What happened
On November 14, 2008, an AMT-600, registration PR-JTR, was performing a ferry flight from Salgado Filho Airport to Belém Novo (SSBN) in Porto Alegre, Brazil. The aircraft was operated by Aeromot Indústria Mecânico Metalúrgica Ltda., carrying a pilot and one passenger.
During the landing roll at Belém Novo, the pilot attempted to use the brakes to maintain directional control. However, the braking system lost effectiveness, causing the aircraft to deviate 30 degrees to the right. The aircraft exited the right side of the runway and came to a stop approximately five meters from a ditch. The pilot and passenger were uninjured, though the aircraft sustained light damage to the propeller and landing gear.
The investigation
CENIPA investigators examined the aircraft's hydraulic system and found evidence of hydraulic oil residue in several locations, including the floor behind the lever box, under the brake valve, and near the pedal assembly. The investigation established that the hydraulic reservoir was empty.
Testing revealed that the leak originated from the junction of the right wing tube with the brake valve, as well as three separate leak points within the brake lines of the right wheel. While the brake valve itself passed a pressure test, the depletion of the reservoir likely allowed air to enter the brake cylinders, rendering the pedals ineffective. Investigators considered two primary hypotheses for the leak: a manufacturing defect in the brake lines or the drying out of seals and connections due to the aircraft sitting unused for six months following its production in March 2008.
Findings
- Loss of braking effectiveness due to an empty hydraulic reservoir caused by multiple leaks in the right-side brake lines.
- The aircraft had been stored without operation for six months, which may have led to the degradation of seals and connections.
- Pre-flight inspections performed by the pilot and a mechanic failed to detect the leaks.
- The lack of a formal engine run-up and subsequent external inspection by maintenance personnel prior to the flight contributed to the undetected hydraulic leak.