v1.6.0 / chapter 1 of 19 / 01 mar 10 / greg goebel / public domain
* The first important use of robot aircraft was as targets for anti-aircraft gunnery training. Target "drones" were introduced into wide-scale service for this application during World War II, forming a basis for their widespread use after the war. This chapter provides a survey of American target drones of World War II and the postwar period.
* The first pilotless aircraft, intended for use as "aerial torpedoes" or what we would now call "cruise missiles", were built during and shortly after World War I, and led to the development of radio-controlled (RC) pilotless target aircraft in Britain and the US in the 1930s. In 1931, the British developed the Fairey "Queen" radio-controlled target from the Fairey IIIF floatplane, building a batch of three, and in 1935 followed up this experiment by producing larger numbers of another RC target, the "DH.82B Queen Bee", derived from the de Havilland Tiger Moth biplane trainer. Through some convoluted path, the name of "Queen Bee" is said to have led to the use of the term "drone" for remote-controlled aircraft.
The US Navy began experimenting with radio-controlled aircraft during the 1930s as well, resulting in the Curtiss "N2C-2" drone in 1937. By the outbreak of World War II, obsolescent aircraft were being put into service as target drones as the "A-series" targets. Since the "A" code would be also assigned to "Attack" aircraft, later "full-sized" targets would be given the "PQ" designation. During the war the US Army Air Forces (USAAF) would acquire hundreds of Culver "PQ-8" target drones, which were radio-controlled versions of the tidy little Culver Cadet two-seat civil sportplane, and thousands of the improved Culver "PQ-14" derivative of the PQ-8, with such refinements such as retractable landing gear. The US also used RC aircraft, including modified B-17 and B-24 bombers, in combat on a small scale during World War II as aerial torpedoes, though with no great success.
The first large-scale production, purpose-built drone was the product of an interesting fellow named Reginald Denny, born Reginald Leigh Deymore in Britain. He served with the British Royal Flying Corps during World War I, and after the war emigrated to the United States to seek his fortunes in Hollywood as an actor. Denny played a lead role in a number of his earlier films, generally as a comedic Englishman, and later had reasonably steady work as a supporting actor in dozens of movies, including a screen version of ANNA KARENINA with Greta Garbo and the Frank Sinatra "caper" movie ASSAULT ON A QUEEN. Between acting jobs, he pursued his interest in RC model aircraft, opening a model-airplane shop on Hollywood Boulevard in the early 1930s. The shop evolved into the "Radioplane" company.
Denny believed that low-cost RC aircraft would be very useful for training anti-aircraft gunners, and in 1935 he demonstrated a prototype target drone, the "RP-1", to the US Army. This led to demonstration of an "RP-2" in 1938, with flights of the "RP-3" and "RP-4" in 1939. The Army placed an order for 53 RP-4s, designating them the "OQ-1", the "OQ" meaning a "subscale target". This small order led to a much bigger 1941 order from the US Army for the company's similar "RP-5", which became the US Army "OQ-2". The US Navy also bought the drone, designating it "Target Drone Denny 1 (TDD-1)". Thousands were built, manufactured in a plant at the Van Nuys Airport in the Los Angeles metropolitan area.
The OQ-2 was a simple aircraft, powered by a two-cylinder two-cycle engine,
providing 4.5 kW (6 HP) and driving contra-rotating propellers. It really
looked like nothing more than a plain and simple, if big, hobbyist RC flying
model aircraft. The RC control system was built by Bendix.
RADIOPLANE OQ-2:
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spec metric english
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wingspan 3.73 meters 12 feet 3 inches
length 2.65 meters 8 feet 8 inches
takeoff weight 47.2 kilograms 104 pounds
maximum speed 137 KPH 85 MPH / 74 KT
service ceiling 2,440 meters 8,000 feet
endurance 70 minutes
launch scheme Conventional runway takeoff.
recovery scheme Parachute or runway landing.
guidance system Radio control.
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The OQ-2 led to a series of similar but improved variants, with the "OQ-3 /
TDD-2" and "OQ-14 / TDD-3" produced in quantity. It should be emphasized
that many other targets were built by Radioplane and a number of other
companies during the war, most of which never got beyond prototype stage,
which might be suspected by the gaps in the designation sequence between
"OQ-3" and "OQ-14".
