NTSB Factual Report

On November 29, 1993, about 1749 hours Pacific standard time, a Mooney M20K, N5788U, collided with mountainous terrain about 7 miles west of June Lake, California. The airplane was being operated as a personal flight by the pilot. The airplane was destroyed. The certificated commercial pilot and passenger received fatal injuries. The weather conditions at the accident site at the time of the accident are unknown. The airplane departed the Carson City Airport, Carson City, Nevada, at an unknown time and was destined for Chino, California, where the airplane was based. No flight plan was filed for the accident airplane.

Family members reported the airplane's occupants missing to local law enforcement authorities after they failed to return home. On December 4, 1993, the Civil Air Patrol (CAP) was notified of the airplane being missing. The CAP conducted a search for the missing airplane without success.

The airplane was found by a hiker on July 5, 1994, in a saddle several hundred feet west of Blacktop Peak at an elevation of 12,200 feet above mean sea level. According to a Mono County Sheriff's deputy, snow depths of twenty feet deep are common in the saddle during the winter months.

Documents recovered from the airplane by the Mono County Sheriff's Office were dated November 29, 1993. The airplane was last seen at the Carson City Airport on November 29, 1993, about 1500 hours.

The airplane's clock was found stopped at 5:49; the pilot's wrist watch was found stopped at 6:00; and the passenger's watch was found stopped at 12:39. The Mono County Coroner is listing the time of death for the occupants at 1749 hours.

Pilot Information

The pilot held a commercial pilot certificate, which was issued on November 22, 1972, with a single engine airplane rating. The pilot subsequently added a multiengine airplane rating, an airplane instrument rating, and a helicopter rating. The most recent rating was obtained on April 16, 1989, with the addition of a Lear Jet type rating. The pilot was issued a second class medical certificate on July 8, 1993. The medical certificate contained the limitation must wear glasses for near and distant vision.

No personal flight records were located for the pilot, and the aeronautical experience listed in this report was obtained from a review of the airmen Federal Aviation Administration (FAA) records on file in the Airman and Medical Records Center located in Oklahoma City, Oklahoma. Also, information was obtained from one of the pilot's former insurance companies.

According to the FAA , the pilot listed total aeronautical experience of about 12,263 hours at the time of his application for a medical certificate. The pilot also indicated his flight time in airplane make and model was in excess of 2,000 hours.

There were no records found delineating the pilot's flight experience at the time of the accident, or the accomplishment of a biennial flight review.

AIRCRAFT INFORMATION

The airplane was registered as N5788U, serial number 25-0852. The airplane was manufactured on December 21, 1984. No maintenance records were located for the airplane, and no determination of the airplane's total time or maintenance history was discovered.

A Teledyne Continental engine, serial number 309167, was installed in the airframe. According to the engine manufacturer, the engine was shipped to Mooney Aircraft Company on April 8, 1979. Mooney Aircraft Company delivery documents indicate the engine was installed in a Mooney M20K, N231CQ, on June 12, 1979.

Review of aircraft registration and airworthiness records maintained by the FAA Aircraft Registration Branch revealed that the Mooney M20K, N231CQ, was registered to the accident pilot on July 26, 1980, and later reported stolen to AIG Aviation Insurance on July 3, 1982.

Further investigation revealed that 17 out of 18 avionics components manufactured by Allied Signal, Inc., General Aviation Avionics, (formally King Radio) were installed in N231CQ at the time of airframe manufacture. The warranty registration cards for the avionics also indicate they were installed in N231CQ. Review of the aircraft delivery documents also revealed that every serialized flight instrument, engine instrument, and electrical system component was installed in N231CQ.

The airplane had three means of direct navigation installed in or onboard at the time of the accident; a King KNS 80 Area Navigation System, a Morrow II Loran C, and a portable Magellan GPS 5000A.

Additionally, the airplane's emergency locator transmitter battery was dated in 1980. The battery should be replaced every 2 years.

Review of Mooney Aircraft Corporation delivery documents for N5788U indicated the airplane was painted in a three color scheme. The paint colors were called Gray Stone, Black Diamont, and Sky Gray. During a visit to the Chino Airport, Chino, California, a pilot from a neighboring hangar to the accident airplanes, presented to the Safety Board several pieces of sheet metal from a "chopped airplane." The pieces were identified from a Mooney airplane's empennage with portions of the registration number, and pieces containing the oxygen system servicing port. The paint scheme of the pieces matched that of N5788U, to include portions of the registration number.

Meteorological Information

The closest official weather observation station is the Lake Tahoe Airport, South Lake Tahoe, California, which is located 76 nautical miles north of the accident site.

On the day of the accident the National Weather Service at Reno, Nevada, 106 nautical miles northwest of the accident site was forecasting a cold front passing through slowly with winds at 30 knots from the south. By 1030 hours PST rain showers and mountain obscurement was forecasted for the area all day. The area forecast for Reno predicted at the time: 3,700-foot overcast, changing to 2,100-foot overcast in early afternoon and lowering to 1,200-foot overcast later.

WRECKAGE AND IMPACT INFORMATION

The airplane was found at the 12,200 foot level in a bowl west of Blacktop Peak. The accident area is 2.1 nautical miles west of a 329 nautical-mile-long direct course line from the airplane's departure point in Carson City to its destination in Chino. The location was plotted at North 37-47.49 degrees latitude and west 119-11.89 degrees longitude.

