Investigation Summary
The accident sequence began approximately two miles east of the crash site while the helicopter was in level cruising flight. Investigation revealed that the main rotor blades, identified by color codes (black, yellow, blue, red, and white), experienced severe over-travel in their lead/lag axis. The yellow blade's pitch change control rod was subjected to downward and rearward forces far exceeding its design strength, causing it to detach from the rotating swashplate. Once the yellow blade was no longer constrained by its control rod, it struck the right side of the fuselage near the baggage door. The resulting imbalance and subsequent strikes by the remaining four blades severed the tail rotor pylon and destroyed the structural integrity of the aircraft. The fuselage fell nearly vertically into a cow corral at a dairy farm. Investigators focused on the rotor blade dampers, which are designed to restrain lead/lag movement. A critical portion of the black blade's damper and its horizontal hinge pin were never recovered, preventing a definitive determination of why the damping system failed. At the moment of impact, the NTSB found that the main rotor was turning very slowly, if at all, and there was little power development from either engine, consistent with the mid-air disintegration.
Final Conclusions
The NTSB determined the probable cause was the loss of main rotor blade damper integrity, originating from either a failure of the black blade damper or a loss of effective damping action by the white blade damper. This failure allowed uncontrolled lead/lag excursions that overloaded the yellow blade's pitch control rod, leading to its detachment and subsequent catastrophic blade strikes on the airframe. The precise reason for the initial damper malfunction remained undetermined due to unrecovered components.
Video Analysis
1968 Los Angeles Airways Flight 841 — A detailed look at the deadliest helicopter accident in U.S. history at the time, involving a Sikorsky S-61L shuttle flight from Disneyland.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Systems & Failure Modes
Main Rotor Blade Dampers
Hydraulic units designed to restrain the lead and lag (fore and aft) movement of the rotor blades during rotation.
Pitch Change Control Rod
A mechanical linkage that transmits control inputs from the swashplate to the rotor blade to change its angle of attack.
Rotating Swashplate
A component that translates non-rotating control inputs from the pilot into rotating inputs for the rotor blades.
Interesting Facts
- 01The accident was the deadliest civilian helicopter crash in U.S. history at the time of the occurrence.
- 02Many passengers were tourists returning from Disneyland; the flight was a scheduled shuttle service.
- 03The tail rotor assembly was found in a truck yard a block away from the main wreckage site.
- 04The NTSB found that the main rotor was turning very slowly or not at all at the moment of ground impact.
- 05The aircraft involved was the first Sikorsky S-61L delivered to a commercial operator.
- 06The crash occurred near the intersection of Alondra Boulevard and Minnesota Street.
Safety Actions & Advisories
Airworthiness Directive (AD) 68-16-05
Issued on August 14, 1968, this AD mandated the use of only new main rotor blade spindles on S-61 aircraft and established a lifetime limit of 2,400 hours. While issued following this crash, the NTSB specifically identified damper integrity, not spindle failure, as the probable cause for Flight 841; the AD was a broader fleet safety measure.