Article by Capt. Catie Hague
Public Affairs
2/13/04 – EDWARDS AIR FORCE BASE, Calif. To control the atmospheric environment may seem impossible, but what better way to prove its possibility than by creating a rain cloud in the desert.
The Global Reach Combined Test Force at Edwards did just that Jan. 26 and 28, generating man-made clouds to support the F/A-22 Raptor's performance testing in rain and ice conditions.
"The Raptor was the first aircraft to use our 'rain and ice tanker' for test," said Sean Hamilton, Global Reach CTF chief engineer. "For eight years [since 1996], the flying community has been awaiting this reconstituted capability, and two weeks ago we were able to solidify its national worth. This modified KC-135 is a national asset, able to support the military, the Federal Aviation Administration, the National Transportation and Safety Board and the entire aviation industry through its ability to produce specific testing environments for airborne aircraft."
In order to conduct this type of testing, the Stratotanker began its modification process in 2001. "A 'shower head,' three-and-a-half feet in diameter, was attached to the end of a KC-135's boom, normally used for in-flight refueling," said Mr. Hamilton. "Currently, the head - containing 50 air and 50 water nozzles - pumps water and hot air into the atmosphere, creating a saturated cloud."
Three main factors determine the cloud's composition, explained Mr. Hamilton; the amount of water expelled, the size of the droplets formed by the adjustable nozzles and the altitude of the tanker - the higher the aircraft, the cooler the air, resulting in varying consistencies of rain and ice. Typically, ice tests, like those performed with the Raptor, are conducted by flying test aircraft at freezing temperatures. This approach allows the water from the tanker to freeze only when it contacts the aircraft.
In other words, this tanker system is able to focus rain and ice spray on critical areas of the aircraft such as engines, flight control surfaces and air data systems, said Steven Krasiewski, F/A-22 Airborne Ice and Rain Lead Engineer, JT3. "We can target one piece of the aircraft versus the entire airframe; a much safer way to conduct flight test."
Within one month [January], the Global Reach CTF completed the five flight tests needed to verify the tanker's performance and safety of flight, said Mr. Hamilton. And within the last week, the F/A-22 used this new asset to complete two ice tests.
These airborne ice tests required a formation of four aircraft - a tanker, a calibration aircraft, an F/A-22 and a safety/photo chase aircraft. All were supported by a diverse team composed of military and civilian personnel, as well as contractors from Lockheed Martin, Boeing, Pratt and Whitney, JT3, Tybrin and Aeromet.
The F/A-22's performance during the icing tests surpassed expectations.
"From the control room, we saw no degradation
of the Raptor's performance in the icing cloud," said Bruce Wilder, F/A-22
flight test engineer.
"The Raptor was very stable during the icing spray, staying approximately 50
feet from the tanker's nozzles," added John Fergione, F/A-22 test pilot,
Lockheed Martin. "The overall pilot workload was fairly low, and the affect
on the aircraft was negligible."
In the near future, the tanker will be fitted with a new head - six feet in diameter, containing 216 nozzles - expanding its ability to support both military and civilian customers by producing a wider variety of clouds.
"This testing platform not only paves the way for proving the F/A-22's all-weather capability, but it also offers a unique and critical test capability to the entire aviation community," said Mr. Wilder.
Mr. Hamilton agreed, "Every aircraft can benefit from Edwards' ability to produce rain and ice on a day where there are no clouds in the sky and the temperature on the ground is 110 degrees."
