Ryan Model 147

The Ryan Model 147 Lightning Bug was a drone, or unmanned aerial vehicle, developed from the earlier Ryan Firebee target drone series.

Ryan Model 136 Red Wagon and Lucy Lee
In 1959, Ryan Aeronautical performed a study to investigate how the company's Firebee target drone could be used for long-range reconnaissance missions. Ryan engineers concluded they could increase the Firebee's range to allow it to fly south over the Soviet Union after launch from the Barents Sea, with recovery in Turkey. The Firebee has a low radar cross section, making it hard to detect. With lengthened wings, the drone would also be able to fly at high altitude, further increasing its elusiveness. It could be launched by a Lockheed DC-130 Hercules, or RATO-boosted from a land site or ship.

Ryan presented its report on the studies to the US Air Force in mid-April 1960. Meanwhile, on 1 May 1960, an American Lockheed U-2 spy plane was shot down over the USSR, and its pilot, Francis Gary Powers, captured. On 1 July, a Boeing RB-47 reconnaissance aircraft flying an electronic intelligence mission in international airspace near the Soviet border was shot down. Four of its crew were killed and the other two captured. A few days later, the Air Force awarded Ryan a $200,000 USD contract to perform further studies. Ryan conducted radar measurements on sub-scale Firebee models and determined that their radar signature could be reduced by placing a wire screen over the jet intake; painting parts of the drone with non-conductive paint; and placing radar-absorbing pads on both sides of the fuselage. Test flights of the modified Firebees were performed in September and October 1961. The flights were given a cover story, describing the drones as high-altitude targets for surface-to-air missiles (SAMs), in case one of them came down in a public area. The flights demonstrated that the modifications did not compromise the Firebee's performance.

Ryan actually wanted to build a completely new drone, the Ryan Model 136, for the reconnaissance mission. The Model 136, or Red Wagon, was optimized for the role, with long straight wings for high-altitude flight, an engine set on the back of the fuselage to reduce its radar and infra-red signatures as seen from below, and inward-canted twin tail fins to conceal the exhaust plume. However, the project stalled. The incoming Kennedy Administration was certain to reassess many military projects, and Red Wagon was put on hold.

Ryan then proposed another drone named "Lucy Lee", which was a highly modified Firebee intended to perform photographic and signals intelligence (SIGINT) reconnaissance from outside Soviet airspace. Lucy Lee seemed to be on track, but was then abruptly cancelled in January 1962.

Ryan Model 147A Fire Fly
The whole idea of reconnaissance drones seemed to be completely dead, but at the last moment the USAF rescued the program. The Air Force went for the cheapest option, a reconnaissance drone based on a Firebee with minimal changes. A $1.1 million USD contract was issued on 2 February 1962, requesting four Firebee drones modified for photo-reconnaissance. The modified Firebees were funded from a program named "Big Safari", established in the 1950s to fund fast-track conversions of existing aircraft for the reconnaissance mission. Big Safari would continue to work on reconnaissance drones during the Vietnam War, and would also assist in UAV programs in later wars.

The new reconnaissance drones were designated Model 147A and codenamed Fire Fly. Specifications dictated a 1,200 mile (1,930 kilometre) range and a cruise altitude of 55,000 feet (16.8 kilometres).

The first Model 147A was a standard Firebee with a new guidance system, consisting of no more than a timer-programmer, a gyrocompass, and an altimeter. The Fire Fly could be programmed to fly in a certain direction at a certain altitude for a certain time, and then turn around and come back the way it came. This aircraft was intended only as a demonstrator, to evaluate the new guidance system, and carried no cameras. Three test flights were performed in April 1962 and demonstrated the validity of the concept, with the drone performing a mission from New Mexico, north into Utah, and then back again with no guidance from the ground, though accompanied by a B-57 chase plane.

The second Model 147A had an 35 in "plug" inserted into the fuselage to carry an additional 68 US gallons (258 litres) of fuel, increasing the length from 22 feet 10 inches (7 m) to 25 feet 9 inches (7.89 m). It also had a new nose containing a camera from the U-2. Four test flights performed in April and early May 1962 were successful, and so the third and fourth Model 147As, which were almost identical to the second example, were declared operational, and deployed at Holloman Air Force Base in New Mexico with a Lockheed DC-130 Hercules launch aircraft.

