Java Jolt?

Flying Safety, May, 2001 by Msgt Edward L. Warwick

As Flight Safety NCO for the 93rd Air Control Wing, with 20 years experience on large aircraft, I thought I'd seen everything during my career. For the last four years as a safety professional, I've investigated incidents and mishaps that were pretty easy--in-flight engine shutdowns, dropped objects, bird strikes, etc. But last August, I had one of those investigations where as soon as you kick one rock out of the way, you find three more underneath it.

One afternoon the Command Post reported that a crewmember on our E8C had been shocked and the plane was returning to base. As the aircraft came to a stop, I met the flight crew and discovered the navigator had been shocked by a coffee jug. As the Nay was being transported to the hospital, I quickly found out that he didn't just get zapped; he got the $#!% knocked out of him by a jolt powerful enough to drop him to his knees. The aircraft commander also told me that shortly after receiving the shock, the Nay complained of lightheadedness and shortness of breath.

Immediately after the incident, Maintenance inspected the aircraft and the coffee jug. An ohms check revealed resistance between the 115-volt pin and the metal case. At first we thought there was a short in the coffee jug when it was hot, but a continuity check after it cooled down showed no defects. The next day, one of our squadron commanders reported receiving a mild shock from a coffee jug a week earlier. After this incident, the flight kitchen was informed of the mild shocks and was asked to condemn the jug. With no knowledge of maintenance and inspection requirements, they placed the jug back on the shelf for use at a later date. This same jug is believed to have shocked the Nav.

When we talked to the flight kitchen personnel, we discovered that about three and a half years earlier, the wing had coordinated with the kitchen to maintain the jugs. Eventually, the kitchen maintained approximately 50 coffee jugs for three different units on base. We could have just condemned this one jug and pressed on with life, but a team was assembled and began checking the rest of the jugs in the kitchen. As we talked with other individuals within the wing, we soon discovered at least two other incidents involving 93 ACW aircrew members receiving mild shocks from coffee jugs. An inspection of other coffee jugs in the kitchen revealed that five of 50 jugs showed suspect continuity between the pins and the metal case.

At this point, it wasn't known if a technical manual existed for the jugs or how to properly inspect them. We later discovered that T.O. 13A15-4-3 covers this type of coffee jug. It states that the jugs should be inspected every 180 days, and that the reading between all the pins in the plug and metal case must show infinite resistance (zero ohms). In addition, it cautions not to submerge the coffee jugs, due to the severe potential for heating element corrosion and short circuit. Until this incident, qualified personnel were not inspecting these containers according to the technical manual, and the jugs were routinely being submerged in water. After finding the testing procedures in the manual, our electrical backshop personnel began reinspecting 23 of the original 50 jugs. Eighteen of the 23 jugs had enough significant defects to pull them from the shelf.

The inspection of the coffee jug that shocked the Nay revealed the insulation on the wire supplying 115 VAC to the container's heating element had deteriorated and allowed the conductor of the wire to contact the metal case of the container. When the coffee jug was moved around, the wire would reposition and may or may not show a defect when ohms-checked. The heater supply wire contacting the case was one of two malfunctions required to allow the outside of the container to become electrically charged; the other was an insufficient electrical ground. If the container was well-grounded, the current would pass from the wire into the case of the container and out the ground, and there would be no voltage potential between the container and the aircraft structure. If the coffee jug was properly grounded, the circuit breaker would have heated up and popped. An inspection of the circuit breakers revealed no defects. Before the Nay touched the jug, it had no ground available, so the circuit was not closed and no cu rrent flowed through the circuit breaker. The Nay briefly provided a current path when he touched the jug. The relatively high resistance of his body and the small time he was touching the jug limited the current through the circuit breaker to levels below that required for it to actuate.

At first, we weren't sure if this would turn into a mishap, because we didn't know the condition of the Nay for the first couple of days. After he was checked out by the Flight Surgeon and released for duty, we decided to send out a HAP (High Accident Potential) message. To our amazement, we've received numerous calls from other bases noting similar problems with the jugs; the y too had not been inspecting their coffee jugs.