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NTSB Report

September 4, 2004 · Robinson R22 BETA · N176FM

St. Thomas

Overview

Report Status
Final with probable cause
Event Type
Accident
Date
September 4, 2004
Injury Outcomes
No injuries (2 uninjured)
Location
St. Thomas
Aircraft
Robinson R22 BETA
Tail Number
N176FM
Operator
Aviane
Injuries
None
Aircraft Damage
Substantial
NTSB Number
MIA04LA131

The pilot stated that the helicopter was parked on a dock at the Crown Bay Marina in a northeasterly heading. After starting the engine, he performed a pedal turn to the right, and brought the helicopter to a 4 foot hover with all engine indications in the green. He commenced a southeasterly takeoff profile into the 10-15 knot wind while maintaining a steady climb at 30 to 40 knots. When the flight was at approximately 20 foot, the helicopter yawed to the right "sharply." He stopped the climb and was able to correct back to the original heading with left anti-torque pedal input. When the helicopter attained the original heading, it started spinning to the right "uncontrollably." He then entered an autorotation into the water where he and the passenger evacuated the helicopter before it sank approximately 60 yards from the dock. The pilot stated he maintained a southerly heading from the point of hovering to the autorotation and he did not contact any object during the entire flight. Examination of the tail rotor conducted by a Federal Aviation Administration (FAA) inspector revealed that the tailrotor drive shaft was fractured approximately six inches aft of the tailrotor drive shaft damper assembly. NTSB review of pictures provided by FAA revealed both ends of the fracture surfaces of the tailrotor drive shaft exhibited evidence of torsional twisting. The tailrotor blades were found to be fractured approximately 8 inches from the center of rotation. The FAA Rotorcraft Flying Handbook (FAA-H-8083-21) states that unanticipated yaw, also referred to as loss of tail rotor effectiveness (LTE), may occur in all single-rotor helicopters at airspeeds less than 30 knots, and occurs to the right in helicopters with a counter-clockwise rotating main rotor (Robinson 22). It is the result of the tail rotor not providing adequate thrust to maintain directional control. The suggested recovery technique of a sudden unanticipated right yaw is to apply full left pedal while simultaneously moving cyclic control forward to increase speed. As recovery is effected, adjust controls for normal forward flight. Collective pitch reduction aids in arresting the yaw rate but may cause an excessive rate of descent. Any large, rapid increase in collective to prevent ground or obstacle contact may further increase the yaw rate and decrease rotor revolution per minute (RPM). NTSB review of the Robinson R22 Beta Pilot's Operating Handbook revealed that the recommended takeoff profile, from a hover, is to maintain 5 feet until reaching 40 knots. This is where a steady climb may be commenced while accelerating to 60 knots.

NTSB Probable Cause

The failure of the pilot-in-command to comply with performance data related to the recommended takeoff profile and his failure to perform remedial action following reduced tailrotor effectiveness, resulting in subsequent initiation of an autorotation and ditching.

Full Narrative

On September 4, 2004, about 1030 Atlantic standard time, a Robinson R22 Beta helicopter, N176FM, registered to MSE Air Group, Inc., operated by Aviane, experienced a loss of control shortly after liftoff from a dock at Crown Bay Marina in St. Thomas, U.S.V.I. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 personal, local flight. The helicopter was substantially damaged and the private-rated pilot and one passenger were not injured. The flight was originating at the time of the accident. The pilot stated that the helicopter was parked on a dock at the Crown Bay Marina in a northeasterly heading. After starting the engine, he performed a pedal turn to the right, and brought the helicopter to a 4-foot hover with all engine indications in the green. He commenced a southeasterly takeoff profile into the 10-15 knot wind while maintaining a steadily climb at 30 to 40 knots. When the flight was at approximately 20 foot, the helicopter yawed to the right "sharply." He stopped the climb and was able to correct back to the original heading with left anti-torque pedal input. When the helicopter attained the original heading, it started spinning to the right "uncontrollably." He then entered an autorotation into the water where he and the passenger evacuated the helicopter before it sank approximately 60 yards from the dock. The pilot stated he maintained a southerly heading from the point of hovering to the autorotation and he did not contact any object during the entire flight. Examination of the tail rotor conducted by an Federal Aviation Administration (FAA) inspector revealed that the tailrotor drive shaft was fractured approximately 6 inches aft of the tailrotor drive shaft damper assembly. NTSB review of pictures provided by FAA revealed both ends of the fracture surfaces of the tailrotor drive shaft exhibited evidence of torsional twisting. The tailrotor blades were found to be fractured approximately 8 inches from the center of rotation. The FAA Rotorcraft Flying Handbook (FAA-H-8083-21) states that unanticipated yaw, also referred to as loss of tail rotor effectiveness (LTE), may occur in all single-rotor helicopters at airspeeds less than 30 knots, and occurs to the right in helicopters with a counter-clockwise rotating main rotor (Robinson 22). It is the result of the tail rotor not providing adequate thrust to maintain directional control. The suggested recovery technique of a sudden unanticipated right yaw is to apply full left pedal while simultaneously moving cyclic control forward to increase speed. As recovery is effected, adjust controls for normal forward flight. Collective pitch reduction aids in arresting the yaw rate but may cause an excessive rate of descent. Any large, rapid increase in collective to prevent ground or obstacle contact may further increase the yaw rate and decrease rotor revolution per minute (RPM). NTSB review of the Robinson R22 Beta Pilot's Operating Handbook revealed that the recommended takeoff profile, from a hover, is to maintain 5 feet until reaching 40 knots. This is where a steady climb may be commenced while accelerating to 60 knots.

Flight

Event TypeAccident
Event Time14:30 UTC
Nearest Airport0nm
Flight Plan FiledNone
Flight Plan ActivatedNo
Aircraft FireNo
Aircraft ExplosionNo

Aircraft

AircraftRobinson R22 BETA
Tail NumberN176FM
Aircraft CategoryHeli
DamageSubstantial
OperatorAviane
Operating RulePart 91
Engines1
Engine TypeReciprocating
Engine DetailsLycoming · O-360-J2A · Reciprocating · 131
Seats2

People & Injuries

Injury SummaryNo injuries (2 uninjured)
Fatal0
Serious0
Minor0
Uninjured2
Total2
Crew 1Age 42 · Third Class · None

Conditions

ConditionsVMC
LightDaylight
Wind130° @ 15 kt, gusting 20 kt
Visibility10 sm
CeilingNone
Altimeter29.98 inHg
Observation Time14:30
Weather SourceWFAC

Appendix: Source Data