Investigation Summary
The aircraft departed New Orleans with a known inoperative Pitch Trim Compensator (PTC), which was scheduled for repair upon arrival in New York. The PTC is designed to provide nose-up control inputs to offset the natural nose-down pitching tendency of the DC-8 at high speeds. During the climb through 4,000 feet, the aircraft encountered moderate and probably severe wind shear turbulence. The horizontal stabilizer was found to have been trimmed to an extreme nose-down position (2 degrees AND). Investigators believe the crew attempted to counter a perceived nose-up attitude or turbulence-induced oscillation by using the manual trim, which likely introduced pilot-induced oscillations (PIO). However, once the aircraft entered a high-speed dive, the aerodynamic loads on the stabilizer became so great that the electric trim motor could not overcome the physical forces to return the tail to a nose-up position. The situation was further complicated by the aircraft's attitude indicator, which was criticized by investigators for being small, lacking degree indexing, and having a solid black background that was difficult to interpret during night operations.
Final Conclusions
The Civil Aeronautics Board (CAB) determined the probable cause was the degradation of aircraft stability characteristics in turbulence, resulting from abnormal longitudinal trim component positions. Contributing factors included the inoperative pitch trim compensator and the difficulty of interpreting the pitch attitude on the cockpit instruments under the prevailing conditions.
Photographic Evidence (1)
Video Analysis
Eastern Air Lines Flight 304 Aftermath Footage — Historical footage showing the recovery efforts and wreckage of the Eastern Air Lines DC-8 that crashed into Lake Pontchartrain in 1964.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
William B. Zeng, age 47
First Officer
Grant R. Newby, age 39
Flight Engineer
Harry Idol, age 39
Systems & Failure Modes
Pitch Trim Compensator (PTC)
An electrical system that automatically applies nose-up elevator pressure to counter Mach tuck and improve stability at high speeds.
Horizontal Stabilizer
A variable-incidence tailplane used for longitudinal trim; it became physically jammed by aerodynamic loads during the high-speed dive.
Attitude Indicator
The primary flight instrument for pitch and roll; the CAB noted its small size and lack of degree indexing made recovery difficult.
Interesting Facts
- 01The aircraft was operating with a known inoperative Pitch Trim Compensator (PTC).
- 02The First Officer had been involved in a similar DC-8 upset near Houston just three months prior, though that flight recovered safely.
- 03The flight data recorder was recovered but was too badly damaged to provide usable data.
- 04Only 60 percent of the wreckage was recovered from the 20-foot deep water due to the extreme fragmentation of the airframe.
- 05The victims included Marie-Hélène Lefaucheux, a prominent French human rights activist and UN delegate, and Kenneth Spencer, a famous American singer and actor.
- 06The aircraft struck the water at a dive angle in excess of 20 degrees.
Safety Actions & Advisories
Stabilizer Drive Improvements
The investigation led to a re-evaluation of the DC-8's horizontal stabilizer drive motor capability to ensure it could operate under high aerodynamic loads.
Instrument Interpretation Training
Recommendations were made to improve the legibility and indexing of attitude indicators to assist pilots in recognizing extreme pitch attitudes.