Lockheed U-2

Details

The U-2, whose development name at Lockheed was the CL-282 Aquatone, needed an official name. It could not be named with letters such as B for bomber and F for fighter because its purpose was not for any of those specific designations. Also, since the project was under high secrecy, it could not be called a reconnaissance plane. Finally, the Air Force decided to call it a utility plane. Since the names U-1 and U-3 had already been chosen, the name given to the plane was U-2. The plane's nickname is the "Dragon Lady." Initially, Kelly Johnson adapted the F-104 Starfighter, replacing the low aspect ratio blade wings with extremely large glider type wings as a starting point.

Related Topics:
Air Force - U-1 - U-3 - Kelly Johnson - F-104 - Aspect ratio

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High aspect ratio wings give the U-2 glider-like characteristics and make the aircraft extremely challenging to fly, not only due to its unusual landing characteristics, but also because of the extreme altitudes it can reach. When flying the U-2A and U-2C models (no longer in service) the maximum speed (critical mach) and the minimum speed (stall speed) approach the same number, presenting a narrow window of safe airspeed the plane must maintain. In these models over 90% of a typical mission is flown within five knots of stall speed.

Related Topics:
Glider - Critical mach - Stall - Knots

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Because of its high-altitude mission, the pilot must wear the equivalent of a space suit. The suit provides the pilot's oxygen supply and emergency protection in case cabin pressure is lost at altitude (the cabin provides pressure equivalent to approximately 30,000 feet). To prevent decompression sickness, pilots don the pressure suit and begin breathing 100 percent oxygen at least one hour prior to launch; while moving from the building to the aircraft they carry their own oxygen supply.

Related Topics:
Space suit - Cabin pressure - Decompression sickness

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The U-2 is considered one of the most challenging aircraft in the military inventory to fly and requires a high degree of airmanship from its pilots. Its large wingspan and resulting glider-like characteristics make the U-2 highly sensitive to crosswinds. This sensitivity, and the aircraft's tendency to float over the runway, makes the U-2 notoriously difficult to land. Typically, a second U-2 pilot, designated as the mission's backup pilot and referred to as the "mobile," waits in a high-performance chase car at the end of the runway as the aircraft makes it landing approach. As the U-2 passes, the chase car follows it at high speed, with the mobile calling out the aircraft's altitude via radio to the pilot. When the aircraft's main landing gear is within approximately two feet of the runway surface the pilot deploys spoilers located on the top of the wings to reduce lift (spoiling the lift and increasing the stall speed by 2 knots). Retractable stall strips on the wings' leading edges that are deployed prior to entering the landing phase help to produce equal stalling effects. This is done to minimize wing drop, assisting in aircraft control particularly during strong cross winds.

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Another distinguishing characteristic of the U-2 is its landing gear. Instead of the typical tricycle configuration consisting of a nose wheel and two sets of main wheels under each wing, the U-2 uses a bicycle configuration consisting of one set of main wheels located just behind the cockpit and one set of rear wheels located behind the engine. To maintain balance and allow the aircraft to taxi, two sets of auxiliary wheels called "pogos" are installed under each wing by ground crew. The pogos fall out of sockets in the wing onto the runway surface when the aircraft takes off. Ground crew collect the pogos and re-install them after the aircraft lands. U-2 ground crews, in a spirit of playfulness, often perpetuate the idea that the pogos are installed from the back of a pick-up truck that drives alongside the aircraft while it is moving at high speed down the runway. In fact, the pogos are installed after the aircraft has come to a full stop and the wings have settled onto the ground. Skids made of titanium strips are located on the bottom of each wing tip to protect the wing. Once the pogos are installed, the aircraft taxis under its own power back to its parking location.

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The aircraft carries a variety of sensors. The U-2 is capable of simultaneously collecting signals and imagery intelligence. Imagery intelligence sensors include either wet film photo, electro-optic or radar imagery. It can use both line-of-sight and beyond-line-of-sight data links.

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The aircraft completed an upgrade to the General Electric F-118-101 engine in 1998, primarily to increase maintainibility by replacing the aging J-75 (Pratt & Whitney) engine that had first been developed in the '50s. Significant side benefits of the newer GE engine was better fuel economy, reduced weight and increased power. To increase longevity the GE engine was de-tuned to roughly match the output from the PW engine. Other upgrades to the sensors and the addition of the Global Positioning System increased collection capability and provides superimposed geo-coordinates directly on collected images.

Related Topics:
General Electric - 1998 - Global Positioning System

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