BARROW, AK, USA
N750GC
Cessna 208B
The pilot, who was also the station manager, arrived at the airport earlier than other company employees to prepare for a scheduled commuter flight, transporting seven passengers and cargo to another village during hours of arctic, predawn darkness. Heavy frost was described on vehicles and airplanes the morning of the accident, and the lineman who serviced the airplane described a thin glaze of ice on the upper surface of the left wing. The pilot was not observed deicing the airplane prior to flight, and was described by the other employees as in a hurry to depart on time. The pilot directed the lineman to place fuel in the left wing only, which resulted in a fuel imbalance between 450 and 991 pounds (left wing heavy). The first turn after takeoff was into the heavy left wing. The airplane was observed climbing past the end of the runway, and descending vertically into the water. No preimpact mechanical anomalies were found with the airplane or powerplant. The aileron trim indicator was found in the full right wing down position. Postaccident flight tests with left wing heavy lateral fuel imbalances, disclosed that approximately one-half of right wing down aileron control deflection was used to maintain level flight, thus leaving only one-half right wing down aileron control efficacy. Research has shown that frost on airfoils can result in reduced stall angles of attack (often below that required to activate stall warning devices), increases in stall speeds between 20% and 40%, asymmetric stalls resulting in large rolling moments, and differing stall angles of attack for wings with upward and downward deflected ailerons (as when recovering from turns).
HISTORY OF FLIGHT On November 8, 1997, at 0808 Alaska standard time, a Cessna 208B airplane, N750GC, was destroyed when it impacted water in the Arctic Ocean, about one-half mile west of Barrow, Alaska. The airline transport certificated pilot, and the seven passengers on board, sustained fatal injuries. The airplane was operated by Hageland Aviation Services, Inc., of St. Mary's, Alaska, under 14 CFR Part 135, as scheduled commuter Flight 500. The destination was Wainwright, Alaska. Night, visual meteorological conditions (VMC) prevailed at the time of the accident, and a VFR flight plan was filed. At 0802, the pilot radioed to the FAA Flight Service Station (FSS) that he was taxiing for takeoff, and filed a flight plan to Wainwright with eight persons on board, two hours en route, and three hours of fuel. At 0804, the pilot reported that he was back taxiing for runway 24. At 0806, he transmitted that he was departing runway 24. At 0808, two annunciations of an Emergency Locator Transmitter(ELT) were heard on 121.5 MHz by the FSS specialist on duty. The pilot of a Cessna 207 which had earlier departed runway 06 for Wainwright reported hearing the pilot say, "mayday, mayday" and that he saw the airplane's lights descend "straight down into the water." The witness pilot had been talking previously to the accident pilot on 127.77 MHz, and overheard the "mayday" call on that frequency. The witness pilot revealed that he was at 700 feet MSL, and that the accident airplane never reached his altitude. The airplane came to rest submerged in twenty-one feet of water, approximately 200 yards offshore. The fuselage and left wing were recovered the evening of the accident, with the right wing, engine, and various other components recovered separately over the next two day period. One passenger occupied the right-front crew seat, five passengers occupied the installed passenger seats, and a single infant was being held by her mother as a lap child. All occupants were recovered from the interior of the airplane, still restrained in their seats, except for the infant, who was located in the aft cabin. The accident flight was the company's first flight of the day. The lineman who assisted the pilot prepare the airplane for departure, told the NTSB investigator-in-charge (IIC) that after he fueled the airplane's left wing, there were no "ribbons or strings" hanging down from the airplane, and there were no covers on the pitot tubes. The lineman, and the company dispatcher who was helping prepare the flight, described the pilot as "the same as he always was," and in a hurry to make the scheduled takeoff time. DAMAGE TO AIRCRAFT The airplane was destroyed by a combination of impact forces and recovery damage. The airplane was described by the divers who first arrived on scene to be resting upright on the ocean floor in 21 feet of