Private Pilot Flight Training and Instruction Flight Training Article Library | Back To 4VFR.COM The Johnson Bar One unlikely aircraft feature was derived from the steam engine. The Johnson bar was used to control the amount of steam and hence the power of the engine. The Johnson bar is a term used to describe the long handles used in earlier Cessnas and nearly all Pipers to operate the flaps. The term has also been used with reference to the bars used on Mooney aircraft to hand operate the manual gear. Written by Gene Whitt Flight Training Article Library | Back To 4VFR.COM