Tests conducted that summer showed the drone was almost invisible to ground radar, and interceptors that were scrambled to find it ended up chasing each other. The only problem was that the drone generated a contrail, which gave it away. A "no-con (no-contrail)" program was initiated to fix the problem in following variants, though apparently it wasn't fitted to the Model 147A. The system injected chlorosulfonic acid into the engine tailpipe when the drone entered hostile territory, which created very tiny ice crystals, forming a transparent contrail. The scheme was effective, although the chlorosulfonic acid was very corrosive, requiring use of high-grade stainless-steel plumbing.

During the Cuban Missile Crisis, on October 27, 1962, a U-2 was shot down over Cuba by an SA-2 and its pilot killed. Afterwards, the Model 147As were authorized for reconnaissance missions in place of the U-2. They were sitting on the runway under the wings of their DC-130 Hercules controller aircraft, its propellers turning, when the word came down from Air Force Chief of Staff Curtis LeMay that the mission was scrubbed. The U-2s were used for reconnaissance over Cuba instead, with missions resuming on 5 November 1962. LeMay wanted to reserve the Fire Fly for later.

Ryan Model 147B Lightning Bug
Although the Fire Fly had yet to be used operationally, the Air Force was enthusiastic enough about the concept to issue contracts for follow-on variants. The USAF ordered nine "Model 147Bs", including two prototypes and seven production aircraft. The Model 147B was designed for high-altitude reconnaissance, with wingspan extended from the 13 feet (4 m) span of the Model 147A to 27 feet (8.2 m), raising the 147B's operational ceiling to 62,500 feet (19 kilometres).

The delivery schedule for the high-altitude Model 147B was several months out, so the Air Force also ordered seven "Model 147Cs", a production version of the 147A, as an interim solution. The Model 147C had a wingspan extended to 15 feet (4.6 m), and incorporated the no-con system.

Three of this batch of Model 147Cs were modified to become special-purpose "Model 147Ds". The 147Ds combined the functions of reconnaissance and the original Firebee mission of aerial target. They were to be used as bait for SA-2 SAMs to obtain data on signals associated with the SA-2. The SAM was targeted by a radar codenamed Fan Song and it was simple enough to pick up its signals with a normal SIGINT aircraft. However, the SA-2 was radio-controlled to the target by a ground command link, with the missile carrying a transponder that sent back a signal to the Fan Song radar to allow tracking. Picking up these signals was hazardous, since they only came on when a missile was launched. The proximity fuze signal was the most dangerous, because it would only be detected moments before the SAM detonated.

A special "SAM sniffer" payload was installed on the Fire Fly to pick up these signals, with the drone relaying the data to an ERB-47 electronics warfare aircraft. An active radar enhancement device was installed to encourage the enemy to take shots at the drone. The three Model 147Ds were delivered in December 1962. The Fire Fly code name had leaked in the meantime, so the new drones were given the codename Lightning Bug.

In July 1963, the Lightning Bugs reached full operational status, though they had yet to fly an operational mission. In late December 1963, the Air Force ordered fourteen more Model 147Bs. By this time, Fidel Castro was threatening to shoot down U-2s flying over Cuba, and in May 1964 a study concluded that the Lightning Bug was the best alternative. However, after information about the proposal leaked to the press, the administration decided to back up the U-2s with the Lockheed A-12, an early version of the SR-71 Blackbird spyplane.

China overflights
The Lightning Bugs remained a potentially valuable reconnaissance asset. The first opportunity for operational use came in August 1964. On 2 August, the destroyer USS Maddox was sailing in international waters off the North Vietnamese coast when it was allegedly attacked by three North Vietnamese PT boats in what is known as the Gulf of Tonkin Incident, and which became a pretext for a major expansion of US involvement in the war in Vietnam. The Johnson Administration feared Red Chinese intervention in the widening war, and decided to use the Lightning Bugs to monitor Communist Chinese activities. The drones were sent with their DC-130 director aircraft to Kadena Air Base on Okinawa to conduct overflights of southern China.

The first Lightning Bug mission took place on 20 August 1964, though there were problems. The DC-130 controlling the mission was loaded with a pair of Model 147Bs. One failed to launch, and was later lost when it fell off its underwing pylon. The second successfully completed its mission over Communist China, flew back to Taiwan, deployed its parachute, and splashed down in a rice paddy. However, after splashdown the drone was dragged over the ground by the parachute, badly damaging the machine. The film payload was recovered intact, and although the drone's navigation hadn't been as accurate as hoped, images of several primary targets were recovered.

