Investigation Summary
During the approach to Bilbao, the crew was cleared for an ILS approach to runway 30. The captain declined a direct clearance to the approach fix, opting for the standard approach procedure. While descending through 7,000 feet, the crew set the Altitude Alert System to 4,300 feet, which was slightly below the minimum sector altitude of 4,354 feet. As the aircraft continued to descend, the altitude alert horn sounded at 4,040 feet. The crew, however, misinterpreted this as the 'approach mode' alert (indicating they were nearing their target altitude) rather than a 'deviation mode' warning that they were descending through it. The investigation highlighted that the drum-and-needle altimeter design used in the Boeing 727 was prone to misinterpretation, a factor already recognized by the FAA in the United States but not yet addressed in Spain at the time. Furthermore, the television antenna on Mount Oiz was not marked on the navigation charts provided to the crew. The aircraft struck the base of the antenna at 3,398 feet, shearing off the left wing and causing the fuselage to roll and crash into a ravine.
Final Conclusions
The CIAIAC (Comisión de Investigación de Accidentes e Incidentes de Aviación Civil) concluded that the primary cause was pilot error. The crew's over-reliance on the automatic capture of the Altitude Alert System, their misinterpretation of its warnings, and a probable misreading of the altimeter led them to fly below the safety altitude. The presence of an unmarked television antenna on the flight path and the lack of effective crew resource management (CRM), specifically the captain's relative silence and failure to monitor the first officer's actions, were significant contributing factors.
Video Analysis
Crash On Monte Oiz – Iberia Flight 610 | Fatal Approach Into Bilbao — A detailed documentary covering the technical and human factors behind the crash of Iberia 610, including the role of the drum-and-needle altimeter and the unmarked antenna on Mount Oiz.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
José Luis Patiño y Arróspide
First Officer
Emilio López Peña Ordóñez
Flight Engineer
Gregorio Arroba Martín Delgado
Systems & Failure Modes
Drum-and-needle Altimeter
A mechanical altimeter that uses a circular dial for hundreds of feet and a rotating drum for thousands. Studies showed high rates of pilot misinterpretation, leading to its phase-out in several countries.
Altitude Alert System
A system designed to warn pilots when approaching or deviating from a pre-selected altitude. In this case, the crew misinterpreted the deviation warning as an approach notification.
Interesting Facts
- 01The aircraft was a Boeing 727-256 named 'Alhambra de Granada'.
- 02The television antenna struck by the aircraft was not included on the official approach charts.
- 03The crash site was scattered over a radius of 2 to 3 kilometers in rugged mountainous terrain.
- 04Seven victims could not be identified and were buried in a mass grave in Bilbao.
- 05The captain was José Luis Patiño y Arróspide, the 14th Viscount of Perellós.
Safety Actions & Advisories
Altimeter Replacement Mandate
Following the investigation, the CIAIAC issued an order for all Spanish airliners to replace drum-and-needle altimeters with safer designs to prevent misinterpretation.
Chart Updates
The investigation led to the inclusion of the Mount Oiz television antenna and other significant obstacles on Spanish aviation navigation and approach charts.
Known Controversies & Unanswered Questions
ETA Sabotage Allegations
Despite the official finding of pilot error, the family of Captain Patiño and some political figures alleged that the aircraft was brought down by the Basque separatist group ETA, though no evidence of a terror attack was found by investigators.