NTSB Factual Report

HISTORY OF FLIGHT

On April 23, 1997, a Socata TB-20, N20NK, was reported missing by the pilot's family when the aircraft failed to arrive at Centennial Airport, Englewood, Colorado, on a flight from Sedona, Arizona. The aircraft was found on April 28, 1997, at 1130 mountain daylight time (all times are mountain daylight time unless otherwise noted), on the side of a mountain at N37:03.43, W106:38.27. Terrain elevation was 11,100 feet msl (above mean sea level). The location is approximately 25 miles southeast of Pagosa Springs, Colorado. At the time the aircraft was located, snow depth in the area was 5 to 7 feet.

Access to the accident site was not feasible due to snow depth and avalanche danger until August 5, 1997. The wreckage was on the side of a 50 degree slope mountain on the Banded Peaks Ranch, between Banded Peak and Chama Peak in Archuleta County, Colorado.

The aircraft partially burned after impact and the pilot received fatal injuries on this cross-country flight operating under Title 14 CFR Part 91 and a VFR flight plan was on file. No ELT signal was heard via satellite; However, when search aircraft were directly over the accident site a weak ELT signal was received. The pilot's remains were removed from the accident site by helicopter on May 4, 1997.

The pilot of N20NK contacted the local flight service station (FSS) on April 22, 1997, at 1758 and obtained an outlook briefing for a flight from Sedona to Englewood. On April 23rd at 1146 the pilot activated a VFR flight plan for the trip and at 1305 the pilot of N20NK contacted Albuquerque FSS and reported that he was 2 miles south of Farmington, New Mexico, and that due to weather he needed to convert his flight plan to an instrument plan. Albuquerque FSS took the proposed flight plan which was: Current location direct Alamosa, Colorado, victor 210 to GOSIP intersection, victor 19 to COS, direct APA, cruise altitude of 15,000 feet, true airspeed of 140 knots, 2 hours en route, 3 hours 40 minutes fuel remaining and 1 person on board. At the time, the pilot said he was at 13,900 feet and descending due to the cloud base.

Albuquerque FSS put the pilot of N20NK in contact with Denver Air Route Traffic Control Center (ARTCC). This took several attempts on different frequencies due to N20NK's altitude, which made contact difficult. At the time N20NK established communications with Denver Center, the pilot reported he was 56 miles southeast of Farmington at 13,500 feet. Following some identifying/locating discussion between the pilot and the controller, the pilot was asked by the controller if he could climb to 14,000 feet msl under visual conditions because below that altitude the controller could not issue an instrument clearance due to crossing traffic at 13,000 feet. The pilot of N20NK said that he could not climb visually and stated that he thought he was "starting to pick up some tail plane icing." Following further discussion with the controller regarding altitudes and possible routing the pilot of N20NK stated he needed to descend due to icing and that when he got down to "where he could see good" he would try to figure out some alternative routing. The controller gave the pilot the Farmington altimeter setting and told him to change his transponder to the visual flight rules code. This was acknowledged by the pilot and no further communications took place.

At approximately 0200 the following morning, the Sheriff of Archuleta County was notified of the possibility that an aircraft was "down" in the southeast part of his county. At about 0600, the Sheriff's Department in conjunction with the Civil Air Patrol (CAP) initiated a search for the aircraft. Weather in the search area at the time was low clouds, rain, and snow at the higher elevations.

Persons on the Banded Peak Ranch, which was the suspected area of the loss, were interviewed by Sheriff's Department personnel. They said they had heard an aircraft fly over on the 23rd about 1330. They said it flew across the ranch from north to south "headed towards Chama Peak." They said it was snowing at the time and that the weather was deteriorating. They said the engine noise faded and they did not hear it again.

Weather conditions on the 24th continued to deteriorate and search operations were suspended. Weather on the 25th was bad with low clouds rain and snow and no search operations were conducted. The 26th provided better weather conditions and the search resumed without results. On the 27th, a weak ELT signal was picked up in the area of Banded Peak but could not be localized. The search helicopter spotted what appeared to be foot tracks in the area, and a ground team and helicopter inserted team were dispatched to the area. The tracks turned out to be bear tracks. The ground team camped in the area the night of the 27th and on the 28th the ground and air team located the aircraft in a stand of trees at about the same time.

The emergency locator transmitter (ELT) was found by the search team. It was distorted by heat from the fire and the antenna was bent over and laying flat on the fuselage.

DAMAGE TO AIRCRAFT

The aircraft was destroyed by impact and postimpact fire.

PERSONNEL INFORMATION

The pilot held a commercial pilot certificate, single and multiengine land, instrument airplane, and glider certificate aero tow only. His certificate number was 229663714. He also held a flight instructors certificate for single and multiengine land, instrument airplane and glider. The date of his last certificate revision was July 5, 1994.

