ASN Wikibase Occurrence # 318952
| Date: | Monday 16 August 2021 |
| Time: | 14:52 |
| Type: |  Cessna 208B Grand Caravan |
| Owner/operator: | Wright Air Service |
| Registration: | N97HA |
| MSN: | 208B0610 |
| Year of manufacture: | 1997 |
| Total airframe hrs: | 15382 hours |
| Engine model: | Pratt & Whitney Canada PT6A-140 |
| Fatalities: | Fatalities: 0 / Occupants: 9 |
| Aircraft damage: | Substantial, repaired |
| Category: | Accident |
| Location: | near Fairbanks, AK -
 United States of America
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Fairbanks International Airport, AK (FAI/PAFA) |
| Huslia Airport, AK (HSL/PAHL) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
Wright Air Service flight 440, a Cessna 208B, was substantially damaged when it was involved in an inflight upset near Fairbanks, Alaska. The pilot and eight passengers were not injured.
According to the accident pilot, flight 440 departed about 14:24 from the Fairbanks International Airport (FAI), destined for Huslia, Alaska (HLA), located about 220 miles east-northeast of FAI. After departure, she climbed the airplane to her assigned altitude of 10,000 ft mean sea level (MSL), where she encountered what she described as light rime icing conditions. In an effort to exit the icing conditions, she asked and was assigned a block altitude from 10,000 - 12,000 ft msl, and subsequently climbed the airplane to 10,500 ft msl. Unable to exit the icing conditions, she elected to begin a gradual descent back to 10,000 ft msl. She added that instrument meteorological conditions prevailed, and that the autopilot was engaged. The pilot also noted that while en route, the airplanes deicing boots, and heated propeller were operating normally by removing ice accumulations.
She said that while in a gradual descent from 10,500 ft. msl to 10,000 ft. msl, the autopilot suddenly disengaged, without warning, and the airplane entered an abrupt uncommand right bank followed by a steep nose down, spiraling descent. The pilot said that it felt as if the aileron controls were jammed as she tried to regain control of the airplane. After regaining control of the airplane, she declared an inflight emergency and subsequently made an emergency landing at FAI.
A review of preliminary flight track data revealed that after departing FAI, the flight proceeded to the west, northwest for about 47 nm, cruising at about 10,000 ft msl. Prior to the upset, a climb was initiated and the flight reached an altitude of about 10,700 ft msl before descending to about 10,300 ft msl followed by abrupt changes to altitude and ground speed.
A postflight inspection of the airplane revealed substantial damage to the right aileron. Flight control continuity was established continuously from each control surface to the corresponding cockpit controls.
Although the airplane was equipped for flight into known icing conditions, the pilots operating handbook (POH) contained information that flight in freezing rain, freezing drizzle, mixed conditions, or conditions defined as severe were prohibited. In addition, the minimum speed for flight in icing conditions with the flaps up was 130 knots indicated airspeed with a maximum
weight of 8,550 lbs. The POH further required that the autopilot be disconnected once every 10 minutes in icing conditions to check for any out-of-trim conditions caused by ice buildup.
Data obtained from the autopilot revealed that it was not disconnected every 10 minutes through the course of the flight as required. The indicated air speed was consistently below 130 knots, and it was below 100 knots in the seconds preceding the upset. Furthermore, the low airspeed alert activated at 107 kts about 16 minutes, 5 minutes and 2 1/2 minutes before the upset, respectively. Additionally, the estimated gross weight of the airplane at the time of the accident was about 293.5 lbs over its maximum approved gross weight and 805.5 lbs over its approved maximum gross weight for flight in known icing conditions.
Probable cause: The pilots unexpected encounter with supercooled liquid droplets (SLD), which resulted in a loss of control due to ice accumulation. Contributing to the accident were: (1) the pilots failure to maintain the minimum airspeed for flight in icing conditions, (2) the pilots failure to disconnect the autopilot every 10 minutes to check for ice buildup, (3) the overweight airplane, (4) the lack of an SLD forecast product for the state of Alaska, and (5) the Federal Aviation Administration's failure to require weight and balance documentation for each flight in Title 14 Code of Federal Regulations Part 135 single-engine operations.
Accident investigation:
 |
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Sources:
adn.com
flightaware.com
NTSB AIR-22-07
Location
Revision history:
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