What happened
On August 3, 2020, an EMB 820C Carajá, registration PT-RGV, departed from Barreiras, BA, en route to Salvador, BA, to perform a medical transport flight. The aircraft was carrying two pilots and four passengers. Shortly after takeoff, the crew noticed the "Landing Gear in Transit" light remained illuminated after attempting to retract the gear.
The crew decided to proceed to Salvador. Upon entering the Salvador Terminal Control Area, the crew made several attempts to ensure the landing gear was properly extended, including using the emergency manual system. However, only the main gear indicators showed a "Down and Locked" status. During these maneuvers, the manual hydraulic pump lever lost effectiveness. The crew declared an emergency and requested a low pass for visual inspection, which confirmed that the nose gear remained retracted. The aircraft subsequently performed a landing with the nose gear up, resulting in damage to the propellers and the lower forward fuselage. All six occupants escaped without injury.
The investigation
CENIPA's investigation focused on the hydraulic system failure and the inoperability of the emergency backup. Investigators found that a failure in the left engine's main hydraulic pump caused a total loss of hydraulic fluid from the primary system. Furthermore, the investigation revealed that the Quick Click pin (PN 757497) on the manual emergency pump activation lever had fractured, rendering the emergency equipment useless.
Technical analysis using Scanning Electron Microscopy (SEM) identified that the fracture in the Quick Click pin was caused by material fatigue, with cracks originating from two opposite ends and propagating toward the center. The investigation also noted discrepancies in maintenance records; while propeller logs were up to date, the engine and airframe logs were not updated regarding the Time Between Overhaul (TBO) for the hydraulic pumps.
Findings
- A failure in the main hydraulic pump led to the depletion of hydraulic fluid.
- The failure of the Quick Click pin due to material fatigue prevented the manual emergency pump from functioning.
- Inadequate management supervision at both the maintenance organization and the operator level failed to identify a latent error regarding the incorrect tracking of component TBO.
- Maintenance records for the engine and airframe were not properly updated, specifically regarding the 1,000-hour TBO requirement established by Service Bulletin 821-005-0001 for certain hydraulic pumps.
- Existing service manual procedures for inspecting the manual pump assembly were primarily focused on corrosion, which was insufficient to detect the fatigue mechanism observed in the pin.