Date: 201909
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Landing
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Flap Control (Trailing & Leading Edge)
Component problem: Malfunctioning
Reporter organization: FBO
Reporter qualification: Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument
Second reporter function: Instructor
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: My student pilot was completing his long cross country requirement. I reviewed his flight plan and preflight and everything checked out to be a safe flight. The plan; plane; pilot; programming and environment were all checked out to be safe. I received a call from [student] saying his flaps did not work while landing on the second leg of his cross country into ZZZ and said there was a dent in the flap. He stated the flaps worked at his first stop at ZZZ1 and they also worked fine during the preflight. I asked him if he hit anything and he said he did not. Me and another [instructor] flew to ZZZ to see the damage and pick [the student] up. When we arrived we could see that the flaps were about 4 degrees in the down position and a massive dent in the middle of the flap. We looked in one of the connection points of the flap and noticed a metal square jammed against the rod of the flap. [The other instructor] pried at it with a screwdriver and it broke the metal square free creating a loud bang noise and the dent on the flap bumped back into place and the flap retracted to zero. We then proceeded to open the inspection panel near the area and we found a mechanics tool that is used to pop rivets in place left in the wing. We removed the tool and inspected the flap and aileron cables and they seemed to look fine and we returned the plane back to its base ZZZ2. The tool was wedged against the flap extension rod and did not allow the flaps to retract. This could have created a very dangerous situation as the aileron cables run very close to where the tool was discovered. This was the first flight since its annual inspection and it is likely it was left in the wing during that inspection. [The Student] performed how he was trained and executed a no flap landing and did not try to lower the flaps anymore and the pilot and plane landed safely.


Second narrative: A student pilot was on a solo XC (Cross-Country) when flaps failed to extend. Landed at ZZZ and called his CFI (Certified Flight Instructor). Two CFI's flew to pick up student and aircraft. Upon reaching aircraft; [they] found Maintenance had left a rivet bucking bar inside the wing causing flaps and ailerons to bind up. I removed the bucking bar through an inspection panel on the wing. Maintenance states no tool box inventory was completed.


Synopsis: Flight instructors reported C172 student pilot experienced a flap extension issue while preparing to land as the result of a tool left in the wing.