The airplane was painted silver with black and red accent strips on the wing tips and fuselage. The aircraft was found resting in a field of boulders in a run-off area of a snow field located up slope of the wreckage to the north. The airplane was oriented with the nose pointing 160 degrees magnetic. A debris field extends about 1,000 feet north of the fuselage, and south about 500 feet in the run-off area.

The floor of the airplane was crushed upward. The wings remained attached to the fuselage and the empennage and tail flight control surfaces were missing. The landing gear was found retracted in the wheel wells. The landing gear switch was damaged and found in the down position.

The engine was separated from the firewall and held in a displaced position to the left front by the control cables which were still connected. The exhaust system was crushed upward and aft. The oil sump was fractured exposing the internal components of the crankcase for visual inspection.

The left wing had a compression buckle on the leading edge forward of the aileron and a tear on the underside near the fuel tank. The leading edge of the right wing was not damaged. Both wing tips were damaged. Remnants of the both tips were found in the debris field. There was control continuity to both ailerons.

Both wings exhibit hydraulic buckling to the underside. There was no scoring in the paint in the area of the buckles. The flap linkage to the flap panels was found separated. The right flap panel was folded under the wing and the left flap panel was extended slightly. Both flap panels exhibited damage to their trailing edges. The flap switch was found in the up position.

The propeller was separated at a break in the crankshaft propeller flange and was found about 40 feet from the engine. The break exhibited a 45-degree fracture surface. Both propeller blades were loose in the hub and had chordwise scoring and leading edge nicks and gouges.

The empennage was separated at an angular circumferential split that tore the sheet metal skin at a line of rivets at station 131 on the airplane's left side, and tore the sheet metal about station 138 on the belly, right side and roof.

The elevator and rudder counter weights were found in the debris field north of the fuselage. All three were separated through torn sheet metal near the hinge areas. The counter weights exhibited leading edge gouges consistent with hitting rocks with the weighted end first. The aspect of the damage to the counter weight leading edges was not consistent with being attached to their flight control surfaces at the time of impact. There was no evidence of control divergence on the elevator or rudder counter weights or attached sheet metal.

The airplane's instruments and avionics were removed for further examination. It was noted, especially in the removal of the roll servo, that there was no evidence of the attaching bolts or screws being turned counterclockwise since installation. Most of the bolts and screws were torqued and require some force to loosen. In every case the tools used marked the zinc oxide paint on the bolts or deformed the screw heads when turned.

There were no unusual instrument readings or radio settings found during the documentation of the cockpit, however, the autopilot was found switched on. The position of the switches and instrument readings are contained in Supplements A and B of this report.

MEDICAL AND PATHOLOGICAL INFORMATION

Post mortem examinations were conducted by the Mono County Sheriff/Coroner's Office with specimens from the pilot retained for toxicological examination. The results of the toxicological analysis revealed negative results for routine drug and alcohol tests.

TESTS AND RESEARCH

Engine Exam

The engine was recovered from the accident site and examined in June Lake, California. During the examination the right magneto was rotated and one of the cylinders fired as if the engine was trying to start. Further examination did not reveal any evidence of preimpact mechanical failure or malfunction.

Avionics Testing

The airplane's radios and autopilot system were sent to the manufacturer's facilities in Olathe, Kansas, for examination and testing. There was no evidence found in the communication or navigation radios that would have precluded them from operating before the accident. There were some discrepancies noted, but it could not be determined if they existed before impact or as a result of impact forces.

A King KFC-200 Autopilot System was installed in the airplane. Examination of the KS 270 pitch servo revealed a broken trim spring that controls nose-down trim commands. The spring was submitted to the metallurgical laboratory for analysis.

According to the metallurgist's report, the trim spring fracture surface exhibited characteristics of metal fatigue. Striations were seen when viewed through a microscope. The origin of the fatigue was traced to sharp corner of a bend.

The spring is manufactured out of stamped beryllium copper which leaves a sharp corner on the bottom side when cut by the die. Symmetrical right and left springs are formed by bending the stamped shape in opposite directions, leaving one side with a sharp corner on the outside radius of the bend.

The manufacturer published a service aid on October 24, 1988, incorporating an improved spring which increased the bend radius and hardness of the material. After the accident, the manufacturer published a service bulletin recommending the replacement of trim springs with improved spring at the next scheduled maintenance, or during the annual 100-hour maintenance, whichever occurs first.

A copy of the avionics manufacturer's report and metallurgist's reports are attached to this report.

ADDITIONAL INFORMATION

The airplane was not insured at the time of the accident. There was no one representing the pilot's estate willing to receive custody of the wreckage. The fuselage was left at the accident site and its disposition is at the discretion of the U.S. Forest Service. The airplane's engine and instruments were removed for safeguarding and are stored at Lynn's Aircraft Engines, Inc., El Monte, California.

NTSB Probable Cause

THE PILOT ALLOWED THE AIRPLANE TO EXCEED ITS DESIGN LIMITS (AIRSPEED AND/OR STRESS LIMITS) AFTER INADVERTENTLY ENTERING A DESCENT. FACTORS RELATING TO THE ACCIDENT WERE: DARKNESS (NIGHT OR LATE DUSK), THE PILOT'S FAILURE TO ASSURE ADEQUATE MAINTENANCE/INSPECTION OF THE AIRPLANE, AND FATIGUE FAILURE OF A PITCH TRIM SPRING IN THE AUTOPILOT PITCH SERVO.