Investigation Summary
The investigation centered on the elevator boost system, a hydraulic mechanism designed to assist the pilot in moving the large control surfaces of the Constellation. Investigators discovered that a 5/16 inch AN-175-21 nickel steel bolt had backed out of the parallelogram linkage. The absence of this bolt allowed the hydraulic actuator to apply full pressure to the 'up-elevator' side, forcing the aircraft into an extreme nose-high attitude. The crew attempted to counter this by applying heavy forward pressure on the control column, but this very action created enough friction in the linkage to prevent them from successfully shifting the boost system to 'manual' mode. As the aircraft stalled and plummeted, the resulting oscillatory loads were so severe that the right vertical fin and a portion of the horizontal stabilizer tore away from the airframe before impact.
Final Conclusions
The Civil Aeronautics Board (CAB) determined the probable cause was the loss of an AN-175-21 nickel steel bolt from the parallelogram linkage of the elevator boost system. This mechanical failure led to an immediate and uncontrollable pitch-up, followed by an accelerated stall and loss of aircraft control.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
James H. Sanders
First Officer
Dale Tarrant
Flight Engineer
James C. Newlin
Systems & Failure Modes
Elevator Boost System
A hydraulic assist system for the elevators; the loss of a linkage bolt caused it to command full up-elevator.
Parallelogram Linkage
The specific mechanical assembly within the boost system where the AN-175-21 bolt was located.
Interesting Facts
- 01At the time, it was the deadliest single-plane accident in United States history.
- 02The debris field measured approximately 200 feet wide by 1,100 feet long.
- 03The aircraft was named 'Star of Dublin' in official records (sometimes erroneously referred to as 'Star of Paris').
- 04The right vertical fin and a portion of the horizontal stabilizer separated from the aircraft prior to ground impact.
- 05The aircraft was flying at approximately 5,000 feet when the control failure occurred.
Safety Actions & Advisories
Elevator Linkage Inspection
The investigation led to increased scrutiny of the attachment hardware within the Lockheed Constellation's elevator boost systems to ensure bolts were properly secured and safety-wired.