CHI98IA035

The instructor and student were practicing stalls, and on a recovery from a stall the instructor heard a loud 'bang', followed by a roll to the left. After ensuring that the aircraft was under control, the instructor performed a visual inspection of the aircraft, and discovered that the left flap was retracted, while the right flap was still extended. After troubleshooting without success, the instructor had the student fly the aircraft back to the airport. They landed the aircraft without any problems. Post accident examination by the NTSB Materials Laboratory revealed that the flap cable was fatigued and had fractured due to fatigue.

On November 12, 1997, at 1715 central standard time, a Cessna 152, N48863, operated by a certified flight instructor, sustained minor damage after experiencing an asymmetric flap condition while maneuvering in the vicinity of Anoka County Airport, near Blaine, Minnesota. The airplane was landed uneventfully and neither the instructor pilot nor the dual student reported any injuries. The 14 CFR Part 91 instructional flight was not operating under a flight plan. Visual meteorological conditions prevailed at the time of the incident. The local flight originated at the Anoka County Airport at 1630 cst.

According to the instructor pilot, the dual student was in the process of performing an intentional stall, as part of the training for a commercial pilot certificate. The airplane was configured with full flaps extended (30 degrees) and the power at idle. In a statement, the instructor reported that after the stall buffet was encountered, the student initiated a recovery. The airplane was pitched to a nose down attitude and full power was added. Approximately two seconds after the addition of full power, there was a loud 'bang,' followed by a roll to the left. The manipulation of the flight controls was transferred to the instructor pilot, who applied full right rudder and full right aileron to combat the roll. A visual scan of the airplane from the cockpit revealed the left flap to be in the full up, or trail, position with the right flap still extended. The instructor confirmed the circuit breaker to be in, and cycled the flap selector; however, there was no resultant movement from the flaps. The instructor stated that it took about half right rudder and aileron with full power to maintain altitude. The airplane was landed uneventfully with the flaps asymmetric, and the flap selector in the up position. During the transition from the runway to the taxiway, the left flap fell to the fully extended position, and the right flap raised to the fully retracted position. After cycling the flap selector on the ground, the instructor found the right flap to be operating normally, with no movement from the left flap.

The aircraft was inspected by company maintenance personnel and found to have a separated left flap cable. According to one of the A & P mechanics, the fracture occurred approximately one and one-half inches from the end of the cable, opposite from the end where the flap attaches. The longer piece of cable (approximately 62 inches) was sent to the National Transportation Safety Board for metallurgical testing. The smaller piece was not recovered.

On December 2, 1997, the flap cable was sent to NTSB Headquarters for metallurgical testing. The report stated, "The great majority of the fracture contained flat facture areas with microfisures and usually curved boundaries, typical of fatigue cracking."