Invention makes moving patients safer

  • Published
  • By Rita Boland
  • 311th Human Systems Wing Public Affairs
BROOKS CITY-BASE, Texas (AFPN) --  Air Force and civilian engineers have developed a non-sparking electrical outlet for a frequency converter making aeromedical evacuations safer and easier.

Engineers from the 311th Human Systems Program Office’s aeromedical test branch here began working on the new converter because of potential explosion hazards on KC-135 Stratotankers that exist if fuel vapor develops in the cabin. They worked in conjunction with Rohman Services Inc.

Air Mobility Command officials listed the KC-135 as an aeromedical-evacuation platform for transporting patients because of the reduction in C-9A Nightingales and C-141 Starlifters.

"Medical equipment normally operates using standard household power (60 Hz)," said Master Sgt. Robers Eshelman of the 311th SPO. "Most U.S. Air Force aircraft have 400 Hz, thus requiring aeromedical-evacuation crews to bring a frequency converter onboard to convert 400 Hz power to standard household power."

Since the KC-135 is an air refueling tanker aircraft, studies were conducted to determine if the spark generated by a three-prong plug being pulled out of the converter socket could cause an explosion of the fuel vapors.

Officials from the 311th SPO identified and studied the problem in Orlando, Fla., in an explosion test chamber. From outside the chamber, the engineers pulled the cord from the outlet.

"It basically blew the chamber apart," said 1st Lt. David Mandel, chief of the aeromedical test branch. "The rapid removal of a device which is drawing power can cause an arc between the metal prongs of the plug and the metal inside the outlet as they break contact. The same phenomenon occurs when a vacuum (cleaner) cord is ripped from the outlet and a blue spark can be seen. However, in this case, the results could be catastrophic. If this were to occur while fuel vapors (were) present in the air, the arc could have enough energy to ignite the mixture, as we saw in tests."

A team from RSI developed a prototype in 45 days to fix the problem. A small button was placed in the center of the outlet. The button controls a mechanical relay, basically a switch, which is inside the outlet. This switch ensures that no current flows to the outlet until the button is pressed.

"The outlets are designed in a way to cut power to the outlets as soon as the plug is extracted," Eshelman said. "This eliminates any sparks. These outlets were introduced into a modified frequency converter and passed explosive vapor testing."

The invention received approval from AMC officials in mid-May, and a patent is pending.

In an effort to conserve funds, the engineers will reconfigure existing converters with the new safety device instead of producing new converters. All 300 existing converters will be reworked.

The invention will also save the Air Force money on fuel and batteries.

Medical equipment on KC-135s currently runs on batteries, and when batteries lose power, it affects patient care.

"(The outlet provides) uninterrupted care of a trauma patient," said Melissa Corse, an engineer at the 311th SPO. "(Crews) don't want to have to worry about changing out batteries."

With the new converters, aeromedical-evacuation crews can travel longer distances without fearing power failure or carrying extra equipment.

"With the modified converters, crews now have safe access to standard household power onboard the KC-135 and can operate medical equipment indefinitely," Eshelman said. (Courtesy of Air Force Materiel Command News Service)