What happened
On August 8, 2017, an Embraer EMB-721D (registration PT-RNL) departed from the Ourilândia do Norte Aerodrome (SDOW) in Pará, Brazil, bound for São Félix do Xingu. The flight, operated by Piquiatuba Táxi Aéreo Ltda., was transporting one pilot and one passenger.
Shortly after takeoff, during the landing gear retraction sequence, the "Landing Gear / Indicator Lights" circuit breaker tripped, accompanied by a smell of burning. This failure caused the hydraulic pump to disconnect from the circuit, preventing the gear retraction cycle from completing. The pilot subsequently decided to return to SDOW for an emergency landing.
In an attempt to extend the gear, the pilot disarmed the "Landing Gear / Pump" circuit breaker and utilized the emergency gear extension lever. Because the indicator lights circuit breaker remained tripped, the pilot had no cockpit indication of the gear's position. After receiving visual confirmation from a mechanic on the ground that the gear was down, the pilot proceeded to land on runway 32. Upon touchdown, the nose gear retracted, causing the propeller to strike the runway, resulting in damage to the propeller blades, the engine, and parts of the fuselage lower surface.
The investigation
CENIPA investigators examined the electrical systems and the emergency extension procedures. Ground tests conducted on the aircraft showed that the landing gear system functioned normally and no electrical damage from heat was found. Investigators hypothesized that a momentary load variation might have caused the initial breaker trip.
Crucially, the investigation found that the pilot did not reset the "Landing Gear / Indicator Lights" breaker after the initial failure. Furthermore, investigators noted that the emergency extension procedure may have been performed incorrectly, as the emergency lever should have been maintained in the "Emergency Down" position. The investigation also noted that the pilot had disarmed the hydraulic pump breaker, a procedure only authorized for training purposes, not for real-world emergencies.
Findings
- Decision-making process: The pilot's choice regarding the circuit breakers and the handling of the emergency lever contributed to the gear's failure to lock.
- Instruction: Potential gaps in theoretical knowledge regarding the specific emergency procedures for the Embraer EMB-721D were identified.
- The aircraft sustained light damage during the incident, while both occupants remained uninjured.