Parasite Fighters / Composite Aircraft
While many attempts at launch and recovery of aircraft with a host have been envisioned, none have proven practicable at overcoming four constraints simultaneously. These launch and recovery solutions are largely constrained by several factors: relative positioning navigation technology; timing of release and capture; aerodynamic interference between the aerial vehicle and the host; and structural issues and weight, compounded in most cases by speed differentials and ensuing force loads between the aerial vehicle and the launch/recovery vehicle. The costs outweighed the benefits in the final analysis, even if safety could have been assured. The key problem identified highlighted the very real problems around recovery operations between to moving objects. Dramatic modifications and trade-offs to the aircraft and host have been required to achieve safe, repeatable, reliable recovery. Complexity, both in design and operational concepts, and untenable weight growth ensued.
A composite aircraft comprises two component aircraft each capable of independent sustained flight mounted one on top of the other and initially connected together by rigid but releasable locking means in such a manner as to enable the composite aircraft to take off, fly and land with the wings of both components contributing in an efficient manner towards the total lift required for such flight. The concept is more especially applicable to the launching of aircraft of high wing loading and high minimum flying speed, but may be applied to any class of aircraft, or to the launching of an aircraft at a considerable distance from its base thus increasing its eiiective range.
The broad concept of using sky hook airplanes is old, dating back almost to the beginning of the aviation age. Much work has been devoted to and considerable success has been had in making the in-flight connection and disconnection. Thus, the techniques of hook on have become a routine maneuver for trained personnel.
The idea of an aircraft carrier in the sky with parasite aircraft is not new. During the opening years of the Great War the German Zeppelins carried out a ceaseless patrol of the North Sea and maintained such a constant watch that it became difficult for ships of the Royal Navy to operate without full details of their movements being reported to authorities. The area of patrol, was out of range of aeroplanes operating from the English coast, and the flying boats of the period, although they had the range, had not the speed and climb to bring the hostile airships to action except in most favourable circumstances.
An interesting type of composite aircraft was evolved in the latter part of 1915 by Sqn. Cdr. de Courcy W. P. Ireland, of the Great Yarmouth air station. This officer, who had often been thwarted in his efforts to reach raiding enemy airships, conceived the idea of attaching a B.E.2C aeroplane to an S.S. type non-rigid airship. His idea was that, upon receipt of a warning of an impending raid, the composite aircraft should ascend to the height of the approaching Zeppelins. The airship portion would make a rapid ascent possible and, moreover, the aeroplane need not be released until the Zeppelins came within striking distance, thus conserving fuel and giving a longer endurance.
On February 21, 1916, with Sqn. Cdr. Ireland as pilot and Wing Cdr. Usborne as observer, the airship-plane, as it was called, ascended to carry out the first experimental release. When a height of 4,000 feet had been reached, loss of pressure in the envelope of the airship, caused the aeroplane immediately to turn over on its back. Ireland was thrown out and fell to his death. Usborne, remaining in the machine, crashed with it.
It was thought that if a light single-seater could be conveyed to the patrol area by a flying-boat, it could be detached upon sighting a Zeppelin; its superior performance would then enable it to engage the enemy with a good chance of success. A Bristol Scout single-seater (80 h.p. Gnome engine), which weighed about 1,195 lb. had a speed of 100 m.p.h. and could climb 1,000 feet a minute, was chosen as the fighter or upper unit. The lower component was the big Porte "Baby" flying boat. The experiment was made in May, 1916, in Felixstowe Harbour. The experiment was never repeated—partly, it is believed, due to the fact that with full fuel and military load the addition of the Scout would make the take-off too long, and also to the fact that the slow speed and vulnerability of the craft made it unfit for extended North Sea operation.
On January 25, 1918, the German Zepplin L 35 carried an Albatros fighter aloft, but it was not dropped. The next day the plane was released at 4,600 feet, and after diving about 150 feet, it picked up speed and flew away. By June 1918, the capability of launching a “parasite fighter” from an airship was being tested by the British Navy. A Sopwith Camel was suspended from a “little crook anchoring gear” under airship R23. The testing culminated on 06 November 1918 when R23 air-launched the Camel which subsequently landed successfully. The U.S.Navy performed a similar air-launch experiment in 1918 when a few weeks after the Armistice the experiment was tried successfully at Fort Tilden, New York, using the Navy blimp C-1 and an Army JN4 airplane.
