What happened
On September 6, 2011, at approximately 11:00 a.m., a Cessna A-188A, registration HI 897, experienced a sudden engine failure while performing agricultural spraying operations. The aircraft, operated by Fumigaciones Aéreas del Caribe, S.R.L., was flying at an altitude of approximately 50 feet over sugarcane plantations near Batey Guajabo, La Altagracia, Dominican Republic. The pilot was conducting the twentieth flight of the day, applying urea fertilizer, when the engine ceased operation. This loss of power necessitated an immediate forced landing in a westward-to-eastward direction across the uneven terrain of the plantation. The pilot, the sole occupant, sustained only minor bruises and was able to exit the aircraft unassisted. The aircraft suffered substantial damage, including a deformed left wing, a detached main landing gear, a deformed propeller, and damage to the lower fuselage nose.
The investigation
The CIAA investigation focused on determining the cause of the engine'-s sudden cessation. Investigators examined the aircraft at the operator's hangar, where they inspected the spark plugs and checked the continuity of the flight controls. A critical discovery was made when the engine's oil sump was drained, revealing a significant amount of metallic particles. To further the investigation, the Continental engine was sent to the manufacturer, Continental Motors, Inc., for a complete teardown and metallurgical analysis. Laboratory tests focused on the crankshaft and camshaft gears. The investigation also reviewed the pilot's commercial license, medical certification, and the aircraft's maintenance records, which showed the most recent 100-hour inspection had been completed shortly before the accident.
Findings
- The primary cause of the engine failure was a mechanical failure within the engine's internal components.
- Metallurgical analysis confirmed that fatigue on the surface of a gear tooth on the crankshaft caused the tooth to break off.
- This breakage initiated a chain reaction of failure, where teeth from both the crankshaft gear and the camshaft gear also detached.
- The loss of these gear teeth caused the engine to lose proper timing and created obstructions within the moving parts, leading to the sudden engine stoppage.
- The pilot was operating within the parameters of his license and medical certification, and no evidence of pilot fatigue was found.