Almost 12% of all aircraft accident reports state that there was a maintenance factor involved. When the failure or malfunction of equipment is part of the report, one-third of these are due to maintenance errors.
Alaska Airlines Flight 261 crashed into the Pacific Ocean on January 31st 2000. Unfortunately, this accident killed everyone on board. The main cause of this accident was due to maintenance issues. The elevator of this aircraft has a horizontal stabilizer trim, which is where the whole tailplane trims the aircraft and the elevator rotates with this mechanism. This means that if you trim too much, you can lose pitch authority and no longer be able to control the aircraft’s pitch. This horizontal stabilizer trim works on a jackscrew system, and the issue was that there was too much wear as a result of insufficient lubrication during maintenance. The maintenance on this part was supposed to take 4 hours in total, however, on the last maintenance schedule, it was noted that it only took 1 hour.
What seems like a small component of an aircraft caused a catastrophic accident. This shows how diligent and careful maintenance engineers need to be. As a result of this accident, Alaska Airlines increased the maintenance intervals on both the jackscrew and checks on the system.