NTSB Identification: LAX99GA216.
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Accident occurred Tuesday, June 15, 1999 in TUCSON, AZ
Probable Cause Approval Date: 05/16/2001
Aircraft: Hughes OH-6A, registration: N6187C
Injuries: 1 Serious.

: NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this public aircraft accident report.

The pilot was on short final approach to land when he reported an engine failure. He attempted to stretch his glide to avoid buildings and cars on the ground; however, the helicopter struck railroad tracks next to the field boundary. Damage to the main rotor blades was consistent with a low rotor rpm at impact. The pilot did not recall how much time had elapsed since his last refueling. Examination of the navigation and fuel endurance log from the helicopter cockpit (required by the operator) showed the pilot had not completed the fuel endurance calculations at the time of last fueling. The helicopter was equipped with a main fuel system and an auxiliary fuel system. A deferred maintenance item, 'main fuel gauge unreliable in forward flight,' was still open. The same discrepancy had also been entered previously and it, too, had not been cleared. The auxiliary fuel gauge was entered as inoperative on the deferred maintenance log with 'parts on order' but had not been cleared at the time of the accident. The pilot last recalled reading approximately 78 pounds on the main fuel gauge. He did not recall seeing the 20-minute light illuminate before the accident. A check of the low fuel warning system found that float arm contact in the fuel cell occurred at 34 pounds, which approximates 20 minutes of usable fuel; no discrepancies were found in the operation of the system. No evidence of a fuel spill was found around or under the wreckage. The crashworthy main fuel cell was uncompromised and about 12 ounces of trapped fuel was found. No fuel was found in the auxiliary fuel tank. The light bulbs for the 'Engine Out, Fuel Low, and Master Caution' were removed for examination. One 'Master Caution' bulb showed a small amount of filament stretching, consistent with hot stretching from a light to moderate impact force. The filaments of both 'Fuel Low' bulbs were intact and unstretched, consistent with bulbs not being illuminated during a light to moderate impact. The filaments from both 'Engine Out' bulbs showed a small amount of stretching, again consistent with hot stretching from light to moderate impact. There were no other discrepancies found with the engine or engine-related systems.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Fuel exhaustion resulting from pilot's failure to perform adequate fuel consumption calculations. The unreliable and inoperative fuel level indicating system components and the operator's operation of the aircraft with known deficiencies were factors in the accident.

Full narrative available

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