Hughes 269A N90270

Summary

On 27 June 2023 at about 21:30 local time, a Hughes 269A registered N90270 was involved in an accident near Anderson, South Carolina, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

27 June 2023 at 21:30

Classification

Accident

Location

Anderson, South Carolina, United States

Nearest airport

Anderson Regional Airport (AND)

Coordinates

34.4946, -82.7094

Aircraft

Hughes 269A

Registration

N90270

Category

Helicopter

Year built

1966

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Flight Test

Phase of flight

Not recorded

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ERA23LA289

Nobody was injured.

The mechanics’ improper torquing of the main rotor blade dampers, which resulted in a ground resonance event during landing.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

Prior to the accident flight, the pilot reported experiencing vibrations in the helicopter. The pilot (who was also a mechanic) and another mechanic adjusted the main rotor dampers to address the issue. Following this adjustment, a 10-minute ground run was performed without any observed problems. The pilot then conducted a test flight during, which no issues were detected. Upon landing and while reducing the rotor rpm, the helicopter began to shake violently. The pilot attempted to perform the ground resonance recovery procedure and climbed the helicopter, but the vibration worsened, and he subsequently landed. After contacting the ground, the helicopter shook and spun uncontrollably before coming to a stop. The airframe and main rotor were substantially damaged during the accident sequence. Federal Aviation Administration inspectors examined the helicopter after the accident and found that the yellow main rotor blade’s damper had significantly higher torque than the red and blue blades, and that none of the dampers were torqued to the specification in the helicopter’s maintenance manual. The manual also described that incorrect torque adjustments of the dampers could result in “…conditions that may result in ground resonance and destruction of the helicopter. During a subsequent discussion with the assisting mechanic, he stated that he, “may have unintentionally over-torqued the blade [damper].” Based on this information, it is likely that the mechanics’ improper maintenance of the helicopter’s main rotor dampers resulted in the ground resonance event experienced at the conclusion of the post maintenance test flight test flight.

Quoted verbatim from the NTSB record.