# NTSB LAX01LA256: Cessna R172K, N736YR, Mammoth Lakes, CA, July 21, 2001 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: July 21, 2001, 12:30 local (19:30 UTC) - Place: Mammoth Lakes, CA - Coordinates: 37.5625, -119.044723 - Nearby events: https://openairdocs.org/map.md?lat=37.5625&lon=-119.0447&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 2 serious - Status: Completed, report May 28, 2002 - Report: Approved by Office Director - Parties: FAA Flight Standards District Office - NTSB case key (mKey): 52791 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX01LA256 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/52791/pdf - Page: https://openairdocs.org/ntsb/LAX01LA256 ## Probable cause The pilot's inadequate in-flight planning and his failure to maintain sufficient altitude above the terrain. Factors were the high terrain and the blind canyon. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of control - in flight, maneuvering - turn to reverse direction - overconfidence in aircraft's ability, pilot in command (contributing factor) - altitude/clearance - not maintained, pilot in command (cause) - terrain condition - high terrain (contributing factor) - became lost/disoriented, pilot in command - stall - inadvertent, pilot in command - In flight collision with terrain/water, descent - uncontrolled - in-flight planning/decision - improper, pilot in command (cause) - terrain condition - blind/box canyon (contributing factor) ## Analysis The pilot stated that while en route from Van Nuys to Mammoth Yosemite (MMH) via the Friant VOR radial 023, he entered a canyon and later realized that he had entered the wrong one. He said that the canyon was closed and above his altitude. He also stated that he was experiencing moderate turbulence from the time he entered the canyon up to the accident. The pilot began a "full power climb" at 75 knots in an attempt to clear the ridgeline at the end of the canyon. When he realized that he would not clear the terrain, he began a steep left turn. During the turn, the stall warning was activated and the pilot lowered the nose and shallowed the bank angle. He stated that the airplane struck trees on the top of the canyon edge, tearing off the left wing with the airplane striking the ground in a level attitude. He stated that, "The engine was working properly and all the gauges were in the green." According to the San Francisco sectional chart, the Mammoth Pool Reservoir, which is 55 nautical miles southwest of the MMH airport on a magnetic bearing of 213 degrees, is directly under the 023-degree radial of the Friant VOR. The pilot stated that when he saw the reservoir, he turned east toward the MMH airport. The magnetic course from the reservoir to the MMH airport was 033 degrees, or a northeasterly direction. There was a canyon leading northeast from the Mammoth Pool Reservoir along the Friant 023-degree radial, which is also Victor 230. The canyon terminated at Mammoth Lakes, which is 11 miles due west of the MMH airport. Had the pilot followed Victor 230 until reaching the Mammoth Pools, then turned to an easterly heading, he would have been proceeding directly to the airport. ## Factual narrative On July 21, 2001, at 1230 hours Pacific daylight time, a Cessna R172K, N736YR, was destroyed when it collided with trees and mountainous terrain during an attempt to reverse direction in a box canyon 11 nautical miles southwest of the Mammoth Yosemite Airport, Mammoth Lakes, California. The accident site is at 9,500 feet mean sea level (msl) in the Sierra Nevada Mountains. The airplane, operated by American Aviation of Van Nuys, California, and rented by the pilot, was destroyed. The private pilot and one passenger were seriously injured. Visual meteorological conditions prevailed for the personal flight conducted by the pilot under 14 CFR Part 91. The airplane departed Van Nuys approximately 1000 for the flight to the Mammoth Yosemite airport. No flight plan was filed. An accident report was submitted by the pilot. He stated that he had received a weather briefing by computer prior to the flight. He departed the Van Nuys airport approximately 1000 and proceeded to the Friant VOR. Upon reaching Friant, he tracked the 023-degree radial outbound until he was over a lake. When he saw the lake, he turned east toward the Mammoth Yosemite airport. He entered a canyon and later realized that he had entered the wrong one. He said that the canyon was closed and above his altitude. He also stated that he was experiencing moderate turbulence from the time he entered the canyon up to the accident. The pilot began a "full power climb" at 75 knots in an attempt to clear the ridgeline at the end of the canyon. When he realized that he would not clear the terrain, he began a steep left turn. During the turn, the stall warning was activated and the pilot lowered the nose and decreased the bank angle. The airplane struck trees on the top of the canyon edge, tearing off the left wing with the airplane striking the ground in a level attitude. He stated that, "The engine was working properly and all the gauges were in the green." According to the San Francisco sectional chart, the Mammoth Pool Reservoir, which is 55 nautical miles southwest of the Mammoth Yosemite airport on a magnetic bearing of 213 degrees, is under the 023-degree radial of the Friant VOR. The pilot stated that when he saw the reservoir, he turned east toward the Mammoth Yosemite airport. The magnetic course from the reservoir to the airport was 033 degrees, or a northeasterly direction. There was a canyon leading northeast from the Mammoth Pool Reservoir along the Friant 023-degree radial, which is also a Low Altitude Federal Airway (Victor 230). The canyon terminated at Mammoth Lakes, which is 11 miles due west of the Mammoth Yosemite airport. The sectional chart indicated that no mountain pass was present in the area. The closest mountain passes depicted were the Tioga Pass, 25 miles north-northwest, and the Piute Pass, 25 miles south east of the accident site, respectively. A review of the pilot's operating handbook (POH) for this aircraft was conducted. At 10,000 feet msl, with an outside air temperature of 20 degrees Celsius, the published best rate of climb (Vy) speed was 76 knots indicated airspeed (IAS), which would result in a climb rate of 320 feet per minute. The temperature at the Mammoth Yosemite airport was 24 degrees Celsius at the time of the accident. ## Aircraft - Registration: [N736YR](https://openairdocs.org/deregistered/N736YR-2005-04-26), registration cancelled 2005-04-26, S/N R1722898, built 1978 (OpenAirDocs) - Reported make and model: Cessna R172K - Registry model: [Cessna R172K](https://openairdocs.org/model/cessna-r172k) (registry code 2072431) (OpenAirDocs) - Registry engine: [Continental IO-360 series](https://openairdocs.org/engine/continental-io-360-series) (registry code 17025, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 1722898 - Airframe hours: 3366.6 - Engines: Continental IO-360-K 195 horsepower reciprocating - Damage: Destroyed - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, December 22, 2000, 57.5 hours before - Departed: VNY, Van Nuys, CA - Destination: MMH, Mammoth Lakes, CA - Airport: MMH, Mammoth Yosemite, runway 09, 7,000 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 47; injuries: serious; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; last flight review May 10, 2001; seat: left; flight hours: 250 total, 2 in this make and model, 200 as pilot in command, 1 in the last 90 days, 1 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 210° at 18 knots, gusting 23 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 75 °F, dew point 27 °F - Altimeter: 30.15 inHg - Observed at: KMMH, 11 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 20010721016819A](https://openairdocs.org/incident/20010721016819A), Jul 21, 2001: Cessna R172K, Mammoth Lakes, CA, Destroyed. (-23) Pilot misjudged intended canyon and flew up a nearby canyon. As the canyon began to close in, he turned left and the aircraft stall warning horn sounded.… 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.