Joined: 11 Dec 2005
|Posted: Sun Mar 02, 2008 9:55 am Post subject: Jammed or Restricted Flight Controls in 737-300
|Although rare, jamming of the flight control system has occured on commercial airplanes. A flight control jam may be difficult to recognize, especially in a properly trimmed airplane. A jam in the pitch axis may be more difficult to recognize than a jam in other axes. In the case of an elevator, the jammed control can be masked by trim. Some indications of a jam are:
- Unexplained autopilot disconnect
- Autopilot cannot be engaged
- Undershoot or overshoot of an altitude during autopilot level-off
- Higher than normal control forces required during speed or configuration changes
If any jammed flight control condition exists, both pilots should apply force to try to either clear the jam or activate the override feature. There should be no concern about damaging the flight control mechanism by applying too much force to either clear a jammed flight control or activate an override feature. Maximum force may result in some flight control surface movement with a jammed flight control. If the jam clears, both pilot's flight controls are available.
A jammed flight control can result from ice accumulation due to water leaks onto cables or components. In this case the jam may clear when moving to a warmer temperature. Other causes of jammed flight controls are dirt accumulation, component failure such as cable break or worn parts, improper lubrication or foreign objects.