What happened
On July 11, 1981, a Boeing 707, registration PP-VJT, operating a cargo flight from Los Angeles to Manaus via Panama, experienced a runway excursion at Manaus Airport. While the initial flight stages proceeded normally, weather conditions deteriorated rapidly during the descent due to heavy rain and the passage of a cumulonimbus cloud.
As the aircraft approached runway 10, visibility was significantly reduced. Although the pilots could still see the runway lights after crossing the outer marker, the intensity of the rain increased on short final, accompanied by fluctuating wind speeds and directions. Upon touchdown at approximately 148 KT, the aircraft immediately experienced dynamic hydroplaning. The combination of the wet runway surface, high touchdown speed, and a significant crosswind component caused the aircraft to veer toward the right side of the runway. As the aircraft drifted off the paved surface, the right landing gear struck several electrical junction boxes located near the runway edge. One specific impact with an uncovered and unevenly set junction box caused the failure of the right landing gear, forcing the aircraft completely off the runway.
The investigation
The CENIPA investigation examined the mechanical, human, and operational factors involved in the accident. Investigators analyzed the aircraft's maintenance records, which showed no deficiencies, and verified that the pilots were properly licensed and experienced.
Regarding the mechanical components, a fractured bolt in the right landing gear assembly was inspected. Metallurgical testing determined this was a static tensile fracture resulting from the impact with the junction box, rather than a pre-existing fatigue failure. Investigators also confirmed that the aircraft was within weight and balance limits, though it was operating at a high landing weight. The investigation also noted that the airport's fire services were slow to respond because the tower was unaware the aircraft had left the runway, as the pilot had cut the engines and ceased communications after the excursion.
Findings
- Human Factors: The pilot's decision to continue the approach was influenced by a false sense of security provided by the visible runway lights, despite the deteriorating weather and increasing rain.
- Operational Factors: The pilot failed to execute a missed approach (go-around) despite clear indicators of hazardous conditions, including heavy rain, a high crosswind component, and the visible accumulation of water on the runway.
- Infrastructure: The presence of uneven and uncovered electrical junction boxes near the runway edge contributed to the severity of the landing gear failure.
- Meteorology: Rapidly changing weather conditions, including heavy precipitation and significant crosswind variations, created a high risk of hydroplaning.