Investigation Summary
Shortly after departing Miami, Flight 705 encountered a line of severe thunderstorms. While climbing through 17,500 feet, the aircraft entered a powerful updraft that caused a rapid increase in altitude and a sharp drop in airspeed. The flight crew responded with full nose-down elevator and trim to counter the climb. As the aircraft peaked at 19,285 feet, the vertical forces shifted violently from positive to high negative Gs, throwing the pilots upward and making control nearly impossible. The aircraft entered a steep, high-speed dive that exceeded its structural limits. As the pilots attempted to pull out of the dive at lower altitudes, the extreme aerodynamic forces caused the forward fuselage, wings, and tail surfaces to fail, resulting in a complete mid-air disintegration.
Final Conclusions
The Civil Aeronautics Board (CAB) determined the probable cause was the unfavorable interaction of severe vertical air drafts and large longitudinal control displacements. This resulted in a longitudinal upset from which a successful recovery was not made. The investigation highlighted the dangers of over-controlling an aircraft during severe turbulence, a phenomenon later termed 'turbulence upset.'
Video Analysis
Thrown To The Ground | Northwest Orient Airlines Flight 705 — A detailed look at the 1963 crash of Northwest Orient Flight 705, which broke up over the Florida Everglades due to severe turbulence and pilot control inputs.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Roy W. Almquist, aged 47.
First Officer
Robert J. Feller, aged 38.
Second Officer
Allen R. Friesen, aged 29.
Systems & Failure Modes
Horizontal Stabilizer
The crew applied full nose-down trim during the updraft, which contributed to the severity of the subsequent dive.
Elevators
Large displacements of the elevators in response to vertical drafts led to the loss of control.
Interesting Facts
- 01The aircraft reached a peak negative acceleration of approximately -2.8G during the upset.
- 02Nearly 97% of the aircraft wreckage was recovered and reconstructed in a hangar for the investigation.
- 03The breakup was virtually symmetrical, with wings and horizontal stabilizers failing in a downward direction.
- 04This was the first major accident involving a jetliner where the primary cause was a 'longitudinal upset' in turbulence.
Safety Actions & Advisories
Revised Turbulence Penetration Procedures
The FAA and manufacturers revised pilot training to emphasize maintaining a level attitude rather than strictly maintaining altitude or airspeed during severe turbulence.
Cockpit Instrumentation Improvements
The accident led to improvements in attitude indicators and radar systems to help pilots better navigate and survive storm activity.
Known Controversies & Unanswered Questions
Conflicting Casualty Reports in Social Media
Some social media posts and historical society pages have incorrectly reported 96 fatalities and 76 survivors for Flight 705. Official records from the Civil Aeronautics Board (CAB), the National Park Service, and the FAA confirm there were 43 people on board (35 passengers and 8 crew) and no survivors.