Cessna 182S N661SP incident near Springfield, Illinois

Probable cause

The improper installation of a doubler patch, which prevented the right flap from actuating and moving properly and led to the subsequent interference with the aileron.

NTSB analysis

During a proficiency flight for one of the pilots, he was demonstrating a slow-flight recovery procedure, and he added power and began retracting the flaps. When the flaps passed through 10 degrees toward fully retracted, the pilot felt an uncommanded right yoke control movement. As the pilot applied more pressure to the control yoke to maintain level flight, both pilots heard a loud pop, and the uncommanded right yoke control movement stopped. The pilots assessed the airplane and noted that the right flap was buckled. They then conducted a precautionary landing without incident.

A postaccident examination of the airplane found that the inboard portion of the right flap had become dislodged from its track and that the flap had shifted outboard and contacted the aileron. Further examination of the flap system found that a doubler patch had been improperly installed on the lower trailing edge skin; the improper installation altered the curvature of the lower trailing edge skin and infringed on the normal actuation of the flap rollers. Both the inboard and outboard brackets surrounding the flap track had fractured due to the repeated stress applied during the flap roller actuation. A review of the public agency's fleet of airplanes found similar curvature of the lower trailing edge skin and bracket damage due to the improper installation of doubler patches.

Text from the NTSB. Open the NTSB docket for CEN15IA076 for the full record.