water. The wings were attached to the fuselage, but the engine was not. These divers described the leading edges of both wings as damaged. During recovery of the airplane, ropes were attached to the wing struts and landing gear, for towing by boats. While being towed, the airplane rolled over, and the right wing separated. The left wing remained attached by cables. PERSONNEL INFORMATION The pilot held an airline transport pilot certificate for multiengine airplanes, and a commercial pilot certificate for single-engine airplanes. His first class medical certificate contained no restrictions. He also possessed an airframe and powerplant mechanic license. The pilot was first hired by the company as the station manager at McGrath, Alaska, on June 23, 1994. He had been employed by the operator as the station manager in Barrow since June of 1997, and had flown 220 hours in the Barrow area. According to the company president, the pilot's primary duty was to manage the station, and he was not required to fly as a pilot. The pilot's wife said he enjoyed flying, and normally would take the first flight in the morning, which then allowed him to concentrate on his management duties for the remainder of the day. The pilot was qualified in Cessna 185, 206, 207, and 208 airplanes. At the time of the accident, he had accumulated about 3,500 hours of flight time. Between June 23 and 27, 1997, he attended initial training in the Cessna 208B at Flight Safety International, Inc., Wichita, Kansas. The pilot had accrued 161 hours of experience in the Cessna 208B, and had flown 20.1 hours in the week prior to the accident, all in the Cessna 208B. The pilot's most recent 14 CFR Part 135 proficiency check was conducted on June 27, 1997, as part of his initial qualification in the Cessna 208B. AIRCRAFT INFORMATION General The airplane was a Cessna 208B "Grand Caravan," manufactured in January 1996, by the Cessna Aircraft Company, Inc., of Wichita, Kansas. The airplane was operated as a company demonstration aircraft by Cessna Aircraft Company, Inc., until it was sold on May 16, 1997, to Gussic Ventures, Inc., of Anchorage, Alaska, who leased it to Hageland Aviation Services, Inc. The airplane was powered by a single Pratt & Whitney PT6A-114A turboprop engine, rated to produce 675 shaft horsepower. The airplane had accumulated 1,438 total hours in operation at the time of the accident. The airplane was equipped with the capability of seating up to nine passengers. At the time of the accident, five passenger seats were installed. The remaining seats were stowed in the aft cargo compartment, to make room for a casket being carried as cargo in the cabin. The airplane also carried a cargo pod installed underneath the belly of the airplane. The airplane was equipped for flight into instrument meteorological conditions (IMC), although at the time of the accident, the company's FAA approved Operating Specifications did not authorize passenger carrying operations in single-engine airplanes during IMC. The airplane was maintained on a Cessna periodic maintenance schedule, under an Approved Aircraft Inspection Program (AAIP). This was approved on the company's Operations Specifications in paragraph D73. This AAIP was developed from the Cessna Aircraft Company Recommended Maintenance Program for the Cessna 208B airplane. It was comprised of 12 "Phase" inspections, one accomplished each 200 hours, with "mini" checks each intermediate 100 hours. When utilizing this AAIP, the entire aircraft is inspected with the completion of any four consecutive phase inspections. All inspections were current at the time of the accident. The most recent maintenance performed was a "Phase 4" inspection completed on November 1, 1997, 28 hours prior to the accident. A review of maintenance records revealed no repetitive maintenance problems, except for a captain's Heading Situation Indicator (HSI) replacement on June 19, October 27, October 28, and October 29, 1997. No further discrepancies with the captain's HSI were noted. The accident airplane was flown on three flights by a different pilot on November 7, the day prior to the accident. This pilot did not recall any discrepancies with the airplane. Weight and Balance When questioned on how much fuel remained in the airplane when he returned from the final flight on the evening of November 7, the previous pilot told the Safety Board that he believed the airplane had approximately 600 to 700 total pounds of fuel, with 350 pounds in each wing. He did not fuel the airplane upon his return from the flight