Big Pine, CA, USA
N9141Y
Piper PA-28-161
The certified flight instructor (CFI) and the pilot under instruction (PUI) were going on a series of cross-country flights to allow the PUI to build flight time. Motorists observed the wreckage near a road that was in the flat bottom of a canyon whose floor width varied from an estimated 50 yards at the narrowest point to 200 yards at the widest point. The canyon made several left and right turns as it wound its way uphill in a general southeasterly direction. The canyon sides appeared to be several hundred feet higher than the accident site elevation and the rim appeared to be about 100 feet higher at the head of the canyon. An evaluation of the ground scars and impact signatures on the wreckage disclosed that the airplane was in a left turn attempting to reverse course out of the box canyon when the left wing tip dug into the ground. The airplane then tumbled so that it was pointing down canyon when it came to rest. No evidence of a mechanical failure or malfunction was noted during the post accident inspection.
HISTORY OF FLIGHT On December 21, 2006, about 1300 Pacific standard time, a Piper PA-28-161, N9141Y, collided with terrain near Big Pine, California. Flying Vikings was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. The certified flight instructor (CFI) pilot and the private pilot undergoing instruction (PUI) were killed, and the airplane sustained substantial damage. The cross-country instructional flight departed Bishop, California, about 1240, en route to an undetermined destination. Visual meteorological conditions prevailed, and no flight plan had been filed. The operator reported that the CFI and PUI were going on a series of cross-country flights to allow the PUI to build flight time. Fueling records at Bishop established that the PUI purchased 22.4 gallons of 100 LL (low lead) fuel at a self-service gas pump at 1228. A note pad in the airplane noted the departure time from Bishop. Motorists observed the wreckage about 1520, and reported the discovery to the Inyo County Sheriff's Department. The main wreckage was in the flat bottom of a canyon whose floor width varied from an estimated 50 yards at the narrowest point to 200 yards at the widest point. The canyon made several left and right turns as it wound its way uphill in a general southeasterly direction. The canyon sides appeared to be several hundred feet higher than the accident site elevation; the rim appeared to be about 100 feet higher at the head of the canyon. The GPS indicated that the site elevation was about 6,075 feet. PERSONNEL INFORMATION Flight Instructor The operator reported that the 27-year-old CFI held an airline transport pilot certificate with a rating for airplane multiengine land, and a commercial certificate with ratings for airplane single engine land and airplane single engine sea. He held a CFI certificate with a rating for airplane single engine land. The CFI held a first-class medical certificate issued on August 28, 2006. It had the limitation that the pilot must wear corrective lenses. The operator reported that the CFI had a total flight time of 4,800 hours. Pilot Under Instruction The operator reported that the 22-year-old PUI had a private pilot certificate with a rating for airplane single engine land. He had a first-class medical certificate issued on October 28, 2004. It had no limitations or waivers. He had a total flight time of 95 hours. AIRCRAFT INFORMATION The airplane was a Piper PA-28-161, serial number 28-8616014. The operator reported that the airplane had a total airframe time of 9,908 hours at the last annual inspection. It had an annual inspection dated September 28, 2006. The engine was a Textron Lycoming O-320-D3G serial number L-14069-39A. Total time recorded on the engine at the last annual inspection was 9,908 hours, and time since major overhaul was 803 hours. Fueling records at Bishop established that the airplane was last fueled on December 21, 2006, with the addition of 22.4 gallons of 100-octane low lead aviation fuel. WRECKAGE AND IMPACT INFORMATION The National Transportation Safety Board investigator-in-charge (IIC) and the Federal Aviation Administration (FAA) accident coordinator examined the wreckage on scene. The first identified point of contact (FIPC) was a ground scar that was about 6 inches wide. It contained red lens fragments, and extended about 30 feet, ending at the main wreckage. The ground scar's orientation was 020 degrees. The airplane came to rest on a heading of 262 degrees. The left wing separated at the production splice outboard of the left main landing gear. However, the control cables remained connected, and the IIC established continuity to the deformed cabin area. The right wing remained attached, and the IIC established continuity to the deformed cabin area. Both wings exhibited crush damage that tapered aft from the mid-wing leading edge to the spar at the wingtip. The left wing exhibited more damage than the right wing. The fuselage buckled aft of the cabin area. The empennage remained relatively intact. The left horizontal stabilator buckled near the outboard edge. The IIC established continuity for the rudder and stabilators to the deformed cabin area. MEDICAL AND PATHOLOGICAL INFORMATION The Inyo County Coroner completed an autopsy. The FAA Forensic Toxicology Research Team, Oklahoma City, Oklahoma, performed toxicological testing of specimens of the pilots. Analysis of the specimens for the CFI contained no findings for carbon monoxide, cyanide, volatiles, and tested drugs. Analysis of the specimens for the PUI contained no findings for carbon monoxide, cyanide, volatiles, and tested drugs. TESTS AND RESEARCH Investigators examined the wreckage at Aircraft Recovery Service, Littlerock, California, on February 14, 2007. Investigators removed the engine. They slung it from a hoist, and removed the top spark plugs. All spark plugs were clean with no mechanical deformation. The spark plug electrodes were gray, which corresponded to normal operation according to the Champion Aviation Check-A-Plug AV-27 Chart. A borescope inspection revealed no mechanical deformation on the valves, cylinder walls, or internal cylinder head. Investigators manually rotated the crankshaft with a tool in an accessory drive gear. The crankshaft rotated freely, and the valves moved approximately the same amount of lift in firing order. The gears in the accessory case turned freely. Investigators obtained thumb compression on all cylinders in firing order. The left magneto sustained mechanical damage, separated from its mounting pad, and would not rotate. The right magneto remained in its mounted position. It produced spark at all posts in firing order when manually rotated. The oil sump sustained mechanical damage, and was breached. The oil sump screen was clean and open. The oil screen was clean. The carburetor sustained mechanical damage; the finger screen was clean. The carburetor's metallic floats sustained crush damage on the outboard sides. The fuel selector valve was in the right main position. The airframe manufacturer's investigator determined that the elevator trim measured 6 threads; 5 threads represent neutral. The flap control was set to the 10-degree position; the torque tube was in the 25-degree position. The propeller separated from the crankshaft flange at the mechanical attachment area of the hub. The hub was bent, and distorted. The propeller blades exhibited leading edge gouging, torsional twist, and trailing edge s-bending.
The inadequate in-flight/planning decision of both pilots to fly up a box canyon at low altitude, and their failure to maintain clearance from the terrain.
Source: NTSB Aviation Accident Database
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