The Lockheed U-2, nicknamed Dragon Lady, is an American single-jet engine, high altitude reconnaissance aircraft operated by the United States Air Force and previously flown by the Central Intelligence Agency.
It provides day and night, high-altitude (70,000 feet, 21,300 meters), all-weather intelligence gathering.
Lockheed Corporation originally proposed it in 1953, it was approved in 1954, and its first test flight was in 1955.
It was flown during the Cold War over the Soviet Union, China, Vietnam, and Cuba.
In 1960, Gary Powers was shot down in a CIA U-2C over the Soviet Union by a surface-to-air missile (SAM).
Major Rudolf Anderson Jr. was shot down in a U-2 during the Cuban Missile Crisis in 1962.
U-2s have taken part in post-Cold War conflicts in Afghanistan and Iraq, and supported several multinational NATO operations.
The U-2 has also been used for electronic sensor research, satellite calibration, scientific research, and communications purposes.
The U-2 is one of a handful of aircraft types to have served the USAF for over 50 years, along with the Boeing B-52, Boeing KC-135, Lockheed C-130 and Lockheed C-5.
The newest models (TR-1, U-2R, U-2S) entered service in the 1980s, and the latest model, the U-2S, had a technical upgrade in 2012.
The design that gives the U-2 its remarkable performance also makes it a difficult aircraft to fly.
Martin Knutson said that it “was the highest workload airplane I believe ever designed and built you’re wrestling with the airplane and operating the camera systems at all times”, leaving no time to “worry about whether you’re over Russia or you’re flying over Southern California”.
The U-2 was designed and manufactured for minimum airframe weight, which results in an aircraft with little margin for error.
Most aircraft were single-seat versions, with only five two-seat trainer versions known to exist.
Early U-2 variants were powered by Pratt & Whitney J57 turbojet engines.
The U-2C and TR-1A variants used the more powerful Pratt & Whitney J75 turbojet.
The U-2S and TU-2S variants incorporated the more powerful General Electric F118 turbofan engine.
High aspect ratio wings give the U-2 glider-like characteristics, with an engine out glide ratio of about 23:1, comparable to gliders of the time.
To maintain their operational ceiling of 70,000 feet (21,000 m), the early U-2A and U-2C models had to fly very near their never-exceed speed (VNE).
The margin between that maximum speed and the stall speed at that altitude was only 10 knots (12 mph; 19 km/h).
This narrow window is called the “coffin corner”, because breaching either limit was likely to cause airflow separation at the wings or tail.
For most of the time on a typical mission the U-2 was flying less than five knots (6 mph; 9 km/h) above stall speed.
A stall would cause a loss of altitude, possibly leading to detection and overstress of the airframe.
The U-2’s flight controls are designed for high-altitude flight; the controls require light control inputs at operational altitude.
However, at lower altitudes the higher air density and lack of a power-assisted control system make the aircraft very difficult to fly control inputs must be extreme to achieve the desired response, and a great deal of physical strength is needed to operate the controls.
The U-2 is very sensitive to crosswinds, which, together with its tendency to float over the runway, makes the aircraft notoriously difficult to land.
As it approaches the runway, the cushion of air provided by the high-lift wings in ground effect is so pronounced that the U-2 will not land unless the wings are fully stalled.
A landing U-2 is accompanied on the ground by a chase car, which is driven by a second U-2 pilot who assists the landing U-2 by reporting the aircraft’s altitude and attitude.
In practice, once the aircraft has descended to an altitude of two feet (0.61 m) above the runway the pilot initiates a stall, and the aircraft falls from this height.
Chase cars and live calling of aircraft altitude are necessary because the landing gear is not designed to absorb the weight of the aircraft when falling from altitudes much above two feet (0.61 m).
Instead of the typical tricycle landing gear, the U-2 uses a bicycle configuration with a forward set of main wheels located just behind the cockpit and a rear set of main wheels located behind the engine.
The rear wheels are coupled to the rudder to provide steering during taxiing.
To maintain balance while taxiing and take-off, two auxiliary wheels called “pogos” are attached under the wings.
These fit into sockets underneath each wing at about mid-span and fall off at take-off.
To protect the wings during landing, each wingtip has a titanium skid.
After the U-2 comes to a halt, the ground crew re-installs the pogos, then the aircraft taxis to parking.
Because of the high operating altitude and the cockpit’s partial pressurization, equivalent to 28,000 feet (8,500 m) pressure altitude, the pilot wears a partially pressurized space suit, which delivers the pilot’s oxygen supply and provides emergency protection in case cabin pressure is lost.
While pilots can drink water and eat various liquid foods in squeezable containers through a self-sealing hole in the face mask, they typically lose up to 5% of their body mass on an eight-hour mission.
Most pilots chose to not take with them the suicide pill offered before missions.
If put in the mouth and bitten, the “L-pill” containing liquid potassium cyanide would cause death in 10–15 seconds.
After a pilot almost accidentally ingested an L-pill instead of candy during a December 1956 flight, the suicide pills were put into boxes to avoid confusion.
When in 1960 the CIA realized that a pill breaking inside the cockpit would kill the pilot, it destroyed the L-pills, and as a replacement, its Technical Services Division developed a needle poisoned with a powerful shellfish toxin and hidden in a silver dollar.
