Incident
Shortly after lift-off, the right engine of the aircraft lost power. The pilot executed a wheels-up landing in an alfalfa field. The aircraft sustained damage during the landing.
Investigation
Examination of the right engine's top spark plugs revealed evidence of operation at a rich fuel mixture. During the takeoff roll, both auxiliary fuel pumps were in the on position. Investigators noted that Cessna Service Bulletin MB88-3, which mandates the removal of the fuel pressure sensing system and auxiliary fuel pump switches, had not been accomplished on the aircraft.
Functional testing of the auxiliary fuel pump confirmed it was operating. However, further testing determined that an excessively rich fuel mixture was being delivered to the right engine by the fuel servo. The combination of the auxiliary fuel pumps being on and the unaddressed service bulletin likely contributed to the fuel mixture imbalance, but no explicit causal link was established in the report.
Findings
The investigation documented that the right engine experienced a power loss shortly after takeoff. Evidence from spark plugs indicated a rich mixture condition. The auxiliary fuel pumps were active during the takeoff run, and the required service bulletin had not been implemented. Testing confirmed the fuel servo was delivering an overly rich mixture to the right engine. The precise reason for the power loss remains unstated in the source, but the rich mixture condition is a notable finding.