which preceded the accident. The morning of the accident flight, the pilot directed that the left wing be "topped off" by a new employee. This was the employee's second day on the job, and he had no previous experience working on, or around, airplanes. When interviewed by the NTSB operations group chairman, he described unrolling the fueling hose from its storage location, and fueling the left wing until fuel "sloshed" out of the overwing fueling receptacle. He assumed this meant the tank was full, and then stopped. He said he placed no fuel in the right wing. In order to determine how much fuel the lineman may have actually placed in the left wing tank, the investigation team asked the employee to fill a Cessna 208B left wing in the same manner as he fueled the accident airplane. The fuel level in the test wing was then read from the fuel gauges in the cockpit to be 800 pounds. Each wing has a total capacity of 1,122 pounds of Jet-A fuel (167.5 gallons). Cargo on board the airplane consisted of an estimated 280 pounds of passenger's personal baggage, 98 pounds of freight, 354 pounds of bypass mail located in the belly mounted cargo pod, and a 418 pound casket containing a deceased relative of the passengers. The casket was secured in the cabin by one-inch wide, tubular nylon webbing cargo straps, and located aft of the passenger seats. The dispatcher said that as she placed the passenger's luggage on the scales, the pilot removed them for loading before she could record the weights. The airplane's published maximum allowable takeoff weight was 8,750 pounds. The takeoff weight of the airplane on the morning of the accident was calculated by the NTSB to be between 8,560 pounds and 8,882 pounds (considering the minimum and maximum fuel combinations), with a longitudinal center of gravity between 197 inches and 198 inches aft of datum. The longitudinal CG limits at these weights are between 196 and 204 inches aft of datum. These weights were derived from available weight and balance records, occupant weights provided by the FAA, coroner records, cargo/baggage information provided by the operator, and estimated fuel in each wing as described below: Empty weight of airplane -- 4,948 pounds Pilot and Passengers -- 1,228 pounds Cargo(freight and casket) -- 516 Cargo(Bypass mail) -- 354 pounds Cargo (baggage) -- 364 pounds Zero Fuel Weight -- 7,410 pounds Estimated fuel right wing -- 350 pounds Estimated fuel left wing -- 800 to 1,122 pounds Total weight at takeoff -- 8,560 to 8,882 pounds The fuel in the airplane at takeoff was derived by using the estimated fuel remaining in the wings from the previous flight, and the estimated fuel added to the left wing by the company lineman immediately prior to the accident flight. Lateral fuel loading imbalance has a limit published in the Pilot Operating Handbook of 200 pounds. The lateral fuel imbalance (left wing heavy), is estimated to have been between a minimum of 450 pounds, to a maximum of 991 pounds. METEOROLOGICAL INFORMATION Morning civil twilight at Barrow on November 8 was 0924. The reported weather at 0750 was a few clouds at 14,000 feet, 7 miles visibility, with winds from 170 degrees at eight knots. The outside air temperature was 12 degrees Fahrenheit, with a dew point of 7 degrees Fahrenheit. The pilot of a DC-6 which landed about one hour before the accident indicated he was able to see Barrow from about 100 miles away. This pilot was preparing to depart when the accident occurred, and described light winds. He said in a written statement that he did not notice any ice or frost in the air, and that none formed on his airplane during his approximately one hour of ground time. Heavy frost was described as having formed on vehicles and aircraft which were parked outside overnight, by the pilot of the Cessna 207 who witnessed the accident. The witness pilot told the NTSB that his airplane had accumulated a "heavy frost" and it took him approximately 15 minutes to clean it off. He said that it usually took him about five minutes to clean frost off his airplane. The company lineman who fueled the left wing of the accident airplane said he noticed a coating on the wings and described it as a "rough glaze like you get on a car window." He demonstrated what the ice looked like to the NTSB operations group by sliding a piece of ice off an automobile window. This piece was a very thin, fragile, transparent, piece of ice. The lineman said the lower surfaces and windows were free of ice and frost. Other town residents also described frost on vehicles. The