* Although small piston engines were the normal powerplant for targets in this era, there was something of a fad for pulsejet propulsion as well, though it doesn't appear that the US military ever acquired any pulsejet-powered targets in more than modest numbers. McDonnell built a pulsejet-powered target, the "T2D2-1 Katydid", later the "KDD-1" and then "KDH-1". It was an air-launched cigar-shaped machine with a straight mid-mounted wing, and a vee tail straddling the pulsejet engine. The Katydid was developed in mid-war and a small number were put into service with the US Navy.
After the war, the Navy obtained small numbers of another pulsejet-powered target, the "KD2C Skeet" series, built by Curtiss. It was another cigar-shaped machine, with the pulsejet in the fuselage and intake in the nose. It featured straight, low-mounted wings with tip tanks, and a triple-fin tail.
* In the postwar period, Radioplane followed up the success of the OQ-2 series with another very successful series of much improved piston-powered target drones, what would eventually be called the "Basic Training Target (BTT)" family. The BTTs remained in service for the rest of the century.
The BTT family began life in the late 1940s, evolving through a series of refinements with the US Army designations of "OQ-19A" through "OQ-19D", and the US Navy name of "Quail" with designations of "KD2R-1" through "KD2R-5". Early models had a metal fuselage and wooden wings, but production standardized on an all-metal aircraft. Radioplane developed an experimental "XQ-10" variant that was mostly made of plastic, but though evaluation went well, it wasn't any major improvement over existing technology and it did not go into production.
In 1963, when the US military adopted a standardized designation system, the surviving US Army BTT variants became "MQM-33s" and the Navy KD2R-1, the only member of the family still in Navy service, became the "MQM-36 Shelduck". The "BTT" designation wasn't created until the 1980s, but is used here as a convenient way to resolve the tangle of designations.
The MQM-36 was the most highly evolved of the BTT family, but retained the
same general configuration as the other members. It was larger and more
businesslike than the first-generation OQ-2A series, and was powered by a
more powerful flat-four four-stroke McCulloch piston engine with 71.2 kW (95
HP). The MQM-36 could carry radar enhancement devices on its wingtips.
RADIOPLANE MQM-36 SHELDUCK:
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spec metric english
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wingspan 3.5 meters 11 feet 6 inches
length 3.85 meters 12 feet 8 inches
height 0.76 meters 2 feet 6 inches
empty weight 123 kilograms 271 pounds
launch weight 163 kilograms 360 pounds
maximum speed 370 KPH 230 MPH / 200 KT
service ceiling 7,000 meters 23,000 feet
endurance 1 hour
launch scheme RATO booster or bungee catapult.
recovery scheme Parachute.
guidance system Radio control.
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Over 73,000 BTT targets were built in all, and the type was used by at least
18 nations. Some may still be lingering in service.
* A variant of the BTT named the "MQM-57 Falconer" was built for battlefield reconnaissance, with first flight in 1955. The Falconer was similar in appearance to the Shelduck, but had a slightly longer and definitely stockier fuselage. It had an autopilot system with radio-control backup, and could carry cameras, as well as illumination flares for night reconnaissance. Equipment was loaded through a hump in the back between the wings.
Although it only had an endurance of a little more than a half-hour, making it of limited use, about 1,500 Falconers were built and the type apparently was used internationally with several different military forces, remaining in service into the 1970s. There were other BTT derivatives that didn't have much impact, one of the most interesting being the "NV-101" of the early 1960s, which was effectively an autogyro variant. Exactly why it was built remains unclear, it may have possibly been intended to simulate helicopter targets, but it is certainly clear that nothing came of it.
Radioplane was bought out by Northrop in 1952 to become the Northrop Ventura Division, though it appears that the "Radioplane" name lingered on for a while. Reginald Denny died in 1967 at age 75, after what sounds like an interesting and profitable dual career in the movie and aviation industries.