He had numerous pilot logbooks dating back to 1991. According to available information, he had accumulated approximately 1,600 hours of flight time 75 of which were in the accident aircraft. Approximately 50 hours time was spent in multiengine aircraft, 1220 in tricycle landing gear aircraft, and 263 in retractable landing gear aircraft. The last entry in the pilot's computer generated flight log was January 18, 1997. At that time, the pilot had recorded 22 hours of actual instrument time, 56 hours of simulated instrument time, 453 hours of cross-country flying, and 363 hours of glider flight time. The logs also provided information the pilot had accumulated 927 hours of pilot in command time and 340 hours as a flight instructor.

The pilot's last biennial flight review was conducted July 19, 1996, in the accident aircraft.

The pilot held a second class medical certificate, dated September 14, 1994, with the limitation that he wear corrective lenses for distant vision and possess corrective lenses for near vision. He had a Statement of Demonstrated Ability for defective color vision, dated December 27, 1991.

AIRCRAFT INFORMATION

Airframe

The TB-20 (Trinidad) is an all metal, five place, cantilever low wing, single engine airplane equipped with retractable tricycle landing gear and is designed to be used in the normal category. It is manufactured by Socata, a division off Aerospatiale.

The cabin portion is constructed with metal panels assembled to form a rigid structure. Metal floor panels extend the length of the cabin area and baggage compartment. The aft fuselage is constructed of sheet aluminum alloy panels which form a monocoque structure.

Passenger and pilot entrance into the cabin area is provided by two "butterfly" doors.

Access to the baggage compartment (behind the rear seat) is provided by a baggage door on the left side of the fuselage.

Airframe time at the time of the accident is unknown. Airframe time at the last annual inspection, conducted on February 24, 1997, was 697.8 hours. Investigation revealed that all Airworthiness Directives and Service Bulletins had been complied with.

Engine

The engine is a Lycoming IO-540-C4D5D, six cylinder, direct drive, air cooled, horizontally opposed engine which produces 250 brake horsepower (BHP) at 2,575 revolutions per minute (rpm) at sea level. The engine serial number on this aircraft was L-23362-48A. It was installed on the aircraft by the aircraft manufacturer on September 23, 1986. At the last annual inspection, conducted on February 24, 1997, a 100 hour inspection was completed on the engine. At that time, the engine had accumulated 697.8 hours of operation. The engine time between the inspection and the accident is unknown.

Approved fuels for use in this engine are 100 LL grade aviation gasoline or 100 grade aviation gasoline (formerly 100/130).

Propeller

The manufacturer normally installs a Hartzell HC-C2YK-IBF/F8477-4 to bladed propeller during manufacture. Other propeller types are approved and this aircraft was equipped with a McCauley B3D32C412-C three bladed propeller. The blade model was G-82NDA-5 and the blade serial numbers were LI053, LI070, and LI075. The hub serial number was 912045.

Certificated Weights

Ramp 3,097 pounds Takeoff 3,086 pounds Landing 3,086 pounds Baggage compartment 143 pounds Standard empty weight 1,764 pounds Maximum useful load 1,333 pounds

Wing loading 24.1 pounds per square foot Power loading 12.3 pounds per BHP

Endurance

According to information given to Albuquerque FSS when the pilot was attempting to file an instrument rules flight plan, he was flying the aircraft at "best power." According to performance information provided in the Aircraft Operating Manual, the maximum endurance when using "best power" is 6 hours and 49 minutes without reserve fuel and 6 hours and 18 minutes with reserve fuel. Using this information, calculations provide information that the flight would have arrived in Englewood with approximately 1 hour and 30 minutes fuel remaining.

Limitations

Vne Never exceed speed 187 KIAS (knots indicated airspeed) Vno Maximum structural cruising speed 150 KIAS Va Maneuvering speed 129 KIAS Vfe Maximum flap extended speed Takeoff 129 KIAS Landing 103 KIAS Vlo Maximum landing gear operating speed 129 KIAS Vle Maximum landing gear extended speed 139 KIAS

Flight load limits are: +3.8 g flaps up +2.0 g flaps down Negative 'g' limits are not provided.

Center of gravity limits are: Forward 42.2 inches aft of datum at 3,086 pounds. Aft 47.4 inches aft of datum at all weights.

The actual center of gravity on this flight is unknown; however, with one person aboard, full fuel at takeoff, and less than 100 pounds of baggage (based on recovered items), calculations provide that the center of gravity limits could not have been exceeded.

Operations Limits

This aircraft was equipped for day and night visual operations and day and night instrument operations. Operating in known icing conditions was prohibited.

