737Ng Flight Controls

Flight controls

Moving the control column in the opposite direction to electric trim will stop the trim, unless the STAB TRIM switch is set to OVERRIDE. This function could be used to control thepitch of the aircraft with trim say in the event of a jammed elevator.

The trim authority varies according to aircraft series and method of trim. The full range is only available with the manualtrim wheel, but if at an extreme setting, electric trim can be used to return to the normal range. There are two electric trim switches on each control column, the right is for the direction and theleft is an earth return for protection against spurious electrical signals.

Speed trim is applied to the stabilizer automatically at low speed, low weight, aft C of G and high thrust - i.e. on mosttake-offs. Speed trim is a dual channel system. Sometimes you may notice that the speed trim is trimming in the opposite direction to you, this is because the speed trim is trying to trim the stabilizerin the direction calculated to provide the pilot with positive speed stability characteristics. The speed trim system adjusts stick force so the pilot must provide significant amount of pull force toreduce airspeed or a significant amount of push force to increase airspeed. Whereas pilots are typically trying to trim the stick force to zero. Occasionally these may be in opposition.

As themach increases, so the centre of pressure moves aft and the nose of the aircraft will tend to drop (mach tuck). MACH TRIM is automatically applied above M0.615 (classics & NG's), M0.715 (-1/200) to theelevators to counteract this and to provide speed stability.


A Stab Trim Override Switch, located on the aft electronic panel, bypasses the Control Column actuated Stabilizer Trim Cutout Switch.When the switch positioned to OVERRIDE, main electric trim can be used regardless of control column position.


° The stabilizer is held in position by a dual brake system. Either stabilizer brake...