* Just to confuse matters, the US military acquired a number of other drones similar in many ways to the Radioplane drones. The Globe company built a series of targets, beginning with the piston-powered "KDG Snipe" of 1946, which evolved through the "KD2G" and "KD5G" pulsejet-powered targets and the "KD3G" and "KD4G" piston-powered targets, to the "KD6G" series of piston powered targets. The KD6G series appears to have been the only one of the Globe targets to be built in substantial numbers. It was similar in size and configuration to the BTT series, but had a twin-fin tail. It was redesignated "MQM-40" in the early 1960s, by which time it was generally out of service.
In the late 1950s, along with the Falconer, the US Army acquired another reconnaissance drone, the Aerojet-General "MQM-58 Overseer". It had a similar configuration to the Falconer, but featured a vee tail and was about twice as heavy. It does not appear to have been built in large quantities, and may have never been much more than an experimental platform to evaluate more sophisticated reconnaissance sensors than could be carried by the Falconer.
* The Northrop Ventura division went on to build improved jet and rocket propelled targets. In the late 1940s, the company developed a set of prototypes of the "Q-1" target series, which used pulsejet or small turbojet engines. Although the Q-1 series was not put into production as a target, it did evolve into the USAF "RP-54D / XB-67 / XGAM-67 Crossbow" anti-radar missile, which was first flown in 1956. It was also considered as a platform for reconnaissance, electronic countermeasures, and decoy roles.
The Crossbow had a cigar-shaped fuselage, straight wings, a straight twin-fin
tail, and an engine inlet under the belly. It was powered by a Continental
J69 turbojet, which was a French Turbomeca Marbore II engine built in the US
under license, with 4.41 kN (450 kgp / 1,000 lbf) thrust. Two Crossbows
could be carried by a Boeing B-50 Superfortress bomber, while four Crossbows
could be carried by a Boeing B-47 Stratojet bomber.
NORTHROP GAM-67 CROSSBOW:
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spec metric english
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wingspan 3.81 meters 12 feet 6 inches
length 5.82 meters 19 feet 1 inch
height 1.37 meters 4 feet 6 inches
loaded weight 1,270 kilograms 2,800 pounds
maximum speed 1,090 KPH 675 MPH / 587 KT
service ceiling 12,200 meters 40,000 feet
range 480 kilometers 300 MI / 260 NMI
launch scheme RATO booster or air launch.
recovery scheme Parachute.
guidance system Autopilot with radio control backup.
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Only 14 Crossbows were built before the program was cancelled in 1957, in
favor of more sophisticated technology that ended up being cancelled in turn.
However, it did point the way to the range of missions that would be
performed by UAVs in later decades.
* The Northrop Ventura "AQM-38" was a rocket-propelled target that was used for training Army Nike anti-aircraft missile crews and Navy fighter pilots. It started life in 1957 under a US Navy contract as the "RP-70 / XKD4R-1", with initial flight in January 1958. After a bit of redesign that changed its lines somewhat, it went into service with the Army and the Navy from 1959.
The Army version was originally designated the "RP-76", with this designation changed in 1963 to "AQM-38A"; while the Navy version was originally designated the "RP-78", with this later changed to the "AQM-38B". The Army AQM-38A had slightly subsonic performance, while the Navy AQM-38B had a more powerful engine, giving it a top speed of Mach 1.25.
Like the Crossbow, the AQM-38 had a cigar-shaped fuselage and guidance
provided by an autopilot with RC backup, but it was much smaller and was
powered by a solid rocket engine, with an exhaust nozzle just behind each
wing. It had shoulder mounted delta wings, three fins around the nose, and a
peculiar downward-mounted "tee" tail along with a smaller dorsal fin. It was
air-launched and recovered by parachute.
NORTHROP AQM-38B:
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spec metric english
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wingspan 1.52 meters 5 feet
length 2.95 meters 9 feet 8 inches
height 0.46 meters 1 foot 6 inch
empty weight 90 kilograms 200 pounds
launch weight 135 kilograms 300 pounds
maximum speed 1,530 KPH 950 MPH / 826 KT
service ceiling 22,000 meters 72,000 feet
endurance 23 minutes
launch scheme Air launch.
recovery scheme Parachute.
guidance system Autopilot with radio control.
