- Education and Science
The faulty lubrication kills all 88 people on board the flight Alaska 261
On January 31, 2000, Alaska Airlines Flight 261 was a scheduled passenger flight from Puerto Vallarta, Mexico to Seattle, Washington. This flight was a McDonnell Douglas MD-83.
The captain and the First officer were experienced pilots. The captain had 17,500 hours of flying under his belt. While the First officer had accumulated 8,140 total flight hours.
After take-off, the plane climbed to its cruising altitude of 35,000 feet. The flight was real smooth. There was not a single clue of what was coming ahead?
After 2 hours into the flight, the pilot contacted the company's maintenance facilities in SeaTac, Washington. They discussed the problem of the jammed horizontal stabilizer and were unable to determine the cause of the jam.
The pilots requested the air traffic controller to allot them a block altitude and a low populated area.The pilots choose to divert the flight to Los Angeles. Later, in the investigation their action was found to be appropriate.
After trying hard, the pilots were able to unjam the horizontal stabilizer. Upon being freed the plane suddenly went into a nose down position. In around 80 seconds the plane got down from 33000 feet to 24000 feet.
However, the pilot struggled and finally brought the flight under control. They put an enormous 500 N force on the controls and only then were able to stabilize the plane. But this didn't last long.
At 16:19 the flight again suddenly went into a nose down position for the second time in the flight. The nearby planes reported to air traffic controller about the flight 261's situation. The plane was not in a position to recover and at one point they tried to fly the plane upside down. A deadly event occurred and all 83 passengers including 5 crew members were dead.
Path of Alaska Airlines Flight 261| before crash
What is NTSB?
If you are an Aviation enthusiast, then you will have probably heard of NTSB and black boxes. For those who don't know, National Transport Safety Board (NTSB) is US government investigative agency, responsible for civil transportation accident investigation.
All the commercial planes are equipped with cockpit voice recorder and Flight data recorders and are called as black boxes. Don't go by the name black boxes are not black, but are orange.
These boxes have a storage which can record up to 2 hours of latest flight data. The black boxes will help the investigators to know, what happened in the last few minutes of the flight?
Listen to the original cockpit recording of Alaska Airlines Flight 261
The NTSB findings . . .
The National Safety Transport Board(NTSB) rushed to the crash site immediately.
A part in the tail section of the plane caught their immediate attention. It was the jack-screw which connects the flight controls with the horizontal stabilizer.
The NTSB was astonished to see that the screws of jack-screw had ripped off. The probability of jackscrew failure is very less.
Okay, here is what happened with the jack-screw.
When the flight first went into a deep dive there was a slight connection with rudder. In a bid to stabilize the plane, the captain hit the controls hard. The pilot successfully pulled the plane out of dive.
But, his bid to stabilize the plane further damaged the jackscrew assembly. Now the all the aerodynamic force acting on the plane was just holding on a locking nut. Locking nuts are never designed for such high aerodynamic forces.
Finally, the locking nut broke apart and this time there was no chance for the pilots to control the plane.
After nearly 2 years of studying the retrieved data from the black box, the final report was published. The NTSB raised several safety concerns in MD- 83 and its predecessor MD -80.
Upon the closer inspection, the NTSB found that there was no proper lubrication on jackscrew assembly and cited as the main reason for the crash. Also, the questions were raised on the design of the horizontal stabilizer.
Every system on the plane has a backup system. The designers of this plane assumed the failure of jackscrew as next to impossible and no backup systems were designed. Though the main reason for the crash remains improper lubrication.
Because of the improper lubrication, the catastrophe occurred. All the people on board were killed. Who was responsible for this??
For any airplane after a set period or distance traveled, each part of the plane is closely inspected. For MD - 83 this period is 4 years.
Surprisingly, Months ago the crash this particular flight had undergone such full-scale inspection. Then how did the maintenance crew miss out to lubricate the jackscrew??
Actually, they didn’t miss it. The mechanic had checked the screw and recommended to lubricate it. He didn’t clear the plane as fit for flying and was suspended.
The plane was cleared of due to the cost-cutting system of the airliner. The fate of this plane had been decided. There was no way for pilots to control the plane.
Watch the flight simulator of Alaska Airlines Flight 261
Interested to read the entire report by NTSB on this incident? If so, then have a look at NTSB's official website.
A small lubrication problem costed 88 lives, Do you think air travel is safer?
© 2016 Vasant