N4704B

History of the Flight

On November 26,1996, at 1101 Alaska standard time, a Cessna 208B, N4704B, crashed into snow covered terrain following takeoff from the Bethel Airport, Bethel, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country cargo flight under Title 14 CFR Part 135 when the accident occurred. The airplane, registered to and operated as flight 1604 by Arctic Transportation Services, Anchorage, Alaska, was destroyed. The certificated airline transport pilot, the sole occupant, received fatal injuries. Visual meteorological conditions prevailed. VFR company flight following procedures were in effect.

At 1057:56, the pilot contacted the Bethel Air Traffic Control Tower (ATCT) ground control and requested a southwest departure. The air traffic control specialist cleared the flight for taxi to runway 36. The pilot then contacted the Bethel ATCT local controller, and at 1059:39, the pilot was cleared for takeoff.

The pilot did not communicate with the Bethel ATCT after takeoff. Following departure, the company dispatcher attempted to contact the pilot to obtain his liftoff time. The pilot stated "stand by." After departure from runway 36, tower personnel observed the airplane in a left turn back toward the airport at an estimated altitude of 100 to 200 feet above the ground. The angle of bank increased and the nose of the airplane suddenly dropped toward the ground. The airplane struck the ground in a nose and left wing low attitude about 1101:55, about 1 mile west of the airport.

The accident occurred during the hours of daylight at latitude 60 degrees, 47.434 minutes north, and longitude 161 degrees, 51.515 minutes west.

Crew Information

The pilot held an airline transport pilot certificate with an airplane multi-engine land rating. He also held commercial pilot privileges with airplane single-engine land and sea ratings. In addition, the pilot held a flight instructor certificate with an airplane single-engine rating and a mechanic certificate with airframe and powerplant ratings. The most recent second-class medical certificate was issued to the pilot on February 10, 1996, and contained no limitations.

According to the pilot/operator report submitted by the operator, the pilot's total aeronautical experience consisted of about 3,622.7 hours, of which 474.4 were accrued in the accident airplane make and model. In the preceding 90 and 30 days prior to the accident, the report listed a total of 270.4 and 98.8 hours respectively.

Aircraft Information

The airplane and engine had accumulated a total time in service of 3711.3 hours and 5,069 cycles. Examination of the maintenance records revealed the airplane was maintained under an approved inspection program (AAIP). The most recent inspection was a phase 3 inspection completed on November 6, 1996, 61.1 hours before the accident. The engine, propeller, and airframe, received an annual inspection on March 19, 1996, 648.1 hours before the accident.

The engine has a time between overhaul (TBO) requirement of 3,500 hours. The FAA granted a 10 percent extension to a TBO of 3,850 hours with an "on-condition" inspection program of the engine hot section. The extension was granted with the stipulation the operator continue utilizing a trend monitoring program to track the engine parameters. The engine performance parameters were recorded by company pilots on each flight and then entered into a computer tracking program where the performance data was displayed in a graphical format. The performance graphs were reviewed by the operator's director of maintenance. The graphical results revealed an inconsistent pattern of engine performance and a scattering of recorded engine values, but did not reveal any obvious degradation of engine power.

The airplane utilizes a constant speed, full feathering, and reversible propeller. The airplane's propeller assembly has three composite construction propeller blades. The leading edge of each blade is metal. The inboard end of each blade consists of an aluminum base. The blades are retained in their respective hub positions by a steel clamp attached around the base of the blade. The clamp halves are bolted together around the base of the blade. Following assembly of the blades in the propeller hub, each blade is required to be subjected to a 200 ft/lb torque test to see if a blade slips in the clamp. A red mark on the blade and one on the clamp are utilized to provide a visual reference point to check for any sign of blade slippage in the clamp.

At the time of the accident, the propeller assembly had accrued 5,066.9 hours, 746.5 hours since being overhauled. It was overhauled on July 12, 1995, after accruing 4,319.9 hours, total time. The propeller assembly was installed on the accident airplane on February 23, 1996, at 4,399.5 hours total time and 79.1 hours since the overhaul. On July 26, 1996, at 4,699.0 hours total time and 378.6 hours since being overhauled, the propeller blades sustained ground damage and were replaced. Factory overhauled blade serial numbers 9195, 9272, and 9273, were installed by Dominion Propeller Corporation, Anchorage, Alaska. The blades accrued an additional 367.9 hours before the accident.

