Johnson bar (vehicle)

A Johnson bar is a hand lever with several distinct positions and a positive latch to hold the lever in the selected position. The latch is typically activated with a spring-loaded squeeze handle on the lever so that only one hand is needed to release the latch, move the lever, then re-engage the latch in a different position. This is an American English term; in British English, the lever is named for its function.
Many steam locomotives have valve gear controls which are set using a Johnson bar as referenced in Fred Eaglesmith's song "Back There": "Hey Porter, tell that engineer, tell him this train's too slow. Tell him to let go that Johnson bar. I got places I got to go."
Many trucks and buses use a hand brake which is controlled with a Johnson bar. These are sometimes called "Johnson bar brakes".
Truck drivers call the lever control for air-operated trailer brakes "Johnson bars".
On Caterpillar tractors, the forward/reverse lever is also called a Johnson bar.
Some light general aviation aircraft (including Piper Cherokees, Beech Musketeers, and some early model Cessnas – such as the Cessna 140) use Johnson bars to actuate flaps and wheel brakes. The Cessna 162 Skycatcher uses a Johnson bar for flap operation. A small number of older aircraft (including the Mooney M-18, some older M20s and some Progressive Aerodyne SeaReys) also have landing gear actuated by Johnson bars.
The Boeing 707/720 aircraft had a Johnson bar for manually extending the nose landing gear, in case the normal gear extension failed.