Incident Overview
On a scheduled cargo and personnel flight (O6 6393) from Senador Nilo Coelho Aerodrome (SBPL), Petrolina - PE, to Presidente Juscelino Kubitschek International Airport (SBBR), Brasília - DF, the aircraft experienced a hydraulic system 1 low-level indication during level flight approximately thirty minutes after takeoff. The crew performed planned operational procedures and continued to Brasília with the hydraulic system degraded.
Hydraulic System Failure
During the flight, the crew noted low level in hydraulic system 1. The exact cause of the hydraulic fluid leak was later attributed to extrusion of the EDP1 gasket, though the root cause of the extrusion could not be determined. The crew followed procedures and continued with the degraded system.
Landing Gear Issue
During landing procedures at SBBR, the crew utilized the alternative system to lower the landing gear. The main landing gears lowered and locked successfully, but the nose landing gear unlocked without lowering. After coordination with air traffic control, the aircraft was instructed to land on runway 11R.
Landing and Evacuation
The aircraft touched down at 2042 UTC. It traveled 900 meters before coming to a full stop. The initial 750 meters were on the main landing gears only, and the final 150 meters were supported by the main landing gears and the lower front fuselage, resulting in substantial damage to structural elements near the nose section. The evacuation was safe and orderly. The copilot suffered fractures of the thoracic spine; all other crewmembers and passengers were unharmed.
Probable Cause Findings
The official investigation identified a restriction on the articulation movement of the right nose landing gear door. Inspection revealed no signs of recent lubrication, suggesting possible deviation from or non-adherence to manufacturer inspection and lubrication requirements. This could have created a scenario favorable to the right door movement restriction. Additionally, maintenance issues may have related to non-adherence to requirements for widening hinge holes regarding coating and corrosion protection, potentially increasing susceptibility to corrosion. The manufacturer's maintenance program may have contributed by not establishing adequate preventive maintenance parameters for landing gear doors that had been modified by reworking hinges with larger radial pins and widened lobe holes. The causal root of the EDP1 gasket extrusion causing hydraulic system 1 failure could not be determined.