WPR11CA101

NTSB accident investigation · Bell 206B3 · Three Forks, MT · January 15, 2011

Accident · No injuriesData collectionFinal report
Date
January 15, 2011, 13:00 local (20:00 UTC)
Place
Three Forks, MT
Injuries
2 uninjured
Damage
Substantial damage
Phase of flight
Emergency descent
Aircraft
N78BRBell 206B3
Defining event
Autorotation: Hard landing
Weather
Visual (VMC) · Day
Status
Completed · report May 26, 2011
Report
Approved by Office Director
NTSB office
Western Pacific Region
Parties
FAA FSDO
FAA report
20110115001329A
Case key
78171

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

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Probable cause

The pilot’s inadequate use of throttle during the practice autorotation that resulted in a hard landing.

Findings · 2

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.

Engine controls: power leverAircraft › Aircraft power plant · Incorrect use/operationBell 206B: 2 casesAll aircraft: 95 casesProbable cause
Use of equip/info: use of equip/systemPersonnel issues › Task performance · PilotBell 206B: 5 casesAll aircraft: 1,391 casesProbable cause

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.

Analysis

The pilot practiced several maneuvers and then entered a straight-in practice autorotation. He pointed the helicopter into the wind at 800 feet above ground level near midfield and above the runway. He reduced the throttle to flight idle and lowered the collective while gently flaring the nose of the helicopter to set up the appropriate main rotor rpm and airspeed. He reported that he monitored those parameters carefully during the descent and noted that they remained well within the normal range. At the bottom of the descent, the pilot flared a little high to allow a margin of safety for tail boom clearance as he was planning a power recovery from the autorotation. The pilot stated that he did not add power at that point and that there was inadequate rotor inertia to dampen the landing, even though he applied full collective deflection. The helicopter hit hard and sustained substantial damage. The aft portion of the tail boom and tail rotor separated due to a main rotor blade contact and the skids were damaged.

Factual narrative

The pilot practiced several maneuvers, and then entered a straight-in practice autorotation. He pointed the helicopter into the wind at 800 feet above ground level (agl) near midfield and above the runway. He rolled the throttle to flight idle, and lowered the collective while gently flaring the nose of the helicopter to set up the appropriate main rotor revolutions per minute (rpm) and airspeed. He monitored those parameters carefully during the descent, and noted that they remained well within the normal range. At the bottom of the descent, the pilot flared a little high to allow a margin of safety for tail boom clearance as he was planning a power recovery from the autorotation. However, the pilot stated that he did not add power at that point, and there was inadequate rotor inertia to dampen the landing, even though he applied full collective deflection. The helicopter hit hard, and sustained substantial damage. The aft portion of the tail boom and tail rotor separated due to a main rotor blade contact, and the skids were damaged. The pilot performed an emergency shut down; he closed the throttle, and switched off the battery, generator, and fuel valve. After exiting the helicopter he secured the battery.

Aircraft

Registration
N78BR
Reported as
Bell 206B3
Category
Helicopter
Serial number
4001
Airframe hours
2,701
Engine
Rolls-Royce Allison 250-C20J, 420 horsepower, turbo shaft
Damage
Substantial damage
Flight
Personal · Part 91
Operator
Skymission LLC
Registered owner
Skymission LLC
Airworthiness certificate
Standard, Normal
Last inspection
Annual · June 23, 2010
Departed
BZN · Bozeman, MT
Destination
BZN · Bozeman, MT
Airport
9S5 · Three Forks, runway 02, 5,100 × 60 ft, asphalt

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
57
Injuries
None
Certificate
Private
Medical
Class 3, With waivers/limitations
Last flight review
April 11, 2009
Seat
Right
Flight hours
692 total · 674 in this make and model · 607 as pilot in command · 26 in the last 90 days · 4 in the last 30 days

Weather

Conditions
Visual (VMC) · Day
Wind
310° at 4 knots
Visibility
10 statute miles
Lowest ceiling
None
Temperature
41 °F, dew point 27 °F
Altimeter
30.11 inHg
Observed at
KBZN

Docket · 1

The files NTSB released with the investigation on February 17, 2011, on NTSB’s docket system: statements, records, photos and specialists’ reports. 2.8 MB in all.

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.