Investigation Summary
The accident was initiated during routine maintenance at Lima, where a worker applied masking tape over the three static ports on the left side of the fuselage to protect them during cleaning and polishing. This tape was not removed before the flight, and its presence was missed during the subsequent walk-around inspection by the captain. Upon takeoff, the lack of pressure changes at the static ports caused the altimeters to remain 'stuck' at zero or near-ground level. As the aircraft climbed, the trapped air in the static lines created a pressure differential that led to increasingly erratic readings. The flight management computer began generating a 'rudder ratio' warning because it sensed a discrepancy between the actual speed and the static pressure data. This was followed by 'mach speed trim', 'overspeed', and 'underspeed' warnings. The crew, unable to determine their true flight parameters, requested altitude and speed data from ATC. However, the ATC radar was receiving its altitude data from the aircraft's own transponder, which was also fed by the blocked static system, leading the controller to confirm the pilots' erroneous altitude readings as correct.
Final Conclusions
The primary cause was the failure of maintenance staff to remove protective tape from the static ports and the failure of the flight crew to detect the tape during the pre-flight walk-around. A significant contributing factor was the 'bewildering' array of contradictory cockpit warnings that saturated the pilots' cognitive capacity. Crucially, the Ground Proximity Warning System (GPWS) functioned correctly based on the radio altimeter, providing a valid 'Too Low, Terrain' warning as the aircraft descended through 2,500 feet. However, the crew, conditioned by a series of false alerts, disregarded this as another erroneous warning. The investigation also noted that the air traffic controller inadvertently provided false reassurance by reading back the erroneous altitude data generated by the aircraft's compromised systems.
Photographic Evidence (1)
Video Analysis
Aeroperú Flight 603: The Fatal Maintenance Error — This video examines how adhesive tape left on static ports led to instrument failure and the crash of a Boeing 757 into the Pacific Ocean in 1996.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Eric Schreiber Ladrón de Guevara
First Officer
David Fernández Revoredo
Systems & Failure Modes
Pitot-static system
The system of pressure-sensitive instruments that provides airspeed, altitude, and vertical speed; blocked static ports rendered these instruments useless.
Air Data Computer (ADC)
Processes pitot and static pressure to provide digital flight data; the ADCs provided conflicting warnings because of the static blockage.
Radio Altimeter
Measures height above the ground using radio waves; it was functioning correctly but was ignored by the crew in favor of the barometric altimeters.
Interesting Facts
- 01The aircraft was a Boeing 757-23A delivered in 1992.
- 02All three static ports on the left side were found covered with masking tape during the investigation.
- 03The tape had been applied by maintenance worker Eleuterio Chacaliaza to protect the ports during cleaning.
- 04The ATC radar altitude was derived from the aircraft's Mode C transponder, which was using the same corrupted static data as the cockpit instruments.
- 05The captain had nearly 22,000 total flight hours.
- 06The aircraft impacted the water while the captain's instruments indicated an altitude of 9,500 feet and a speed of 450 knots.
Safety Actions & Advisories
Maintenance Procedure Revision
Source ↗Aviation authorities reinforced the requirement for highly visible (brightly colored) covers for static ports rather than transparent or standard masking tape.
Crew Resource Management (CRM) Training
The accident highlighted the need for pilots to cross-check independent instruments like the radio altimeter when primary flight data is suspect.