FORT RUCKER, Ala. (Oct. 4, 2017) - The mission began as a routine night vision goggle aerial refueling proficiency mission. The MH-47 crew of six preflighted, briefed and filed their crew packet and flight plan with operations. The aircraft was ready, as was the crew.

In accordance with standing operating procedures, the crew chief carried an aircraft mechanics toolbox with the necessary tools for MH-47 repair and maintenance. The toolbox was stored securely on the floor in front of the 800-gallon Robertson auxiliary fuel tank in the forward cabin area. In the toolbox were two 14.4-volt DC batteries and a drill driver used for removing panel screws. The toolbox had foam inserts, neatly cut out to account for and secure the tools and two batteries. With the exception of the odds and ends crew chiefs carry to complete those minor unscheduled maintenance tasks, the toolbox also included assorted common cotter pins, nuts, washers and a spool of .020-inch safety wire.

The crew departed shortly after the end of evening nautical twilight and had about 45 minutes of en route time before the air refueling control time. The ARCT is a "hard" time where the receiver, in this case the MH-47, and the tanker, an MC-130, must join up for the aerial refueling.

About 20 minutes into the flight, while still low level, one of the pilots reported smelling smoke. After a short discussion, the pilots realized the aircraft was flying over an area that was conducting a controlled forestry burn. However, the smell increased in intensity and the crew began looking for the source of the smoke. The pilots immediately turned back to base.

The crew chief in the forward cabin area followed the odor to the vicinity of the toolbox. When he raised the lid of the toolbox, the tray holding the spool of .020-inch safety wire was glowing red and producing fumes and light smoke. The red glow when viewed through NVGs amplified the scene and he reported "FIRE!" on the internal communication system. The cry of "fire!" ranks right up there with "wires!" as a pilot's least favorite thing to hear on the ICS.

Immediately following the cardiac episode, the pilots began a descent and prepared for an emergency landing. What the crew chief had seen was a spool of .020-inch safety wire resting against the terminals of one of the 14.4-volt DC batteries for the drill driver. The spool was smoking, glowing red and melting the plastic surrounding the battery terminals. The crewmember calmly reported the clarified version of what he saw to the rest of the crew and the pilot aborted the landing and turned the aircraft back to base.

The crew chief then carefully pushed the safety wire away from the battery, but it came to rest on the other battery and began to glow and smoke exactly like the first. With one more attempt, he was able to separate the safety wire from the battery and remove the source of smoke and fumes. After a hectic minute or two, the crew was able to relax and again changed course to resume the route back to the tanker for their aerial refueling mission.

This crew was lucky they found the fire source in time. The hazard of storing a spool of safety wire in close proximity to the drill driver battery could have resulted in a fire and/or explosion. The 800 gallons of JP-8 conveniently placed within a foot of the toolbox presented a ready fuel source. This could have easily resulted in a destroyed aircraft and possible fatalities.

The remedy was extremely simple. In our case, we moved the safety wire to another drawer in the toolbox, away from the conductive material in the batteries. This was a valuable lesson learned.

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