As soon as large rigid airships became available, plans for aeroplane-carrying experiments were put forward. Early in 1918 a Sopwith Camel single-seater aeroplane, with locked controls, was carried aloft by airship R23. When released, without pilot, it assumed a normal glide and made a good landing. Some time afterwards another Camel, piloted by Lieut. Keys, was safely released from the same airship. The success of these experiments gave rise to the hope that airships might be used as fast carriers for aeroplanes. The signing of the Armistice, however, delayed the experiments until 1925.
In the later months of 1925 Sqn. Ldr. R. A. de Haga Haig carried out a series of experiments in releasing a D.H.53 light aeroplane from the airship R33 and subsequently re-attaching. Various difficulties were encountered, particularly with regard to hooking-on to the airship, but sufficient information had been obtained to enable experiments to be carried out in 1926 with two Gloster Grebes. These were successful, but the closingdown of the Airship Establishment brought about the cessation of the experiments.
The capability to carry fighter aircraft for defense was included in the design specification for the US Navy's USS Akron and the USS Macon airships. Early tests that contributed to, but were not directly related to the development of the Akron-class rigid airships, occurred in late-1924 when the U.S. Army Air Service conducted air-launch and hook-on tests between a Sperry “Messenger” aircraft and non-rigid blimps. The Messenger was equipped with a hook above the top wing of the bi-plane; the blimps were equipped with a rigid “trapeze” secured to the bomb racks below the envelope. The first test was conducted between the dates of October 2-4, 1924. Blimp TC-5 carried the Messenger aloft and released it from an altitude of 1500 feet above the ground. Subsequently, on December 14, 1924, the Messenger made the first successful hook-on landing to blimp TC-3 and subsequent air-launch release.
In the early 1930s, the Navy airships Akron and Macon were designed with an internal 60- by 75-foot hangar deck that included an overhead trolley system to store four Sparrowhawk scout planes, launching and recovering them with a retractable trapeze and winch assembly. Vulnerability to weather limited the operational concept. Also in the 1930s, Russia experimented with parasite fighters carried by a Tupolev TB-3 bomber to provide defensive escort, offensive air-to-air sweep, and long-range offensive strikes. The most ambitious experiment used a large bomber with fighters carried above and below each wing and one under the fuselage on a trapeze.
The idea of carrying one vehicle aloft with another began during the earliest days of powered flight. There was one basic conceptual difference in those early piggyback configurations, however. Instead of one aircraft mounted on another, the mother ship was a balloon. Several other "parasite" concepts existed during World War I, including the Fieseler Fi-103 and some drone aircraft experiments. During the mid-1920s, the British carried out a series of airship experiments with the de Havilland Hummingbird.
The composite aircraft, devised by Maj. Robert H. Mayo, was designed to permit takeoffs with heavier loads than would be possible if the Mercury had to depend upon it own lifting power to get into the air. The mother plane, a modification of the four-engined Empire flying boat, carried the smaller craft on its back in taking off releasing it high in the air. The Mayo Composite aircraft carried out two successful trans-Atlantic flights in July 1938, and later a successful non-stop flight from England to South Africa.
Zveno ["Link" or "Flight"] was a parasite aircraft concept developed in the Soviet Union during the 1930s. It consisted of a Tupolev TB-1 or a Tupolev TB-3 heavy bomber acting as a mothership for between two and five fighters. Depending on the Zveno variant, the fighters either launched with the mothership or docked in flight, and they could refuel from the bomber.
In the United States, at McCook Field, Dayton, Ohio, in 1922, the concept was reintroduced with an airship once again serving as the airborne platform. The experimental work evolved around the Army's tiny Sperry Messenger biwing aircraft and was carried out by Lawrence Sperry, who volunteered to test the feasibility of hooking on to the airship. Keeping the propeller out of the airship's dangling trapeze grappling system proved to be the major operational problem during the tests. The little Messenger joined the airship by a hook that was mounted on its top wing. The hook was designed to open when a 2-mph speed differential was experienced; its supporting structure was carried forward to form a unique propeller guard. Shock absorbers were fitted to the rigid airship trapeze to ease the jolt of contact.