accident pilot was already at work loading his airplane when other employees arrived. Company employees interviewed by the NTSB were not aware of the pilot removing frost or ice from the airplane. The accident pilot had been observed on other occasions applying an unknown fluid to wing surfaces with a garden sprayer. This was not noted by company employees the morning of the accident. COMMUNICATIONS The local FSS and traffic advisory frequency is 123.6 MHz. The unofficial common frequency used by local pilots for air to air communications is 127.77 MHz. The pilot filed his flight plan and made common traffic advisory transmissions on 123.6 MHz. All recorded voice transmissions from the pilot on 123.6 MHz were ground transmissions. No inflight transmissions were received or recorded. The accident pilot was also communicating with the pilot of the Cessna 207 who departed before him, on 127.77 MHz. The frequency 127.77 is not recorded. The NTSB IIC, and members of the Operations Group, listened to recorded radio transmissions between the airplane and the FSS. None of the members could discern any noises on 123.6 MHz which corresponded to any cockpit warning horns. AERODROME INFORMATION The Will Rogers-Wiley Post Memorial Airport is located on the coast of the Arctic Ocean, and consists of a single, paved, 6,500 feet long runway, oriented 06-24. The runway is equipped with runway end identifier lights, runway edge lights, and medium intensity approach lights located at the approach end of runway 06. The accident airplane's takeoff from runway 24 departed over the water, and made a left turn toward Wainwright. The intended route of flight paralleled the shoreline. During hours of darkness, this direction of departure is toward dark water and featureless ice. The airport is uncontrolled, and has an FAA Flight Service Station located at the field. This facility provides weather observations and traffic advisory services to pilots. WRECKAGE AND IMPACT INFORMATION The NTSB on site investigation began at 2200 on November 8, 1997. The NTSB IIC, and two FAA inspectors from the Fairbanks, Alaska, Flight Standards District Office (FSDO) arrived in Barrow and began an inspection of the wreckage which had been initially recovered. Additional NTSB and FAA representatives from Washington, DC, arrived on November 9. The investigative team then formed an Operations Group comprised of members from the NTSB, FAA, and the operator; and an Airworthiness / Maintenance Group comprised of members from the NTSB, FAA, the operator, Cessna Aircraft Company, and Pratt & Whitney. The airplane was towed to the beach, with the left wing attached, where it was not disturbed until the NTSB conducted the initial examination. The airplane was then relocated to a hangar facility at the Navy Arctic Research Laboratory in Barrow, along with the right wing and powerplant, which were recovered separately. The four aileron balance weights, and all attaching screws, were intact, tight, and showed no evidence of binding on the flight controls. The control column was inspected with no evidence that the control lock was installed at impact. The aileron trim control indicator was found on the full right wing down trim index. No indications of flight control system anomalies were noted. The trailing edge flaps were found in the zero (0) degrees, or retracted position. The wing spoilers were retracted. The company procedure is to rotate the airplane for takeoff at 75 knots with flaps set at 20 degrees. Flaps are then retracted to 10 degrees at 85 knots, and retracted to 0 degrees at 95 knots. The engine and propeller assembly separated from the fuselage and was recovered. Two of the three propeller blades fractured at the blade hubs and were not located. A witness mark on the Interstage Turbine Temperature (ITT) gauge face read 850 degrees Centigrade. The takeoff temperature limits for the PT-6A-114A engine are 805 degrees Centigrade. The 2 second transient limit for ITT is 865 degrees Centigrade. The leading edges of both wings were crushed aft along their entir
The pilot's disregard for lateral fuel loading limits, his improper removal of frost prior to takeoff, and the resulting inadvertent stall/spin. Factors involved in this accident were the improper asymmetrical fuel loading which reduced lateral aircraft control, the self-induced pressure to takeoff on time by the pilot, and inadequate surveillance of the company operations by company management.
Source: NTSB Aviation Accident Database
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