Seattle, WA, USA
N19903
Boeing S-307
The crew had originally planned to practice landings at an airport about 20 minutes away, then stop, refuel the airplane, and subsequently return to the original departure airport. Prior to the flight, the crew discussed fuel endurance, which was calculated to be 2 hours based on the captain's knowledge of the airplane's fuel consumption, and the quantity of fuel indicated on the gauges. The fuel tanks were not dipped. The flight was made at 1,500 feet msl. Upon reaching the practice airport, the crew conducted one full stop landing, then taxied back for takeoff. During takeoff, an engine had a momentary overspeed, and the crew decided to return to the original departure airport without refueling. Approaching the original departure airport, the airplane had to delay landing for about 7 minutes for a manual gear extension. Upon completion, it turned back toward the airport, and was about 6 miles from the runway when fuel pressure for one of the engines dropped. The boost pumps were turned on; however, the engine lost power. A low fuel pressure light then illuminated for another engine. The captain called for the flight engineer to switch fuel feed to another tank, but the flight engineer responded, "we're out of fuel." The remaining engines subsequently lost power, and the captain ditched the airplane into a bay. The time from first takeoff until ditching was 1 hour, 19 minutes. The airplane had flown 39 hours since restoration, and exact fuel capacities, fuel flow calculations and unusable fuel amounts had not been established. A dipping chart had been prepared, with one person in the cockpit and one person with a yardstick putting fuel in a main tank in 25-gallon increments. However, the data had not been verified, and dipping was not considered to be part of the pre-flight inspection.
HISTORY OF FLIGHT On March 28, 2002, about 1310 Pacific standard time, a Boeing S-307 Stratoliner, N19903, registered to the National Air & Space Museum and operated by The Boeing Company as a 14 CFR Part 91 maintenance check and proficiency flight, ditched in the waters of Elliott Bay, Seattle, Washington, following a loss of engine power on all four engines. Visual meteorological conditions prevailed at the time, and a company visual flight rules flight plan was in effect. The airplane was substantially damaged. The two airline transport pilots, and two airframe & powerplant mechanics seated at the flight engineer and avionics stations were not injured. The flight departed Snohomish County Airport (Paine Field) (PAE), Everett, Washington, and was destined for Boeing Field/King County International Airport (BFI), Seattle, Washington. The accident flight was the second of two flights that day. The first flight was flown from Boeing Field to Paine Field, where a full stop landing was made. The crew then taxied the airplane back to the approach end of the runway, and took off on the accident flight. On March 29, 2002, the National Transportation Safety Board Investigator-in-Charge, Federal Aviation Administration (FAA) inspectors, and representatives of Boeing interviewed the crew. All four crew members subsequently provided written statements. According to the captain, the crew had originally planned to practice landings at Paine Field, then stop and refuel the airplane. After the refueling, the airplane would return to Boeing Field. Estimated time en route, between the two airports, was 20 minutes. Prior to the first flight's departure, the captain spoke, via telephone, with the maintenance manager about the status of remaining maintenance jobs to be completed before the airplane was released. (Note: The maintenance manager was seated at the avionics station for the accident flight and is hereafter referred to as the observer.) The remaining maintenance consisted of pre-oiling the engines and checking the fuel quantity. After the telephone conversation, the observer met with the captain in his office. Shortly thereafter, the first officer for the flight joined them. The three agreed that prior to the flight, they would conduct a systems and procedures review at the airplane. The three then walked over to the airplane and met with the chief mechanic. (Note: The chief mechanic was seated at the flight engineer's station for the accident flight and is hereafter referred to as the flight engineer.) The flight engineer briefed the three other crewmembers about the maintenance work that had been performed on the airplane since its last flight. See Airplane Information for details. The captain, first officer and observer then boarded the airplane and conducted the systems and procedures review. The review was concluded by 1100. At that time, the flight engineer reported to the captain that the pre-flight inspection had been completed, and the airplane was released for flight. The captain asked the flight engineer how much fuel was onboard, and the flight engineer reported that 425 gallons of fuel were in the main fuel tanks. Flight endurance was discussed with the given fuel quantity, which was calculated to be two hours based on the captain's knowledge of B-307 fuel consumption. The amount of fuel onboard was determined to be sufficient for the planned flight. About 1200, the engines were started and warmed-up, and a run-up was completed with no anomalies noted. The airplane was taxied to runway 13R (13 right), and at 1224, full power was applied for takeoff. The flight was flown to Paine Field at 1,500 feet, and carburetor heat was used en route. Upon reaching Paine Field, the captain set up for a full stop landing on runway 16R. Touchdown was about 1247. The airplane was taxied back to runway 16R, and it was decided that the captain was going to make two more take-offs and landings, then stop to have the airplane refueled. The takeoff was made at 1251. During the initial climb-out, it was noted that the tachometer for the number three engine (right side; inboard) indicated a momentary overspeed to approximately 3,000 rpm. With no crew action, it then returned to 2,500 rpm, which