What happened
On July 1, 1966, a scheduled domestic flight operating under Visual Flight Rules (VFR) departed Manila for San Jose, with an intended stop in Mamburao. After completing the first leg of the journey without incident, the aircraft departed Mamburao at 12:04 local time. At 12:15, the crew contacted the San Jose Radio Station to request terminal weather updates; however, while the information was broadcast, the flight did not acknowledge receipt.
Shortly thereafter, an eyewitness reported seeing the aircraft flying at a very low altitude toward a mountain on a heading of roughly 065°. Following this observation, a loud explosion was heard originating from the mountains east of the observer's location. Attempts by air traffic controllers to re-establish contact via both HF and VHF frequencies were unsuccessful.
Search efforts later located the wreckage at an elevation of 2,300 feet AMSL within a ravine on the northern slope of Mt Rabangan. The crash site was situated roughly 10 nautical miles inland, positioned midway between Mamburao and San Jose. The accident resulted in 26 fatalities and left two passengers seriously injured.
Findings
Investigations concluded that the primary cause of the accident was a misjudgement of terrain clearance, which led to the aircraft striking trees. While the flight was operating under VFR, the pilot encountered instrument meteorological conditions (IMC) during the flight. Contributing factors included severe turbulence and strong, gusty winds at the crash site. At the time of the incident near Sablayan, weather conditions were characterized by heavy rain, thick dark clouds, and high winds, which matched the briefing provided to the pilot prior to departure.