During a descent into the UK’s Farnborough Airport, the majority of the right engine upper cowling on Cessna Citation 560XL broke free, damaging the leading edges of the vertical and horizontal stabilizers, according to a UK investigation report released last week on the Nov. 29, 2015 incident. Safety investigators concluded that the cowling “probably detached because a number of the quick-release fasteners had not been secured during maintenance.” Cessna has confirmed that there have been two other similar incidents on Citation 560XLs, both in 2008.
In the most recent mishap, the cowlings had been removed and refitted several times to allow engine troubleshooting. The fasteners had been removed from the cowlings as part of a periodic inspection for retention-hole wear. After all maintenance was concluded, the cowlings were reinstalled with one of the mechanics confirming in writing, “Engine cowlings closed and attachments tightened.”
Since the incident, the maintenance organization has changed its inspection procedures to ensure that, following installation, an independent mechanic checks the security of engine cowlings.