What happened
On 8 September 2018, a DHC-1 Chipmunk 22, registration G-BCPU, was performing an aerobatic display near White Waltham Airfield in Berkshire. Following the completion of an aileron roll at approximately 600 ft agl, the aircraft failed to respond to the pilot's inputs, continuing to roll and pitching the nose downward.
The pilot immediately reduced engine power and issued a MAYDAY call. During the period of instability, the pilot performed vigorous movements of all flight controls. This action successfully cleared a restriction within the rudder control circuit. The pilot regained effective control of the aircraft at an altitude of 50 ft agl, turned back toward the airfield, and performed a successful emergency landing with no injuries and no damage to the aircraft.
The investigation
Following the incident, an immediate inspection of the aircraft suggested the flight controls were undamaged and operating normally. A more comprehensive technical examination conducted several days later found no mechanical defects in the control systems.
However, investigators discovered a partially crushed pen inside the fuselage. The physical condition of the pen suggested it had become lodged in a manner that obstructed the rudder controls. While the pilot had previously removed a pen top from the rear cockpit during a pre-flight check, no other loose items had been identified prior to the flight.
Findings
- The primary cause of the control malfunction was a restriction in the rudder control circuit caused by a loose article (a pen) located within the fuselage.
- The pilot was able to restore control by physically manipulating the flight controls to dislodge the object.
Safety action
- The pilot has implemented more stringent pre-flight and post-flight inspections to identify loose objects.
- A new protocol has been established where pens are only permitted in the cockpit if they are securely tethered to the pilot's or student's flying suit.