# NTSB LAX00LA250: Thorp T211, N91313, Grass Valley, CA, July 4, 2000 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: July 4, 2000, 11:45 local (18:45 UTC) - Place: Grass Valley, CA - Coordinates: 39.179141, -120.979347 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.1791&lon=-120.9793&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 2 serious - Status: Completed, report October 17, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 49601 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX00LA250 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/49601/pdf - Page: https://openairdocs.org/ntsb/LAX00LA250 ## Probable cause the pilot encountered a mountain wave at an altitude too low to maintain clearance from trees. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight collision with object, cruise - weather condition - mountain wave (contributing factor) - altitude - low, pilot in command (cause) - altitude/clearance - not maintained, pilot in command (cause) - object - tree(s) ## Analysis The pilot was cruising the local area about 1,000 feet agl, at 2,500 rpm, when the airplane suddenly started to descend. Although he hadn't noticed any evidence of strong winds, he was on the lee side of a peak. He turned to avoid the wind shear and applied full power, but his descent continued. The airplane collided with 100-feet tall trees after he maneuvered to avoid hitting one straight on with the cabin area. ## Factual narrative On July 4, 2000, about 1145 hours Pacific daylight time, a Thorp T211, N91313, sustained substantial damage when it collided with trees while maneuvering near Grass Valley, California. The private pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The pilot and one passenger sustained serious injuries. The personal flight departed Auburn Municipal Airport, Auburn, California, about 1130, and was scheduled to terminate at the Alta Vista, California, airport. Visual meteorological conditions prevailed and no flight plan was filed. The pilot stated he was cruising the local area about 1,000 feet agl, at 2,500 rpm, when the airplane suddenly started to descend. Although he hadn't noticed any evidence of strong winds, he was on the lee side of a peak. He turned to avoid the perceived wind shear and applied full power, but his descent continued. The airplane collided with 100-feet tall trees in a private campground after he maneuvered to avoid hitting one straight on with the cabin area. One wing folded and the airplane came to rest on its side. The pilot suffered a broken leg, while the passenger suffered a broken arm. An examination of the airplane's engine by the manufacturer's representative, under the supervision of a Safety Board investigator, did not reveal any discrepancies that would preclude normal operation. The wreckage was released to the owner's agent. ## Aircraft - Registration: [N91313](https://openairdocs.org/deregistered/N91313-2014-11-24), registration cancelled 2014-11-24, S/N 4, built 1947 (OpenAirDocs) - Reported make and model: Thorp T211 - Registry model: [Thorp T-211](https://openairdocs.org/model/thorp-t-211) (registry code 8950104) (OpenAirDocs) - Registry engine: [Lycoming 0-145B series](https://openairdocs.org/engine/lycoming-0-145b-series) (registry code 41502, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 4 - Airframe hours: 1255 - Engines: Lycoming O145-C2 65 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Robert L Riddle - Airworthiness certificate: Standard, Normal - Last inspection: Annual, November 12, 1999, 5 hours before - Departed: AUN, AUBURN, CA - Destination: Q62, ALTA VISTA, CA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 59; private; airplane ratings: single-engine land; medical: class 3, valid medical--no waivers/lim.; seat: left; flight hours: 1,800 total, 200 in this make and model, 5 in the last 90 days, 3 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 0° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 142 °F, dew point 102 °F - Altimeter: 30.00 inHg - Observed at: BLU, 14 nm away ## 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 20000704006629A](https://openairdocs.org/incident/20000704006629A), Jul 4, 2000: Grass Valley, CA, No damage. (-23) The pilot was conducting scenic flying with his son approx. 1000 AGL over in the area of alto sierra, CA. He noticed that the airplane was developing a… 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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.