Bell 407 N11SP

Summary

On 31 August 2012 at about 14:45 local time, a Bell 407 registered N11SP, operated by State of New York, was involved in an accident near Bath, New York, 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

31 August 2012 at 14:45

Classification

Accident

Location

Bath, New York, United States

Coordinates

42.3733, -77.3503

Aircraft

Bell 407

Registration

N11SP

Category

Helicopter

Engines

1

Operator

State of New York

Operating rule

Public Use

Phase of flight

Not recorded

Route

Batavia → Batavia

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ERA12TA538

1 person had minor injuries.

The pilot's improper recovery from an in-flight upset, which resulted in the main rotor striking and separating the tail boom. Contributing to the accident was the helicopter manufacturer's failure to warn pilots of unanticipated and unequal aft cyclic pressure in the single-pilot configured helicopter compared to the dual-pilot configured helicopter, which resulted in the in-flight upset when the pilot momentarily let go of the cyclic control.

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

Read the full NTSB narrative

The pilot stated that the accident helicopter was configured for single-pilot operation (the copilot controls had been removed for the assigned mission). While in cruise flight between 110 and 120 knots and about 2,500 feet mean sea level, the helicopter began pitching up and yawing right, because the force trim was the "off" position, which rendered the altitude hold feature inoperative, and the pilot responded by pushing the cyclic forward and left. The helicopter then pitched "severely" nose down and entered a right spin. At that time, the pilot saw a portion of the tail boom, tail rotor, and tail rotor gearbox falling away separately from the helicopter. The pilot entered an autorotation and landed in wooded terrain. About 1 year after the accident, another pilot for the operator performed a maintenance test flight in a similarly configured make and model helicopter. While in cruise flight and with the force trim in the "off" position, the pilot released the cyclic momentarily, and the helicopter pitched up and rolled right. The flight scenario was duplicated several times with the copilot controls installed on the helicopter and, when the pilot released the cyclic, it maintained its same relative position, even with the force trim in the "off" position. Therefore, it appears that aerodynamic forces drove the cyclic aft in the single-pilot configured helicopter because the added weight and lever arm in a dual-pilot configured helicopter was not available to neutralize the forces. The manufacturer should have known about this characteristic of the helicopter and warned pilots of unanticipated and unequal aft cyclic pressure in the single-pilot configured helicopter compared to the dual-pilot configured helicopter. Detailed examination and testing of the helicopter and its components revealed no preaccident anomalies and no evidence of foreign object damage.

Quoted verbatim from the NTSB record.