What happened
On February 25, 2018, an M-18A Dromader, registration VH-FOS, departed from the Keratong Airstrip in Pahang, Malaysia, for a routine crop spraying mission. Shortly after takeoff, the pilot noticed a significant drop in engine power, which fell from 55% to 35%. Despite attempts to restore power by engaging the fuel pump and increasing the throttle, the power fluctuated before dropping further.
As the aircraft descended toward a nearby patch of shrubbery for an emergency landing, the engine suffered a total failure. To mitigate the impact, the pilot dumped the spraying agent and flared the aircraft into the vegetation. The aircraft crashed approximately 3 nautical miles northeast of the airstrip. While the pilot escaped without injury, the aircraft was destroyed, with the engine separating from the airframe upon impact.
The investigation
AAIB Malaysia investigators examined the wreckage and conducted fuel sampling from the airframe filter and the Fuel Control Unit (FCU) filter. Tests using water detector tablets confirmed the presence of water in the fuel.
Investigators also reviewed the conditions at the Keratong Airstrip, noting that the area had experienced heavy rainfall the previous day. While the fuel drums, pump, and hoses were covered, the investigation focused on how water entered the fuel supply. The inspection of the portable fuel pump and its accessories was delayed by 11 days, by which time any visible moisture had evaporated due to high temperatures.
Furthermore, the investigation looked into the fuel testing procedures used by the ground handler. It was discovered that the handler was using a method of simply dropping the water detector capsule into the fuel rather than the manufacturer-recommended technique of using a syringe to draw fuel through the capsule. Additionally, the capsules in use had expired in 2014.
Findings
- The primary cause of the accident was fuel contamination which resulted in engine failure during flight.
- Heavy rain on the day prior to the accident likely contributed to the introduction of water into the fuel supply.
- The ground handler had not received formal training or refresher courses regarding fuel management or ground handling.
- The use of expired water detector capsules and an incorrect testing methodology hindered the detection of water in the fuel.
- The fuel drums used by the operator were found to be rusted and dented.