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The AQM-38 appears to have been largely made of plastics, and carried radar
enhancement devices to simulate larger aircraft. It went into service in
1959 and over 2,000 were built. It appears to have been replaced by the
Beech AQM-37, discussed later, and was phased out in the early 1970s.
* By the late 1950s combat aircraft were capable of Mach 2, and so faster targets had to be developed to keep pace. Northrop designed a turbojet-powered Mach 2 target in the late 1950s, originally designated the "Q-4" but later given the designation of "AQM-35". In production form, it was a slender dart with wedge-shaped stubby wings, swept conventional tail assembly, and a GE J85 turbojet engine, like that used on the Northrop F-5 fighter, with 17.1 kN (1,745 kg / 3,850 lb) thrust mounted under the tail. It was 10.7 meters (35 feet) long and weighed 1,500 kilograms (3,300 pounds).
The AQM-35 was air-launched by a Lockheed DC-130 Hercules drone controller aircraft, or other carrier aircraft. The AQM-35 was only built in limited quantities and never reached full operational service.
* In the late 1940s, Lockheed developed an air-launched high-speed ramjet research vehicle designated the "X-7" for the USAF. It was a long dart with trapezoidal wings, and used two solid-fuel booster rockets to get it up to ramjet speeds. The X-7 was used for engine and flight research through the 1950s. The Air Force ordered a minimally-modified target variant of the X-7 in the late 1950s as the "XQ-5 Kingfisher", later redesignated "AQM-60". The program was transferred to the US Army and then killed in the mid-1960s after the construction of about 61 vehicles. Some sources claim that it was cancelled simply because it was too fast to be caught by existing surface to air missiles (SAMs), but that sounds a bit glib.
It was more likely that it redundant. During the same timeframe, North American also built a Mach 2 target drone for the US Army, designated the "MQM-42A Redhead / Roadrunner". It was another sleek dart, with mid-mounted small delta wings, an inverted vee tail, and a Marquardt ramjet engine on the back. It was launched by RATO booster, derived from the solid fuel motor for the Honest John battlefield rocket, and was recovered by parachute. The MQM-42A had a length of 7.57 meters (24 feet 10 inches), a weight of 400 kilograms (900 pounds), speed of up to Mach 2, and ceiling of up to 18,000 meters (60,000 feet). First flight was in 1961. The MQM-42A was apparently built in modest numbers, and used for training Hawk SAM crews. It remained in service into the 1970s.
* While the Radioplane BTT was a popular piston-powered target, such a simple target was relatively easy to build and it had competition, particularly in the form of the Beech "Cardinal" target.
In 1955 Beechcraft, now part of Raytheon, designed the "Model 1001", as the initial version of this target drone was designated, in response to a US Navy requirement for gunnery and air-to-air combat training. Production of the type began in 1959, with the drone being given the Navy designation of "KDB-1", later "MQM-39A". The Model 1001 led to the similar "Model 1025" for the US Army, which gave it the MQM-61A designation. Beech also designed a variant powered by a turbojet engine and designated "Model 1025-TJ", but nobody bought it.
The MQM-61A was a simple monoplane with a vee tail. It was substantially
larger than the Shelduck, and powered by a 94 kW (125 HP) McCulloch
TC6150-J-2 flat-six, air-cooled, two-stroke piston engine driving a two-blade
propeller. It could tow banners or targets of its own, with two targets
under each wing, and also carried scoring devices.
BEECHCRAFT MQM-61A CARDINAL:
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spec metric english
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wingspan 3.95 meters 13 feet
length 4.60 meters 15 feet 1 inches
height 1.02 meters 3 foot 4 inches
launch weight 301 kilograms 664 pounds
maximum speed 560 KPH 350 MPH
service ceiling 13,100 meters 43,000 feet
endurance > 1 hour
launch scheme RATO booster.
recovery scheme Parachute.
guidance system Autopilot with radio control.
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A total of 2,200 Cardinals of all variants was built, the majority for the US
Army, with the rest operated by the US Navy, the US Marine Corps, and by
Spain. Some may have also been operated by Germany and Switzerland. It is
now out of production, though a few may linger in service.
