UNIONTOWN, OH, USA
N35WT
Piper PA-31-310
The commercial pilot departed on the last segment of his 5-leg trip with an estimated 44-48 gallons of fuel in the inboard tanks, and no fuel in the outboard tanks. While on final approach, both engines stopped producing power and the pilot performed a forced landing 4 1/2 miles short of the runway. Examination of the fuel tanks revealed that the left and right inboard tanks were empty. With the battery off, the left fuel gauge read approximately 1/16 full and the right fuel gauge read approximately 1/2 full. The two left and one right inboard fuel probes were checked for variable resistance using a calibrated digital VOM. None of the probes that were tested were within the manufacturer's published resistance limits. The operator stated that the normal procedure for checking fuel quantity was by referencing the fuel gauges, and that the airplane would burn an average of 40 gallons per hour. Fuel burn for the five trip legs was about 41 gallons per hour. The pilot reported a total of 1,706 flight hours, of which 365.6 hours were in make and model. The pilot reported no additional mechanical deficiencies.
On May 22, 2001, at 0806 eastern daylight time, a Piper PA-31-310, N35WT, was substantially damaged during a forced landing to a field near Uniontown, Ohio, while on final approach to runway 23 at Akron-Canton Regional Airport (CAK), Akron, Ohio. The certificated commercial pilot sustained serious injuries. An instrument flight rules (IFR) flight plan was filed for the flight that originated at Port Columbus International Airport (CMH), Columbus, Ohio, at 0725. Visual meteorological conditions prevailed for the flight conducted under 14 CFR Part 135. Examination of dispatch records revealed that the pilot was on the last segment of a five-leg trip that was estimated to take 5.7 hours to complete. The first leg of the trip was from Canton to Columbus. The trip then continued on to Madison, Wisconsin (MSN), Chicago, Illinois (ORD), then back to Columbus, and finally back to Canton. Before the first leg of the trip, the Hobbs meter time was 3,930.9 hours. According to the pilot, the airplane departed on the first leg of the trip with full fuel, and at Madison he purchased 61 gallons of 100 LL fuel at a Hobbs meter time of 3933.7 hours. Prior to departure on the last leg of the trip, from Columbus to Canton, the pilot reported that the fuel quantity gauges indicated just below half on the inboard tanks, which he estimated to be about 44-48 gallons of fuel onboard. The outboard tanks were empty. He departed at 0725, and within 10 miles of Canton he was cleared for the ILS 23 approach. In a written statement, the pilot said: "I powered back for the approach and was vectored twice more for the inbound course. Before my last turn onto final, I checked my fuel gauges and noticed they were indicating slightly above 1/8 of a tank for each main tank, which should have given me 8 to 9 gallons per side. This should have been enough fuel for at least 25-30 minutes flying time, even at reduced power for approach and landing." Just after intercepting the final approach course and about to pass over the outer marker is when I experienced the first fuel interruption from the right engine. The right engine surged about 3 times and then the left started to do the same. The controller notified me that I was getting low and left of course, which at that time I notified him that I was experiencing engine problems." Two Federal Aviation Administration (FAA) inspectors examined the airplane at the accident site on May 22, 2001. According to one of the inspectors, the airplane landed gear up about 4 1/2 miles northeast of the airport in a freshly planted cornfield. The Hobbs meter read 3,936.8 hours. The fuselage was twisted, and both wings, the ailerons, and right elevator were substantially damaged. Examination of the wing fuel tanks revealed that the left wing inboard, right wing inboard, and right wing outboard fuel tanks were empty. About 3/4-inch of residual fuel was observed at the bottom of the left wing outboard fuel tank. None of the fuel tank sump drains were found open, and there were no breeches of the fuel tanks. The left and right fuel selector valves were positioned to the inboard fuel tanks. Due to impact damage, the selector valve could not be examined. With the battery off, the left fuel quantity gauge read approximately 1/16 full, and the right fuel quantity gauge read approximately 1/2 full. Two FAA inspectors returned to examine the fuel quantity indicating system on June 21, 2001. According to one of the inspector's written report, when no power was applied to the electrical bus and the fuel selectors positioned to the inboard tanks, the left fuel quantity gauge indicated just below 1/4-full. The right fuel quantity gauge read just less than 1/2-full. When the power was turned on, the right fuel quantity gauge immediately dropped to just less than 1/4-full. The left fuel gauge did not move. The two left inboard fuel tank probes and one right inboard fuel tank probe were checked for variable resistance using a calibrated Ohmmeter. The readings were as follow: Left inboard fuel tank probe (closest to fuselage) with float position: Empty: 6.8 Ohms; Full: 55.5 Ohms Left inboard fuel tank probe (outboard of nacelle) with float position: Empty: 0.6 Ohms; Full: 43.6 Ohms Right inboard fuel tank probe (closest to fuselage) with float position: Empty: 2.5 Ohms; Full: 53.5 Ohms According to Piper Navajo Service Manual, page 3B2, the resistance limits for the main inboard fuel tank probes were: with float position Empty: 0 to 0.5 Ohms; and Full: 48-52 Ohms. Examination of the airplane's operating manual revealed that there were two bladder cells in each wing. The outboard cells held 40 gallons each, and the inboard cells held 56 gallons each; for a total of 192 gallons, of which 182 gallons were usable. The operator reported that the airplane would burn an average of 40 gallons per hour. Additionally, the operator stated that there was no way to visually check the amount of fuel in the tanks, and the normal procedure to check fuel quantity was by referencing the fuel gauges in the cockpit. According to the Piper PA-31-310 Pilot's Operating Manual, page 8, "Two electric fuel gauges indicate the fuel quantity in each cell. The electric fuel gauges indicate the fuel quantity in the cell selected by the fuel selector handle located in the fuel control panel." The pilot reported a total of 1,706.1 flight hours, of which 356.6 hours were in make and model. He also reported that there were no mechanical deficiencies. Weather at Akron-Canton Airport, at 0808, was reported as winds from 150 degrees at 5 knots, visibility 5 statute miles, mist, ceiling scattered at 2,100 feet, broken at 3,100 feet, overcast at 10,000 feet, temperature 61 degrees F, dewpoint 57 degrees F, and altimeter setting 29.73 inches Hg.
Fuel exhaustion due to the pilot's failure to perform fuel calculations. A factor was the inboard fuel tank probes not being within the manufacturer's resistance limits, which resulted in inaccurate fuel gauges.
Source: NTSB Aviation Accident Database
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