Incident Overview
On April 17, 2020, at about 11:30 JST, a Cirrus SR22, registration JA017C, operated by the Independent Administrative Institution Civil Aviation College, experienced a serious incident during landing at Obihiro Airport. The aircraft was conducting continuous touch-and-go training with a flight instructor and three trainees on board. After a normal approach and touchdown, the nose landing gear (NLG) was damaged upon landing, causing the aircraft to tilt forward. The instructor shut down the engine and braked to a stop on the runway. The aircraft became unable to continue taxiing.
Flight History
The flight was the fourth of the day for the aircraft. The captain, a commercial pilot with 4,994 flight hours, was in the right seat. A trainee with 30 flight hours was piloting. Two other trainees observed from aft seats. The aircraft had performed three previous touch-and-go landings without issue. Meteorological conditions at 11:00 JST included wind from 150° at 5 kt, visibility 10 km or more, and few clouds at 5,000 ft.
Injuries and Damage
No injuries to persons were reported. Damage to the aircraft included: separation of the NLG oleo (shock absorber) piston rod from the cylinder; all three propeller blades bent backward; inward deformation of the lower nose fairing; broken NLG strut fairing; and two dents on the firewall struck by the NLG strut.
Examination of the Nose Landing Gear Oleo
Detailed examination revealed that the piston rod locknut had detached from the piston rod. The grub screw, which secures the locknut, was missing and not found inside the oleo or elsewhere. No contact marks from the grub screw were present on the piston rod surface, indicating the screw had most likely not been installed during manufacturing. The oleo manufacturer stated that if the grub screw had been tightened at an incorrect position, loss after installation was possible but unlikely.
The same type of oleo had experienced four previous failure cases worldwide where the piston rod separated. These failures were possibly due to improper tightening of the grub screw at manufacturing. The aircraft manufacturer issued a service bulletin on December 11, 2020, after this incident, recommending replacement of oleos manufactured between February 28, 2014 and August 28, 2018. The oleo on JA017C was shipped on August 28, 2018.
Maintenance History
The NLG oleo was installed on the aircraft on December 18, 2018. The incident occurred on the 1,588th landing after installation. The most recent inspection, during regular maintenance on April 15, 2020, found no defects. However, inspection items were limited to exterior checks; internal inspection of the oleo was not required by the maintenance manual.