Investigation Summary
The accident was the result of a chain of events beginning with a technical fault in the R2-5 ground-sensing relay. This relay controlled multiple systems, including the RAT probe heater and the TOWS. When the relay failed in the 'in-flight' mode while the aircraft was on the ground, it caused the RAT probe heater to activate, leading the pilots to return to the gate. Maintenance staff deactivated the heater as per the MEL, but the underlying relay failure also silently disabled the TOWS. During the second taxi, the crew was interrupted and failed to set the flaps and slats. Because the TOWS 'believed' the aircraft was already airborne due to the relay fault, no warning sounded when the throttles were advanced for takeoff.
Final Conclusions
The CIAIAC concluded the direct cause was the crew's failure to configure the aircraft for takeoff and their failure to detect this during three separate checklist checks. A major contributing factor was the failure of the TOWS to alert the crew, caused by a malfunction in the R2-5 relay. The investigation also highlighted deficiencies in the operator's CRM and the manufacturer's failure to account for a single-point failure that could disable both the RAT heater and the TOWS.
Video Analysis
Spanair Flight 5022: The Madrid MD-82 Takeoff Stall — An analysis of the 2008 crash at Madrid-Barajas Airport caused by improper flap configuration and a failed takeoff warning system. The video examines the maintenance issues and checklist errors leading to the stall.
Watch on YouTube ↗If playback is blocked, the owner has disabled embedding — use the link above.
Systems & Failure Modes
TOWS (Take-off Warning System)
An aural warning system designed to alert pilots if throttles are advanced while the aircraft is not in a safe takeoff configuration.
R2-5 Relay
A ground-sensing relay that switches various aircraft systems between 'ground' and 'flight' modes based on landing gear extension.
RAT Probe Heater
A heating element for the Ram Air Temperature probe; its abnormal activation on the ground was the first sign of the relay failure.
Interesting Facts
- 01The aircraft was configured with 0° flaps and slats, a 'clean' configuration unsuitable for takeoff.
- 02The R2-5 relay failure was a single point of failure that affected both the RAT heater and the TOWS.
- 03The crew performed the 'After Start' and 'Takeoff Imminent' checklists but missed the flap settings both times.
- 04154 people died, making it Spain's deadliest aviation accident in 25 years.
- 05The MD-82 involved, EC-HFP, was 15 years old and named 'Sunbreeze'.
Safety Actions & Advisories
TOWS Operational Check
The FAA and EASA mandated that MD-80 series operators perform a functional check of the TOWS before the first flight of every day.
MEL Revision
Revised the Minimum Equipment List to ensure that if a RAT heater is inoperative, the underlying cause (like a relay) does not also affect the TOWS.
Known Controversies & Unanswered Questions
Maintenance Responsibility
Reference ↗There was significant legal and public debate regarding whether the maintenance technicians should have identified that the RAT heater failure was symptomatic of a wider relay failure affecting the TOWS.