AIR CRASH INVESTIGATIONS:
Episode 2, ‘Hidden Danger – US Airlines’
Wednesday June 6
In tonight’s episode of AIR CRASH INVESTIGATIONS, ‘HIDDEN DANGER – US AIRLINES’, two 737 planes crash within several years of each other. The similarities are striking but investigators are stumped. It takes a third near miss, for investigators to get the break they need and crack the case.
In 1991, moments from landing, United Airlines 585 starts spinning out of control and falls out of the sky at 450 kilometers per hour. Everyone on board is killed. In ten violent seconds, the crash site has become one of the most mysterious air disasters in aviation history.
Almost two years after the crash, the NTSB had studied the crew, the weather, the rudder, and thousands of other pieces of evidence – but they can’t solve the mystery. For only the fourth time in its history, the NTSB release a report stating the cause of the crash of flight 585 was undetermined.
On September 7, 1994, a year after the report on Flight 585 is released, the killer strikes again. Another 737 – this time US Air 427 – crashes near Pittsburg. All 132 passengers and crew are killed. Investigators begin to quickly see some striking similarities between US Air 427 — and the unsolved case of United 585.
But, like the earlier accident, investigators have plenty of theories, but can’t nail down a cause. With two crashes just a few years apart, serious questions are now being raised about the safety of 737s around the world. Billions of dollars, perhaps the airline industry itself, are at risk. Investigators need a break in the case, and fast.
It’s only when another 737 has a similar problem – but doesn’t crash – that investigators crack the case open. The pilot of Eastwind 517, is on final approach into Richmond Virginia when, without warning, his 737 twice rolls sharply to the right. The pilot is able to recover, and land the plane safely. NTSB investigators quickly determine that what happened on board Eastwind 517 is alarmingly similar to events on flights 427 and 585. The pilot’s testimony leads investigators to zero in on the 737’s rudder controls. After a series of grueling tests, investigators discover that a key piece of equipment – a small hydraulic valve – jams and then functions in reverse under the right circumstances. It means that any time a pilot tried to correct a roll over, by pushing on the rudder, the rudder might turn in the opposite direction, causing a fatal accident.
In the aftermath of the investigation, sweeping changes were made to improve the safety of the 737 — and the entire aviation industry. New training protocols were designed to help pilots react to unusual in-flight events, upset recoveries and advanced maneuver training. The FAA also directed Boeing to redesign the rudder’s dual servo valve to eliminate the potential for reversal. Boeing spent more than a billion dollars to replace the valves on thousands of 737’s around the world.
PLEASE NOTE: Screens this day and time in Sydney and Brisbane only