What happened
On February 2, 2016, a Piper PA-25-235, registration PR-DAT, was performing an agricultural spraying mission near Chapada Gaúcha, Minas Gerais. The aircraft had departed from Fazenda Mato Grande, carrying 400kg of agricultural product and 100 liters of ethanol. During the initial flight phase, while surveying the area for obstacles, the pilot experienced intense vibration and a sudden drop in engine RPM, accompanied by loud noise.
Despite attempts to increase power and adjust the mixture, the engine remained at idle, and the aircraft's airspeed dropped from 90kt to 70kt. Unable to maintain level flight, the pilot performed an emergency landing in a grass field. The impact caused the agricultural product reservoir to rupture, resulting in substantial damage to the aircraft and serious injuries to the pilot.
The investigation
CENIPA's investigation focused on the engine's performance and the legality of the aircraft's fuel system. While engine analysis showed no evidence of mechanical malfunction, investigators confirmed that the fuel system had been modified to operate on ethanol. However, this conversion had not been submitted to the National Civil Aviation Agency (ANAC) for the required Special Flight Authorization (AEV). Additionally, the investigation found that the aircraft's maintenance logs for the airframe, engine, and propeller were not up to date.
Findings
- The engine's fuel system had been modified for ethanol use without obtaining the necessary regulatory authorization.
- The pilot, while properly licensed and rated, lacked practical experience in real-world agricultural spraying missions.
- The pilot failed to jettison the agricultural product reservoir during the emergency, which may have impacted the landing outcome.
- Maintenance records for the engine, propeller, and airframe were not updated.