Introduction
On 18 March 1968, a Piper Cub L4J with registration LN-TVN, owned by Mo flyklubb, crashed near Røssvoll Airport. The aircraft was equipped with ski landing gear and was being flown by the club's pilot, who held a private pilot certificate, with a passenger on board. Both occupants sustained injuries in the accident. The aircraft was considered a total loss.
Accident Details
The accident occurred on the afternoon of 18 March 1968. The pilot had earlier completed a flight with the club's instructor, practicing maneuvers with ski landing gear. Later, the pilot took the aircraft for a 10-15 minute flight with the passenger. The flight departed from Røssvoll Airport at approximately 1530. The aircraft climbed to an indicated altitude of 800 meters, then flew toward Langevatn. The pilot performed a stall with the engine idling, recovered at 600-700 meters. Heading back toward the airport, the pilot attempted a second stall with engine power set to 1400 RPM. The aircraft stalled and rolled left; the pilot recovered. A third stall was attempted, again with 1400 RPM. The aircraft stalled, rolled violently left, and entered a spin. Despite control inputs, the spin continued until the aircraft struck treetops and crashed approximately 600 meters from Hauahei farm, about 1 km west of the airport. The time was approximately 1545. Both occupants exited the aircraft unaided and were taken to a hospital.
Investigation
The accident site was located at about 75 meters above sea level, near the foot of Risfjellet. The aircraft was found nose-down in about 1.5 meters of snow, with the tail pointing up. Four spruce trees had their tops cut off at about 6 meters above the snow. The investigation revealed that the throttle and fuel valve were in the full-open position, and the elevator trim indicator showed half nose-down. A non-approved trim tab (273 x 60 mm) was attached to the right elevator at a 68-degree angle relative to the control surface. This trim tab had been installed in August 1967 by the club to ease control during glider towing, but it had not been approved by the Norwegian aviation authority. The altimeter was found to read 1000 feet low due to a misassembled pointer, a known issue among club members since July 1964. However, no mechanical faults were found in the aircraft, engine, propeller, or instruments that could have caused or contributed to the accident. The airspeed indicator was serviceable.
Aircraft Information
The Piper Cub L4J, serial number 12570, was a two-seat landplane with ski landing gear. It was powered by a Continental C90-12F engine and a McCauley 1A90 propeller. The aircraft had a valid airworthiness certificate (No. 693) issued 17 July 1964, last renewed 6 October 1967, valid until 30 September 1968. It was certified for flight training. The aircraft had accumulated 923.4 hours since last major overhaul as of 16 March 1968. The last 25-hour inspection was performed on 3 March 1968, and the last daily inspection on 18 March 1968. Maximum takeoff and landing weight was 530 kg, with a useful load of 170 kg.
Conclusion
The investigation did not identify any specific cause for the accident. No mechanical deficiencies were found, and the flight was conducted in conditions not further specified. The known altimeter error and unapproved trim tab were noted but not directly linked to the crash.