Fueling records at Hanger One, Bethel, established that the aircraft was last fueled on the accident date with the addition of 50 gallons of Jet A aviation fuel. A Peninsula Airways airplane also received fuel from the same fuel vender as that of the accident airplane, and departed before the accident flight.

A fuel selector "OFF" warning system is located in the inboard end of each wing. The system includes redundant warning horns and an annunciator warning light to alert the pilot if one or both of the fuel tank selectors are in the "OFF" position.

Meteorological Information

The closest official weather observation station is Bethel, which is located about 1 nautical miles east of the accident site. At 1052, an aviation routine weather report (METAR) was reporting, in part: Wind, 010 degrees (true) at 12 knots; visibility, 40 statute miles; Sky condition and ceiling, few clouds at 4,000 feet, few clouds at 10,000 feet; temperature, -14.0 degrees C; dew point, -16.6 degrees C; altimeter, 29.71 inHg; remarks: Ice crystals ended 45 minutes past the hour.

At 1101, the Bethel ATCT automated airport advisory service (ATIS) was reporting, in part: Bethel tower information Yankee at 1052; wind, 010 degrees at 12 knots; visibility, 40 miles; few clouds at 4,000 feet, a few clouds at 10,000 feet, temperature, -14 degrees; dew point, -16 degrees; altimeter, 29.70; visual approach in use to runway 36; notice to airmen, runway 11/29, thin snow, the taxiways and ramps have thin snow over patchy thin ice, advise on initial contact you have information Yankee.

Communications

Review of the air-ground radio communications tapes maintained by the FAA at the Bethel ATCT revealed the pilot successively and successfully communicated with the positions of ground and local control. A transcript of the air to ground communications between the airplane and the Bethel ATCT is included in this report.

Aerodrome and Ground Facilities

The Bethel airport is equipped with a hard-surfaced runway on a 360/180 degree magnetic orientation. Runway 36 is 6,398 feet long by 150 feet wide. A second gravel surface runway is oriented on a magnetic heading of 110/290 degrees. Runway 11 is 1,850 feet long by 75 feet wide.

The Bethel ATCT is a Federal Contract Tower (FCT) operated by Barton ATC International, Inc.

Wreckage and Impact Information

The National Transportation Safety Board investigator-in-charge (IIC) examined the airplane wreckage at the accident site on November 27, 1996. A path of wreckage debris and ground scars from the initial point of ground contact to the wreckage point of rest was observed on a magnetic heading of 140 degrees. (All heading/bearings noted in this report are oriented toward magnetic north.)

All of the airplane's major components were found at the main wreckage area. The first observed point of ground impact was a small gouging of soil in a fan shaped pattern located in tundra and snow covered terrain. The left wingtip position light assembly was located about 25 feet from the first observed point of impact along the wreckage path. A line of snow and soil disruption was present from the first observed point of ground contact along the wreckage path to about a 4 foot diameter crater in the soil and rocks. This was about 36 feet after the first observed point of impact. About 18 inches of the metal leading edge of one propeller blade was located in the crater area. The remaining portion of the blade was shattered and destroyed.

About 10 feet to the left of the crater was a second propeller blade, serial number 9273. The blade was broken at the inboard end of the blade and the face side of the blade displayed several spanwise splintering fractures. The cambered side of the blade displayed minor chordwise scuff marks, about mid-span. Broken pieces of Plexiglas, the pilot's windshield heat assembly, pieces of engine cowling, and portions of the nose wheel assembly were located adjacent to the crater. Wreckage debris, including portions of the cargo, were located along the wreckage path from the crater to the fuselage point of rest.

A third propeller blade was located between the impact crater and the instrument panel. It separated from the hub assembly and displayed extensive spanwise fractures. About 4 inches inboard from the tip, the leading edge exhibited about a 1 inch deep and 4 inch wide indentation and crushing of the blade material. The trailing edge of the blade displayed a similar indentation and crush. The metal leading edge of the blade was fractured and missing from the blade.

The right control yoke of the airplane was located about 36 feet beyond the impact crater along the wreckage path. The lef...