Cessna 560XL N607QS incident near Toledo, Ohio

Probable cause

The manufacturer's inadequate initial design and subsequent modifications of the tailcone, which allowed moisture to collect and freeze around rudder cables during flight levels above the freezing level and resulted in a loss of rudder authority. Contributing to the accident was the lack of oversight of the manufacturer's design and production by the Federal Aviation Administration.

NTSB analysis

The Cessna 560XL airplane encountered ground and/or in-flight moisture/rain, that collected in the tailcone stinger and subsequently froze around the rudder cables during flight at an altitude above the freezing level. When the pilot attempted to use the rudder to initiate a crosswind correction during the landing flare, he was unable to move the rudder pedals, but was able to land the airplane uneventfully. In the days and weeks that followed, several other 560XL airplanes encountered the same problem. As a result, the airplane manufacturer issued a service bulletin recommending that drain holes be added in the tailcone stinger. The manufacturer had already added the drain holes in production airplanes, yet some production airplanes had drain holes that were not the indicated size. The manufacturer then issued an alert service letter to modify the stinger drain. However, the alert service letter still did not remedy the problem; another 560XL airplane, modified in accordance with the alert service letter, sustained ice-bound rudder cables. The manufacturer subsequently issued a mandatory service bulletin that required the installation of a seal and drain to improve water drainage from the stinger. The misdrilled holes on production airplanes were not detected by the Federal Aviation Administration (FAA) district office assigned to oversee the incident airplane. The manufacturer has subsequently instituted a specific inspection criteria to verify the drain hole installation on production airplanes, and the FAA has verified engineering requirements, planning changes for technicians to follow, and actual holes, including their dimensions.

Text from the NTSB. Open the NTSB docket for CEN11IA087 for the full record.