It's the 1990s and a Alaskan Airlines jet take off to bring passengers home from Puerta Vallarta to the north. Half-way up the Mexican coast over the Pacific Ocean, the horizontal stabilizers on the tail get stuck in such a way as to point the nose slightly down and the pilots have to fly the airplane manually to keep it level. It's a nuisance. The pilots run through the troubleshooting manual but nothing changes. They call Alaska Airlines and ask to land there at Los Angeles until the problem is fixed but the controller discourages them -- there will be a long wait before they can land.
Meanwhile the frustrated pilots are whanging away the controls. Without warning, the airplane flips over and begins a rapid descent from which they recover only with the greatest difficulty. One can only imagine the horrors experiences by both the crew and the passengers during that long drop.
The recovery is short-lived. Something in the tail breaks and the airplane plunges towards the sea. Nearby pilots report to Los Angeles in short sentences embodying barely concealed sympathy. "Yes, he's inverted." "He's definitely out of control." It hits the ocean at more than 250 miles an hour and everyone aboard is killed. The airplane was a revised and improved version of the DC-9. The engines were in the rear and the high T-shaped tail was unique. Since the first problem reported was with the horizontal stabilizers, the investigatory team directs its attention to the tail, as the Navy laboriously recovers pieces of the shattered aircraft.
The fault lay in the tail, exactly where expected. A thick threaded bolt moves the elevators up and down but the team found no grease on the bolt, the threads worn away, and a retaining nut missing. These technical details are presented in a way that's not too difficult to follow. The causes included corner cutting. Alaska Air had a good reputation until the 90s when pressure was applied to keep as many of the fleet in the air as possible.
One inspector at the time recommended replacement of the threaded bolt -- the same that had failed -- and in the absence of any response from the airlines executives, he contacted higher authorities, for which he was put on paid leave and was never to work in the industry again. His written recommendation in the log was penciled over. A short time later, the crash occurred.
The NTSB found the primary cause to be extended maintenance intervals, long enough to cause damage to some of the parts of the airplane. That was the responsibility of the executives trying to save money. The team also found that this particular model had no back-up system in case the jack screw failed. The designers had never envisioned such a failure because of the maintenance schedule were adhere to, there would never have been a failure. There is still no redundancy in the control of the horizontal stabilizers.
Meanwhile the frustrated pilots are whanging away the controls. Without warning, the airplane flips over and begins a rapid descent from which they recover only with the greatest difficulty. One can only imagine the horrors experiences by both the crew and the passengers during that long drop.
The recovery is short-lived. Something in the tail breaks and the airplane plunges towards the sea. Nearby pilots report to Los Angeles in short sentences embodying barely concealed sympathy. "Yes, he's inverted." "He's definitely out of control." It hits the ocean at more than 250 miles an hour and everyone aboard is killed. The airplane was a revised and improved version of the DC-9. The engines were in the rear and the high T-shaped tail was unique. Since the first problem reported was with the horizontal stabilizers, the investigatory team directs its attention to the tail, as the Navy laboriously recovers pieces of the shattered aircraft.
The fault lay in the tail, exactly where expected. A thick threaded bolt moves the elevators up and down but the team found no grease on the bolt, the threads worn away, and a retaining nut missing. These technical details are presented in a way that's not too difficult to follow. The causes included corner cutting. Alaska Air had a good reputation until the 90s when pressure was applied to keep as many of the fleet in the air as possible.
One inspector at the time recommended replacement of the threaded bolt -- the same that had failed -- and in the absence of any response from the airlines executives, he contacted higher authorities, for which he was put on paid leave and was never to work in the industry again. His written recommendation in the log was penciled over. A short time later, the crash occurred.
The NTSB found the primary cause to be extended maintenance intervals, long enough to cause damage to some of the parts of the airplane. That was the responsibility of the executives trying to save money. The team also found that this particular model had no back-up system in case the jack screw failed. The designers had never envisioned such a failure because of the maintenance schedule were adhere to, there would never have been a failure. There is still no redundancy in the control of the horizontal stabilizers.
