National Transportation Safety Board
Aviation Accident Final Report
Big Bear, CA
Date & Time:
10/16/2014, 1400 PDT
Loss of engine power (partial)
Flight Conducted Under:
Part 91: General Aviation - Personal
The commercial pilot was conducting a personal cross-country flight during daytime visual meteorological conditions over mountainous terrain. He reported that, about 30 minutes into the flight, the engine began to lose power. The airplane descended into a box canyon, and the pilot then attempted to maneuver the airplane to initiate a 180-degree turn out of the canyon toward lower terrain. The airplane continued to descend, and the stall warning horn sounded, so the pilot decided to land in trees.
First responders reported that the wing fuel tanks were breached and that fuel had drained out through holes in the wings. A postaccident examination of the airframe and engine revealed no evidence of any preexisting mechanical malfunctions or failures that would have precluded normal operation. The reason for the partial loss of engine power could not be determined.
The National Transportation Safety Board determines the probable cause(s) of this accident to be:
A partial loss of engine power for reasons that could not be determined because postaccident examination of the airframe and engine did not reveal any anomalies that would have precluded normal operation.
Mountainous/hilly terrain - Contributed to outcome
Tree(s) - Contributed to outcome
Not determined - Unknown/Not determined (Cause)
History of Flight
Loss of engine power (partial) (Defining event)
Collision with terr/obj (non-CFIT)
On October 16, 2014, about 1400 Pacific daylight time, a Cessna 172S, N612SP, was substantially damaged when it collided with terrain near Big Bear City Airport (L35), Big Bear, California. Sohail Air Ventures LLC was operating the rental airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot and two passengers sustained serious injuries. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight. The cross-country flight departed Corona, California, at an undetermined time with an intended destination of L35.
According to a Federal Aviation Administration (FAA) inspector, the pilot reported that he intended on flying to L35 for lunch prior to returning to Corona. Prior to the flight, he verified the fuel level of each fuel tank at 11 to 12 gallons of fuel and noted that the airplanes log sheet indicated 13 gallons of fuel should have been in each wing's fuel tank. The pilot further reported to the inspector that he anticipated getting fuel at Big Bear and that he planned to fly directly above the box canyons of the mountainous terrain west of the airport.
The pilot stated that thirty minutes into the flight, he noticed that he could not maintain altitude above the canyons and the engine was losing power. Once inside a box canyon, he maintained a position on the left side of the canyon with the intent to execute a right turn out of the canyon toward lower terrain. As the airplane continued to sink, he noticed that he did not have enough engine power to maintain a close proximity to the face of the mountain. The pilot further stated that when he heard the stall warning horn, he decided to initiate a landing on top of the trees instead of stalling [the airplane]. The pilot added that he had adjusted the mixture early in the flight, but the events of the flight happened too fast to attempt corrective adjustments immediately prior to the accident.
First responders confirmed that the wing fuel tanks were breached, and fuel had drained out through holes in the wings.
Multi-engine Land; Single-engine Land
Other Aircraft Rating(s):
Second Pilot Present:
Class 2 Without Waivers/Limitations
Last FAA Medical Exam:
Last Flight Review or Equivalent:
Aircraft and Owner/Operator Information
Year of Manufacture:
Landing Gear Type:
Date/Type of Last Inspection:
Certified Max Gross Wt.:
Time Since Last Inspection:
Airframe Total Time:
1959 Hours as of last inspection
SOHAIL AIR VENTURES LLC
SOHAIL AIR VENTURES LLC
Operating Certificate(s) Held:
Meteorological Information and Flight Plan
Conditions at Accident Site:
Condition of Light:
Observation Facility, Elevation:
Distance from Accident Site:
8 Nautical Miles
Direction from Accident Site:
Lowest Cloud Condition:
10 knots /
Turbulence Type Forecast/Actual:
Turbulence Severity Forecast/Actual:
30.15 inches Hg
20°C / -17°C
Precipitation and Obscuration:
No Obscuration; No Precipitation
Corona, CA (AJO)
Type of Flight Plan Filed:
Big Bear, CA
Type of Clearance:
Type of Airspace:
An aviation routine weather report (METAR) for L35, elevation 6,756 feet msl, located about 8 miles northeast of the accident site was issued at 1415. It indicated wind from 260 degrees at 10 knots, 10 miles or greater visibility, sky clear, temperature at 20 degrees C, dew point -17 degrees C, and an altimeter setting at 30.15 inches of mercury. The relative humidity was 7%.
A METAR for San Bernardino International Airport (SBD), elevation 1,159 feet msl, located about 15 miles southwest of the accident site, was issued at 1350. It indicated wind calm, 10 miles or greater visibility, sky few at 5,000 feet, temperature at 24 degrees C, dew point 8 degrees C, and an altimeter setting at 29.96 inches of mercury.
Wreckage and Impact Information
34.243611, -117.019444 (est)
Tests And Research
Examination of the recovered wreckage was conducted on October 28, 2014, by representatives of the FAA, Cessna, and Lycoming Engines under the supervision of the National Transportation Safety Board investigator-in-charge.
The electrical master switch was in the ON position. The ignition switch was in the BOTH position with the key in the switch. The auxiliary fuel pump switch was in the ON position. Investigators determined that the fuel selector valve was in the BOTH position. The gascolator contained a clear blue fluid that smelled like aviation gasoline; a water finding paste test had no response indicating that there was no water contamination. The screen was clean.
Investigators manually rotated the crankshaft with a tool in the vacuum pump drive pad. The crankshaft rotated freely, and the valves moved approximately the same amount of lift in firing order. The accessory gears turned freely. Investigators obtained thumb compression on all cylinders in firing order. A borescope inspection revealed no mechanical deformation on the valves, cylinder walls, or internal cylinder head. When each magneto drive shaft was rotated by hand, both magnetos produced spark at all posts.
The fuel pump's rubber diaphragm was intact and the pump contained a fluid consistent with the appearance and odor of aviation fuel.
The two blades were bent and twisted. Both blades exhibited leading edge gouges and chordwise striations.
No evidence of any preexisting mechanical anomalies with the airframe or engine was found that would have precluded normal operation. For further information, see the NTSB Airframe and Engine Examination Notes within the public docket for this accident.
Neither the pilot nor the operator submitted an NTSB form 6120.1, Pilot/Operator Aircraft Accident/Incident Report.
Investigator In Charge (IIC):
Howard D Plagens
Additional Participating Persons:
Rod Ealy; Riverside; Riverside, CA
Mark Platt; Lycoming; Williamsport, PA
Jan Smith; Cessna Aircraft; Wichita, KS
The NTSB did not travel to the scene of this accident.