NTSB Factual Report

HISTORY OF FLIGHT

On January 31, 2011, approximately 1525 Pacific standard time, a Cessna 172, N6922A, sustained substantial damage when it impacted mountainous terrain while maneuvering near Glendora, California. The flight instructor received serious injuries and the commercial pilot receiving instruction received minor injuries. The flight instructor/owner was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the local instructional flight, which had originated from Brackett Field (POC), La Verne, California, about 2 hours 30 minutes before the accident. No flight plan had been filed.

The flight instructor said that this was a training mission for his student to get more experience in a tail wheel equipped airplane and flying in mountainous terrain. After approximately 2 hours of traffic pattern work with touch-and-go landings, they departed for a local practice area for some air work. Due to air traffic congestion in the practice area, they flew to more mountainous terrain to practice utilizing orographic lift.

The flight instructor said the lift they were flying in began to dissipate. He took the flight controls and added full power to depart the area. Suddenly, they encountered a strong downdraft and moments later they impacted the terrain. Rescue teams were sent to the area, and because of the steepness of the terrain a helicopter was used to evacuate the two injured occupants.

The flight instructor told local authorities, at the time of his rescue, that “they had no problems with the airplane.”

PERSONNEL INFORMATION

The 53-year-old flight instructor’s most recent second-class Federal Aviation Administration (FAA) medical certificate was issued on February 2, 2010. He held a flight instructor certificate with single engine land airplane rating, a commercial pilot certificate with a single engine land and multi-engine land airplane ratings, and an instrument airplane rating. He estimated that his total flight time was about 1,800 hours.

The 37-year-old commercial pilot receiving instruction held a second-class FAA medical certificate, which was issued on January 7, 2010. He held a commercial pilot certificate with a single engine land airplane rating. At the time of his rescue, he told local authorities that he had approximately 300 hours of flight experience.

AIRCRAFT INFORMATION

The airplane was a single-engine, propeller-driven, four seat airplane, with dual flight controls, which was manufactured by Cessna Aircraft Company in 1956. Its maximum takeoff gross weight was 2,300 pounds. It was powered by a Continental O-300-A reciprocating, direct-drive, air-cooled, normally aspirated engine, which had a maximum takeoff rating of 145 horsepower at sea level. Maintenance records indicate that the last 100-hour inspection was performed on January 30, 2011. The airplane had been converted from a tricycle landing gear configuration to a tail wheel landing gear configuration.

METEOROLOGICAL INFORMATION

At 1553, the reported weather conditions at Chino, California, located 130 degrees for 16 nautical miles from the accident site, were as follows: wind from 260 at 8 knots; visibility 10 statute miles; few clouds at 4,000 feet and scattered clouds at 25,000 feet; temperature 63 degrees Fahrenheit; dew point 45 degrees Fahrenheit; altimeter setting 30.09 inches of Mercury.

WRECKAGE AND IMPACT INFORMATION

The airplane was found about 400 feet below a 2,300-foot elevation ridge line on steep terrain. Examination of photos taken by local authorities revealed that a ground scar of approximately 100 degrees led to the wreckage. The nose of the airplane was compressed aft and up into the cockpit. The fuselage, just in front of the empennage, was compressed and wrinkled; both horizontal stabilizers were bent and wrinkled. Half of the left elevator was torn away, and both wings were bent and wrinkled.

An airframe and engine exam was performed on February 9, 2011, by a National Transportation Safety Board Senior Air Safety Investigator and representatives from both the airframe and engine manufacturers. Flight control cable continuity was confirmed for all flight controls, though several of the cables had been cut for aircraft recovery. The propeller assembly remained attached to the engine’s crankshaft. The upper spark plugs were removed from the engine and noted to exhibit normal wear. The engine’s crankshaft was free to rotate and thumb compression was observed in proper order on all six cylinders. Mechanical continuity was established throughout the rotating group, valve train, and accessory section during hand rotation of the propeller.

No evidence of any preimpact mechanical anomalies were noted with the airframe or engine that would have precluded normal operation.

NTSB Probable Cause

The flight crew's failure to maintain adequate terrain clearance while maneuvering in downdraft conditions over mountains.