You use a gapping tool to make sure the gap between the spark plug's center electrode and the ground electrode above it are the right distance apart. This is where the spark fires on your spark plug. You may also want to have on hand a pair of boot pliers, a length of rubber tube...
But in the 1950s, these piston-powered prop planes strained to fly fast enough to safely refuel the newly minted jet fighters and bombers of the day. Fighters could be hanging in the air at low airspeeds while the tanker was at full throttle. A fast jet-powered tanker was needed quickl...