LAS VEGAS, NV, USA
N42597
de Havilland DHC-1B-2
THE AIRLINE TRANSPORT PILOT, WHO IS ALSO AN AIRFRAME AND POWERPLANT MECHANIC, WAS CONDUCTING A LOCAL AREA MAINTENANCE TEST FLIGHT. THE ENGINE BEGAN MISFIRING SHORTLY AFTER TAKEOFF. THE PILOT EXECUTED A RIGHT TURN TO RETURN TO THE AIRPORT, BUT INADVERTENTLY STALLED THE AIRPLANE. THE AIRPLANE NOSED DOWN SHARPLY AND CRASHED. EXAMINATION OF THE ENGINE FUEL SYSTEM REVEALED THAT THE FUEL INLET PASSAGE WAS CLOGGED WITH AN UNIDENTIFIED BLACK, SPONGE-LIKE MATERIAL. THIS CONDITION PREVENTED FUEL FROM GETTING TO THE FUEL INJECTOR ASSEMBLY RESULTING IN FUEL STARVATION. ALSO, TWO OF THE FUEL INJECTOR NOZZLE SCREENS WERE OBSTRUCTED; THE REMAINING SCREENS WERE PARTIALLY OBSTRUCTED. A FIXED-BASE OPERATOR AND THE REGISTERED OWNER REPORTED THAT THE FUEL NOZZLES HAD RECURRING CLOGGING. THE PILOT WAS COMPLETING A 100-HOUR INSPECTION AT THE TIME OF THE ACCIDENT. THE ENGINE EXAMINATION DISCLOSED EXTENSIVE FRETTING OF BOTH CRANKCASE HALVES AND ALL OF THE CYLINDERS BASES. THE ENGINE EXAMINATION, HOWEVER, DID NOT REVEAL ANY ABNORMALITIES WHICH WOULD HAVE PREVENTED THE ENGINE FROM PRODUCING POWER.
On November 19, 1993 at 1053 hours Pacific standard time, a Dehavilland DHC-1B-2 (aka Chipmunk), N42597, crashed and burned shortly after departing runway 30 at North Las Vegas Airport, Las Vegas, Nevada. The pilot was conducting a local visual flight rules maintenance test flight. The airplane, operated by Gerard Morgan, Las Vegas, Nevada, was destroyed. The certificated airline transport pilot, the sole occupant, sustained fatal injuries. Visual meteorological conditions prevailed. The flight originated at North Las Vegas Airport at 1050 hours. Mr. Dale Nelson, Principal Maintenance Inspector, Federal Aviation Administration (FAA), Las Vegas Flight Standards District Office, conducted the on-scene investigation. A fixed- based operator (herein referred to as the operator) provided Inspector Nelson with a written statement concerning his previous conversations with the pilot and his observations of the accident. The operator said that a few days before the accident the pilot told him the accident airplane was "...experiencing fuel system contamination problems." These problems resulted in the engine fuel injectors becoming clogged. Two days before the accident the pilot asked the operator about the fuel pressure limits on the accident airplane's engine. The operator told the pilot the fuel pressure limits were between nine (9) and twelve (12) pounds per square inch (psi) and offered him the appropriate maintenance manual. Later the pilot told him that he reset the fuel pressure on the engine and that the engine was operating properly. On the day of the accident, the pilot told the operator he was going to test fly the airplane, but expressed reservations about the surface winds. Later he observed the pilot taxiing the airplane to his (the pilot's) hangar. The operator thought the pilot was returning from the test flight, but later learned he was experiencing a "...weak brake...." The airplane's engine sounded normal during the taxi phase. While in his hangar, the operator heard an engine malfunctioning which he described as "...after firing with engine surges." He proceeded to the hangar door and then saw the accident airplane in a right shallow dive. The airplane continued in this attitude until it disappeared behind some hangars. He did not see the impact. The consensus of other ground witnesses was that the airplane's engine was misfiring. When the airplane was between 200 and 300 feet above the ground, it entered into a right turn and abruptly nosed down and crashed. The pilot held an airline transport pilot certificate with a multiengine land and a Boeing B-727 type rating; the certificate was endorsed with commercial pilot privileges for airplane, single-engine land. The pilot also held an aircraft mechanic certificate with airframe and powerplant ratings. The mechanic certificate was endorsed with an inspection authorization. A designated airman medical examiner issued the pilot a first-class medical certificate on February 18, 1993. The certificate contained a "must wear lenses for distant - possess glasses for vision [and a] miscellaneous restriction" assigned. National Transportation Safety Board investigators did not recover the pilot's flight records. The pilot's flight hours listed on page three of this report were obtained from the FAA, Civil Aeromedical Institute, Oklahoma City, Oklahoma. The medical records showed the pilot indicated he had accrued 13,936 hours, of which 28 hours were flown within