1990-05-23: Hughes 269C — Rialto, CA

Casualties unknown • Rialto, CA, US

Probable cause

IMPROPER MAINTENANCE PROCEDURE BY MAINTENANCE PERSONNEL TO TROUBLESHOOT A REPORTED DEFICIENCY AND THE PILOT'S DECISION TO DEMONSTRATE THE VIBRATION, EXCEEDING THE DESIGN LIMITS OF THE HELICOPTER AND INDUCING GROUND RESONANCE. CONTRIBUTING TO THE ACCIDENT WAS THE LOW NITROGEN CHARGE OF THE LANDING GEAR DAMPERS.

— NTSB Determination

Accident narrative

THE HELICOPTER ENCOUNTERED GROUND RESONANCE DURING A MAINTENANCE TEST FLIGHT. THE CFI NOTICED AN UNUSUAL VIBRATION DURING STUDENT TRAINING. THE PILOT SUSPENDED THE TRAINING AND INFORMED MAINTENANCE. THE PILOT THEN ATTEMPTED TO DUPLICATE THE VIBRATION FOR ONE OF THE MAINTENANCE MECHANICS. AFTER TWO UNSUCCESSFUL ATTEMPTS, THE PILOT LANDED THE HELICOPTER ON A SLIGHT SLOPE. AFTER ONE SKID TOUCHED DOWN, THE HELICOPTER BEGAN TO VIBRATE. THE PILOT REDUCED THE THROTTLE AND THE VIBRATION BECAME MORE SEVERE. ACCORDING TO THE PILOT, THE HELICOPTER BEGAN TO DISINTEGRATE.

Frequently asked questions

What happened in the 1990-05-23 Hughes 269C accident near Rialto, CA?

What aircraft was involved and where did it happen?

The accident on 1990-05-23 involved a Hughes 269C, registration N7441F, at Rialto, CA.

What was the probable cause of the accident?

IMPROPER MAINTENANCE PROCEDURE BY MAINTENANCE PERSONNEL TO TROUBLESHOOT A REPORTED DEFICIENCY AND THE PILOT'S DECISION TO DEMONSTRATE THE VIBRATION, EXCEEDING THE DESIGN LIMITS OF THE HELICOPTER AND INDUCING GROUND RESONANCE. CONTRIBUTING TO THE ACCIDENT WAS THE LOW NITROGEN CHARGE OF THE LANDING GEAR DAMPERS.

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