N451SA

HISTORY OF FLIGHT

On March 25, 1997, about 1115 Alaska standard time, a Short SC7 airplane, N451SA, and a Cessna 207A airplane, N800GA, collided in mid-air, about 1.49 nautical miles east-northeast of Nunapitchuk, Alaska. The accident location is about 18.3 miles west of Bethel, Alaska. Both airplanes were being operated as visual flight rules (VFR) cross-country positioning flights to Bethel under Title 14 CFR Part 91 when the accident occurred. N451SA, registered to and operated by Arctic Circle Air Service Inc., Anchorage, Alaska, and N800GA, registered to and operated by Grant Aviation Inc., Anchorage, Alaska, were destroyed by impact and postimpact fire. The pilots of each airplane, the sole occupants of their respective airplanes, received fatal injuries. Visual meteorological conditions prevailed. VFR company flight following procedures were in effect for both flights. N451SA departed the village of Nunapitchuk about 1112 for the flight to Bethel. N800GA departed the village of Scammon Bay, Alaska, about 1000 for Bethel.

The operators of each airplane reported their respective flights were returning to Bethel after delivering all of their cargo. A ground witness (a pilot for another operator), reported he landed at Nunapitchuk about 1107, and was taxiing to the airport ramp. N451SA was beginning to taxi away from the ramp for departure. The ground witness heard the pilot of N451SA announce his departure intentions from Nunapitchuk on an aircraft radio. N451SA then departed on runway 36. N451SA did not circle over the airport or return to the vicinity of the airport. About 1 and 1/2 minutes later, the witness' attention was directed toward the northeast by a ground agent. The witness observed N451SA descending toward the ground in a nose low attitude. The airplane was rotating counter-clockwise in a descending spiral about 800 feet above the ground.

Several villagers, and the ground witness, responded to the accident scene, and observed the wreckage burning on the surface of a small frozen lake. At the point of rest on the ground, the wreckage of N800GA was located entangled with the wreckage of N451SA. N800GA was positioned toward the aft end of N451SA.

The accident occurred during the hours of daylight at latitude 60 degrees, 55.068 minutes north, and longitude 162 degrees, 23.700 minutes west.

CREW INFORMATION

The pilot of N451SA held an airline transport pilot certificate with an airplane multi-engine land rating. He held commercial pilot privileges with airplane single-engine land and sea ratings. In addition, the pilot held a flight instructor certificate with airplane single-engine, multi-engine, and instrument airplane ratings. The most recent first-class medical certificate was issued to the pilot on February 21, 1997, and contained no limitations.

According to the pilot/operator report submitted by the operator, the pilot of N451SA accrued a total aeronautical experience of about 3,170 hours, of which 130 hours were in the accident airplane make and model. In the preceding 90 and 30 days prior to the accident, the report listed a total of 220, and 91 hours, respectively.

The pilot of N800GA held a commercial pilot certificate with airplane single-engine land, multi-engine land, and instrument airplane ratings. The pilot also held a flight instructor certificate with airplane singe-engine, multi-engine, and instrument airplane ratings. The most recent first-class medical certificate was issued to the pilot on February 28, 1997, and contained no limitations.

According to the pilot/operator report submitted by the operator, the pilot of N800GA had accrued a total aeronautical experience of about 2,437 hours, of which 1,136 hours were in the accident airplane make and model. In the preceding 90 and 30 days prior to the accident, the report listed a total of 125, and 55 hours, respectively.

AIRCRAFT INFORMATION

N451SA had accumulated a total time in service of 7,473 hours. The airplane is maintained under the manufacturer's inspection program. A 100-hour inspection was completed on March 17, 1997, 23 hours before the accident. The colors of the airplane included blue paint on the upper end of the vertical stabilizers.

N800GA had accumulated a total time in service of 10,192.5 hours. The most recent annual inspection was accomplished on April 3, 1996. A 100-hour inspection was completed on February 15, 1997, 61 hours before the accident. The colors of the airplane included white paint on the fuselage and wings, with a maroon or red strip along the side of the airplane.

METEOROLOGICAL INFORMATION

The closest official weather observation station is Bethel, Alaska, which is located about 18.3 nautical miles east of the accident site. On March 25, 1997, at 1051, an Aviation Routine Weather Report (METAR) was reporting in part: Wind, 012 degrees (magnetic) at 15 knots; visibility, 60 statute miles; sky clear; temperature, 6.1 degrees F; dew point, -6.7 degrees F; altimeter, 29.89 inHg.

