Schweizer 269C N557DC

Summary

On 13 June 2018 at about 17:59 local time, a Schweizer 269C registered N557DC was involved in an accident near Las Vegas, Nevada, United States. One person was on board and one had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

13 June 2018 at 17:59

Classification

Accident

Location

Las Vegas, Nevada, United States

Nearest airport

North Las Vegas (VGT)

Coordinates

36.2106, -115.1944

Aircraft

Schweizer 269C

Registration

N557DC

Category

Helicopter

Year built

1993

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Las Vegas → Overton

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR18LA170

1 person had minor injuries.

The pilot’s failure to take the appropriate corrective action for ground resonance, which resulted in a loss of helicopter control.

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

Read the full NTSB narrative

The pilot was preparing to depart in the helicopter on a local flight. He stated that he powered up the helicopter and that, with the engine/rotor rpm at the “very bottom of [the] green range” and the helicopter still on the ground, the helicopter began to vibrate. The vibrations worsened, and in response to the ground resonance, he lowered the collective and rolled off the throttle to abort the takeoff. The vibrations increased in severity and lasted about 20 seconds. The main rotor and engine then shut down, and the helicopter had rotated about 45° to the left. A nearby witness stated that the helicopter was shaking and that it never came to full power or left the ground. Postaccident examination of the helicopter, including the landing gear dampers, skid attachments, and main rotor blade dampers, revealed no anomalies that would have precluded normal operation. Further, the main rotor dampers were tested about 7 flight hours before the accident flight with no anomalies noted. The Federal Aviation Administration’s (FAA) Helicopter Flying Handbook (FAA-H-8083-21A) stated the following about ground resonance: "If the rpm is low, the only corrective action to stop ground resonance is to close the throttle immediately and fully lower the collective to place the blades in low pitch. If the rpm is in the normal operating range, fly the helicopter off the ground." However, this guidance for ground resonance corrective action was listed in the same paragraph after discussion of hard contact with the ground and when one other landing gear strikes the surface. Although the pilot noted that the engine/rotor rpm was at the very bottom of the green range, the rpm was still in the normal operating range; his decision to lower the collective instead of taking off led to increased (and/or continued) ground resonance vibrations and the subsequent substantial damage to the fuselage.

Quoted verbatim from the NTSB record.