NTSB Factual Report

HISTORY OF FLIGHT

On February 27, 2008, about 1400 Alaska Standard time, a tundra tire-equipped Cessna 170B airplane, N8458D, sustained substantial damage when it collided with trees and snow-covered terrain, about 8 miles southwest of Tyonek, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country personal flight under Title 14, CFR Part 91, when the accident occurred. The airplane was operated by the pilot. The private certificated pilot, the sole occupant, was killed. Visual meteorological conditions prevailed. The flight originated at Merrill Field, Anchorage, Alaska, about 1328, and was en route to Igiugig, Alaska. No flight plan was filed.

Federal Aviation Administration (FAA) personnel notified the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) at 1922, that the accident airplane had been reported overdue by friends of the pilot. The pilot was returning to his home in Igiugig with a load of groceries. Search and rescue personnel located the accident site about 1953, and the pilot was transported to a hospital in Anchorage.

PERSONNEL INFORMATION

The pilot held a private pilot certificate with airplane single-engine land, and single-engine sea ratings. His most recent third-class medical certificate was issued on February 14, 2007, and contained the limitation that he must wear glasses for distant vision, and possess glasses for near vision.

No personal flight records were received for the pilot, and the aeronautical experience listed on page 3 of this report was obtained from Federal Aviation Administration (FAA) airmen records on file in the Airman and Medical Records Center in Oklahoma City. On the pilot's application for medical certificate, dated February 14, 2007, he indicated that his total aeronautical experience was about 2,400 hours, of which 275 were in the previous 6 months.

AIRCRAFT INFORMATION

The airplane and the engine had a total time in service of about 2,627 hours. Review of the maintenance records revealed that the most recent annual inspection of the airframe and engine was on October 30, 2007, about 40 hours before the accident.

The engine had a major overhaul on April 18, 2002, about 1,535 hours before the accident.

METEOROLOGICAL INFORMATION

The pilot received a weather briefing via telephone from the Kenai Automated Flight Service Station (AFSS), Kenai, Alaska, at 1233, for a planned flight from Anchorage to Igiugig, via Lake Clark Pass, departing at 1330. The flight service station specialist advised the pilot to expect mostly VFR conditions along the route of flight, with scattered snow showers, especially near higher terrain. A transcript of the weather briefing is included in the public docket of this report.

At 1353, an aviation routine weather report (METAR) at Kenai, about 27 miles south-southeast from the accident, was reporting, in part: Wind, 030 degrees (true) at 13 knots; visibility, 10 statute miles; clouds and sky condition, few at 6,500 feet; temperature, 30 degrees F; dew point, 16 degrees F; altimeter, 29.71 inHg.

At 1350, Big River Lakes, Alaska, about 21 miles west-southwest of the accident, was reporting calm winds, overcast skies at 6,000 feet, with a visibility of 20 miles.

COMMUNICATIONS

The pilot contacted the Merrill Field Air Traffic Control Tower (ATCT) at 1325, and was cleared for takeoff at 1328. No further communication was received from the pilot.

WRECKAGE AND IMPACT INFORMATION

The NTSB IIC, and an FAA inspector from the Anchorage Flight Standards District Office (FSDO), examined the airplane at the accident site on February 28. The airplane was in a forested area, having collided with the snow-covered ground on about a 50 degree, nose-down attitude.

At its point of rest, the nose and engine of the airplane were against the base of a large birch tree. The bark of the tree facing the airplane, had been stripped in patches from about 10 feet above the ground to the base, and branches of the tree were broken about 20 feet above the ground. Trees immediately next to the point of rest had broken branches about 40 feet above the ground, but no other trees in the area had evidence of impact.

The engine was partially buried in the ground, resting against the base of the birch tree. The tree trunk was between the engine case and the propeller, with one propeller blade resting against the backside of the tree trunk. The backside of the tree trunk had a 45 degree cut into the bark, about 5 feet above the ground, which almost severed the tree. A second cut partially through the tree was about 3 feet above the ground, which split a section of wood from the backside of the tree trunk to the ground. The other propeller blade was buried in the ground.