was normal for takeoff. Because of the overspeed, the flight crew decided to abandon the original plan, and return to Boeing Field to investigate the problem. The return flight utilized a flight profile similar to the outbound flight. The return flight was uneventful; however, while on approach to Boeing Field, during landing gear extension, the left main landing gear did not indicate that it was down. The approach was broken off, and the manual gear extension procedure was begun. The manual gear extension procedure required that a section of the carpet in the cabin be pulled up to open a hatch, and someone would climb into the belly of the airplane to manually crank down the gear. The observer was assigned the task. The first attempt was unsuccessful; however, during the second attempt, the gear was fully extended with a green light indication noted. The procedure took several minutes to complete. The airplane was then turned back toward the airport to begin another approach for landing. The airplane was about 6 miles from the runway when fuel pressure for the number three engine (right side; inboard) dropped below minimum. The boost pumps were turned on; however, fuel pressure did not recover, and the engine lost power. The low fuel pressure light then illuminated for the number four engine (right side; outboard). The captain commanded the flight engineer to switch fuel feed to another tank. The flight engineer's response was, "There is no other tank. We're out of fuel." The captain pushed the throttles forward and called for the number three engine to be feathered. When the throttles were pushed forward, multiple engine surges occurred. Then the surging stopped, and it appeared that the remaining engines had also lost power. The airplane was rapidly losing altitude and the captain decided to ditch in Elliott Bay. The captain called a Mayday to the tower about 1309, and touchdown on the water occurred at about 1310. After landing, the airplane remained afloat while the crew evacuated. They were quickly picked up by rescue boats. The airplane was subsequently towed to shallower water by a Seattle Police Department boat before it partially sank in the water just offshore. The first officer's statement of the events leading up to the ditching was similar to the captain's statement. The first officer reported that during the preflight discussions, he was led to believe that the fuel onboard the airplane was 400 gallons. The first officer stated that from previous flights, the airplane's fuel consumption was about 40 gal/hour/engine. Fuel consumption for the accident flight was calculated using 50 gal/hour/engine for simplification, which equaled 2 hours of flight time. The first officer also stated that during the preflight discussion, the observer was asked by the captain about the airplane's status. The observer replied that all that remained was to "pull the airplane out, pre-oil the engines and dip the (fuel) tanks." The first officer subsequently conducted a walk-around inspection before boarding the airplane to ensure all panels were closed and that all was secure. The crew boarded the airplane, and the normal checklist began. The first items on the checklist were fuel, oil and hydraulics, and the response from the flight engineer was "checked and set." The engines started easily, and ran at 1,000 rpm until the oil warmed up, taking about 10 minutes. When all checks were complete, the airplane took off. After the engine overspeed condition was detected during the takeoff from Paine Field, the captain transferred control of the airplane to the first officer to fly it back to Boeing Field, and complete at least one landing. The first officer maintained control of the airplane until he noted the low fuel pressure light on the number three engine. He then turned on the fuel boost pump for that engine. The flight engineer also noted the low fuel pressure and stated the same, then subsequently reported, "We don't have any fuel." The captain then asked the flight engineer, "What do you mean we don't have any fuel?" The flight engineer replied, "The tanks are showing empty." The captain then took control of the airplane, and the emergency procedures were begun. The number three engine was feathered shortly before the number four engine lost power. Before the number four engine was feathered, engines one and two surged, then subsided. Engines one, two and four were not feathered prior to the ditching. During the interview, and in his subsequent written statement, the flight engineer reported that his shift started at 0600 and several volunteers arrived by 0630. Since the engines had not been run in about a month, he decided to pre-oil them, which took several hours. He also involved himself in arranging when to pull the airplane out of the hangar, as well as other airplane-related issues. Volunteers not involved in the pre-oiling process conducted the preflight inspection. Later in the morning, the captain arrived to discuss with the flight engineer what had been done with the airplane since it last flew in late August 2001. After the briefing, the airplane was pulled out of the hangar, and the preflight inspection was completed. When the airplane was ready for flight, the fuel quantity was discussed. The flight engineer reported a "little less then half in the main tanks." During interviews with the flight engineer, he stated that the fuel quantity was determined by looking at the main fuel tank fuel gage in the cockpit. The flight engineer also reported that the fuel tanks had not been "dipped" with a calibrated fuel stick. The flight engineer noted that the flight to Paine Field was uneventful. After the airplane landed and taxied back to the runway, he saw that the fuel gages for the main fuel tanks were indicating 1/4 tank, but did not report it to the captain. After takeoff, the flight engineer noted a loss of power to the number three engine. He turned his attention to the engineer's panel to try and determine the problem, when engine power came back to full, and the propeller oversped. The