LAX98FA031

The aircraft was destroyed when it impacted trees in mountainous terrain at about 7,850 feet msl. The density altitude was calculated to be about 8,400 feet. Examination of the trees and the aircraft wreckage disclosed that the aircraft was in near level flight at the time of initial tree contact. The aircraft gross weight at the time of impact was calculated to be about 3900 pounds; the maximum certificated takeoff weight was 3500 pounds. No mechanical malfunction was found in the airframe or the engine. The owner had personally installed a set of amphibious floats and a three-blade propeller. The installation was not inspected or signed off for return to service, and there was no evidence that the weight and balance had been recomputed.

History of flight:

On October 26, 1997, at 1600 hours Pacific standard time, a Cessna U206B, N4982F, was reported overdue on a flight from Minden, Nevada, to Calaveras County Airport, Angel's Camp, California. On November 5, 1997, the aircraft was located approximately 14 statute miles southwest of Markleeville, California. The aircraft was destroyed when it impacted mountainous terrain and the pilot and three passengers were fatally injured. Weather reports disclosed that visual meteorological conditions prevailed along the route of flight on the day of the accident. No flight plan had been filed for the personal flight and there was no evidence of any air-to-ground communications from the aircraft prior to the accident.

Aircraft information:

The aircraft logbooks indicated that the last airframe and engine annual inspection had been performed on November 9, 1996. At that time, the airframe had a total time of 8,623 hours and the engine 576.2 hours since last overhaul. The person who performed the inspection stated that the owner did most of the airframe and engine preventive maintenance with occasional supervision by a mechanic.

The aircraft logbooks indicated that on July 5, 1997, a set of "Wipline" floats, Model 3730, Serial No. 37280, and a new three-blade, McCauley propeller, model D2A34C58/90AT-2 were installed on the aircraft by the owner. The mechanic stated that he did not participate in this activity and there was no entry of inspection or return to service signoff in the logbook. Also, the most recent weight and balance form that could be found was dated October 9, 1995.

Meteorological information:

The South Lake Tahoe airport is the closest weather observation station to the accident site and is located 18 miles northwest. At 1400 on the day of the accident, the Tahoe Airport reported the surface wind as 190 degrees at 8 knots; the temperature and dew point as 49 and 17 degrees Fahrenheit, respectively; clear skies, 30 statute miles visibility; and an altimeter setting of 30.04 inches of mercury. Based on an accident site pressure altitude of approximately 7,800 feet msl and a free air temperature of 45 degrees Fahrenheit (extrapolation from Tahoe Airport temperature using the standard dry parcel temperature lapse rate), the density altitude at the accident site was calculated to be approximately 8,400 feet.

Wreckage and impact information:

All of the aircraft parts were located in a shallow, tree studded canyon, approximately 2 statute miles northwest of Lower Sunset Lake at GPS coordinates 38 degrees 36.76 minutes north latitude by 119 degrees 52.90 minutes west longitude.

A path of disturbed 80- to 90-foot-tall pine trees were noted on a magnetic bearing of approximately 210 degrees. The aircraft was found in an inverted attitude with the tail pointing along the reciprocal of the disturbed tree bearing. Fragmented parts of the airframe, such as the wings, tail section, and floats were all found within 10 feet of the main fuselage. The engine, and detached propeller, were found buried beneath the main fuselage in a hole approximately 3 feet deep. The measured distance from the last disturbed tree, estimated to be approximately 60 feet agl, to the ground impact site was 50 feet.

Semicircular indentations found on the wings and floats matching the dimensions of the upper trunks of the first disturbed trees were oriented vertically to the aircraft's longitudinal axis. Distributed along the ground between the initial tree and the aircraft wreckage were several tree branches of 4- to 6-inch diameter that had been cut; paint transfer was noted on the cut sections that matched the propeller. A postimpact fire had extensively burned the airframe, and the burn area was contained within the wreckage footprint with no observable damage to surrounding trees and bushes.

All of the aircraft's flight controls and airframe components were accounted for at the accident site. There was no evidence of in-flight structural failure or flight control malfunction. There was fuel in both wing tanks, but fuel continuity to the engine could not be established due to fire damage. No on-site effort to determine engine state was attempted due to extensive dirt and debris contamination.

Medical and pathological information:

Toxicological tests performed on the pilot were negative for carbon monoxide, alcohol, and pertinent drugs.

Tests and research:

The aircraft engine was retrieved from the site and shipped to the Teledyne Continental factory in Mobile, Alabama, for teardown inspection. The FAA inspector who witnessed this inspection stated that there was no evidence of internal failure, excessively worn parts, or incorrect assembly.

Using available information for the weight of all passengers, and assuming full fuel at takeoff and no baggage, the Cessna Aircraft Air Safety Investigator calculated that the aircraft weighed over 3,900 pounds at the time of the accident and was not within the recommended center of gravity envelope. The pilot's handbook states that for the float equipped model the maximum takeoff weight is 3,500 pounds.

Additional information:

The airframe wreckage was verbally released to the registered owner's representative on November 10, 1997, at the conclusion of the on-site examination. The representative advised that he would assume the responsibility for extraction from the accident site. The aircraft engine, Serial No: 570586, was verbally released to the owner's representative at the conclusion of the engine examination.