The KC-135 aerial refueling tanker consists of a refueling boom that extends out to receiving aircraft to refill their gas tanks. The operator who manages the boom is called, appropriately enough, the boom operation. The 135 provides the boom operator with a window to view the receiving aircraft. Lying on his stomach, the operator maneuvers two joystick-like controls to move the refueling boom to the receiving receptacle. Sounds simple enough, oh wait, they are at some twenty thousand feet in the air and flying at aircraft speed, which would be fast.
Bring in the next generation refueling tanker and we now have a remote system whereby the boom operator views this whole scene through external camera lenses that are mounted to give a stereoscopic, three dimensional, view. Sitting upright in a fairly comfortable chair, each hand controlling the joystick, I experienced some difficulty in convincing the boom operators that the camera view was just as good if not better than the window. To aid in convincing the operators of the value of the remote control many tests were run to prove out the new system. These tests are often termed ‘human-in-the-loop’ (HITL) tests.
One of the HITL tests looked at the ability of the KC-135 to refuel the new tanker. Someone decided the new tanker needed a new design for the receiving receptacle. This is basically the gas tank connection that is pierced by the refueling boom to allow the flow of fuel to the receiving aircraft.
This new design had no markings or lighting to give the boom operator cues to guide the boom. A pattern was developed and painted on the test receptacle as a cheaper alternative to the expensive lighting. The concept was so new, although admittedly low-tech, that it needed some lab testing to prove it would work.
A refueling boom hung from the ceiling of the hangar that was our test lab and crude controls, think cables and pulleys, were mapped to a couple of joysticks that the test subjects would manipulate to simulate a refueling operation. Measurements included the time to mate up with the receptacle and how close to the ‘target’ the boom fell. A piece of chalk taped to the end of the boom marked how close or far away from the receptacle the operator made it. The geometry of the boom operator’s view to the new tanker receptacle required raising the boom operator station to some fifty feet above the floor of the hangar.
This was accomplished using a scissor lift. Not a bad tool for reaching stuff at twenty feet. Fifty feet was a little precarious. The lift was top heavy and swayed, but was stable at the bottom through the use of outriggers. The only thing we were missing was a net. The lift carried with it a test subject, this would be the boom operator, an instrumentation person to ensure the equipment worked, and me, the test conductor.
To make the test as real as possible, the hangar was darkened. Nighttime is the worst time in a lot of ways for refueling. The only lights available are some spotlights on the tanker and a lone light in the receiver’s receptacle.
During an orientation with the test subjects, one of the boom operators, I’ll call him Dave, expressed some anxiety with the task. He was retired from the military and had been a KC-135 boom operator. Seems he had developed a fear of heights in his retirement. Try getting that around your head: he can lay down looking out a window at twenty thousand feet of air with a live aircraft buoyed just feet from the tail of the tanker, but getting on a lift scared him.
I needed a good number of test subjects for the test results to be valid and worried that he would bail at the last second. Test day came and I’d already been up and down on the lift a couple of times. Then it was Dave’s turn.
Sweaty and shaky, he climbed onboard the lift. As we approached the fifty-foot height, the instrumentation person and I were moving around on the lift a little bit getting ready for the test. Dave said, “You have to quit shaking. It’s moving. Stop it RIGHT NOW.” I looked at him and he was looking straight ahead, his body frozen. I realized his fear was for real and started to worry he might start puking. I knew we forgot something: the barf bag.
Once he started the refueling motions, things went well and he hit the marks he needed to within the time constraints. Finally he relaxed, well, it was relaxed for him. As soon as he completed the tasks he indicated that we needed to go down and we lowered the lift.
Kudos to Dave for completing the task in spite of his fears. Our new markings passed with flying colors and the team was awarded a special recognition for our efforts. We saved the company some eleven million dollars and I have a nice chunk of acrylic recognizing my role in this task.
Dave? Well Dave kept his lunch down. It doesn’t get better than that some times.