Because airplanes must fly in the real world, the Air Force built a fake one.
- By Ed Regis
- Air & Space magazine, May 2006
U.S. Air Force
(Page 3 of 4)
“I hate to talk about stuff like that,” Velasco admits. Nevertheless: “I remember vividly—and I won’t mention the name of the aircraft—but we had a large aircraft in here and we did a rain test on it, and we filled it up with water. I mean, water was draining out of that aircraft for two days after we shut down. We could open panels and there were wing cavities filled with it. It was like a swimming pool, you could jump in and swim in it. It was leaking in because of the way they built the access panels—they were not sealed properly.
“Believe it or not, rain is a tough test to pass,” Velasco adds. “We create a windblown rain, we don’t just rain overhead and sprinkle on the thing. We have big wind machines blowing 50-mph winds, and you can blow it up under the wings and from all angles. You blow water everywhere.”
Then, because it’s ancient history, he talks about a B-52 test of a much-touted hydraulic fluid that wasn’t supposed to catch on fire the way conventional fluids did when the bomber’s hydraulic lines got hit by ground fire in Vietnam. “This B-52 had a rotating launcher inside of it that carried cruise missiles,” says Velasco. “The thing’s got to rotate and drop a bomb, rotate and drop a bomb, at minus 65 degrees. We were trying a newfangled type of hydraulic system—that was the whole test. The fluid was less flammable, but at the same time it was much more viscous. It was like molasses at minus 65 versus the old stuff, which would flow relatively freely at minus 65.” So much for the new hydraulic fluid, which the Air Force summarily discarded.
The alternative response to the discovery of a defect is to modify the system at fault. “You’ll have landing gear that won’t come up because they made the hydraulic lines too small, so they have to go back and mod the lines, make a bigger hydraulic line,” says Velasco. “They might have an eighth-inch line down to the gear and it’s just too small, not enough fluid getting there fast enough, so they have to put in a quarter-inch line or a three-eighth-inch line.”
At the other end of the temperature spectrum, heat poses a problem for avionics systems, especially those based on cathode-ray-tube displays, which generate lots of heat, compared to conventional gauges, which don’t. An avionics meltdown, when it happens, prompts the company in question to beef up its “environmental control systems” (air conditioning).
After five days in the deep freeze, the Raytheon Hawker Horizon was covered by a light layer of frost. This was not another sign of lab-induced weather trauma but rather the result of technicians (most of them clad in parkas) repeatedly entering and exiting the hangar, letting in minute amounts of Florida humidity.
During a previous cold test at McKinley, the Hawk had been raised up on jacks so that its gear could be cycled, something that was done without difficulty. On this occasion, with an FAA representative in attendance to verify the results, the flight crew performed a series of low-temperature starts of the auxiliary power unit’s battery, tested oxygen mask operation and the crew alerting system, monitored normal and emergency exit door forces, and so on. All challenges were met successfully. You might say that the whole thing was anticlimactic.
“There’s lots of experience to draw upon,” says Velasco, “and so the newer stuff is a lot better than it used to be in the old, old days.”