Investigation Summary
Post-accident examination revealed that the two-piece throttle control tie rod assembly had disconnected in flight. The internally threaded rod and the externally threaded rod-end bearing showed damage to the three end-threads of each, consistent with vibratory thread-to-thread wear. This separation occurred because the assembly was incorrectly adjusted with insufficient thread engagement, rendering the pilot unable to control engine power. During the emergency, the pilot was advised by three instructors on the ground—including a company flight instructor, a Federal Aviation Administration (FAA) inspector, and a Designated Pilot Examiner (DPE)—to perform a run-on landing or, if performing an autorotation, to wait until the helicopter was over the runway surface. The final radio reminder from the DPE occurred while the helicopter was on a 2-mile final approach. The pilot instead shut down the engine at 950 feet AGL while still 1/4 to 1/2 mile south of the runway. As the helicopter fell short of the runway, the pilot likely increased collective pitch to extend the glide, which further decayed the rotor RPM and led to a near-vertical descent.
Final Conclusions
The NTSB determined the probable cause was the pilot's early entry into and failure to maintain rotor RPM during a forced landing autorotation after performing an engine shutdown in flight. A contributing factor was the failure of maintenance personnel to properly rig the throttle control tie-rod assembly, which resulted in in-flight separation and loss of engine RPM control. The investigation noted that while maintenance manuals required throttle rigging after engine, cable, or carburetor changes, the mechanic was not certain if the procedure was fully followed during previous service.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Held commercial and flight instructor certificates.
Systems & Failure Modes
Throttle Control Tie Rod
A two-piece assembly consisting of an internally threaded rod and an externally threaded rod-end bearing that transmits throttle inputs to the carburetor. Inadequate thread engagement led to its separation.
Main Rotor System
A fully articulated three-bladed design. During the autorotation, the pilot's attempt to extend the glide by increasing collective pitch caused the rotor RPM to decay below controllable limits.
Interesting Facts
- 01The passenger was Troy Gentry, a member of the country music duo Montgomery Gentry.
- 02The throttle tie rod assembly separated at the threaded joint due to reduced thread engagement.
- 03The pilot had 480.9 total flight hours, with approximately 300 hours in the Schweizer 269.
- 04The helicopter had undergone a 100-hour inspection only 15 flight hours prior to the accident.
- 05Post-crash examination of the rotor blades showed little to no damage at the tips, confirming low rotor RPM at impact.
Safety Actions & Advisories
Sikorsky Alert Service Bulletin ASB-C1B-048
Issued on November 16, 2017, requiring a one-time inspection of the throttle control tie rod assembly to verify the correct length and thread engagement.