Eureka, CA, USA
N693CC
Sikorsky S61A
The twin engine helicopter experienced a dual loss of engine power while en route to the landing area during external long line logging operations and made a forced landing into trees. The flight crew noticed the low fuel caution lights began to flicker on and off just prior to the last logging run. The co-pilot indicated there was 225-250 pounds of fuel left in each fuel tank. The captain decided that they had enough fuel remaining in each fuel tank to finish the last log run, pickup an empty fuel tank on the long line, and return to their base to refuel with about 200 pounds of fuel in the tanks at landing. As the flight crew started the last log cycle, the number 1 LOW PRESSURE light illuminated, but the captain determined it was not an emergency situation and they continued with the flight. After the flight crew picked up the empty fuel tank, it swung toward some ground personnel. The captain pulled the nose up so that the tank would clear the ground crew. Shortly thereafter, the number 1 engine lost power. The captain initiated a landing to a field, but the number 2 engine lost power and the captain performed an autorotational landing to some soft pine trees. As part of the post accident helicopter recovery efforts, the salvage company drained the fuel tanks and found that approximately 167 pounds of fuel in the forward tank and 154 pounds in the aft tank (in his statement, the captain said that 10 gallons were drained first, set aside as the unusable fuel quantity and not counted in the totals reported by the salvage company). Post accident examination of the fuel system found that the aft fuel tank ejector pump, which fills the collector can that supplies fuel to the engine, was 90 percent blocked by a material that resembled old fuel tank sealant and/or disintegrating fuel bladder remnants. The forward fuel tank ejector pump was not obstructed. The helicopter's flight manual indicates that the low fuel caution lights will illuminate when approximately 210-280 pounds of fuel per tank remain while the helicopter is in a 3-degree nose down attitude, or between 170-200 pounds of fuel per tank remain when in a hover. A caution note is incorporated in the flight manual indicating that when the fuel low-level caution lights illuminate, attitudes in excess of 6 degrees nose up should be avoided due to the possibility of engine fuel starvation. The limitations section of the flight manual indicates that the minimum planned fuel on final landing shall not be less than 450 pounds total. According to the manual, the total unusable fuel is 17.75 pounds of fuel per tank. The captain said that the versions of the S61 that he had been flying have modified fuel tanks that reduce the minimum landing fuel to 200 pounds and he was unaware that the accident helicopter had the standard military fuel tanks with a higher 450-pound landing minimum. The captain also said that in the weeks before the accident he had found "dried up adhesive in the fuel samples" taken during preflight inspections. A former crew chief for the company said that the standard procedure the company used in response to fuel leaks was to "repaint" the fuel tanks with sealant and return the helicopter to service.
HISTORY OF FLIGHT On May 10, 2000, at 1700 Pacific daylight time, a Sikorsky S61A twin engine helicopter, N693CC, experienced a dual loss of engine power while maneuvering to an off-airport landing site, and made a forced landing approximately 2.8 miles east of Eureka, California. The helicopter, which was owned and operated by Croman Corporation, White City, Oregon, sustained substantial damage. The airline transport pilot (captain) and the commercial co-pilot sustained minor injuries. The helicopter was being operated under the provisions of 14 CFR Part 133 as an external load operation. The local logging flight originated from a remote landing site at 1349. Visual meteorological conditions prevailed, and a company visual flight rules flight plan had been filed. According to the captain's written statement, he and the co-pilot conducted a preflight inspection of the helicopter, which included a sampling of the fuel. On the last cycle of the flight, the flight crew discussed how much fuel was remaining. According to the captain, in a stable hover, the co-pilot estimated "250 pounds of fuel per side" with the FUEL LOW LEVEL caution lights beginning to flicker on and off. According to the captain, this was "normally enough [fuel] for one more" cycle and landing at the service area with approximately 200 pounds of fuel per side remaining. As the flight crew started their last cycle, the number 1 LOW PRESSURE light illuminated. The captain said he experienced a low pressure light illumination a year prior to the accident and according to maintenance personnel, the illumination of the low pressure light "did not require an emergency landing." The captain elected to continue with the last cycle. The captain dropped off the logs they were carrying, and picked up an empty fuel barrel, which swung toward ground personnel working nearby. The captain "raised the nose" of the helicopter to ensure that the barrel cleared the ground personnel. While the captain was flying toward their service area and watching the barrel (approximately 1 minute later), the captain noticed the number 1 engine lose power. The co-pilot announced that they had an engine problem. As the captain slowed the helicopter to autorotation speed (65 knots) and reduced power, he advised the co-pilot to place the throttles in the full forward position, which he did. The captain turned the helicopter toward a clearing on the rim of a canyon and electrically released the long line and barrel. Approximately 20 seconds elapsed before the number 2 engine lost power, and rotor rpm began to decay. The captain realized that he did not have enough altitude to reach the clearing and advised the co-pilot they were going to conduct an autorotation into the softest trees he could find. The captain flared the helicopter into some trees. According to the co-pilot's written statement, the co-pilot and captain discussed the fuel status during the fifth cycle of the day. The co-pilot indicated there was approximately 225-250 pounds of fuel per side, with "one flash of the [fuel] low level light, which is normal." He and the captain decided this would be the last cycle before heading back to the landing area. As they were en route to pickup the last log, the co-pilot noticed the number 1 FUEL PRESSURE light flicker on and off. He mentioned this to the captain, who told to co-pilot that he experienced the same scenario a year prior and had been told