The Final Mission: The USAF’s QF-4 Target Drones by Mark Munzel
Wearing the "stars and bars" insignia of the US Air Force, an F-4 Phantom cruises in level flight. Unobserved, another USAF aircraft falls in trail behind the Phantom and fires an air-to-air missile at it. The F-4 performs an aggressive slice in hopes of evading the missile, releasing countermeasures all the while. But it’s no use – tracking unerringly, the missile cuts the F-4 in half. Debris rains from the resulting fireball, but there are no parachutes.
What’s going on? Why is one US fighter being shot down by another? Strange as it sounds, this is a typical day for the 82 Aerial Target Squadron (ATRS). The 82nd flies the USAF’s last active-duty Phantoms as full-scale aerial targets (FSATs) for weapons tests.
They Shoot Airplanes, Don’t They?
Under United States law (Title 10, Section 2366 of the U.S. Code) a missile system must undergo lethality testing before it can enter full-scale production. This means it must be fired at a combat-configured target, which for air-to-air or surface-to-air missiles is a full-size, fully capable aircraft. The cost and hazards of using a manned aircraft from the active-duty inventory for this purpose are obvious. Instead, the target is an unmanned FSAT drone. As one 82 ATRS pilot summarizes it, "the F-4 is dying, to give birth to new weapons systems."
In support of U.S. test and evaluation activities, Phantom drones also act as targets for non-lethal tests of missiles, radar and other sensors, and defensive systems. They also support Air Force and Navy training, such as "Combat Archer" missile shoots.
Both services also employ sub-scale target drones, which are less costly to operate than FSATs. But only a full-scale target offers the flight characteristics, performance envelope – including subsonic and supersonic flight at altitudes up to and above 50,000 feet – endurance, radar and infrared (IR) signatures, and damage resistance of a real aircraft.
The QF-4 – the "Q" prefix signifies a drone conversion – is the latest of many distinguished Air Force fighters to adopt the drone role at the end of its days, following the Convair PQF-102 Delta Dagger (used from 1974 to 1985), North American QF-100 Super Saber (1983-1992), and Convair QF-106 Delta Dart (1990-1998). The F-4 was a logical choice to succeed the QF-106. Hundreds of surplus Phantoms were available following the type’s phase-out. Its suitability for drone use had been proven by the Navy, which had operated QF-4s in its own drone program since 1972. And as the QF-106 had suffered several accidents due to landing-gear failure, the F-4s’s ruggedness and reliability were selling points.
The Making of a Drone
QF-4 conversions are performed by BAE Systems in Mojave, California. Over 230 Phantoms have been "droned" since 1995, and conversions will continue through 2011 if all contract options are exercised. Production at first concentrated on F-4E tactical fighters and F-4G "Wild Weasel" defense-suppression aircraft. As the last models retired from active duty, these airframes were in good condition and still had a military supply chain. The earliest conversions included a few RF-4C photo-reconnaissance variants, which were found harder to control than later models because they lacked slats. Nonetheless, with no suitable F-4Gs left and stocks of candidate F-4Es depleted, RF-4C conversions resumed in 2007.
Candidate aircraft are taken from storage at the Aerospace Maintenance and Regeneration Group, at Davis-Monthan Air Force Base (AFB), Arizona. Following depot maintenance, the aircraft are flown to Mojave, where the drone conversion is performed. Completed aircraft are ferried to Tyndall AFB, Florida for Air Force acceptance tests. The process takes about seven months from storage at AMARG to active status and costs about $800,000 U.S. per aircraft.
The QF-4 conversion adds a digital control system for remote operation of the aircraft’s steering, throttles, flaps, landing gear, brakes, braking parachute, and tailhook. Also fitted are a vector Doppler scoring system, transponder, second autopilot, and GPS for navigation and formation-keeping in remote flight. Non-essential equipment such as the F-4E’s 20mm cannon is replaced with ballast, while unused avionics like radar are left aboard but disabled. Finally, the wingtips and tail are painted orange to distinguish the aircraft as a drone.
The QF-4s are assigned to the 82nd ATRS at Tyndall, part of the 53rd Weapons Evaluation Group. The squadron operates full-scale and sub-scale drones over Tyndall’s air weapons range in the Gulf of Mexico. Detachment 1 of the 82 ATRS, based at Holloman AFB, New Mexico, provides target services for the Army and civilian contractors over the Army’s White Sands Missile Range (WSMR).
Flying the QF-4
Both 82 ATRS and Det 1 maintain a few "primary flier" aircraft for manned flight, approved for up to 300 flight hours. Other FSATs are cleared for 100 hours, and are kept ready for unmanned flight with non-essential items like ejection seats removed, or held in non-flying storage.
Despite having over 60 aircraft on strength, 82 ATRS has a small military staff: six USAF pilots split between the two bases and a few sergeants to oversee maintenance. All other personnel are civilians employed by Lockheed Martin, including pilots, ground controllers, and maintainers. All are ex-military with a tremendous level of expertise – for example, contract pilots typically have over 1000 F-4 flying hours.
QF-4s are almost always flown with a pilot aboard, unless a weapons launch will occur. Usually he does not touch the controls but stands ready to take over if ground control is lost or the aircraft departs. The pilots fly the aircraft themselves on chase missions and to maintain proficiency.