All of the airplane's major components were found at the main wreckage area. The wings were displaced forward of their normal position, and each had extensive spanwise leading edge aft crushing. The leading edge of the left wing had a semicircular aft crush area, about 2 feet inboard from the wingtip. The leading edge of the right wing had two pronounced areas of semicircular aft crushing, with evidence of tree bark at the impact areas. The aft portion of the right wing at the fuselage carry through was torn open at the top of the fuselage. The upper surface of the airplane at its point of rest was on about a 020 degree heading. (All heading/bearings noted in this report are oriented using magnetic north.)

The main landing gear struts were broken in an aft direction, and were resting on the surface of the snow. The fuselage, aft of the cockpit, was crushed forward, and the empennage was bent to the left. The horizontal stabilizer, elevator, vertical stabilizer, and the rudder received minor denting.

About 5 inches of fuel was found in the left wing fuel tank, and about 1 inch of fuel was found in the right wing fuel tank. The right fuel tank lines were breached. The flight control surfaces remained connected to their respective attach points.

The cockpit area was extensively damaged. The engine and firewall were displaced aft and upward, and the instrument panel was crushed forward and upward, almost to the top of the windshield. The engine tachometer was about 2,000 rpm, and the hour meter was 1573.5.

Following recovery of the airplane, it was examined in Wasilla, Alaska, on April 8, 2008. The engine was examined at a maintenance facility in Anchorage, on April 9. The parties noted in this report participated in the examination.

The fuel selector was on the left tank, and fuel was found within the selector housing.

Due to impact damage, the flight controls could not be moved by their respective control mechanisms, but continuity of the flight control cables was established to the cockpit area.

The propeller assembly remained connected to the engine crankshaft. One propeller blade had chordwise scratching and aft bending. The second blade had "S" bending, torsional twisting, and aft bending.

The engine had impact damage to the nose of the case, the underside, and the left aft portion of the engine. The accessory case at the aft end of the engine was punched through the firewall. The exhaust tubes had malleable bending and folding, producing sharp creases that were not cracked or broken along the creases.

Gear and valve train continuity was established, and lubricating oil was found throughout the engine. The oil screen was free of contaminants. The crankshaft accessory gear starter ring had 2 broken gear teeth. The propeller flange was bent and cracked near the radius of the flange base.

The magnetos and spark plug leads sustained impact damage, but produced spark at all terminals when functionally tested on a test stand. The massive center electrode sparks plugs had no unusual combustion signatures.

The carburetor bowl was fractured, and the butterfly assembly was broken away from the carburetor housing.

No evidence of any preimpact engine anomalies were discovered during the inspection.

MEDICAL AND PATHOLOGICAL INFORMATION

A postmortem examination of the pilot was done under the authority of the Alaska State Medical Examiner, 4500 South Boniface Parkway, Anchorage, Alaska, on February 29, 2008. The examination revealed that the cause of death for the pilot was attributed to multiple blunt force injuries.

A toxicological examination by the FAA's Civil Aeromedical Institute (CAMI) on April 10, 2008, was negative for any alcohol or drugs.

SEARCH AND RESCUE

Search and rescue personnel at the Alaska Rescue Coordination Center (RCC) received a composite emergency transmitter locator (ELT) signal in the area of the accident about 1555. They also received a report from an overflying airplane that an ELT signal was being heard. No ELT signal was heard when rescue satellites made another pass over the accident area at 1602. The Alaska State Trooper post in Soldotna, Alaska, was notified about 1618. The RCC requested search aircraft from the Civil Air Patrol (CAP), Kenai, Alaska, about 1702, and they were airborne about 1751. About 1757, CAP aircraft reported that they were unable to cross the waters of the Cook Inlet due to insufficient cloud ceiling height, which required their aircraft to be able to reach 3,500 feet msl in order to cross the inlet.

About 1806, the RCC requested search and rescue personnel from the 212th Rescue Squadron to initiate a search. About 1902, the airplane was reported overdue by a friend of the family. About 1930, the 212th helicopter reported that they were searching the area of the accident, and located the accident site about 1953.

ADDITIONAL INFORMATION

The Safety Board released the wreckage, located at Wasilla, Alaska, to the owner's representatives on May 19, 2008. No parts or components were retained by the Safety Board.

NTSB Probable Cause

The pilot's failure to maintain adequate airspeed to prevent a stall while maneuvering, which resulted in an uncontrolled descent and collision with terrain.