A total of five Lightning Bug missions were performed over Red China into early September 1964, with only two of them successful. However, The Nationalist Chinese were very enthusiastic about the Lightning Bugs. They had been flying U-2 spyplanes over mainland China on behalf of the Central Intelligence Agency, and had been suffering increasing losses from SA-2 SAMs.

Lightning Bugs in combat, 1964-1965
In early October, 1964, in order to expand reconnaissance flights to North Vietnam, operations were shifted to Bien Hoa Air Base in South Vietnam. The first Lightning Bug mission flown from Bien Hoa took place on October 11, 1964. A rising number of Model 147B missions were flown over North Vietnam and southern China, with a total of 20 reconnaissance drone flights in 1964. The flights were controlled by the Strategic Air Command from Monkey Mountain in South Vietnam. The controller was stationed at Bien Hoa and the support staff was located at Danang Air Base, The support staff consisted uf two SAC Single Sideband Operators, SSgt Willie V Collier nicknamed "Willie VC" and SSgt Walter J Dawson from the 46th Comm Gp Barksdale AFB. The Communist Chinese were extremely eager to shoot the drones down and managed to destroy one on November 15, 1964. Lightning Bug overflights continued and so did Chinese efforts to intercept them. The Red Chinese succeeded in destroying five drones by mid-April, and on April 20, 1965 put the wrecks of three of them on public display. With every shoot-down, the Chinese issued verbose press reports praising China's "great victory" in shooting down "reconnaissance planes of the imperialist United States".

Although self-destruct charges were considered, it was finally decided against it, and the US simply adopted a policy of "no comment" when asked about the reconnaissance drones. With no American crews lost in the shoot-downs, the US press paid very little attention to the Chinese reports.

Ryan Model 147G
The Air Force had enthusiastically embraced the Lightning Bug and was trying to refine the type, working with Ryan to obtain an improved version of the high-altitude Model 147B, designated the Model 147G. The Model 147G featured a more powerful Continental J69-T-41A turbojet, with 1,920 pounds of thrust (871 kgp), replacing the J69-T-29A used in its predecessors, and a fuselage stretched to 29 feet (8.85 m), to accommodate more fuel. The no-con system was also installed. The first 147G was delivered to the USAF in July 1965. By this time, U-2 over flights of defended airspace had been phased out, with that mission left to the Lightning Bugs. The Model 147G performing its first mission in October 1965, and the Model 147B flew its last mission that December.

Ryan Model 147J
High-altitude reconnaissance over North Vietnam proved somewhat impractical. During the monsoon season, from November through March, the skies were mostly overcast, and even in fair weather smoke or ground haze could obscure reconnaissance targets. For this reason, the Air Force decided to develop a low-altitude version of the Lightning Bug. In October 1965, the service issued a contract to Ryan to develop the Model 147J, a fast-track modification of the Model 147G with a low-altitude navigation system. Low-altitude flight was more demanding than high-altitude flight, since there were many more things to run into, and a number of Model 147J drones were lost in development.

Ryan Model 147E
Among the 77 missions flown by the drones in 1965 were three flights by a special SIGINT modification of the Model 147B, designated the "Model 147E", another "SAM sniffer" variant. Three Model 147Es were sent to South Vietnam in October 1965 as part of a program codenamed UNITED EFFORT. The SIGINT packages failed on all three initial missions, and the Model 147Es were sent back to the US for environmental tests to track down the problem. It turned out that the SIGINT package failed when overheated. The problem was corrected and the Model 147Es were sent back to the combat zone.

On February 13, 1966, on the fourth mission of the Model 147E, the drone was destroyed by an SA-2, but not before it relayed the vital signal data. The US had been desperate to get this data ever since the deployment of the SA-2, and officials claimed that this single flight justified the entire Model 147 program. The information was immediately put to use to develop a simple warning system that would tell the pilot when an SA-2 command signal was turned on, meaning a missile launch was imminent; this device would go into production as the "AN/APR-26".

Ryan Model 147F
Another box, the "AN/ALQ-51 Shoe Horn", had been developed to help deal with the Fan Song radar. The AN/ALQ-51 was a "deception jammer", meaning it manipulated the radar signals to mislead the radar into thinking the target was somewhere other than where it actually was. Since the Americans hadn't actually got their hands on a Fan Song at the time, the box had been tested in the US against a radar simulating a Fan Song. The jammer worked well in tests, but fielding it without sending it up against a real Fan Song was out of the question. The Model 147 was then used to operationally test the box. A single Model 147B was fitted with the package and redesignated "Model 147F", flying a number of missions in July 1966. It was finally lost after almost a dozen SA-2s had been fired at it.