The aircraft are controlled remotely by the Gulf Range Drone Control System (GRDCS) at Tyndall or the Drone Formation Control System (DFCS) at WSMR. Drone controllers have a flight instrument display on a monitor, but no direct visual contact with the aircraft. A controller may fly, using a joystick and keyboard instead of stick, throttles, and rudder pedals; however, most test and evaluation flights are steered by computer. This allows a test to be flown within exact parameters and repeated exactly if necessary. Up to six QF-4 aircraft can be controlled in formation, using GPS to maintain each in position relative to the flight track.
The programmed flight track may include an automatic landing, but if the telemetry signal is degraded or the aircraft is damaged, a Ground Mobile Control System (GMCS) is used to perform a visual landing. GMCS is a panel van with two control positions on the roof. It is parked by end of the runway so the controllers can watch the aircraft as they steer it. One controller controls pitch and throttles, while the other controls bank and heading. Two controllers are needed due to the workload – where an onboard pilot would sense the aircraft’s attitude and speed, the controllers must interpret it from instruments.
Missile vs. Aircraft
Typically, several practice runs precede a test mission, to confirm that all test parameters are being met – many trial runs are less expensive than one failed test. If a missile will be fired at the drone, the actual test will use a NULLO aircraft – NULLO stands for "not under live local operation" but is also Latin for "zero," the number of crew aboard. The NULLO aircraft carries a destruct charge (the warhead from an AIM-9 missile) to ensure the jet’s demise if it is damaged during the test or control is lost.
Accompanied by a manned chase plane, the drone is launched from the 7,000x300-foot "droneway" at Tyndall or the 11,000x300 foot one at Holloman, heading south to avoid populated areas. At Tyndall, two DeHavilland Canada E-9A aircraft are launched as well. These converted Dash-8 airliners use sideways-looking airborne radar to establish a "shoot box" that will not endanger civilian boats on the water below the Gulf Range.
To evade the weapon system under test, the drone’s flight profile may include defensive maneuvers (including 6-G turns and vertical maneuvers), chaff and flare releases, and radar jamming. Test results are recorded by telemetry and, at WSMR, by optical systems. If the drone is destroyed, its wreckage falls onto the range. But if it survives and the chase pilot confirms it is intact, the aircraft is recovered at base. A straight-in approach is made from the south with the hook down, and the aircraft is stopped by an arresting cable.
A NULLO drone will usually complete three or four missions before being destroyed. Except during a lethality test, the missiles fired may lack warheads and the drone’s flight track may be programmed to evade a direct hit. This saves the cost of replacing the drone and prolongs the life of the QF-4 inventory. The drone’s onboard scoring system will tell if the missile achieved "kill" parameters. Occasionally a lethality test will fail to take down the aircraft, an occurrence that confirms the importance of Title 10 testing. The QF-4 attrition rate is about one aircraft per month at Tyndall and one to four per year at Holloman.
"Live fire" projects for Tyndall’s QF-4s have included Operational Test and Evaluation (OT&E) of Raytheon’s AIM-9X Sidewinder and AIM-120 AMRAAM missiles. Holloman drones have participated in OT&E of Lockheed Martin’s Patriot Advanced Capability (PAC-3) air defense missile and the F-22 Raptor. But more than missiles are tested: a Holloman QF-4 has flown development tests of the BAE Systems Common Missile Warning System, which can identify surface-to-air missiles launched at an aircraft and automatically release suitable countermeasures.
QF-4 pilots are fond of their aircraft and do not enjoy seeing one depart on a one-way, final mission. But they are philosophical about the loss, noting, "It’s a better way for an aircraft to die than rotting away in the ‘Boneyard’ or on a pole. The taxpayer is getting his money’s worth from these aircraft."
After 13 years, the number of F-4 airframes at AMARG that may be droned without excessive rework is shrinking. Moreover, the QF-4’s ability to represent the performance and signatures of modern fighter aircraft decreases with each new design that appears. The QF-4’s successor as a full-scale target looks set to be the QF-16, starting around 2014.
While on test duties, QF-4 drones are rarely seen away from their Tyndall and Holloman bases. But the people who fly and maintain the Phantoms are extremely proud of their aircraft, the last operational US tactical fighter from the Vietnam era.
In 2004, 82 ATRS personnel sought to add the QF-4 to the USAF’s Heritage Flight program, to fill a gap in historical coverage between World War Two and Korean War warbirds and modern fighters. Six QF-4Es were repainted in camouflage schemes from the F-4’s operational service, four at Tyndall and two at Holloman. Following USAF approval, they took part in Heritage Flight formations at a few airshows on each coast in 2005. In 2006, the QF-4s received Heritage Flight funding from Air Combat Command – the 2005 flights had been funded from the 53 WEG operating budget! – allowing the QF-4s to appear at approximately 20 shows. As well, a simple QF-4 solo display routine was introduced.
Except for their camouflage, the Heritage Flight QF-4Es are standard "primary flier" drones and are used for normal 82 ATRS operations when not at airshows. As the first six aircraft began to run out of flight hours in 2007, a new batch was painted. These aircraft all wear the same Southeast Asia scheme to simplify maintenance.
While the Heritage Flight QF-4s salute those who served in the 1960s and ‘70s, they are also a reminder why full-scale targets are important. Early in its USAF career, the F-4 was hobbled in air-to-air combat when its AIM-4 Falcon and AIM-7 Sparrow missiles failed to work properly in real engagements over North Vietnam. Today, the QF-4’s final duty is to ensure such failures never happen again.
Thanks to Kevin Jackson, Paul Filmer, and Gary Chambers for the additional photos. Special thanks to the F-4 Phantom II Society for providing photographic access to 82 ATRS and "The Det" over the years.