What happened
On March 26, 2021, an Airbus A320-251N, registration CC-AZE, operated by Sky Airline Perú S.A.C., departed Arequipa's Alfredo Rodríguez Ballón International Airport for Lima. During the initial climb phase, the crew noticed a progressive decrease in the fluid level of the Yellow hydraulic system reservoir.
As the aircraft reached the cruise phase, approximately 40 nautical miles from Pisco, the crew received multiple ECAM warnings, including low reservoir level and low system pressure. The loss of the Yellow hydraulic system rendered several critical components inoperable, including the nose wheel steering, parking brake, second engine reverser, and certain spoilers. The crew followed the established abnormal procedures and requested priority handling and towing assistance from Lima Control.
The aircraft landed successfully at Jorge Chávez International Airport in Lima. Due to the loss of steering and braking capabilities, the aircraft had to be towed to its final parking position. There were no injuries among the 142 passengers or the 4 crew members.
The investigation
The CIAA investigation focused on the cause of the hydraulic fluid depletion and the damage to the aircraft's structure. Post-flight inspections by maintenance personnel revealed that the number 2 tire on the left main landing gear had experienced significant tread separation (stripped ribs).
Investigators determined that pieces of rubber from the departing tread struck the aircraft's underside, causing dents in the left inboard flap and the aft inboard lower wing panel. Crucially, the impact of this rubber debris cracked a return line within the left main gear well, which led to the continuous and total loss of hydraulic fluid from the Yellow system.
Analysis of the tire by Goodyear laboratories in the United States showed significant wear on the tire shoulders, suggesting the tire may have been operated under low-pressure conditions or at high speeds. While the airline's most recent daily check on March 25, 2021, recorded all tires within limits, the investigation highlighted the difficulty in visually detecting low pressure in aviation tires.
Findings
- The primary cause of the hydraulic failure was a crack in the Yellow hydraulic system return pipe located in the left main gear well.
- The crack was caused by the impact of rubber debris from the number 2 left main gear tire tread.
- The tire experienced significant tread separation (stripped ribs) during takeoff from Arequipa.
- The tire showed evidence of shoulder wear, likely due to operation in an underinflated state or at high speeds.
- The crew successfully managed the emergency by following the Flight Crew Operating Manual (FCOM) procedures.