What happened
On February 1, 2021, at approximately 09:20 UTC, a Cessna A188B, registration PR-STO, was performing a crop-dusting flight from a private landing area in Viamão, Rio Grande do Sul. During the second takeoff of the day, the pilot experienced a loss of engine power. In an attempt to maintain flight, the pilot jettisoned the product from the hopper and applied landing flaps while pitching up the nose, but was unable to sustain the climb.
The aircraft's landing gear collided with a perimeter fence located at the end of the runway. Following this impact, the left wing struck a drainage ditch. The aircraft skidded approximately 115 meters before coming to a stop. The aircraft sustained substantial damage to the landing gear, left wing, tail section, and propeller. The pilot suffered no injuries.
The investigation
CENIPA investigators examined the engine, a Teledyne Continental IO-520-D, and found several mechanical discrepancies. While the engine was not stuck, the investigation revealed that the magneto timing was significantly incorrect; the timing light illuminated at approximately 14° after the top dead center, rather than the manufacturer-specified 22° before top dead center. This late sparking meant the fuel-air mixture was burning while the piston was already moving toward the bottom of its stroke.
Further inspection of the spark plugs revealed excessive play in the central electrodes. Additionally, a bench analysis of the fuel pump showed a flow rate of approximately 2/70 PPH, which far exceeded the maximum limit of 153 PPH. The investigation also noted that while the aircraft's center of gravity was slightly beyond the rear limit, this was not considered a primary cause of the accident.
Findings
- The loss of engine power during takeoff was likely caused by the combined effect of incorrect magneto timing, excessive spark plug electrode gap, and excessive fuel pump pressure.
- These mechanical discrepancies may have resulted from deficiencies in maintenance procedures during either scheduled or unscheduled inspections.
- The aircraft's landing gear struck a fence and the left wing struck a ditch during the takeoff roll.