Ryan Model 147N
Although the virtue of the Lightning Bugs was that they were far more expendable than piloted reconnaissance aircraft, by early 1966 an average of four out of five Lightning Bugs failed to return from missions. This was unacceptable even for a relatively cheap drone, and the Air Force asked Ryan to quickly convert ten standard Firebee target drones to expendable decoys. They were fitted with traveling wave tube (TWT) active radar enhancement devices to make them look like a bigger aircraft on radar. There were no provisions for recovery or long-range fuel capacity, since their missions were to be one-way only.

The decoys were designated Model 147N, with the first mission performed by one alongside a Model 147G on March 3, 1966. The two drones followed a parallel path until they reached the target area, where they diverged. North Vietnamese air defenses tracked the "brighter" 147N instead of the 147G, which was recovered. As an added bonus the 147Ns resulted in a few "kills" of North Vietnamese fighter aircraft. One fighter ran out of fuel when the pilot chased the drone out to sea, and other fighters were lost due to "friendly fire" accidents while hunting the drones.

The decoys worked so well that the Air Force ordered another batch of ten, with a few minor improvements, and designated them Model 147NX. The initial Model 147Ns had been programmed to turn back and head for home in order to simulate a normal operational drone flight profile, and a few of them surprisingly did make it back, even with their limited fuel supply. They crashed, since they were not designed to be recovered, but the recovery system was not expensive and so the Model 147NX was fitted with recovery parachutes and gear, as well as a cheap camera. If the decoy survived the mission, it might provide useful intelligence.

Lightning Bugs over South-east Asia 1966
By March 1966, the low-altitude Model 147J was ready for operational service. The Model 147J featured a "barometric altitude control system (BLACS)", a dual camera payload featuring a front-to-back scan camera, a side-to-side scan camera and a new paint job. The high-altitude Lightning Bugs had been painted black, but since that was a high-visibility color at low altitude, the Model 147Js were painted gray on top and white underneath.

The fast-moving drones streaked low over the ground, making them difficult targets and increasing their odds of returning from a mission. Up to that time, the drones had parachuted to the ground when they returned, but were often damaged by the impact, and so the USAF came up with a scheme where a big Sikorsky CH-3 Jolly Green Giant helicopter snagged the parachute in mid-air and winched it in. This proved effective, with an eventual 2,655 successful recoveries in 2,745 attempts.

A total of 105 drone missions were flown over North Vietnam and Communist China in 1966. Most of these were 147G flights, along with some 147Js, as well as the 147E and 147F SIGINT missions and the 147N and 147NX decoys. One of the 147Js actually took a picture of an SA-2 SAM streaking past it.

Ryan Model 147NP,147NRE and 147NQ
The USAF was very pleased with the low-altitude Model 147J and feared there would not be enough of them to keep up with operational attrition. Some Model 147Gs were modified to the 147J configuration, but the USAF also asked Ryan to come up with a new low-altitude reconnaissance drone on a fast track. The new variant was the Model 147NP, which was derived from the initial Model 147A. The Model 147NP had the older J69-T-29A engine and a 15 foot (4.8 m) wingspan, plus a fuselage stretched to 28 feet (8.5 m).

While Ryan was working on the Model 147NP, the Air Force also came forward with an urgent requirement for a low-altitude night reconnaissance drone. Four Model 147NPs were pulled from production and modified as Model 147NREs, where "NRE" stood for "night reconnaissance electronic". The Model 147NREs had a dual-camera payload synchronized to a bright white strobe light fitted into the drone's belly. The strobe lit up the sky when it went off.

Both the 147NREs and the 147NPs went into action in Vietnam at about the same time, in the spring of 1967. The first 147NRE mission was in late May, with the first 147NP mission following a week later. The Model 147NREs were painted black as appropriate to their night mission, while the Model 147NPs were painted in jungle camouflage colors.

The Model 147NPs performed as desired, but the Model 147NREs did not quite meet expectations. The "footprint" of the strobe light was fairly small, and the drone's navigation system lacked the accuracy to put the cameras precisely on target. However, the Air Force did obtain useful intelligence from the drone's cameras even when they were not on target, as well as some minor psychological warfare effect from the startling bright strobe flashes, and felt that the concept was worth further development.

