NTSB Factual Report

On December 16, 2003, at 1107 mountain standard time, an Allison KR-2, a single-engine experimental airplane, N82KR, lost engine power on final approach and made a forced landing in an open field, 1/2 mile short of runway 01 at Glendale Municipal Airport (GEU), Glendale, Arizona. During the landing rollout, the airplane came to rest inverted after the main landing gear wheels dug into the plowed field. The pilot/owner operated the airplane under the provisions of 14 CFR Part 91. The private pilot, the sole occupant, was not injured, though the airplane sustained substantial damage. Visual meteorological conditions prevailed for the cross-country flight that departed the Las Cruces International Airport, Las Cruces, New Mexico, at 0830 mountain standard time. A visual flight rules (VFR) flight plan had been filed, and the flight was scheduled to terminate at GEU.

According to the pilot's written statement there were no problems encountered during the flight until he reached Glendale. On final approach, the pilot reduced the throttle to idle and the engine "died." He made an unsuccessful attempt to restart the engine and informed the tower that he was not able to reach the runway. He made a forced landing in a plowed field.

Federal Aviation Administration (FAA) inspectors examined the airplane on-scene. According to the inspectors, the airplane traveled about 350 feet before the airplane nosed over and came to rest inverted. The inspectors noted that there were no ground scars that were associated with the tail wheel. They were able to verify flight control continuity. A blue colored liquid was removed from the fuel sump that had the odor and appearance of 100-low lead aviation fuel. There were no contaminates observed in the liquid. A visual examination of the engine was conducted. All ignition leads, magneto, electronic components, spark plugs, and electrical wiring were intact. The fuel system plumbing was not compromised. The carburetor was secured at its attachment point. A functional check of the throttle linkage, mixture linkage, and carburetor heat linkage was conducted with no discrepancies noted.

The FAA conducted an engine run at Air Transport, Phoenix, Arizona, on December 31, 2003. The FAA indicated that a four-cylinder Mosler Motor Inc. engine had been installed in the airplane. The FAA inspectors utilized a Mosler Motors Inc. installation and operation manual, as well as the airplanes checklist, which had been found in the airplane. The electrical system was activated, and the fuel pump was turned ON to check the system for leaks. There were no mechanical problems encountered. The FAA noted that there were two separate ignition systems installed on the airplane. One ignition system utilized a magneto independent of the electrical system, and the other was an electronic ignition system dependant on the electrical system. The instrument panel had a placard to start the engine with the magneto system only.

The FAA inspectors primed and started the engine using the airplane's checklist. The engine started, and they maintained 1,000 rpm using the throttle during the warm up period. After the warm up period, with the oil pressure indicating normal, the throttle was advanced to 2,500 rpm. The engine began to run "very rough" with varying vibrations. Each ignition system was individually checked with the same varying vibration and roughness. The inspectors noted that in all ignition configurations the engine ran rough. Carburetor heat was applied with a 150-200 rpm drop. The mixture cable was pulled to lean and the engine continued to run rough and then lost rpm "rapidly." The throttle was then reduced to the idle position (carburetor heat off, mixture full rich, both ignition systems on), and the engine "immediately died." The engine was restarted and run three times through the same scenario with the same results; a rough running engine and engine stoppage at the idle throttle position each time.

The FAA inspectors used the Mosler Motors Inc. operation manual and determined that the power jet needle located on the left side of the carburetor appeared to be loose with very little spring tension. They also noted that the power jet needle was not screwed all the way in. Following the instructions, the power jet needle was turned three full turns "before it bottomed out." According to the manual (page 18), the power jet needle was then backed out a half turn. The engine was test ran again, and it ran smooth at 3,000 rpm. The throttle was reduced to the idle position, and the engine continued to run smoothly at an indicated idle speed of 800 rpm. The carburetor heat as well as each individual ignition system was checked with no discrepancies noted.

The FAA inspectors interviewed the pilot. He had experienced two propeller strikes in the accident airplane during ground operations in October 2003, and had to replace the propeller in both cases. The pilot indicated that an internal engine inspection in both instances was not done. According to the pilot, between December 2 and 12, 2003, repair work had been done on the throttle that involved safety wiring something around the throttle linkage. The pilot stated that Boerne Stage Aero Service did the work conducted on December 13, 2003. The pilot further indicated that the mechanic refused to enter the work performed in the maintenance records because it was an experimental aircraft; however, he made an entry in his flight logbook that a test flight was conducted after magneto and ignition work was completed. The entry in his personal logbook did not indicate who conducted the maintenance work. There was no corresponding entry in the airframe or engine logbooks regarding any maintenance work for the December 2003 time period.

The Safety Board investigator reviewed the airframe and engine logbooks. The airplane was issued a special airworthiness certificate on December 15, 1993. The last conditional (annual) inspection was conducted on October 21, 2002. On October 20, 2003, an entry in the engine logbook indicated that when the throttle was "pulled back abruptly" the engine "stalled." The entry for December 13, 2003, indicated that the electronic ignition coils were replaced, the carburetor heat control cable was freed, the exhaust tube was removed and welded, and the propeller spinner was modified to fit over propeller.

According to the airplanes Experimental Operating Limitations, a condition inspection "shall be recorded in the aircraft maintenance records." The Operating Limitations further indicated that no person "shall operate this aircraft unless within the preceding 12-calendar months it has had a condition inspection performed."

The Safety Board investigator interviewed the Chief of Maintenance for Boerne Stage Aero Service. He stated that Boerne Stage worked around the carburetor, but did not make any adjustments or any work on the carburetor. The electronic ignition coil had been replaced because a portion of it had been burned away after being exposed to exhaust gases. The pilot conducted a ground run, and maintenance personnel from Boerne Stage observed black smoke emanating from the engine compartment. The pilot was instructed to lean the engine, and the engine ran "smoothly with no black smoke observed." When the pilot departed from the airfield, witnesses observed black smoke coming from the engine.

NTSB Probable Cause

loss of engine power due to a loose carburetor jet. A contributing factor was the owner/operators failure to have a condition inspection performed on the aircraft.