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 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 used to call lever controls on 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) use Johnson bars to actuate flaps and wheel brakes; a small number of older aircraft (including the Mooney M-18 and some older M20s) also have landing gear actuated by Johnson bars.
On the Boeing 707/720 aircraft the Johnson bar was used to manually extend the nose landing gear. This was only used if the normal gear extension failed.
Famous quotes containing the words johnson and/or bar:
“Dr. Johnson was a lazy learned man who liked to think and talk better than to read or write; who, however, wrote much and well, but too often by rote.”
—William Hazlitt (1778–1830)
“Even the most incompetent English actor, coming on the stage briefly to announce the presence below of Lord and Lady Ditherege, gives forth a sound so soft and dulcet as almost to be a bar of music. But sometimes that is all there is. The words are lost in the graceful sweep of the notes.”
—Robert Benchley (1889–1945)