What happened
On July 27, 2019, a Cessna 441 (Conquest II), registration OB-1971, operated by Horizons South America S.A.C., was conducting a photographic flight mission near Arequipa. After experiencing a pressurization failure at FL180, the pilot descended to FL160 and diverted to Pisco Airport to address the issue.
During the approach to Pisco, the pilot attempted to extend the landing gear but discovered that the nose gear remained in a partially extended position, indicated by a red warning light. Simultaneously, the crew observed low hydraulic fluid level warnings. Despite attempting various maneuvers, including pitch changes to use gravity for gear extension, and following the emergency landing gear extension procedures—which included disconnecting the landing gear circuit breaker—the nose gear failed to lock.
To reduce weight and fuel load, the pilot performed a low-speed pass before declaring an emergency. The aircraft landed on runway 22 with the engines shut down prior to touchdown. The pilot maintained the nose high as long as possible, but as the aircraft slowed, the nose descended and made contact with the runway, resulting in the aircraft sliding approximately 300 meters. There were no injuries to the three occupants, though the aircraft sustained significant damage to the nose section and the loss of a pitot tube.
The investigation
An investigation by the CIAA examined the aircraft's maintenance history and the physical condition of the hydraulic system. Investigators found that a high-pressure hydraulic line responsible for the nose gear extension had developed a perforation. This leak caused the loss of both hydraulic fluid during normal operation and nitrogen during the emergency extension attempt.
Laboratory analysis confirmed that the perforation was caused by localized pitting corrosion that progressed from the exterior to the interior of the tube. While the aircraft had undergone recent Phase 8 and Phase 54/56 inspections, these checks focused on structural corrosion and hydraulic leaks but did not specifically include the detection or prevention of corrosion within the hydraulic lines themselves. Furthermore, the aircraft was operating in Pisco, an area identified by the manufacturer as a severe corrosion zone.
Findings
- The primary cause of the incident was a corroded hydraulic line that leaked hydraulic fluid and nitrogen, preventing the nose gear from fully extending and locking.
- The aircraft was operating in an environment characterized by high corrosion severity.
- Existing maintenance inspections lacked specific tasks for the detection and treatment of corrosion within the hydraulic extension lines.