Another low-altitude reconnaissance variant was derived from the Model 147NP, the Model 147NQ. The main distinction was that instead of an automatic guidance system, it was radio-controlled by a crewman on its DC-130 launch aircraft.

Ryan Model 147H
Despite the Air Force's attention to the low-altitude mission, the service hadn't given up on using Lightning Bugs for high-altitude reconnaissance, and in fact continued to improve the high-altitude variants. The result was the Model 147H, the third-generation high-altitude Lightning Bug. The Model 147H had the more powerful J69-T-41A engine of the Model 147G, a lighter airframe, and a wing further stretched to 32 feet (9.8 m). The wings had internal fuel tanks to increase range. The Model 147H was capable of reaching altitudes of 65,000 feet (19.8 kilometres), and had a new camera payload that provided both greater area coverage and better resolution.

The "stealthy" features that had been originally built into the Lightning Bug had been proving less and less effective, and so the Model 147H was designed with new features to improve survivability, including a radar warning receiver (RWR) to alert the drone if it was illuminated by fighter or SAM radars, an improved guidance system that sent it into a right turn when alerted by the RWR, an ECM box named "Rivet Bouncer" to jam the SA-2 Fan Song radar, a coating in the jet intake to reduce radar reflectivity and an improved no-con system.

The Model 147H was more optimized for its mission than earlier Model 147s, many of which had been modified and put into service as quickly as possible. In contrast, the Model 147H took two years to develop, with the first operational flight in March 1967. Model 147Gs continued high-altitude missions in parallel with the Model 147H drones until the Model 147Gs were phased out in August 1967. Although the 147H drones suffered losses, their survivability did prove better than that of the 147B and 147G.

Ryan Model 147S
The Air Force also pursued a refined solution for the low-altitude mission, and "refinement" meant balancing optimization for the mission against cost. The initial low-altitude drone, the Model 147J, had been derived from the high-altitude Model 147B and retained the 147B's wide wings. These were a drawback at low altitudes, since they reduced the drone's manoeuvrability. The new optimized low-altitude drone, the Model 147S, had a J69-T-41A engine and featured the original Firebee wings with a 13 foot (4 m) wingspan, which had the benefit that they were also cheaper. The fuselage was stretched to a length of 29 feet (8.8 m).

The Model 147S carried a single camera that cost less but provided better coverage than the earlier dual-camera payloads. At typical operating altitudes, the camera system of the 147S could image a strip of land 60 miles (96 kilometres) long, with a resolution of up to 1 foot (30 centimetres), or even six inches (15 centimetres) under optimum conditions. Cost of a production Model 147S was about $160,000 USD in contemporary dollars, which was about 60% of the cost of a Model 147G or 147H.

The Model 147S drones were built in a number of different production "blocks". The initial 147S block was designated the "Model 147SA", and the subtype performed its initial operational flight in December 1967.

The Air Force was impressed by the results of the Model 147SA missions, and so ordered a second batch of "Model 147SBs". The Model 147SB carried a "multiple altitude control system (MACS)" that allowed it to shift in flight between three preprogrammed altitudes ranging from 1,000 to 20,000 feet (300 meters to 6,100 meters), making it much more unpredictable. It also had improved gyros to permit tighter turns. Initial flights began in March 1968, with the Model 147SAs then being phased out by attrition.

The next block of Model 147S family was the "Model 147SRE", which was intended for the night reconnaissance role. Instead of the white-light strobe used on the Model 147NRE, the 147SRE used an infra-red strobe and infra-red film. The infra-red strobe was barely noticeable from the ground. The 147SRE also featured an improved guidance system, featuring Doppler navigation radar. The first Model 147SRE mission was flown in November 1968. Although the 147SRE performed well, photo interpreters found the infra-red images difficult to inspect and sometimes failed to spot targets.

The low-level 147S flights were "exciting" by the standards of robot warfare. One suffered a malfunction in its flight-control computer and decided to fly at an altitude of 150 feet (45 m) instead of 1,500 feet (450 m) as planned. The drone made it back safely, though photo interpreters were startled to find out that the images included a picture of a power line tower, taken from underneath the power lines. The picture was posted on the unit bulletin board, with a caption provided by the commander: "The FAA frowns on this bullshit!"

