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Incorrect Altitude Clearance and Procedural Lapses: A Review of Independent Air Flight 1851 Independent Air Flight IDN1851, a Boeing 707-331B, was involved in a catastrophic accident on February 8, 1989. The aircraft, en route from Bergamo, Italy, to Punta Cana, Dominican Republic, with a planned stop at Santa Maria, Azores, impacted Pico Alto mountain during its approach phase. All 144 individuals on board perished, and the aircraft was completely destroyed. The aircraft had accrued 44,755 total airframe hours and 12,589 cycles since its first flight in 1968. It was powered by four Pratt & Whitney JT3D-3B engines. The crew consisted of seven members, all of whom had limited experience in international flights. Notably, there were evident lapses in crew training, particularly concerning Ground Proximity Warning System (GPWS) emergency maneuvers. Upon nearing Santa Maria, the aircraft was cleared to descend to 3,000 feet for a runway 19 ILS approach by Santa Maria Tower. Notably, the trainee controller erroneously transmitted a QNH of 1027 hPa, which was 9 hPa higher than the actual QNH of 1018.7 hPa. This miscalculation placed the aircraft at an actual altitude 240 feet lower than what was indicated onboard. A communications overlap occurred between the tower and the first officer, complicating the scenario. Moreover, the Santa Maria Aerodrome Control Tower violated established procedures by not insisting on a complete read-back of the descent clearance. Post-clearance, the crew neglected to conduct an approach briefing, an essential step that would have made them aware of the minimum sector altitude of 3,000 feet and the topographical challenges presented by Pico Alto mountain. The flight initiated a descent to 2,000 feet, misunderstanding the minimum safe altitude. Apathy toward cockpit discipline and standard phraseology exacerbated the situation. The aircraft entered heavy turbulence and clouds, rendering visual cues unreliable. Ignoring the activated GPWS and the oscillating radio altimeter, the crew did not take corrective actions. Ultimately, the aircraft impacted Pico Alto mountain ridge at an altitude of 1,795 feet AMSL. The Board of Inquiry attributed the primary cause of the accident to the crew's disregard for established operating procedures, leading to a descent to 2,000 feet, a violation of the published minimum sector altitude of 3,000 feet. Additional factors contributing to the accident included incorrect QNH transmission, communication flaws, procedure violations by the control tower, insufficient crew training, and general apathy in adhering to safety protocols. Subscribe to our Aviation Safety Newsletter NOW and get the hot stuff free and without delay:?https://lnkd.in/e92dTX6f