinced the British to develop a new generation of high-pressure steam plants for their late-war and postwar fleets.

Because Mitchell’s catapult was adapted to the conditions of earlier British ships, it was by no means obvious that steam was the appropriate choice if new British carriers using higher steam pressures were built. Similarly, American observers of British catapult development knew that it was by no means obvious that a catapult adapted to British steam systems would succeed on board an American carrier. Wartime U.S. Navy boilers operated at about three times the temperature and twice the pressure of British plants, and by 1950 the U.S. Navy was contemplating doubling the pressure used during wartime, to 1,200 pounds per square inch.

British wartime analysis produced the conceptual foundation for the modern aircraft carrier operating high-performance jet aircraft. Because jets accelerated slowly, jet aircraft would need assistance at takeoff. Because jets landed at higher speeds and needed to do so with their turbines turning over at close to maximum revolutions per minute, the axial deck—with the deck park forward, shielded by a barrier—had to be modified. In effect, the Royal Navy had defined the “problem set” by the end of the summer of 1945. From that point forward, attention focused on possible solutions.

The choice of the steam catapult coincided with the beginning of design work on carrier modernization. As originally envisaged, modernization would have combined a steam catapult, new heavier-duty arresting gear, and a U.S.-style deck-edge elevator, the latter to provide an easier flow of aircraft between hangar deck and flight deck. For the British, the new elevator—the one major American-inspired element of modernization—was by far the most expensive part of the project. It was incompatible with the enclosed, protected hangars that had formed the cores of the existing British fleet carriers. To install the U.S.-style elevator the British had to remove the carrier’s flight deck and tear open its hangar deck. That they were willing to do so suggests the extent to which they considered the U.S. wartime experience, rather than their own, the key to the future.

In effect, the Royal Navy ended World War II with a policy of developing jet aircraft to replace propeller-driven types; experimenting with the flexible and angled flexible deck; and placing steam catapults in its new and modernized aircraft carriers. A lack of funds limited the speed with which these innovations could be developed, tested, and installed. However, incremental development of new equipment and techniques, rather than concurrent development, allowed RN engineers and aviators to identify problems and potential “dead ends” before large sums had been appropriated or spent.

A classic “dead end” they encountered was the “carpet,” or flexible, flight deck, which was tested successfully at sea on the carrier Warrior in the fall and winter of 1948-49. The combination of the flexible deck and jet fighters without landing gear appeared successful, but it had a major flaw. As Rear Adm. Dennis R.F. Cambell, RN, who is closely identified with the origin of the angled deck for carriers, put it years later:

It soon became obvious that there was a world of difference between one-off trials [of the flexible flight deck proposed by Lewis Boddington] and practical front-line operation. Two major points needed to be resolved—how were aircraft with no wheels to be dealt with ashore? . . . The one other big problem was how to ensure that speed of operation wasn’t to be sacrificed by imposing some elaborate mechanical substitute for the previous easy routine of just taxying [sic] forward into the deck parks; and the vulnerability of the whole scheme was surely obvious.

Moreover, it took a very skilled pilot to put his aircraft down on the “carpet” safely. For example,in the first test of the flexible rubber deck at Farnborough at the end of December 1947, RAE’s test pilot, Eric Brown, crashed his aircraft. Brown was fortunate to survive, and his description of what happened is vivid:

After crossing the arrester wire the plane continued to swing nose-down towards the deck and plunged into it with such violence that the nose completely vanished and penetrated right down to the bottom layer. . . . Then it was thrown harshly up again in a nose-up attitude. I opened it up to full power and was climbing away safely when I realized that the stick was jammed solid, with the elevators keeping the plane in a nose-up attitude. I throttled back gently and she settled on to the grass ahead of the deck. The crash split the cockpit all round me.

This initial accident, however, was followed by many successful attempts, once formal tests began again at Farnborough in March 1948. Brown says in his memoir (Wings on My Sleeve) that he made forty successful landings on the flexible deck at Farnborough in the spring and summer of 1948. By November of that year, the light carrier HMS Warrior had been fitted with a full-scale flexible deck, and Brown landed a small jet fighter (a Vampire) on it. As his memoirs have it, “The plane’s belly scraped the wire, the hook caught. The arrester wire and the deck had been deliberately set hard and the chock was uncomfortable, though only for a split second.” Not all his landings were as successful, but Brown nevertheless came away from the trials confident that the system would work. He noted in his official report, “It may even be that future swept-back and delta plan form aircraft will be forced to adopt this method of landing on carriers, since all calculations point to serious wheeled landing problems on such aircraft.”

Films of Brown landing his aircraft on the flexible deck were shown to staff in the U.S. Navy’s Bureau of Aeronautics when Lewis Boddington and two colleagues visited the United States in March 1949. The British team members spent most of their time at the naval aviation test center at Patuxent River, Maryland, the Naval Aircraft Factory in Philadelphia, and five aircraft manufacturing firms—Grumman, McDonnell, Chance Vought, Douglas, and North American. In his report of the trip, Boddington noted that “discussions were at all times free and open” and that “in general, similar methods of solving difficulties [were] in progress in both countries.” Facilitating this exchange of ideas was Capt. Frederick Trapnell, who had commanded an escort carrier in World War II and was in March 1949 the chief test pilot at Patuxent River.

The discussions among the technical specialists went into great detail and covered such topics as carrier-landing approach techniques, the coordination problems associated with high-speed approaches, the gravitational forces imposed on airplane structures by arrested landings and catapulted takeoffs, safe and functional barriers to shield the already-recovered aircraft in the deck park from those still landing, the problems associated with getting a jet to an adequate airspeed at the end of its catapult run, and the difficulties of moving increasingly heavy aircraft around on a carrier’s flight deck. Boddington and his colleagues observed that it was evident to officers in BuAer that “the direct application of present requirements and methods for catapulting and arresting is not satisfactory,” especially for large (hundred-thousand-pound) aircraft. This need to place very large aircraft on U.S. carriers was based on the formal requirement to develop nuclear-capable bombers. It drew the Americans away from the British, though the two navies otherwise shared the same basic problems that stemmed from the innovations—jet aircraft, radar, and missiles—produced during World War II.

The parallels between the two navies in the immediate postwar period are striking. Because of their wartime experiences, both naval air arms wanted larger, heavier, and longer-range aircraft for their carriers. Both had officers and engineers who believed that it was possible to develop ways to launch and recover high-performance jet aircraft on carriers. Although, as Boddington observed, American engineers in aircraft firms and military and civilian officials were working on similar problems, it was the British who first grasped all the problems entailed in adapting existing carriers to jet aircraft. Their initial solution to this set of problems—the flexible landing deck—did not survive careful scrutiny, but the idea of the slightly offset flexible deck led to the angled deck, and it was the angled deck that opened the way for the large modern carrier.

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