# NTSB LAX92LA360: Socata TB-10, N20BN, Big Bear, CA, August 23, 1992

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: August 22, 1992, 17:00 local (Aug 23, 1992, 00:00 UTC)
- Place: Big Bear, CA
- Coordinates: 34.25962, -116.840095 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=34.2596&lon=-116.8401&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 4 minor
- Status: Completed, report September 14, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27740
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX92LA360
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27740/pdf
- Page: https://openairdocs.org/ntsb/LAX92LA360

## Probable cause

THE PILOTS DECISION TO ATTEMPT CROSSING A RIDGE LINE AT AN ALTITUDE INSUFFICIENT TO ALLOW FOR CONTINGENCY ACTIONS IN THE EVENT OF AN ENCOUNTER WITH DOWN DRAFTS OR TURBULENCE.  FACTORS IN THE ACCIDENT WERE THE HIGH DENSITY ALTITUDE AND THE FLIGHT'S ENCOUNTER WITH A DOWN DRAFT.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- In flight collision with object, climb - to cruise
  - terrain condition - mountainous/hilly
  - weather condition - high density altitude (contributing factor)
  - weather condition - downdraft (contributing factor)
  - in-flight planning/decision - improper, pilot in command (cause)
  - altitude - inadequate, pilot in command (cause)
  - compensation for wind conditions - not possible
  - descent - not corrected, pilot in command
  - object - tree(s)
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

IN HIS WRITTEN STATEMENT THE PILOT SAID THAT AFTER DEPARTURE ON RUNWAY 25 HE TURNED IN A SOUTHWEST DIRECTION TO CROSS A RIDGE LINE AT AN ALTITUDE OF ABOUT 7,900 FEET MSL. HE SAID THAT NEAR THE RIDGE LINE THEY ENCOUNTERED A SUDDEN DOWN DRAFT AND HE COULD NOT ARREST THE DESCENT PRIOR TO COLLIDING WITH TREES. AN EYE WITNESS TO THE CRASH SAID THE AIRCRAFT NEVER ACHIEVED MORE THAN ABOUT 300 FEET AGL AT ANY TIME AFTER TAKEOFF. THE WITNESS OBSERVED THE AIRCRAFT IN A NOSE HIGH ATTITUDE BEGIN A RIGHT TURN, THEN IT DESCENDED BELOW THE TOPS OF SOME TREES AND OUT OF VIEW. TWO OTHER WITNESSES REPORTED HEARING THE SOUNDS OF A LOUD AND STRONG ENGINE UNTIL THE SOUNDS OF TREE IMPACTS WERE HEARD. THE AIRPORT IS IN A MOUNTAIN VALLEY AT AN ELEVATION OF 6,750 FEET. MOUNTAIN RIDGES AND PEAKS RISE AN AVERAGE OF 2,000 FEET ABOVE THE VALLEY FLOOR ON ALL SIDES OF THE AIRPORT. THE AIRPORT IS AT THE EAST END OF THE VALLEY AND A LARGE LAKE. A DAM IS AT THE WEST END OF THE VALLEY AT A 'V' NOTCH IN THE SURROUNDING MOUNTAINS. WEST OF THE DAM THE TERRAIN DROPS OFF RAPIDLY TO THE GREATER LOS ANGELES BASIN. THE DENSITY ALTITUDE WAS CALCULATED TO BE ABOUT 9,400 FEET. OTHER PILOTS WHO DEPARTED FROM THE AIRPORT REPORTED THAT TURBULENCE EXISTED OVER THE VALLEY NEAR THE SURROUNDING RIDGES.

## Aircraft

- Registration: [N20BN](https://openairdocs.org/deregistered/N20BN-1992-10-21), registration cancelled 1992-10-21, S/N 494 (OpenAirDocs)
- Reported make and model: SOCATA TB-10
- Registry model: [Socata TB 10](https://openairdocs.org/model/socata-tb-10) (registry code 8680696) (OpenAirDocs)
- Category: Airplane
- Serial number: 494
- Airframe hours: 1336
- Engines: LYCOMING O-360-A1AD 180 horsepower reciprocating
- Damage: Destroyed
- Flight: Personal, Part 91
- Operator: General Aviation Company
- Registered owner: Curtis H. Thomas
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, May 8, 1992, 39 hours before
- Departed: L35
- Destination: FUL, FULLERTON, CA

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 32; private; airplane ratings: single-engine land; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 213 total, 50 in this make and model, 151 as pilot in command, 15 in the last 90 days, 12 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 250° at 10 knots
- Visibility: 20 statute miles
- Lowest ceiling: none
- Temperature: 81 °F
- Altimeter: 30.00 inHg

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19920822032529A](https://openairdocs.org/incident/19920822032529A), Aug 22, 1992: Socata TB10TOBAGO, Big Bear, CA, Destroyed. Encountered severe downdraft trying to cross a ridge on climbout. Factors include density altitude and 80 degrees

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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