A ground witness at the Nunapitchuk Airport reported the weather conditions at the time of the accident included clear skies; visibility, about 60 miles; wind, 045 degrees at 15 knots.

The position of the sun, in relation to the accident site, was 137.4 degrees (magnetic), at an elevation of 24.4 degrees above the horizon.

COMMUNICATIONS

The pilot of N451SA announced his departure from Nunapitchuk on the common traffic advisory frequency (CTAF) of 122.9 Hz. The operator's company radio frequency is 123.30 Hz.

The pilot of N800GA notified his company's dispatcher of an expected time of arrival (ETA) of 13 minutes on the company radio frequency of 123.12 Hz. The exact time of the call was not noted, but the company dispatcher noted an ETA of 1120 on their flight planning log sheet. Based on an average ground speed for N800GA of 120 knots, the ETA was estimated to have been provided when the airplane was about 26 miles from Bethel.

No further communication was received from either pilot.

AERODROME AND GROUND FACILITIES

The Nunapitchuk Airport has a single gravel runway on a 360/180 degree magnetic orientation. Runway 36 is 2,040 feet long by 60 feet wide. The airport is surrounded by Class E airspace that begins 700 feet above the ground.

WRECKAGE AND IMPACT INFORMATION

The National Transportation Safety Board investigator-in-charge (IIC) examined the wreckage at the accident site on March 26, 1997. During the on-scene examination of the wreckage, strong winds, exceeding 35 knots, hampered efforts to keep items of wreckage from blowing away. The wreckage of N800GA was located within the wreckage of N451SA. Both airplanes were lying flat, and upright on the surface of a frozen lake. Areas of wind blown snow covered the surface of the lake. No evidence of ground impact gouges, or evidence of a wreckage path, were noted. The surface of the snow exhibited sooting in an area around, and downwind, from the wreckage.

N451SA

The wreckage of N451SA exhibited extensive fire damage. The nose of N451SA was oriented at the point of rest on a magnetic heading of 303 degrees, (all heading/bearings noted in this report are oriented toward magnetic north). The left wing remained attached to the fuselage, but all of the outer skin was melted. The aileron and flap assemblies remained attached to the airplane. The left engine remained attached to the wing, and was extensively consumed by fire. It was canted about 45 degrees toward the left wing tip. The propeller blades were broken, and the exposed blade ends were melted, about 8 inches outboard from the hub.

The right wing remained attached to the fuselage, but was displaced slightly forward from its normal geometry, and oriented with the leading edge canted downward. The inboard end of the wing at the fuselage attach point was fire damaged. The rest of the wing was not damaged by fire, and exhibited slight upward crushing of the underside of the leading edge at the wing tip. The outboard wing tip cap was separated from the wing, and was located about 6 feet to the right of the wing tip. The aileron and flap assemblies remained attached to the airplane, and were drooped downward about 50 degrees.

The right engine was attached to the wing. The propeller blades were loose in the hub. Each blade exhibited "S" bending, and torsional twisting. The outer glass of the right wing landing light bulbs was broken. Each bulb filament was tightly coiled and unbroken.

The cockpit area, and the instrument panel were upright and damaged by fire. Examination of the panel revealed the number 2 communication radio was set on a frequency of 119.80 (Bethel ATIS). The number 1 communication radio was destroyed. A navigation radio was set to a frequency of 114.10 (Bethel VOR). The automatic direction finder radio (ADF) was set to a frequency of 795. The nose of the airplane, forward of the instrument panel, including the radome, was not fire damaged. This area displayed vertical crushing and flattening.

The entire fuselage, from the instrument panel to just forward of the horizontal stabilizer was consumed by fire. The left vertical stabilizer was bent and folded to the right, downward over the horizontal stabilizer. It was consumed by fire. The left rudder trim tab separated from the stabilizer, and was located about 200 yards downwind from the wreckage. The trim tab was bent to the right about midspan at an angle of about 45 degrees. The leading edge of the trim tab exhibited a red paint smudge about 6 inches below the top end of the tab.

The right, outboard end of the horizontal stabilizer was fractured about 3 feet inboard from the right vertical stabilizer attach point at the outboard end of the horizontal stabilizer. The right vertical stabilizer, and the fractured portion of the horizontal stabilizer was folded to the left, in an aft and upward direction. The bottom end of the right vertical stabilizer exhibi...