Only one was made because the agency decided if any pilot needed to use it the program would probably be cancelled.
Like the suicide pill, not all pilots carried the coin, and Knutson did not know of any that intended to commit suicide; he carried it as an escape tool.
To decrease the risk of developing decompression sickness, pilots breathe 100% oxygen for an hour prior to taking off to remove nitrogen from the blood.
A portable oxygen supply is used during transport to the aircraft.
Since 2001, more than a dozen pilots have reportedly suffered the effects of decompression sickness, including permanent brain damage in nine cases; initial symptoms include disorientation and becoming unable to read.
Factors increasing the risk of illness since 2001 include longer mission durations and more cockpit activity.
Conventional reconnaissance missions would limit pilot duties to maintaining flight paths for camera photography.
Operations over Afghanistan included more real-time activities, such as communication with ground troops, increasing their bodies’ oxygen requirements and the risk of nitrogen bubble formation.
U-2 pilots now exercise during oxygen pre-breathing.
In 2012, modifications were initiated under the Cockpit Altitude Reduction Effort (CARE), increasing the cabin pressure from 3.88 psi to 7.65 psi, a 15,000-foot (4,600 m) altitude equivalent.
The urine collection device also was rebuilt to eliminate leakage.
Initial production, single-seat; Pratt & Whitney J57-P-37A engine; 48 built
Proposed missile warning patrol aircraft; not built.
Enhanced single-seat model with Pratt & Whitney J75-P-13 engine and modified engine intakes
2-seater used for various IR detection programs, not a trainer aircraft.
Enhanced 2-seat trainer.
Aerial refuelling capable, J57-powered
Aerial refuelling capable, J75-powered
C-models modified with reinforced landing gear, added arresting hook, and lift dump spoilers on the wings for U.S. Navy carrier operations; three converted
Re-designed airframes enlarged nearly 30 percent with under wing pods and increased fuel capacity; 14 built
Enhanced two-seat R-model trainer; one built
Proposed U.S. Navy maritime surveillance R-model; two built
A third production batch of U-2R aircraft built for high-altitude tactical reconnaissance missions with side-looking radar, new avionics, and improved ECM equipment; 33 built.
Re-designated U-2S after the fall of the Soviet Union
Two TR-1A airframes completed as two-seat conversion trainers
New redesignated TR-1B two-seat trainer with improved engine; five converted
Two TR-1A airframes, AF Ser. No. 80-1063, and Ser. No. 80-1097, modified as Earth resources research aircraft, moved from USAF to NASA and operated by the NASA High-Altitude Missions Branch, Ames Research Centre.
NASA flies Ser. No. 80-1097 as N809NA and Ser. No. 80-1063 as N806NA.
Redesignation of the TR-1A and U-2R aircraft with updated General Electric F118 engine, improved sensors, and addition of a GPS receiver; 31 converted
Atmospheric/weather research WU-model
In May 1961, in an attempt to extend the U-2’s already considerable range, Lockheed modified six CIA U-2s and several USAF U-2s with aerial refuelling equipment, which allowed the aircraft to receive fuel from either the KC-97 or from the KC-135.
The U-2R, first flown in 1967, is significantly larger and more capable than the original aircraft.
A tactical reconnaissance version, the TR-1A, first flew in August 1981.
A distinguishing feature of these aircraft is the addition of a large instrumentation “superpod” under each wing.
Designed for standoff tactical reconnaissance in Europe, the TR-1A was structurally identical to the U-2R.
The 17th Reconnaissance Wing, RAF Alconbury, England used operational TR-1As from 1983 until 1991.
The last U-2 and TR-1 aircraft were delivered to USAF in October 1989.
In 1992 all TR-1s were re-designated to U-2R for uniformity across the fleet.
The two-seat trainer variant of the TR-1, the TR-1B, was redesignated as the TU-2R.
After upgrading with the GE F-118-101 engine, the former U-2Rs were designated the U-2S Senior Year.
A derivative of the U-2 known as the ER-2 (Earth Resources 2), in NASA’s white livery, is based at the Dryden Flight Research Centre (now Armstrong Flight Research Centre) and is used for high-altitude civilian research including Earth resources, celestial observations, atmospheric chemistry and dynamics, and oceanic processes.
Programs using the aircraft include the Airborne Science Program, ERAST and Earth Science Enterprise.
Landings are assisted by another pilot at speeds exceeding 120 miles per hour (190 km/h) in a chase car.
5,000 lb (2,300 kg) payload
63 ft 0 in (19.20 m)
103 ft (31 m)
16 ft 0 in (4.88 m)
1,000 sq ft (93 m2)
16,000 lb (7,257 kg)
Max take-off weight
40,000 lb (18,144 kg)
2,950 US gal (2,460 imp gal; 11,200 l)
1 × General Electric F118-101 turbofan engine,
17,000 lbf (76 kN) thrust
Cruise Mach number
Mach 0.715 (412 kn; 470 mph; 760 km/h) at 72,000 ft (22,000 m)
413 kn (475 mph, 765 km/h) at 65,000 ft (20,000 m)