What happened
On July 15, 1992, a private flight was organized for members of the Kiwanis Club of Neuchâtel. The president of the club, a licensed professional pilot, took control of a Cessna CE 210 L, HB-CHZ, following two previous flights conducted by other pilots. He invited three additional club members aboard for an extra twenty-minute scenic flight.
Prior to departure, the pilot observed that both fuel quantity indicators showed levels slightly below the first white mark. He interpreted this as indicating just under one-quarter of a tank's capacity but did not perform the visual inspection recommended by the aircraft manual. The aircraft departed from Neuchâtel Aerodrome with the right fuel tank selected.
Approximately twelve minutes into the flight, while cruising at roughly 5,500 feet over the Sagne Valley and Val de Travers junction, the engine power dropped significantly. The pilot realized the right tank was empty and immediately switched the selector to the left tank, enriching the mixture and applying full throttle. However, the engine failed to respond with power. Suspecting the propeller was windmilling but the engine was not firing, he attempted to restart it but omitted engaging the auxiliary electric fuel pump, a critical step for clearing air from the lines after fuel exhaustion.
With no power available, the pilot decided to return directly to Neuchâtel Aerodrome. In the final approach, he found himself too high and fast for a standard landing on Runway 05. He attempted to lose altitude using tight turns, which further compromised fuel flow due to uncoordinated flight attitudes. The aircraft touched down on the 530-meter grass taxiway adjacent to the runway rather than the main paved strip. It overran the grass, crossed the boundary, and flipped upside down in an adjacent wheat field.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the wreckage and maintenance records. Technical inspections confirmed the aircraft was airworthy and that the fuel system had no mechanical defects or leaks. Post-accident analysis revealed the right tank was empty, having provided approximately twelve minutes of flight time with only 10–15 liters usable fuel remaining at takeoff. The left tank contained 18 liters, which remained untouched during the flight.
The investigation highlighted several critical discrepancies between the pilot's actions and standard procedures:
- Fuel Gauge Misinterpretation: The first white mark on the HB-CHZ’s gauges indicated one-sixth of capacity, not one-quarter. The pilot’s reliance on these indicators without visual confirmation led to a severe underestimation of fuel reserves.
- Failed Restart Procedure: To restart an engine after fuel starvation, the auxiliary electric fuel pump must be engaged momentarily to purge air from the lines. The pilot failed to do this.
- Uncoordinated Flight: The aircraft manual explicitly warns that with tanks one-quarter full or less, prolonged uncoordinated flight (slips or skids) can uncover fuel outlets, causing starvation. The pilot’s tight turns exacerbated this issue.
- Landing Site Selection: The pilot chose the shorter grass taxiway over the main 700-meter runway plus its 200-meter emergency overrun area, limiting his options for a safe stop.
Findings
The accident was caused by a combination of factors:
- Fuel Starvation: The engine stopped because the pilot misread the fuel gauges and failed to manage the remaining fuel correctly. He did not realize the right tank was empty until power loss occurred.
- Procedural Error: The failure to engage the auxiliary fuel pump prevented a successful in-flight restart.
- Loss of Control: In the final approach, the pilot lost control due to excessive speed and altitude, compounded by uncoordinated flight maneuvers that further restricted fuel flow to the engine.
Safety action
The report emphasized the necessity of visual fuel checks before every flight, particularly when gauges indicate low levels. It also reinforced the specific procedures for restarting an engine after fuel exhaustion, including the mandatory use of the auxiliary pump and maintaining coordinated flight attitudes until landing is assured.