On February 8, 1989, the Boeing 707 of the American company Independent Air took off from Bergamo, Italy, with 137 tourists (mostly Italian) and seven crew members. The destination was Punta Cana, Dominican Republic, but the IDN1851 flight crashed into Pico Alto (547 meters), when it was approaching and a few kilometers from Santa Maria landing for a technical stopover.
The report of the then General Directorate of Civil Aviation, which was finalized three years after the disaster and which the Lusa agency now had access to, concluded that the probable cause of the charter accident was “due to the crew’s failure to comply with established operating procedures. which led to the deliberate descent of the aircraft to 2,000 feet, disrespecting the minimum altitude in that area, which was 3,000 feet. “
According to the inquiry commission, the co-pilot’s “poor communication skills” situation, which initiated its “read back” of the 3000-foot descent clearance provided by the air traffic controller, has been message, resulting in an overlap of communications and consequent confusion / error in the transmission / reception of the message. The control tower also violated the rules by not requiring a full read back of its clearance permit. In addition, the air traffic controller (27-year trainee) transmitted a higher than actual QNH (barometric pressure-related adjustment to sea level), which put the aircraft at a lower real altitude of 240 feet (74 meters) to that indicated on board by the altimeter.
The report notes that regardless of the wrongly supplied QNH, the Boeing-707 “would always be in a potentially dangerous situation and at risk of collision with the ground when descending to an altitude of 2,000 feet.” If the crew had respected the minimum authorized altitude (3,000 feet), the error of the QNH “would not have had any consequence”. The disrespect of the crew for the discipline in the cockpit, the fact that there was no briefing or reading the checklist with the approach procedures to the airport, as well as the general apathy of the crew in the face of the mistakes made regarding the altitude minimum and sound warnings of proximity to the land, are other factors that have potentiated the disaster. In addition, the Ground Proximity Warning System (GPWS) warned the crew, for seven seconds, to “pull” the plane before it crashed. “The crew has had enough time to try to get the aircraft out of the situation because the average reaction time of the pilots to the GPWS warning is about 5.4 seconds” , stresses the report.
The inexperience of the 41-year-old pilot, and especially the 36-year-old co-pilot, who had 488 hours and 64 hours of flight time on the Boeing 707 on international flights, is another factor contributing to the worst air disaster occurred in Portugal. According to the report, “there was no possibility of survival of the occupants”.