the preceding 6 months of his last medical application date. The registered owner told Safety Board investigators the airplane's latest maintenance records were in the airplane at the time of the accident. The records were destroyed during the postimpact fire. The owner said the pilot had maintained the airplane during the preceding year of the accident. He said the pilot told him that due to the recurring fuel nozzles clogging the pilot was going to remove the fuel tank to determine the source of the contamination. The pilot was in the process of completing a 100-hour inspection at the time of the accident. At the request of the Safety Board, the operator removed the engine fuel injection system components, including the airframe electrical driven fuel pump. These components were sent to the NTSB, Materials Laboratory, Washington, D.C., for examination. The metallurgical examination disclosed that the fuel outlet fitting separated. The Safety Board materials engineer conducted a bench binocular microscope examination of the fitting's fracture surfaces. The binocular examination revealed "...features typical of an overstress separation." The fuel inlet fitting remained attached to its mating surfaces. When the metallurgist removed the fitting, he found the mating ends blocked with a foreign black and sponge-like material. This material was hard, brittle, and densely packed in the fuel passage. The materials engineer did not determine the identity of the foreign material. Bench binocular microscopic examination of the injectors revealed the exposed portion of the screens of the numbers "1" and "2" injectors were covered with deposits that extended all around the screen circumference. The exposed portion of the screens for the remaining injectors contained a partial obstruction that extended all around the screen circumference. The materials engineer conducted a fiber optic light examination of the six fuel injector nozzles, disassembled fuel control, fuel flow divider, strainer, and electric driven fuel pump. This examination revealed no obstruction in the fuel passages. The engine was disassembled under the supervision of Mr. John Moeller, FAA, and examined at Teledyne Continental Motors (TCM), Mobile, Alabama. Mr. Moeller reported the engine had been assembled with an unapproved sealant. Both crankcase halves and all of the cylinder pads displayed extensive fretting. Mr. Moeller said, in part, "...this type of fretting occurs when the through bolts are improperly torqued or lose their stretch from some other cause. The blue sealant used on the cylinder decks and crankcase parting surfaces had been extruded and may have released the stretch on the through bolts..." He also said all the pistons crown deposits were normal for content and color. There was no evidence of preignition or detonation. He said the crankshaft fractured at the propeller/hub assembly. TCM metallurgists reported the fractured surface displayed bending overload characteristics. TCM maintenance personnel functionally tested both magnetos on a test stand. Both magnetos produced a weak spark across a 7- millimeter gap. The maintenance personnel disassembled both magnetos and found no evidence of any cross firing in the distributor blocks; however, TCM maintenance personnel found both blocks contaminated with debris. The internal components showed extensive high temperature distress from the postcrash fire. Mr. Moeller concluded: "Within the returned hardware, no abnormalities were noted that would have prevented the engine from producing power at the time of the accident. The movement of the main bearings within their supports, and the cylinders operating loose on the crankcase would have resulted in future operational problems." Dr. G. Sheldon Green, Chief Medical Examiner, Clark County Coroner/Medical Examiner Office, Las Vegas, Nevada, conducted the postmortem examination on the pilot. The examination did not disclose any evidence of any preexisting condition or disease which would have detracted from the pilot's ability to fly an airplane. Neither the FAA, Civil Aeromedical Institute, Oklahoma City, Oklahoma, nor the Clark County Coroner/Medical Examiner Office performed any toxicological examinations.
Were the fuel injection line contamination resulting in fuel starvation; the pilot's inadequate 100-hour inspection; the pilot's improper decision to return to the airport at a low altitude; and his failure to maintain the proper airspeed which resulted in a stall.
Source: NTSB Aviation Accident Database
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