A look Into Unmanned Aerial Vehicles

Courtesy Of: YouTube
Added: February 07, 2007
From: Hindsightis2020
RunTime: 07:21

UAVs have become so popular with the mil UAVs have become so popular with the military that over 50 organizations are flying, researching or developing such products - many by companies not known for designing and producing aircraft. As expected, the major aircraft companies are involved: Boeing, Lockheed and Northrop Grumman. But, consider the following company names: Aurora Flight Sciences, Chapy Corporation and Orion Aviation all working on such products, and there are 20 to 30 more "unknowns".

In the past UAVs have been placed in five or more categories; however, a more recent movement is to define them as Local, Regional and Endurance. The size, weight and capability within these categories vary widely from small, lightweight (a few pounds) to the 100,000 pound behemoths. Among past efforts to develop types of UAVs, the Hiller Aviation Museum has two examples on exhibit that span the range of size and endurance. These are the spectacular Boeing Condor and the miniature MLB Trochoid.

The Condor with its 200-foot wingspan and the Trochoid with a blended body about eight inches across are certainly the extremes in the range for size. And for endurance, the spread is equally dramatic. The Condor had a design goal of 150 hours and the Trochoid about 20 minutes. In weight the two are even further separated - 20,000 pounds for the Condor and only 12 ounces for the Trochoid.The Boeing Condor is from the mid'80s, having first flown on October 9, 1988 for 1hr & 33 min. (the video at the Hiller Museum is of this flight). It flew seven more times including the last flight of 58:11. All flights originated and ended at Moses Lake, Washington, using the 13,600 foot run way at Lawson Air Force Base. Boeing has used this facility (now Moses Lake airport) for a wide variety of test flights including the 747 airliner. Japan Air Lines used it for pilot training.The Condor project is reported to have been initiated by Boeing but was subsequently funded up to an estimated $300 million by the Defence Advanced Research Projects Agency (DARPA).

One estimate places the aircraft cost at $40 million. The unique aircraft was designed for electronic surveillance at high altitudes and extended durations. However it is known that it only flew over Eastern Washington State. Considering the location of all flights, it is unlikely the electronics installed was used for anything other than evaluation. Information is not available regarding which US Government agencies participated in the testing activities other than DARPA.DARPA provided the "payload" but it was classified so it is not known what was included. Though the primary structural parts of the Condor are a carbon fiber laminate, a few sections are Kevlar to allow radio frequency signal penetration by the electronics. Though the Condor has an ungainly appearance it did achieve some measure of success by reaching a record altitude of 67,028 feet, powered only by two 175-horsepower, six cylinder engines. The engines were boosted with two stages of exhaust-driven superchargers.

To save weight, a "dolly" and two outrigger wing mounted wheels were used for take off but remained on the ground. For landing, there was a tandem positioned nose wheel and skid lowered from the fuselage. In order to achieve the performance specifications the aircraft had to be very, very light with very long, thin wings (even an engine starter was eliminated).

To maintain structural integrity the fuel load was distributed across the length of the wings. It was subsequently determined that the wing design precluded air speed in excess of about 140 knots. In fact, external weights we re added to the wing tips to reduce torque and possible flutter. The engine choice required a special propeller, which was very light Kevlar, 16 feet in diameter. Because of the lightweight propeller, low horsepower engine and two-speed gearbox, the engines had to be started using an external hydraulic unit with a shaft inserted into the prop spinner.

This type of starting mechanism is called a "Hucks" starter and was from the World War I era. Once started there was sufficient momentum to continue. However, the engine/propeller combination was sized for 60,000 foot operation; hence the drag on the blades at sea level was too much for the engine. So, the two-speed gear had to be shifted at 43,000 feet to reach maximum altitude. Flight control was quite unique and different from many current UAVs. The total flight mission was pre-programmed in an on-board computer and was completed without any input from a ground station (the Global Hawk is also pre-programmed). Experience is a great teacher...