Embraer EMB-120 N288SW

Summary

On 26 February 2001 at about 05:55 local time, a Embraer EMB-120 registered N288SW, operated by Skywest Airlines, Inc., was involved in an accident near Monterey, California, United States. 33 people were on board and one was seriously injured. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

26 February 2001 at 05:55

Classification

Accident

Location

Monterey, California, United States

Coordinates

36.4167, -121.8333

Aircraft

Embraer EMB-120

Registration

N288SW

Category

Airplane

Engines

2

Operator

Skywest Airlines, Inc.

Operating rule

Part 121: Air Carrier

Phase of flight

Not recorded

Route

Los Angeles → Monterey

Aircraft damage

Not recorded

Weather

VMC

Light

Night

NTSB number

LAX01LA105

1 person was seriously injured.

moisture contamination of the elevator trim actuators, which allowed the units to freeze at altitude resulting in an abrupt pitch change when the units thawed at lower altitudes.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The lone cabin attendant in the aft end of the airplane sustained a broken ankle when she was thrown to the floor after the airplane experienced an abrupt pitch change during descent. The captain had the autopilot engaged as the airplane descended through 10,000 feet mean sea level. The nose pitched down violently about 10 degrees, and then the nose pitched back up. The captain disengaged the autopilot and hand flew the airplane to touchdown. The Brasilia has two elevator trim actuators. The manufacturer discovered moisture and corrosion in some of the actuators submitted for repair after similar occurrences. They suspected that leaking seals allowed moisture into the actuators, which froze at altitude. In numerous instances, the actuators functioned properly after descent to lower altitudes and warmer temperatures, where the units thawed. One unit was dirty, corroded, and had overspray on it. It leaked from the shaft seals and autoloc seal. It failed the non-jamming stop test. It's two shaft housings contained moisture. The chain and pins were corroded, the packing had deteriorated, and the springs were weak. One side of the rollers was not chamfered, and staking warped some screws. The hub was worn and not functioning properly. The second unit was dirty and had overspray on it. The actuator leaked from the shaft seals. The actuator had excessive backlash and failed the tangential free play test. It's two shaft housings contained moisture. The chain, pins, shafts, and housings were corroded. The packing had deteriorated, and the bearings were rough and binding. The rollers only had one chamfered side. The shim was not with the unit.

Quoted verbatim from the NTSB record.