Investigation Summary
The flight was a multi-stop service originating in Providence, Rhode Island, with scheduled stops in Boston, New York City, Syracuse, Rochester, Detroit, Chicago, St. Louis, Springfield, and Joplin. The journey was plagued by a 100-minute delay in Chicago due to a faulty fire alarm system. By the time the aircraft departed Joplin for the final leg to Tulsa, the crew had been on duty for 15 hours. During the approach to Tulsa, the first officer was at the controls while the captain supervised. The crew utilized two altimeters set to different references: the captain's was set to ground level (QFE) while the first officer's was set to mean sea level (QNH). Investigators determined that when the captain instructed a descent to 700 feet, the first officer likely targeted 700 feet on his sea-level altimeter. Because the Tulsa airport elevation was 674 feet, this target placed the aircraft only 26 feet above the ground. The aircraft struck the terrain before the crew could recognize the error. Post-crash examination also revealed significant discrepancies in both altimeters: the captain's read -200 feet when it should have read zero, and the first officer's read 220 feet when it should have read 674 feet (the airport elevation).
Final Conclusions
The Civil Aeronautics Board (CAB) concluded that the probable cause was a lack of alertness on the part of the captain in failing to properly supervise the first officer during the final approach. The captain's failure to ensure the aircraft maintained a safe altitude, combined with a likely miscommunication regarding altimeter references, led to the controlled flight into terrain. The CAB also noted that the captain had previously observed a 100-foot error in his altimeter earlier in the day but failed to report it or seek corrective action as required by company regulations.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Wesley G. Mims
First Officer
Paul H. Johnson
Systems & Failure Modes
Altimeters
The aircraft was equipped with two altimeters; post-crash, the captain's read -200 feet and the co-pilot's read 220 feet, indicating significant calibration errors or impact damage.
Fire Alarm Warning System
A malfunction in this system caused a significant delay in Chicago, contributing to crew fatigue, though the system functioned correctly for the remainder of the flight.
Interesting Facts
- 01The aircraft was a Convair CV-240-0 named 'Flagship Mount Vernon'.
- 02The captain had 8,655 total flight hours, with 4,100 hours on the Convair CV-240.
- 03The crew had been on duty for 15 hours at the time of the accident.
- 04The sole fatality was a 70-year-old female passenger who died from her injuries after being pinned in the wreckage.
- 05The captain's altimeter was set to ground level (0 feet at airport), while the first officer's was set to sea level (674 feet at airport).
- 06The captain reported seeing a reading of 700 feet on his altimeter just before the crash.
Safety Actions & Advisories
Pilot Certificate Suspension
The CAB suspended Captain Mims' command rating for six months, citing carelessness in monitoring the first officer's approach.