that it was not an emergency situation. While they were picking up the log, the co-pilot noticed the number 1 FUEL PRESSURE light flicker on and off again, but did not see either LOW LEVEL light. After the flight crew dropped off the log, and while they were picking up the empty fuel barrel, the co-pilot noticed the LOW LEVEL light illuminate again and turn off. He observed the fuel quantity was "well within the 200 [pound] range [on] each side." The co-pilot reported that halfway to the service area, the number 1 engine lost power, after which he placed the throttles to the full forward position. Approximately 10-20 seconds later the co-pilot observed the number 2 engine lose power. The captain then maneuvered the helicopter for an autorotation and flared as the helicopter entered the trees. Both pilots egressed without assistance. The captain added that the fuel filter light had not illuminated during the flight. PERSONNEL INFORMATION The captain held an airline transport pilot certificate with a ratings for helicopters and instrument helicopter operations. In addition, he held a commercial pilot certificate with single engine, multiengine, and instrument airplane ratings. He was issued a first-class medical certificate on September 22, 1999, with a limitation to "possess glasses for near vision." He obtained his last biennial flight review endorsement on March 4, 2000, in a Eurocopter AS-350-B2 helicopter. According to the captain, he accumulated a total of 12,000 flight hours, of which 11,600 hours were in helicopters, and 1,517 hours were in the accident helicopter make and model. He listed having logged a total of 67 hours in the Sikorsky S61 within the preceding 30 days to the accident. The co-pilot held a commercial pilot certificate with a helicopter rating. AIRCRAFT INFORMATION The 1963 model Sikorsky S61A (also known as the SH-3G) was designed for the Navy as a general utility and search and rescue helicopter. According to the S61A Navy flight manual, the helicopter is equipped with two independent pressure-type fuel systems, a forward fuel tank and an aft fuel tank. The systems are joined together by a cross feed system. Each fuel system consists of a fuel tank with two bladder-type cells and collector cans in which two fuel boost pumps are located. A fuel ejector system within each tank pumps fuel from the cell into the collector can. The ejector system and boost pump arrangement provides for a minimum of unusable fuel. The fuel management panel, located on the instrument panel, contains the four fuel boost pump switches, the fuel boost pump failure warning lights, the cross feed switch, and the two engine fuel firewall shutoff valve switches. For normal operation, the forward fuel tank supplies fuel to the number 1 engine and the aft fuel tank supplies fuel to the number 2 engine. There are two fuel low level caution lights located on the caution panel. The lights, marked FWD FUEL LOW and AFT FUEL LOW, will illuminate when approximately 210-280 pounds of fuel per tank remain while the helicopter is in a 3-degree nose down attitude, or between 170-200 pounds of fuel per tank remain when in a hover. A caution note is incorporated in the flight manual indicating that when the fuel low level caution lights illuminate, attitudes in excess of 6 degrees nose up should be avoided due to the possibility of engine fuel starvation. The fuel quantity gages indicate the fuel quantity in each tank in pounds, and the system utilizes capacitance-type fuel probes in each tank. According to the NTSB Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2), the helicopter last took off with 1,600 pounds of Jet A fuel on board. According to the flight manual's Fuel Quantity Data, the unusable fuel quantity is 17.75 pounds in each tank, or a total of 35.51 pounds of fuel. The flight manual's fuel system limitations require at least one boost pump to be operating in each tank during all flight operations. All four of the fuel boost pumps should be operating if the pressure altitude is above 4,000 feet, the outside air temperature is above 43 degrees Celsius, or if there is less than 600 pounds of fuel per tank. The limitations section of the flight manual indicates that the minimum planned fuel on final landing shall not be less than 450 pounds total. The captain said that the versions of the S61 that he had been flying have modified fuel tanks that reduce the minimum landing fuel to 200 pounds and he was unaware that the accident helicopter had the standard military fuel tanks with a higher 450-pound landing minimum. WRECKAGE AND IMPACT INFORMATION According to the wreckage recovery and salvage personnel, the front fuel tank contained approximately 25 gallons of fuel (167.5 pounds), and the aft fuel tank contained 23 gallons of fuel (154.1 pounds). The captain stated that he was present during the fuel measurement process and that 10 gallons of fuel were drained from the tanks (5 gallons from each side) and this amount was set aside as "unusable fuel" and was not counted in the totals reported by the wreckage recovery personnel. The operator conducted a post accident examination of the helicopter's fuel system under the supervision of the Federal Aviation Administration. The operator's director of maintenance said that they tested the fuel gauges and fuel low lights with a known quantity of fuel in the fuel tank. The gauges and fuel low lights "checked good." They also tested fuel the boost pumps, which operated normally. They tested the fuel ejector pumps. The aft fuel ejector pump was 90 percent blocked, while the forward fuel ejector unit operated normally. ADDITIONAL INFORMATION According to the captain, the material found in the plugged ejector was consistent with patching material used in the repair of the rubber fuel bladders. He added that he found "dried up adhesive in fuel samples weeks before the crash." The captain reported that the fuel tanks had been repaired and patched in 1996. In addition, an ex-company crew chief reported "a long history of fuel tank leaks." An ex-company crew chief reported that the standard procedure was to "repaint" the fuel tanks with sealant and return the helicopter to service.
the loss of power in all engines due to the pilot's inadequate in-flight decision to continue flight with fuel level below the landing minimums specified in the flight manual, which resulted in the unporting of the fuel supply line and fuel starvation. A contributing factor was the blocked fuel ejector pump in the aft fuel tank and an inadequate maintenance level on the helicopter's fuel system.
Source: NTSB Aviation Accident Database
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