History of Flight
On August 22, 2013, about 1227 Pacific daylight time, a Piper PA-38 Tomahawk, N2578L, experienced a complete loss of engine power during a cross-country instructional flight. The airplane was substantially damaged during a forced off-airport landing near Madera, California. The certified flight instructor (CFI) and the private pilot under instruction were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91, with visual meteorological conditions prevailing. A Federal Aviation Administration (FAA) flight plan was filed but not activated.
The planned cross-country flight, operated by Mazzei Flying Service of Fresno, California, was to originate and terminate at Fresno Yosemite International Airport (FAT) with an intermediate stop at Napa County Airport (APC). The pilot also intended to perform a touch-and-go landing at Livermore Municipal Airport (LVK) on the return leg. En route to APC, weather deteriorated below visual flight rules minima, prompting a diversion to Buchanan Field Airport (CCR) in Concord, California. The landing at CCR was uneventful, and the pilot re-planned the return flight to FAT. Although fuel was available at CCR, no fuel was taken onboard.
Departure and initial flight from CCR to FAT were normal, including the planned touch-and-go at LVK. About 25 miles from FAT, during the descent, the engine ceased developing power. The CFI landed the airplane in a field shortly thereafter. An on-site examination by an FAA inspector revealed that neither fuel tank was compromised, and both fuel tanks were devoid of usable fuel. No other pre-impact abnormalities were reported.
Personnel Information
The CFI held multiple certificates and ratings, including flight instructor for single-engine airplanes. He reported 1,178 total flight hours, with 915 hours in the accident airplane make and model. He had 117 hours as a flight instructor, of which 100 were in the accident airplane. His most recent flight review was completed in May 2012, and his most recent FAA second-class medical certificate was issued in December 2012.
The private pilot under instruction held a private pilot certificate with an airplane single-engine land rating. He reported 86 total flight hours, all in the accident airplane make and model, including 8 hours as pilot-in-command. His most recent flight review was completed in July 2013, and his most recent FAA first-class medical certificate was issued in July 2012.
Aircraft Information
The Piper PA-38 Tomahawk, manufactured in 1979, was equipped with a Lycoming O-235 series engine. According to the flight school, the airframe had accumulated 12,413 total hours as of its most recent 100-hour inspection on August 6, 2013. The engine had 5,802 total hours, including 434 hours since its most recent overhaul. No recent problems with the fuel system were recorded.
Per the Pilot's Operating Handbook (POH), the airplane had two fuel tanks (one in each wing) with a total capacity of 32 gallons and 30 gallons usable. The fuel selector had LEFT, OFF, and RIGHT positions. Separate fuel quantity gauges for each tank were installed, but the POH did not specify gauge graduations or units.
Meteorological Information
The 1253 automated weather observation at Madera Municipal Airport (MAE), about 5 miles northwest of the accident site, reported wind from 300 degrees at 4 knots, visibility 10 miles, clear skies, temperature 31°C, dew point 11°C, and an altimeter setting of 29.87 inches of mercury.
Wreckage and Impact Information
The accident site was about 5 miles southeast of MAE and about 19 miles northwest of FAT. The airplane came to rest upright in a field of low vegetation. All three fixed landing gear were displaced or collapsed. The left outboard wing, firewall, and right trailing edge flap were crumpled. One blade of the two-blade, fixed-pitch metal propeller was bent aft. No pre-impact damage or mechanical deficiencies were noted.
Pre-Flight Fuel Planning and Observations
A flight school document titled "The Mazzei Standard" indicated that Tomahawks were not designed to carry two average-weight people with a full fuel load and that it was inappropriate to tanker extra fuel unnecessarily. It provided diagrams for determining fuel quantity by visual reference to an embossed "X" on each tank's aft wall, though no airplane attitude requirements were specified.
Another school policy required students to carry a minimum fuel reserve of 1 hour at 65% power.
The CFI reported visually checking fuel quantity at FAT before departure and determining the airplane had exactly 21 gallons. Before departing CCR, the pilot advised the CFI that 14 gallons remained, but the CFI did not independently verify. At the top of descent into FAT, one fuel gauge indicated just under 5 gallons, and the other exactly 5 gallons. The CFI had observed fuel gauges provide erroneous information in the past but had no reason to suspect inaccuracies on this flight.
Pilot's Flight Planning Calculations
The pilot's flight planning documents showed calculated fuel requirements: For the FAT-to-CCR leg, he planned 9.5 gallons burn plus start/taxi, Plan B, and reserve fuel, totaling 14.4 gallons required (excluding 2 gallons unusable). For the CCR-to-FAT leg, he planned 9.6 gallons burn plus start/taxi, Plan B, and reserve, totaling 13.4 gallons required. This did not account for the touch-and-go at LVK. The sum of required fuel for both legs, excluding reserves, was 20.6 gallons; including reserves, 23.9 gallons.
NTSB Fuel Calculations
The NTSB calculated trip fuel requirements using the pilot's leg times, altitudes, POH fuel consumption values, and school reserve requirements. For the first leg, calculated burn was 8.2 gallons, with 5.8 gallons reserve, totaling 14.0 gallons. For the second leg (excluding LVK), burn was 9.0 gallons, reserve 5.8 gallons, totaling 14.8 gallons. The overall required fuel including reserves was 23.0 gallons; excluding reserves, 17.2 gallons. The pilot's and investigation's calculations were similar.
Observed Fuel Discrepancy
When the airplane was approximately over MAE, cockpit fuel gauges indicated nearly 10 gallons remaining, suggesting only about 4 gallons consumed since CCR departure—less than half the planned consumption. No evidence indicated that the pilot or CFI detected or acted on this discrepancy.
FAA Guidance on Fuel Gauges
The FAA Pilots Handbook of Aeronautical Knowledge notes that aircraft certification rules require accuracy in fuel gauges only when reading empty; other readings should be verified. Visual checks are recommended during preflight.