Losses were heavy at the 1,000 to 1,500 foot (300 to 450 meter) altitude set for early Model 147S missions, so the flight altitude was changed to 500 feet (150 m). The drones were used in missions over Hanoi and Haiphong, which had heavy air defenses. One Model 147S took a picture of an SA-2 streaking past, followed by a picture of the missile exploding, and then due to an autopilot programming error the drone skirted a ridgeline, just missing the treetops.


 * The fourth production variant of the Model 147S family was the "Model 147SC", which featured an improved Doppler radar navigation system with digital controls for greater flight accuracy. Initial operational flight of the Model 147SC, known as the "Buffalo Hunter" by USAF crews, was in January 1969. Of the hundreds of Model 147S drones obtained by the Air Force, most were Model 147SCs, which would eventually fly almost half the total number of Lightning Bug missions.

The US Navy also decided to get into the reconnaissance drone business for a while. They ordered a batch of Model 147SCs modified for ship launch using a RATO booster. The Navy Lightning Bugs were designated "Model 147SK". They were generally similar to the 147SC, except that they had a 4.6 m wingspan. First operational flight was in November 1969. After RATO launch, a Model 147SK was guided to an initial checkpoint under radio control from a Grumman E-2A Hawkeye aircraft. From that checkpoint, the drone conducted the rest of the flight with its autonomous navigation system, and then was recovered by helicopter. The Navy performed several dozen operational flights, which they referred to as "Belfrey Express" for some obscure reason, with the last flight in May 1970. The Navy did not pursue the Lightning Bug further.

Ryan Model 147T
Despite the fact that most of the Lightning Bug missions were now low-altitude flights, the Air Force still regarded the high-altitude mission as important enough to obtain a refined version of the Model 147H, the Model 147T. The main improvement was a more powerful engine, the Teledyne CAE J100-CA-100 with 2,800 pounds of thrust (1,270 kgp), allowing the drone to operate at higher altitudes, up to almost 75,000 feet (23 kilometres). The initial 147T mission was in April 1969, but in practice high-altitude reconnaissance missions continued to decline, with the last Model 147T missions over South-east Asia performed during June 1971.

However, in April 1969, a Lockheed EC-121 Super Constellation SIGINT aircraft was shot down in international airspace by North Korean fighters, killing all 31 crew members on the aircraft. The incident led to consideration of using an unmanned drone to do the SIGINT job, and the result was the Model 147TE or Combat Dawn UAV. The first operational flight of the Model 147TE was in February 1970, though this flight and those that followed over two months were really just evaluation tests. The tests proved successful, and an order for fifteen production 147TE drones followed, with the first operational flight of a production 147TE in October 1970.

The Model 147TEs did not overfly hostile airspace. They stayed well out to sea at relatively high altitude, or cruised along the border between North and South Korea. They could fly under their own guidance, or be controlled by their DC-130 launch aircraft. The drones relayed SIGINT data over a datalink to ground stations for analysis. This datalink technology would be developed for use in other reconnaissance aircraft, such as the Lockheed U-2 and the Beech RC-12 Guardrail.

Late in the Model 147TE program, underwing external tanks were added to improve time on-station from five to eight hours. In 1973, an updated version, the Model 147TF, with the external tanks as standard and improved SIGINT gear, went into operation. Almost 500 missions were flown by the Models 147TE and 147TF between 1970 and 1975.

The last days of the Lightning Bugs 1969-1975
In 1969, the US Air Force redesignated the model number (see chart below), although the Ryan number kept their popularity. Back in South-east Asia, Lightning Bugs continued their overflights. A number of missions focused on a prisoner of war (POW) camp near the city of Son Tay in North Vietnam, in order to determine if US POWs were being held there. The drone overflights of the Son Tay camp were halted in favor of overflights with the Lockheed SR-71 Blackbird spyplane, since US intelligence officials felt that too many drone overflights might make the enemy suspicious. Apparently they did, since when the camp was finally raided on November 21, 1970 during Operation Ivory Coast, there were no American POWs there. It was a disappointing result to one of the more daring operations of the war.

By this time, the Model 147 program was beginning to become public knowledge. Aviation Week magazine carried an article on the drones that November, though it was based on informal and unconfirmed information. The following spring, the Air Force released pictures of the drones along with a very general statement that they were used for reconnaissance. No technical or operational details were released.

