CEN15IA076

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.

On December 10, 2014, about 1440 central standard time, a Cessna 182S, N661SP, had a flap malfunction that interfered with the aileron near Springfield, Illinois. The commercial pilots were not injured and the airplane had minor damage. The airplane was registered to and operated by the Illinois State Police, Springfield, Illinois, as a public use airplane flight. Visual meteorological conditions prevailed for the flight.According to a statement provide by the Illinois State Police, the pilots were performing a proficiency check for one of the pilots. While demonstrating slow flight recovery procedures, the airplane was configured with flaps fully extended. During the recovery procedure, power was added to the airplane and pilot began retracting the flaps. As the airplane passed through about 80 knots indicated airspeed and the flaps were retracted from 10 degrees to fully retracted, the pilot felt the yoke being pushed to the right. The pilot ensured that the other pilot was not also on the controls and confirmed that the autopilot was off. As more control authority was needed to maintain level flight, both pilot heard a popping sound and the uncommanded right yoke control ceased. The pilot assessed the airplane and noted that the right flap was buckled. They performed a precautionary landing without incident. A postaccident inspection of the airplane found that the inboard portion of the right flap had become dislodged from its track and the flap had shifted outboard and had contacted the aileron. Further examination of the flap system found cracks in both inboard and outboard brackets surrounding the inboard flap track, with the inboard bracket being completely fractured. Both brackets had been bent downwards. Paint abrasions were found on the brackets consistent with contact from the flap roller support arm. At a time prior to the accident, doubler patches had been added to the lower trailing edge skin in order to repairs cracks in the area where rivets were attached. These doublers flattened the curve of the lower trailing edge skin. A review of other agency maintained airplane found similar discrepancies with regards the curvature of the lower trailing edge skin and bracket damage.