cause of the overspeed was discussed among the flight crew, but only the flight engineer was aware of the power loss that preceded it. The flight engineer thought that it might have been ice ingestion. At that time, it was determined to abandon the flight and return to Boeing Field. During the process of trying to get the left main landing gear down and locked, the flight engineer left his station momentarily to help the observer. When the gear was down and he returned to his station, he noted the number three low fuel pressure light was on. He also noted that the fuel gauges were indicating "0" and reported it to the other flight crew members. The captain asked him to switch to another tank; however, there was no fuel in either the inboard or outboard auxiliary tanks. The observer seated at the avionics station reported that during the preflight discussions about the fuel quantity, he stated that he thought there were a little less than 200 gallons in each of the two main fuel tanks. The fuel gage also read a little less than half for each main tank. He too saw that the fuel gage was indicating 1/4 tank prior to takeoff from Paine Field, but did not mention it to the captain. The observer reported that after the engines began to lose power, the captain asked if the tanks had been "dipped." After some discussion, it was determined that they had not. Radar data depicted the flight path of the airplane from Paine Field to the Seattle area. The data indicated that the straight-in approach to Boeing Field was broken off at Alki Point, and the airplane proceeded westerly, to the eastern shore of Bainbridge Island. Two orbits were made before the flight initiated a second straight-in approach to Boeing Field. The last target before the airplane dropped off radar coverage was located over the southern end of Elliott Bay, west of the accident location. A home video of the events leading up to, and during the ditching, revealed that the airplane made a stabilized, right descending turn to the water. The audio portion of the video revealed surging sounds from the engine(s). Water impact was made in a slightly right-wing-low attitude with the landing gear extended. The airplane initially remained upright and afloat, but subsequently sank nose-low in the shallow water. Several witnesses also reported surging sounds from the engine(s) before the airplane ditched in Elliott Bay, about 50 feet from the shoreline, near Salty's Restaurant, at 1936 Harbor Ave. S.W., in Seattle. PERSONNEL INFORMATION The captain was a certificated airline transport pilot and rated in multi-engine land, single-engine land and sea, glider and instrument airplane. At the time of the accident, he reported a total flight time of approximately 15,000 hours, with 62 hours in the S-307. The captain also reported that he was type-rated, with "several thousand" hours in various older airplanes, including the B-17, DC-3 and B-247. His training for flight in the S-307 was accomplished in a B-17. The first officer was a certificated airline transport pilot and rated in multi-engine land, single-engine land and sea, glider and instrument airplane. At the time of the accident, he reported a total flight time of approximately 7,530 hours, with 40.8 hours in the S-307. The first officer also reported that he was type-rated in several Boeing airplanes, including the B-247. His training for flight in the S-307 was accomplished in a B-17. The captain and first officer had planned to switch crew positions after refueling at Paine Field. The airframe and powerplant mechanic seated at the flight engineer's station also held a private pilot certificate for single-engine land airplane. He reported that he had been onboard the S-307 for the recovery flight in 1994 and all the flights since restoration. In addition, he had been involved in the restoration of the airplane since the beginning of the project. The airframe and powerplant mechanic seated at the avionics station also held a private pilot certificate for single-engine land airplane. He was the project manager for the restoration project, and reported approximately 40 hours of flight time in the S-307. Both mechanics had been approved by the FAA to occupy the flight engineer's station during flight operations, and had planned to switch crew positions after refueling at Paine Field. AIRCRAFT INFORMATION Flight log documentation indicated that the restoration of the airplane was completed in June 2001. A series of ground run tests were conducted through July, with the first flight logged on July 11, 2001. Approximately 39 hours and 30 minutes of flight time had been recorded since the first flight after restoration. The airplane was equipped with four, 900 horsepower, Wright Cyclone R-1820-97 engines. Each engine had a carburetor installed. Maintenance records indicated that engines number one and two were overhauled in July 1996 and October 1996 respectively. Engine number three was overhauled in February 1998, and engine number four was overhauled in June 1995. Time since overhaul, to include the accident flight, totaled approximately 53 hours. The airplane was maintained in accordance with an FAA-approved inspection program, accepted on June 26, 2001, which included "A," "B," and "C" checks, in addition to pre-flight inspections. Specific requirements included: (1) Preflight inspection - accomplished prior to the first flight of the day, and recorded and signed on the Maintenance Discrepancy Sheet in the airplane flight log. (2) A-check inspection - accomplished after 50 flight hours after a previous B check and at 50-hour intervals thereafter until the next B check. (3) B-check/annual inspection - accomplished over 100 flight hou
Loss of all engine power due to fuel exhaustion that resulted from the flight crew's failure to accurately determine onboard fuel during the pre-flight inspection. A factor contributing to the accident was a lack of adequate crew communication regarding the fuel status.
Source: NTSB Aviation Accident Database
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