The numbers of drone missions continued to increase through 1971 and 1972. The North Vietnamese conducted an all-out invasion South Vietnam in the spring of 1972, which was broken by American air power. US President Richard Nixon then retaliated with an all-out bombing campaign against North Vietnam, codenamed Operation Linebacker, to persuade the North Vietnamese to negotiate. The two sides seemed to be close to an agreement, but in December 1972 the talks collapsed, and President Nixon ordered the Operation Linebacker II campaign which continued into the final days of 1972. An agreement was reached in January 1973, and the bombing stopped completely.

The Model 147SC was the workhorse for low-altitude reconnaissance during this time. A modified version, the Model 147SC/TV, was introduced as well in the spring of 1972. This featured a TV camera that relayed imagery to the DC-130 drone controller aircraft.

A variant of the Model 147N, the Model 147NC, was also flown during this time. It had been designed a few years earlier to fly at medium altitude, carrying a "chaff" dispenser under each wing to jam enemy radar systems. It had originally been intended to support bombing raids over North Vietnam, but air strikes on North Vietnam were drastically scaled back in 1968 and the Model 147NC was not used in its intended role. When bombing was scaled back up in 1972, chaff was dropped by piloted F-4 Phantom fighters instead. However, during the "political offensive" of that year, Model 147NCs were used to drop propaganda leaflets. The project was codenamed Litterbug, but the troops called them "bullshit bombers".

Some sources mention a Model 147NA, which was apparently an early version of the Model 147NC with a less sophisticated guidance system, and a low-level version designated the Model 147NC(M1).

The Model 147H was on the way out by this time, performing its last mission in September 1972. The Soviets had updated the SA-2's electronics, and so American electronic countermeasures needed to be updated as well. Cameras were replaced by a "SAM sniffer" payload, and a Model 147H flight on September 28 was able to obtain the necessary data before the drone was destroyed by an SA-2.

Reconnaissance flights continued after the signing of the peace treaty, in order to ensure that the North Vietnamese were honoring their side of the bargain. New drone variants were introduced as well. The Model 147SD featured external underwing tanks; a substantially more accurate navigation system; and a new cooling system to deal with tropical environmental conditions. The Model 147SDL featured a navigation system that obtained position information from the LORAN radio location network, providing the drone with greater accuracy.

By this time, drone technology and operational practice had been refined. While the Model 147SC drones had been designed to survive an average of 2.5 missions, in practice the average was much higher. One, named "Tom Cat", performed a record 68 missions.

The Lightning Bug program had proven highly successful. A series of fast-track adaptations of an existing target drone resulted in a system whose effectiveness was beyond expectations, even with guidance technology that was extremely crude by modern standards. However, the Lightning Bugs could not affect the course of the war. In the end, their reconnaissance clearly showed that the North Vietnamese were violating their agreement with the Americans on a massive scale, but the US wanted no more of an endless war, and when the final North Vietnamese push jumped off in early 1975, the US did little to stop it. Saigon fell on April 30, 1975, and the war was effectively over.

Despite its effectiveness, so was the Lightning Bug program. The last Model 147S drone flight was on the day Saigon fell. The Model 147TF flights continued until June 1975, and then most of the surviving drones were stockpiled.

Post-Vietnam use
A handful of Model 147SC / AQM-34L drones were fitted with upgraded avionics in 1972 and redesignated YAQM-34U, and would later become BGM-34C multi-purpose drones.

In the early 1970s, the airframe of one Model 147G was reinforced by the Air Force Flight Dynamics Laboratory (FDL) to investigate high manoeuvrability flight. The modified drone was originally designated the FDL-23 and later the XQM-103. A few test flights were performed, with the machine able to perform 10-G turns in its final configuration.

In the late 1970s, a number of 147NC AQM-34H/AQM-34J drones were converted to an improved countermeasures specification, with both chaff dispensers and active jamming gear, and redesignated Model 255 / AQM-34V. First flight was in 1976. About 44 were converted, to be joined by about 16 new-build machines. They joined the other Lightning Bugs in storage in 1979.

A number of reconnaissance Firebees were delivered to the Israelis in the early 1970s. These UAVs were fitted to Israeli specifications for low-altitude observation, and were designated Model 124I. The Israelis called them Mabat, meaning "observation". They were ground-launched with a RATO booster and recovered in mid-air by helicopter, saw service in the 1973 Yom Kippur war and later conflicts, and were not retired until the mid-1990s.

