Embraer 120 incident near Fresno, California, February 21, 2000
On February 21, 2000 at about 5:58 pm local time, a Embraer 120, registered N566SW, was involved in an incident near Fresno, California (Fresno-Yosemite International airport). It was a flight of an unrecorded kind under scheduled airline rules (Part 121). No one was hurt; 20 people were on board or involved. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
Moisture contamination of the elevator trim actuator units resulting in their failure to operate at below freezing temperatures
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- February 21, 2000 · about 5:58 pm local time
- Place
- Fresno, California · Fresno-Yosemite International · map
- Type
- Incident
- Injuries
- No one was hurt; 20 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Embraer 120
- Registration
- N566SW · registry record · serial 120341
- Damage
- Not recorded
- Flight
- Flight of an unrecorded kind · scheduled airline rules (Part 121)
The NTSB's narrative final · quoted from the NTSB record
The elevator trim froze in flight. During the initial descent from 22,000 feet mean sea level (msl) to 14,000 feet msl, the trim wheel moved to the forward stop. The trim wheel made a "snapping" motion midway through the movement, and then moved aft. The trim wheel continued to move back and forth, so the crew disconnected the autopilot and trim. The airplane wanted to pitch up, and the captain had to apply moderate forward pressure to maintain pitch control. The trim wheel was still jammed, but one crewmember could control the airplane. At 12,000 feet msl, and approximately 23 degrees Fahrenheit outside air temperature, the trim remained immovable. Between 5,000 feet msl and 4,000 feet msl, the trim wheel became moveable. By the time the airplane reached the traffic pattern altitude, the trim wheel moved freely. The outside temperature at that time was 46 degrees Fahrenheit. Examination of the elevator trim units revealed that one trim actuator had leaking shaft seals. Its packing had cracked, and a bearing had seized. The second actuator was dirty, and minor corrosion was on the hardware. The shaft seals leaked, and a rigging device was installed. Service Difficulty Report (SDR) data from August 30, 1990, to February 29, 2000, contained 19 reports of the elevator trim freezing at altitude. Nine of the reports noted that the trim operated normally after descent to lower altitudes and warmer temperatures. Eleven additional reports referenced binding or stiffness at altitude. Some of the airplanes experienced multiple events. During some of the events, the airplane pitched violently. The manufacturer discovered moisture and corrosion in some of the actuators that were submitted for repair after these occurrences. They suspected that leaking seals allowed moisture into the actuators, which froze at altitude. They developed a modification that included installation of additional seals inside the actuator. However, Skywest maintenance records indicate that both unmodified (Part Number 5299) and modified (Part Number 5299-1) actuators experienced problems. Both actuators on the incident airplane were unmodified units. Total time on the airplane was 3,757 hours.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: airline transport pilot
- Ratings: multi-engine land; instrument: airplane
- Flight time: 4,059 hours in all; 1,659 in this make and model; 1,557 as pilot in command
- Last flight review: November 2, 1999
- Medical certificate: Class 1 (valid medical--no waivers/lim.)
- Seat: left
- Injury: no injuries
Co-pilot
- Certificate: airline transport pilot
- Ratings: multi-engine land; instrument: airplane
- Flight time: 13,851 hours in all; 1,656 in this make and model; 3,981 as pilot in command
- Last flight review: June 21, 1999
- Medical certificate: Class 1 (valid medical--w/ waivers/lim.)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 3,768.4 hours
- Last inspection: continuous airworthiness programme, February 19, 2000; 18 hours since
- Maximum gross weight: 26,433 lb
- Seats: 33
- Landing gear: retractable
- Engine 1: Pratt & Whitney PW118B (turboprop); 0 hours total
- Engine 2: Pratt & Whitney PW118B (turboprop); 0 hours total
The flight
- Departed from: LAX Los Angeles CA at 8:00 am
- Destination: FAT Fresno-Yosemite CA
- Flight plan: IFR
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 120° at 9 knots
- Visibility: 10 statute miles
- Sky: scat at 5,000 ft
- Temperature: 59°F (15°C), dew point 45°F (7°C)
- Altimeter: 29.00 inHg
- Observation at 5:58 pm from FAT
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 3 | |||
| Passengers | 17 |
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The docket at the NTSB holds the report as a PDF and the investigation's photographs and documents. This site never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number LAX00IA106.