METEOROLOGICAL INFORMATION

The nearest weather reporting station was Farmington, New Mexico, located approximately 240 degrees magnetic heading at 62 nautical miles from the accident site. At 1247 mountain daylight time, observed weather at Farmington was broken clouds at 5,000 feet above ground level (agl), overcast at 20,000 feet agl, 50 miles visibility, altimeter 29.76 inches of mercury (Hg), temperature 16 degrees Fahrenheit (F), dew point minus 1 degree F, and wind from 210 degrees magnetic heading at 8 knots. Remarks: Virga all quadrants.

At 1347, Farmington weather was reported as broken clouds at 4,000 feet agl, overcast at 20,000 feet agl, 50 miles visibility, altimeter 29.74 Hg, temperature 14 degrees F, dew point minus 1 F, and wind from 270 degrees at 10 knots. Remarks: Virga all quadrants.

As depicted in the attached Archuleta County Sheriff's Report, weather in the accident area at the time of the accident, as reported by persons on the ranch where the aircraft was found, was low clouds obscuring the surrounding mountain tops, rain, and snow.

Additional weather information including AIRMETS and freezing level information is located in the attached FAA Air Traffic Control Report.

COMMUNICATIONS

Transcripts of pertinent communications with Albuquerque Radio and Denver Air Route Traffic Control Center are attached as part of the Air Traffic Control Report.

WRECKAGE AND IMPACT INFORMATION (for additional detail, refer to attached photographs)

Impact track was 122 degrees magnetic. Access to the wreckage was delayed until August 5, 1997, due to weather conditions.

Witness marks provided evidence that the aircraft cut a level swath through approximately 150 feet of pine trees prior to impacting the terrain.

The wreckage was facing opposite the direction of its entry track and the forward 2/3 of the aircraft had been destroyed by fire and impact. The empennage was intact and control continuity to the cabin area was established. No other control continuity was possible.

Both wings were damaged by impact and the wing root area was destroyed by fire. Control continuity was established through the wings to the cabin area. No fuel was found.

All control surfaces were attached to their respective mountings in a normal fashion.

The engine was found alongside the burned out forward fuselage and was resting on the sump in a slightly nose down attitude. The propeller hub was attached at the crankshaft flange. There were no exterior visible signs of catastrophic mechanical failure or malfunction or preimpact fire.

Continuity through the engine was established and both magnetos produced spark at the top plug leads during hand rotation. The impulse coupler performed in a normal fashion. Magneto to engine timing was not determined due to the position of the engine and maneuver restraints caused by the terrain conditions.

The top spark plugs (Champion RHM-38E) were removed and examined. The electrodes were undamaged and displayed a light gray color which was uniform on all plugs. The bottom plugs were not removed.

The interior of the cylinders was observed through the top spark plug holes. No evidence of internal damage was found.

The fuel injection servo and induction system were examined and observed to be free of obstruction. The injector servo was detached from the engine and the portion that remained attached at the mounting pad was secure. The fracture surface signatures were consistent with overload. The throttle/mixture controls remained attached to the servo unit. The fuel injection flow divider was attached and no internal damage was found. Fuel injector line continuity was established. The fuel pump was attached at the engine and the inlet line was broken off.

The metal three bladed constant speed propeller was attached at the crankshaft flange. The hub was fractured with the separated pieces recovered at the accident site, along with one of the three blades that was found in the debris path approximately 50 feet down slope from the bulk of the wreckage. The detached blade was bent in an 'S' curve and bore chordwise gouges, scratches, and leading edge deformation. The second blade bore leading edge damage and chordwise scarring. It was bent forward with the outer 3 inches of the blade tip missing. The third blade was recovered from beneath the engine and was bent rearward approximately 30 degrees 7 inches from the hub attachment. It exhibited shallow chordwise scratches.

TESTS AND RESEARCH

According to the Air Traffic Control Manual, 4-2-8

c. "When an aircraft changes from VFR to IFR, the controller shall assign a beacon code to Mode -C equipped aircraft that will allow MSAW alarms.

d. "When a VFR aircraft, operating below the minimum altitude for IFR operations, requests an IFR clearance and you are aware that the pilot is unable to climb in VFR conditions to the minimum IFR altitude:

"1. Before issuing a clearance, ask if the pilot is able to maintain terrain and obstruction clearance during a climb to minimum IFR altitude."

"Note- Pilots of pop-up aircraft are responsible for terrain and obstacle clearance until reaching minimum instrument altitude (MIA) or minimum en route altitude (MEA). Pilot compliance with an approved FAA procedure or an ATC instruction transfers responsibility to the FAA; therefore, do not assign (or imply) specific course guidance that will (or could) be

NTSB Probable Cause

inadvertent flight by the pilot into known adverse weather conditions, and his failure to maintain altitude or clearance from terrain. Factors relating to the accident were: low ceiling, rain, snow, icing conditions, and mountainous terrain.