Firebees are still in service as targets, and so it is unsurprising that they are still being configured for reconnaissance missions. In the late 1990s, Teledyne-Ryan configured two Firebees using company funds with cameras and communications electronics to provide real-time intelligence for battlefield target acquisition and damage assessment. These two UAVs, which were named Argus, were used in a USAF "Green Flag" exercise to relay images in real-time from the test range in Nevada to USAF officers in Florida.

Five BQM-34-53 Extended Range Firebees were also used to lay chaff corridors during the American intervention in Iraq in the spring of 2003. The drones were modernized by Northrop Grumman in a fast-response program earlier in the year, being fitted with chaff dispensers and other improvements. They had GPS-based programmable waypoint guidance systems, but it is unclear if they were added by the upgrade program. They were delivered for service in charcoal-black colors.

There was only one DC-130 drone launcher aircraft left in the US military's inventory at the time, and since it was grounded due to a malfunction, two Firebees were ground-launched on the first night of the operation. The other three were air-launched by the DC-130 on the second night of the operation. They flew until they ran out of fuel and crashed. Iraqi TV took footage of the wrecks and broadcast it, saying they were wrecks of piloted aircraft.

The last Firebee was delivered in 2002, but Northrop Grumman is hoping for new orders, and the company is implementing upgrades for existing machines, such as GPS programmable waypoint navigation systems and satellite links. Given the maturity and low cost of the Firebee, it would not be surprising if it remained in service much longer, at least for simpler missions.

Mission summary
A total of 3,435 Lightning Bug missions were flown against Communist China, North Vietnam, and North Korea, with the mission breakdown by year as follows:
 * 1964: 20
 * 1965: 77
 * 1966: 105
 * 1967: >100
 * 1968: 340
 * 1969: 437
 * 1970: >400
 * 1971: 406
 * 1972: 570
 * 1973: 444
 * 1974: 518 (includes flights in first half of 1975)

Almost half of the missions were flown by the Model 147SC, of which about a thousand were built. 578 drones of all types were lost, with over half shot down and the rest lost in various accidents. It is something of a compliment to the usefulness of the Model 147 that the Chinese used the Lightning Bugs shot down over their territory to copy the basic Firebee design and produce it themselves.

Variants

 * 147A: Initial variant, minor mod of Firebee with stretched fuselage.
 * 147C: 147A update, no-contrail system, 4.6 m wingspan.
 * 147D: Modified 147C to "sniff" SAM proximity fuze emissions.
 * 147B: First high-altitude variant, 8.2 m wingspan.
 * 147G: 147B update, fuselage stretch, no-contrail system, new engine.
 * 147H: Optimized high-altitude drone, 9.8 m wingspan.
 * 147T: Improved 147H with more powerful engine.
 * 147E: 147B with 147C SAM "sniffer" payload.
 * 147F: One-off 147B mod to test SA-2 countermeasures.
 * 147J: Fast-track mod of 147B for low-altitude reconnaissance.
 * 147TE: ELINT version of 147T, used in Korea.
 * 147TF: Improved 147TE with external tanks.
 * 147N: Expendable decoy derived directly from Firebee.
 * 147NA: Chaff dispenser variant.
 * 147NC: Chaff / leaflet dispenser variant.
 * 147NC(M1): Low-level version of 147NC.
 * 147NX: Expendable decoy with secondary reconnaissance capability.
 * 147NP: Fast-track low-altitude drone derived from 147A.
 * 147NRE: Night reconnaissance modification of 147NP.
 * 147NQ: Radio-controlled version of 147NP.
 * 147SA: Optimized low-altitude 147, Firebee wings, stretched fuselage.
 * 147SB: 147S variant with multiple-altitude control system.
 * 147SRE: Night reconnaissance 147S with infra-red strobe, Doppler radar.
 * 147SC: Improved Doppler navigation system, largest number produced.
 * 147SC/TV: 147SC with TV camera.
 * 147SK: Naval 147SC with 4.6 m wingspan and RATO launch.
 * 147SD: 147SC with improved navigational system, external tanks.
 * 147SDL: 147SD with LORAN guidance backup.

Military redesignation numbers (Post 1969)

 * AQM-34N: 147H
 * AQM-34G (chaff dispensing): 147NA/NC
 * AQM-34H (leaflet dispensing): 147NC
 * AQM-34J: 147NC(M1)
 * AQM-34L: 147SC
 * AQM-34M: 147SD
 * AQM-34K: 147SRE
 * AQM-34P: 147T
 * AQM-34Q: 147TE
 * AQM-34R: 147TF