About Eastwind flight 517:

On June 9th, 1996, a Boeing 737-2H5 belonging to Eastwind left Trenton, New Jersey for Richmond, Virginia. At that time, the plane was manned at a speed of 250 knots. When the plane was at an altitude of 4,000 feet, captain Brain Bishop felt that the rudder seemed to collide slightly to the right. Suddenly the plane lurched to the right without warning, and the rudder was completely out of control as if it were stuck. So the captain adjusted the uneven output power of the engine in order to restore the plane to horizontal flight. After a while, the plane suddenly returned to horizontal flight. The captain and the co-pilot immediately checked what was wrong, but soon the plane tilted to the right again, deviated from the course and stalled and fell. However, the plane soon returned to its level again. Fearing that there would be a third loss of control, the captain immediately declared a state of emergency and asked the co-pilot to tell the tower what problems they had encountered. Richmond International Airport also made an emergency alert. Finally, the plane landed safely. Except for one flight attendant who was slightly injured, other passengers and crew members were not injured because the plane was about to land, and the plane was not damaged.

Investigation:

Although no one was killed in this accident, the loss of control of the 737 passenger plane is very similar to the two previous air crashes, namely, United Airlines Flight 585 in 1991 and USAir Flight 427 in 1994: all three accidents occurred before the approach; All three are the sudden loss of control of the rudder, which caused the plane to roll over. The most important thing is that the models of the three accidents are all Boeing 737. But in the end, only the plane of Eastwind escaped. The previous two accidents killed 157 people, no one lives. Therefore, the accident was highly valued by investigators, and the day after the accident, investigators arrived in Richmond for investigation.

Probably cause:

Thanks to the fact that the plane was not damaged and the captain's testimony, a breakthrough has been made in the investigation of the two air crashes of Flight 585 and Flight 427. According to the data of Eastwind aviation accident, the investigators made a series of experiments on the hydraulic device in the rudder. The results show that this device will get stuck when it passes through extreme temperature difference, that is, -50 degrees at an altitude of 30 thousand feet to 30 degrees on the ground (assuming).