What happened
On October 22, 2017, a Boeing 737-800, registered JA03GR, operated by Spring Airlines Japan Co., Ltd., was performing a scheduled flight from Narita International Airport to Saga Airport. The flight was operating under challenging weather conditions influenced by Typhoon No. 2 and an active autumnal rain front.
During the descent phase, the aircraft encountered significant atmospheric instability. At approximately 13:38 JST, while flying at an altitude of roughly 12,200 feet near Aso City, the aircraft experienced intense shaking. Flight data records indicate that the aircraft was subject to rapid fluctuations in vertical acceleration, ranging from +0.59 G to as high as +1.67 G, caused by significant vertical wind shear.
During this period of severe turbulence, a cabin attendant was seated in a rear-facing seat in the aft cabin. While she had secured her seat belt tightly, the force of a sudden upward impact caused her to strike her buttocks hard against the seat. The attendant initially did not report the injury, but the physical trauma eventually resulted in a lumbar compression fracture, which was diagnosed several days later.