May 12

The next morning was bright and clear as we returned to Bozeman airport. The first thing we noticed was a pool of hydraulic fluid on the tarmac beneath engine no. 1. Never a good sign, this particular problem was solved in an hour, thanks to Arlin.

The C-47/DC-3 cowl flap system is one way to regulate the heat around the engines. The air flowing through the engine escapes through gaps when the cowl flaps are open. Warm air is retained when the cowl flaps are closed. Cowl flaps often are closed in flight to minimize drag as the engines enjoy massive ram air cooling (the higher the altitude, the colder the air). On the ground, when drag is not an important consideration and there are fewer options for cooling, the cowl flaps generally are open. A somewhat unique feature of the DC-3 is the cowl flap system relies on hydraulic pressure to push an actuator expanding a mechanical ring of rods to move the cowl flaps to the open or closed positions.

The leak on the tarmac was caused by a failed line feeding the cowl flap actuator. The Bozeman fuelers introduced us to Arlin, the senior mechanic at the airport. Arlin visited the airport on Mother’s Day “to do paperwork.” I bet a day’s wages Arlin “does paperwork” at the airport every Sunday. He took the failed line to his shop, returning in about ten minutes with a new line. It fit perfectly. Arlin toured the aircraft. He shared he had maintained DC-3s for Northwest Airlines almost sixty years ago. I asked him what I owed him for the repair. He looked me in the eye and said “have fun.” So we settled on a Historic Flight Foundation cap. A “win, win.”

With this, the pedigree of our aircraft has changed: manufactured by Douglas, converted to DC-3 by Grand Central Aviation, acquired by Historic Flight Foundation, restored by Sealand Aviation, repaired by Arlin.

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