Investigation Summary
Ryan International Airlines Flight 590 was a scheduled mail flight operating from Buffalo to Indianapolis via Cleveland. During the descent into Cleveland, the aircraft encountered conditions conducive to airframe icing. While on the ground for a 35-minute turnaround, light snow continued to fall with temperatures at 23 degrees F. Although the aircraft's Flight Crew Operations Manual (FCOM) reportedly required the First Officer to inspect the wings for ice after landing in such conditions, neither pilot exited the aircraft. The NTSB noted a lack of specific operator requirements or training regarding the critical sensitivity of the DC-9-10 series to wing contamination. The crew likely relied on their experience with larger DC-9 variants equipped with leading-edge slats, which are more resilient to icing than the 'clean wing' DC-9-10 series. During the takeoff roll, the aircraft reached a maximum airspeed of 155 knots. Immediately after liftoff, at an altitude of approximately 50 to 100 feet, the aircraft stalled and rolled 90 degrees. The left wing struck the runway, causing the aircraft to cartwheel and come to rest inverted 6,500 feet from the threshold. Both crew members were killed instantly.
Final Conclusions
The NTSB determined the probable cause was the flight crew's failure to detect and remove ice contamination from the wings. This failure was exacerbated by a lack of appropriate response from the FAA, Douglas Aircraft Company, and Ryan International Airlines regarding the critical sensitivity of the DC-9-10 series to minute wing contamination. The investigation noted that previous accidents, such as Continental Flight 1713, had already demonstrated this vulnerability, yet regulatory and manufacturer warnings remained insufficient to prevent further occurrences.
Video Analysis
Unknown Dangers | Ryan International Airlines Flight 590 — A detailed look at the 1991 crash of Ryan International Airlines Flight 590 in Cleveland, focusing on the dangers of wing icing on the DC-9-10 series.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Described as having average skills; had two prior disciplinary actions at the airline.
First Officer
Had been with the airline for less than one month at the time of the accident.
Systems & Failure Modes
Wing Leading Edges
The DC-9-10 series features a 'clean' wing without leading-edge slats, making it significantly more susceptible to aerodynamic stalls caused by small amounts of ice compared to later DC-9 models.
Engine Anti-Ice
A system using engine bleed air to prevent ice formation on engine components and sensors; it was confirmed to be active at the time of impact.
Stick Shaker
An artificial stall warning system that vibrates the control column; it activated at 150 knots during the takeoff sequence.
Interesting Facts
- 01The aircraft was a 'clean wing' DC-9-10 series, which lacks leading-edge slats and is highly sensitive to ice.
- 02Neither pilot exited the aircraft to inspect the wings during the 35-minute stop in Cleveland.
- 03The temperature at the time of the accident was 23°F with a dew point of 19°F and light snow.
- 04The stick shaker activated at 150 knots during the brief flight.
- 05The aircraft reached a maximum altitude of approximately 100 feet before the roll and impact.
Safety Actions & Advisories
Reiteration of Recommendation A-88-134
The NTSB reiterated the need for DC-9-10 series aircraft to be de-iced with strong glycol during icing conditions due to their unique stall characteristics.
FAA Oversight Improvements
The NTSB issued six new safety recommendations to the FAA regarding the dissemination of information about wing contamination risks on specific aircraft types.