The first Messenger hook-up attempts were undertaken in 1924 at the Army Airship Base at Scott Field, Illinois. On the first two passes of the initial test, the 8S0-pound Messenger missed contact and then broke its propeller on the third. The tests were conducted directly over the field with just such an eventuality in mind. But in December, success was finally realized with the first solid hook-up accomplished. The airship was moving at a blazing 62 mph when the hook-up was made, and the Messenger was released within the current highway speed limit, 51 mph! But the promising Messenger concept proved to be very short-lived, since all the tiny aircraft became surplus in 1926. Fewer than 50 of the model were built. The lone remaining example of this plane can be seen at the Air Force Museum, hanging from the ceiling on a simulated trapeze.
But the Messenger was probably not the best known of the U.S. balloon parasites. That distinction undoubtedly belongs to the Navy's Sparrow Hawk project. Officially designated the XF9C-2, the Sparrow Hawk biwingers received wide publicity in their association with the Navy dirigibles--the USS Macon and the USS Akron. The hook-up configuration of the Sparrow Hawk was not unlike the Messenger rigging. The program was carried out during the early 1930s, but on 12 February 1935, disaster terminated the program when the USS Macon went down with the resulting destruction of three attached Sparrow Hawks. During the next few years the remaining Hawks faded into oblivion.
During the 1940s, the carrier vehicle switched from balloon power to prop power, and a multitude of interesting conglomerations evolved. Initially, the British employed the concept as a means for getting a heavily loaded seaplane airborne. The mother flying boat, the Maia, carried a smaller seaplane, the Mercury, on a pylon. The first separation flight was accomplished in 1938. Then, in July of that year, the strange twosome flew nonstop from Ireland to Montreal. The two four-engine aircraft made numerous composite flights with separations, including one 6000-mile flight--a record distance for seaplanes that still stands today. Maia and Mercury were operating between Southampton and Alexandria, Egypt, when World War II began. Mercury was scrapped in 1941 after serving with a Dutch seaplane squadron attached to the Royal Air Force. Maia was destroyed by a Luftwaffe bomb in May 1941.
In Germany during the Second World War parasite fighters were intended to be carried into a combat zone by a larger aircraft, such as a bomber. If the bomber were threatened, it would be able to release the parasite to defend itself. The tiny fighters were to have been propelled by pulsejets. The Messerschmitt Me 328 was originally designed as a parasite aircraft to protect Luftwaffe bomber formations. A wide variety of other roles were suggested for it, including consideration as a selbstopfer (suicide weapon or kamikaze) aircraft.
The Germans in World War II evolved some interesting mutations of the piggyback concept. The best known concept involved the use of an unmanned Junkers Ju-88 twin-engined bomber loaded with explosives. Mounted on struts above, and attached to the Ju-88, was a Messerschmitt Me-109 fighter. The pilot of the fighter controlled both the joined ~aircraft and, when near the target, cut the Ju-88 loose and guided the bomb-laden bomber to the target. The innovative Germans also investigated integrating an Me-109 above a DFS-230 Troop Glider.
The idea and realization of a need for aircraft-borne fighters probably came about early in World War II when B-17s had to traverse a major portion of Axis bombing missions unescorted. P-51s and P-47s with drop tanks eventually solved this problem, but with new bombers on the drawing boards, the worry about fighter defense intensified. Project MX-472, called the "unconventional fighter," occurred in December 1942. But the fighter that was to evolve from MX-472 would never see the fire of combat.
The piggyback concept was used in a test function by the French at the end of World War II. The purpose of the test setup was to acquire the necessary speed to fire the piggyback vehicle's ramjet engine. The test program lasted into the early 1950s, when it was abandoned because of the lack of official support.
Subsequent attempts by the US Air Force were the XF-85 and RF-84F to be carried by the B-36. Launch and recovery proved to be major problems in these two programs while fighter and carrier capability limited operational usefulness. In-flight refueling of fighters and bombers became a competitive solution for extended range and ultimately B-36 obsolescence terminated all effort.
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