What happened
On June 26, 2019, a Piper PA-32R-301, registration PR-ARJ, was performing a private flight from Itaituba (SBIH) to Santarém (SBSN) carrying a pilot and one passenger. During the approach to Santarém, the pilot noticed that the right main landing gear indication failed to show as down and locked. Consequently, the pilot aborted the landing and returned to the origin airport in Itaitable.
Upon returning to Itaituba, the pilot attempted to extend the landing gear using normal procedures twice, followed by one attempt using the emergency extension procedure. Despite these efforts, the landing gear indication remained unchanged. During the subsequent landing on runway 23 at SBIH, the right main landing gear retracted upon touchdown, causing the aircraft to lose control and veer off the runway to the right. The aircraft sustained substantial damage, but both occupants were unharmed.
The investigation
CENIPA investigators examined the aircraft's maintenance history and mechanical components. While the aircraft's airworthiness certificate was valid, investigators found that the engine, propeller, and airframe logbooks were not up to date.
Technical analysis focused on the hydraulic system. Although recent inspections had not flagged issues, a bench test of the hydraulic pump revealed that it was producing only 1,600 psi, significantly below the manufacturer's required range of 2,000 to 2,500 psi. This insufficient pressure prevented the landing gear from properly locking. Furthermore, investigators noted that the emergency extension procedure, which utilizes a free-fall method to lock the gear via mechanical springs, may not have been executed correctly, as it was uncertain if the pilot followed the official checklist during the emergency attempts.