On June 24, 1997, about 1301 central daylight time, a Piper PA-28-181, N3692M, registered to the Midwest Air Service, Inc., was substantially damaged during a forced landing near Walls, Mississippi. Visual meteorological conditions prevailed at the time and a VFR flight plan was filed for the 14 CFR Part 91 personal flight. The private-rated pilot and two passengers were not injured. The flight originated at 1000 eastern daylight time from the Savannah International Airport, Savannah, Georgia.

The pilot received a standard weather briefing via telephone and when filing a VFR flight plan, she stated that the estimated time en route was 5 hours with 5 hours of fuel on board. The briefing specialist questioned this and the pilot replied that the flight would refuel at an airport en route.

Before departure she confirmed that fuel in the left fuel tank was into the filler neck area and the fuel in the right tank was even with the bottom of the filler neck. The flight departed at 1000 and climbed to 5,000 feet where the pilot was asked to level off momentarily, then, 4 minutes 12 seconds later, the flight was cleared to climb to 8,500 feet. At 1029, the pilot reported to the controller that the flight was level at 8,500 feet, and she leaned the fuel/air ratio until the engine began to run rough then enrichened the mixture. The flight continued and when about 12 nautical miles east of the Holly Springs VORTAC, which in straight line distance is 49 nautical miles southeast of the destination airport, she requested to descend from 8,500 to 3,500 feet. She was advised that the flight would be vectored south of the Memphis International Airport (MEM). The flight continued and about 3 hours 45 minutes into the flight while flying at 1,800 feet mean sea level, the left and right fuel quantity gauges indicated 5 gallons and 2 gallons respectively. About 14 minutes later, when the flight was immediately south of the MEM airport with the fuel selector positioned to the right fuel tank, the engine sputtered. She immediately positioned the fuel selector to the left tank and advised the controller that, "ah sir we just had a problem with the right fuel tank we're only on the left and thats reading just about zero i think we'll have to come down ah before mike zero one [destination airport]." The controller advised the pilot that the nearest airport was located about 6 miles west of her present position. At 1300.51, which was 4 hours after takeoff, the pilot advised the controller that, "all right we're looking um im gliding at the moment ...." At 1301.43, the pilot advised the controller that she spotted a field and was planning on landing in the field. While descending for a forced landing in the field, the airplane collided with the tops of trees then landed hard and remained upright. She further stated that the hand held Global Positioning System (GPS) receiver indicated that the average ground speed for the flight was 125 knots.

Examination of the airplane by an FAA inspector revealed no remaining fuel in the fuel tanks which were not ruptured. The FAA inspector also stated that there was no evidence of fuel siphoning. According to the crew who recovered the airplane, a total of about 1/3 cup of fuel was drained from the left wing fuel tank and no measurable fuel was found in the right wing fuel tank. The recovery crew removed the aft seat and carpeting and noted that there was no evidence of fuel stains. The carburetor was removed from the engine and sent to the manufacturer's facility for further examination.

The carburetor was determined to be manufactured in February 1977. A lead seal on the outside of the carburetor was identified with the letters M-S stamped into it. The carburetor was manufactured by the Marvel Schebler division of the Borg Warner Corporation. Visual examination of the carburetor revealed evidence of fuel stains beneath a carburetor bowl to body screw which was determined to be loose; however, two of the tabs on the associated washer were contacting the flats of the screw head. Additionally, the idle jet was determined to be partially blocked by contaminants. According to the manufacturer, this would result in the finding that the fuel flow in terms of pounds per hour (pph) was unable to be adjusted to specification at the idle setting.

The carburetor was bench tested for comparison with certification standards for a master carburetor of the same model and the fuel flow in pounds per hour was determined to be above the specification limits at three of the four test points. A copy of the examination and bench test reports are an attachment to this report.

Disassembly of the carburetor revealed in part that the air metering pin return spring, Part No. 24-A30, was failed. Metallurgical examination of the spring revealed evidence of fatigue in three areas on the spring. No corrosion was noted.

According to the carburetor manufacturer, the master carburetor was previously placed on a production engine of the same model with a test club propeller and at the same test points of 162, 208, and 230 cubic feet per minute airflow, the recorded rpm was 2352, 2549, and 2615 rpm respectively. The pilot stated that during the flight she set the rpm to between 2525 and 2550. The bench test results from above at the test point closest to the rpm selected by the pilot indicate that the fuel flow in pph was about 3.0 higher than specified.

Review of the maintenance records by an FAA inspector revealed that there was no record that the carburetor had been overhauled since manufacture. Additionally, the engine logbook contained an entry dated October 3, 1989, which indicated that the engine received a major overhaul at a total time of 1,962 hours. According to a Service Bulletin by the Facet Aerospace Products, Co., dated September 9, 1986, pertaining to time between overhaul periods of all Marvel Schebler carburetors, the factory recommended time between overhauls is not to exceed the engine TBO. According to the engine manufacturer, the recommended TBO for the engine is 2,000 hours or 12 years. Compliance with the carburetor manufacturer service bulletin and engine manufacturer recommended TBO is not mandatory for 14 CFR Part 91 operators. At the time of the accident the engine had accumulated 1,846 hours since overhaul in 1989.

The maintenance records also indicated that a 100-hour inspection had been accomplished 5 days and 12 hours earlier. According to the Director of Maintenance who performed the inspection, he partially removed both wing fuel tanks to check each flexible fuel line for condition. After installation of both fuel tanks he added 1 gallon of fuel to each tank which is the unusable capacity and verified that each fuel gauge indicated empty.

Review of the airplane best power range chart revealed that based on the information provided by the pilot, the maximum range at the planned power setting with a 45-minute reserve at 55 percent power was 530 nautical miles. The total distance of the planned flight as documented by the pilot was 515 nautical miles. One of the notes in the performance chart indicates that the mixture is leaned to 100 degrees rich of peak. The pilot stated that she did not adjust the fuel/air ratio using the EGT gauge but rather adjusted the fuel/air ratio until the engine ran rough then enrichened it. Review of the time/fuel/distance to descend chart revealed that the distance to descend from the cruise altitude of 8,500 feet mean sea level to the airport traffic pattern altitude of 1,000 feet mean sea was 41.5 nautical miles. The pilot began the descent a minimum of 49 nautical miles from the destination airport.

The wreckage minus the retained carburetor was released to Mr. Bruce Fox, the Director of Maintenance for the Weiss Aviation Center on August 5, 1997. The retained carburetor was also released to Mr. Fox on December 23, 1997.

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