HISTORY OF FLIGHTOn August 26, 2013, about 1330 Pacific daylight time, a Grumman AA-1A, N61VT, collided with terrain near Desert Center, California. The pilot/owner was operating the airplane under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot and one passenger sustained fatal injuries; the airplane was destroyed by impact forces and a post-crash fire. The local aerial photography flight departed Desert Center Airport at an undetermined time. Visual meteorological conditions prevailed, and no flight plan had been filed. There had recently been heavy rains and localized flooding in the area. The purpose of the flight was to assess any damage to a solar power facility. A Sheriff's Deputy observed the accident. He saw the airplane about 1,000 feet above the ground, and making erratic maneuvers. The airplane was traveling in a westerly direction, and made a sharp U-turn to the east. The deputy started discussing the maneuver with his passengers while observing the airplane's wings dip side-to-side, exposing the top and bottom of the airplane. The nose started to move down toward the ground, and then abruptly moved back up toward the sky while still proceeding in an easterly direction. The airplane started a second nosedive toward the ground, and turned counterclockwise exposing the top of the airplane before it crashed into the ground. Eleven witnesses were involved in work on a nearby fence line. Three of them reported observing the airplane make an abrupt turn from west to the east. Seven reported hearing the engine stop, pop, or sputter at some point in their observations; three did not report any engine cutouts. PERSONNEL INFORMATIONA review of Federal Aviation Administration (FAA) airman records revealed that the 41-year-old pilot held a commercial pilot certificate with ratings for airplane single-engine land, multiengine land, and instrument airplane. The pilot held a third-class medical certificate issued in July 19, 2011, with no limitations or waivers. No personal flight records were located for the pilot. The IIC obtained the aeronautical experience listed in this report from a review of the FAA airmen medical records on file in the Airman and Medical Records Center located in Oklahoma City, Oklahoma. The pilot reported on his medical application that he had a total time of 750 hours with 0 hours logged in the previous 6 months. AIRCRAFT INFORMATIONThe airplane was a Grumman AA1-A, serial number AA1A-0047. No maintenance logbooks were recovered for the airplane. The engine was a Lycoming O-320-E2G, serial number L-48438-27A. METEOROLOGICAL INFORMATIONAn aviation routine weather report (METAR) for Blythe (KBLH), California, elevation 399 feet, 33 nautical miles (nm) east of the accident site, issued at 1352 stated: wind from 330 degrees at 13 knots gusting to 18 knots; visibility 10 miles; sky clear; temperature 32/90 degrees C/F; dew point 21/70 degrees C/F; altimeter 29.88 inches of mercury. AIRPORT INFORMATIONThe airplane was a Grumman AA1-A, serial number AA1A-0047. No maintenance logbooks were recovered for the airplane. The engine was a Lycoming O-320-E2G, serial number L-48438-27A. WRECKAGE AND IMPACT INFORMATIONThe National Transportation Safety Board investigator-in-charge (IIC) traveled in support of this investigation, and performed an examination of the wreckage on scene. A detailed report is in the public docket for this accident. The airplane came to rest upright. The cabin section was consumed by fire. The vertical stabilizer separated, and was 30 feet aft of the empennage. The propeller separated from the flange, and was about 3 feet in front of the engine. The engine was nose down with the propeller flange touching the dirt. The IIC established control continuity on scene for the elevator and rudder. Debris prevented examination of the aileron system. ADDITIONAL INFORMATIONCarburetor Ice The carburetor icing probability chart from FAA Special Airworthiness Information Bulletin (SAIB): CE-09-35 Carburetor Icing Prevention, June 30, 2009, shows a probability of icing at cruise/glide power and serious icing at glide power at the temperature/dew point (90/70 F) reported at the time of the accident. Stalls According to the FAA Airplane Flying Handbook (FAA-H-8083-3A), under the Accelerated Stalls section, "At the same gross weight, airplane configuration, and power setting, a given airplane will consistently stall at the same indicated airspeed if no acceleration is involved. The airplane will, however, stall at a higher indicated airspeed when excessive maneuvering loads are imposed by steep turns, pull-ups, or other abrupt changes in its flight path. Stalls entered from such flight situations are called 'accelerated maneuver stalls,' a term, which has no reference to the airspeeds involved. Stalls which result from abrupt maneuvers tend to be more rapid, or severe, than the unaccelerated stalls, and because they occur at higher-than-normal airspeeds, and/or may occur at lower than anticipated pitch attitudes, they may be unexpected by an inexperienced pilot. Failure to take immediate steps toward recovery when an accelerated stall occurs may result in a complete loss of flight control, notably, power-on spins." MEDICAL AND PATHOLOGICAL INFORMATIONThe Riverside County Sheriff-Coroner completed an autopsy, and determined that the cause of death was multiple blunt impact injuries. The FAA Forensic Toxicology Research Team, Oklahoma City, performed toxicological testing of specimens of the pilot. Analysis of the specimens for the pilot contained no findings for volatiles; they did not perform tests for carbon monoxide or cyanide. The report contained the following findings for tested drugs: diphenhydramine detected in liver; pseudoephedrine detected in muscle and liver; and ibuprophen detected in liver. TESTS AND RESEARCHInvestigators from the NTSB, FAA, and Lycoming Engines examined the wreckage at Aircraft Recovery Service, Littlerock, California, on August 28, 2013. No discrepancies were observed that would have precluded normal operation of the airplane or its components. A full report is contained within the public docket for this accident. Removal of the top spark plugs revealed that all center electrodes were circular and clean with no mechanical deformation. The spark plug electrode for cylinder number one was wet from a black fluid. The other 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. The crankshaft was manually rotated 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. Thumb compression was obtained on all cylinders in firing order. The magnetos' driveshafts were manually rotated and both magnetos produced spark at all posts. The spinner was crushed aft to the hub. One propeller blade had leading edge polishing, and was twisted toward the low pitch, high rpm position. The other blade was twisted toward the low pitch, high rpm position.