On former aircraft without engine starter, hand prop was usual. This video shows how dangerous it is.
After having installed the passenger onboard, the pilot removed the chocks and hand-proped its plane. The engine power increased rapidly. Right wheel brake was functioning, but left wheel brake was released, so the plane started to turn right alone. The passenger, who had never been onboard an aircraft, was paralysed with fear. The pilot couldn’t stop its plane. The aircraft finally collided into two parked airplanes. The pilot and the passenger were seriously injured.