Schweizer 269C N39SH

Summary

On 29 July 2011 at about 20:30 local time, a Schweizer 269C registered N39SH, operated by CVC Helicopter Service, was involved in an accident near Darlington, Maryland, 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

29 July 2011 at 20:30

Classification

Accident

Location

Darlington, Maryland, United States

Nearest airport

Private Heliport

Coordinates

39.6514, -76.2369

Aircraft

Schweizer 269C

Registration

N39SH

Category

Helicopter

Engines

1

Operator

CVC Helicopter Service

Operating rule

Part 91: General Aviation

Purpose of flight

Positioning

Phase of flight

Not recorded

Route

Bel Air → Darlington

Aircraft damage

Substantial

Weather

VMC

Light

Dawn

NTSB number

ERA11LA428

1 person had minor injuries.

Inadequate maintenance of the helicopter's landing gear dampers, which resulted in a main rotor out-of-balance condition and ground resonance encounter.

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

Read the full NTSB narrative

The pilot of the helicopter stated that he conducted a light touchdown on the helipad and reduced engine power and applied collective friction for cooldown, per the helicopter’s checklist. About 1 minute after the touchdown, the helicopter began to vibrate violently. The pilot further reduced engine power, but the helicopter continued to vibrate until it fell apart. Before the day's flights, the pilot performed a preflight inspection of the helicopter, during which he visually inspected both forward and aft landing gear dampers and also squeezed them to confirm that they contained oil and were not leaking. He did not observe any anomalies during this inspection. The landing gear dampers were examined by the manufacturer after the accident, and during load testing three of the four dampers did not meet required specifications. The minority owner of the helicopter stated that, based on the helicopter's fuel consumption during the time since its last inspection, he believed that the helicopter was more than 50 hours overdue for a 100-hour inspection. He also stated that, on one occasion, he found the helicopter's Hobbs meter disconnected. The helicopter manufacturer’s maintenance instructions state that, "Incorrect fluid levels, improper pressure or inoperable valving will deteriorate the damping capabilities of the landing gear dampers. These conditions may result in ground resonance and destruction of the helicopter.”

Quoted verbatim from the NTSB record.