What happened
On October 25, 2021, at approximately 19:50 local time, a Piper Company PA-24 was conducting a cross-country flight between Rancagua and Pichilemu. The flight, which included the pilot and three passengers, was returning to Aeródromo La Independencia (SCRG) when the engine began to sputter and subsequently ceased operation while over the Coltauco sector. Unable to reach the nearby Peumo aerodrome, the pilot performed an emergency landing in an agricultural field. Despite the engine failure, the aircraft sustained no damage, and all four occupants remained uninjured.
The investigation
DGAC Chile investigators examined the aircraft's maintenance records, fuel levels, and the pilot's pre-flight procedures. The investigation focused on why the engine stopped despite the pilot's belief that sufficient fuel was on board for the planned two-hour mission. Investigators inspected the fuel tanks at the crash site and found both tanks were empty.
Testing revealed a significant discrepancy between different fuel measurement methods. While the pilot had used a manual dipstick (measuring rod) to verify fuel levels before takeoff, this tool provided inaccurate readings. Specifically, the investigation found that the dipstick's graduations were incorrect, leading the pilot to believe there were 15 US gallons per tank when there were actually only approximately 10 US gallons per tank. Furthermore, the aircraft's cockpit fuel gauges were also providing inconsistent and erroneous information.
Findings
- The engine stopped in flight due to fuel exhaustion.
- The pilot used a fuel measuring rod with incorrect graduations during the pre-flight inspection.
- The aircraft's internal fuel quantity indicators provided inaccurate readings.
- The pilot did not monitor the fuel quantity via the cockpit instruments during the flight, which might have alerted the crew to the declining levels.
- The pilot's calculated endurance of three hours was inaccurate; the actual fuel on board only allowed for approximately two hours of flight time.
Safety action
Following the investigation, the following safety actions were identified:
- Operators should verify that fuel measuring rods are correctly graduated and provide readings consistent with actual fuel volume.
- Maintenance programs should include the calibration of fuel quantity indicators to ensure accuracy.
- Pilots should be reminded to perform continuous monitoring of fuel levels during flight operations.