Tuesday, June 12, 2012

Cessna 152 Rudder Travel



                      On April 11, 2005, a Cessna 152, crashed after the rudder jammed during spin recovery training. The CFI and the student pilot were killed, and the airplane was
substantially damaged. The flight departed  about 1230 and proceeded to a practice area about 10 miles east of the airport. Witnesses reported that, while at an altitude of about 3,000 feet above ground level, the airplane descended in a nose-down spiral from which it did not recover and crashed into a field.
                Examination of the wreckage revealed that the rudder was jammed approximately 35°, which is beyond its left travel limit. Further examination revealed that the two rudder bumpers had been installed inverted and that the right rudder bumper had traveled beyond the rudder stop and had locked behind it. the accident airplane’s right
rudder bumper had traveled to the right of the rudder stop when it was supposed to be to the left of the rudder stop. The inverted rudder bumpers may have caused the rudder jam because, when a rudder bumper is inverted, the “tang” (portion of the rudder bumper that contacts the rudder stop to prevent the bumper from further travel) points toward instead of away from the curvature of the rudder horn; thus, the rudder bumper can pass over and beyond the stop and result in a jam.
              The rudder travel limit is 23° deflection (left or right) from the hinge line.
              The investigation could not determine whether the incorrect installation of the rudder
bumpers occurred at the time of production or during the airplane’s maintenance history. Review of the maintenance records indicated no record of work having been performed on the rudder bumpers during the airplane’s 28-year history. Maintenance records indicated, however, that work had been performed near the rudder bumpers on several occasions. Also, paint observed on the inverted rudder bumpers during post accident examination was consistent with the maintenance records, which indicate the airplane was painted about 8 years before the accident.There were no maintenance records of work being performed on the rudder bumpers in at least 8 years.

                     The investigation of a similar accident involving a Cessna 152, on July 18, 1998. A CFI and a student pilot were practicing spins and were unable to recover from one. The CFI was killed, the student pilot sustained serious injuries, and the airplane was substantially damaged. During its investigation, the Transportation Safety Board of Canada found that, although the rudder bumpers were installed correctly on this airplane, the rudder had deflected at 34° and had jammed beyond its left travel limit. The TSB also found that the right rudder bumper had traveled beyond the rudder stop and had locked behind it.

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