GAA16CA143

NTSB accident investigation · Bell 47 · Agua Dulce, CA · March 2, 2016

Accident · Minor injuriesData collectionFinal report
Date
March 2, 2016, 09:30 local (17:30 UTC)
Place
Agua Dulce, CA
Injuries
1 minor
Damage
Substantial damage
Phase of flight
Enroute
Aircraft
N568TBBell 47
Defining event
Enroute-cruise: Miscellaneous/other
Weather
Visual (VMC) · Day
Status
Completed · report April 5, 2016
Report
Approved by Office Director
NTSB office
General Aviation Accidents
Parties
FAA Van Nuys FSDO
FAA report
20160302006439A
Case key
92800

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

On this page

Probable cause

The pilot's failure to set the appropriate collective friction prior to releasing the collective in flight, which resulted in decreased main rotor pitch, settling with power, and an impact with terrain.

Findings · 5

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.

Use of equip/info: aircraft controlPersonnel issues › Task performance · PilotBell 47G: 3 casesAll aircraft: 9,295 casesProbable cause
Use of equip/info: use of equip/systemPersonnel issues › Task performance · PilotBell 47G: 2 casesAll aircraft: 1,391 casesProbable cause
Performance/control parameters: prop/rotor parametersAircraft › Aircraft oper/perf/capability · Not attained/maintainedBell 47G: 1 caseAll aircraft: 182 cases
Performance/control parameters: powerplant parametersAircraft › Aircraft oper/perf/capability · Not attained/maintainedBell 47G: 1 caseAll aircraft: 81 cases
Performance/control parameters: descent rateAircraft › Aircraft oper/perf/capability · Not attained/maintainedBell 47G: 1 caseAll aircraft: 242 cases

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 helicopter pilot reported that while flying about 300 feet above a ridge with an elevation of 4,900 feet at 10 miles per hour (8.68 knots), he could not hear very well in his headset and needed to adjust the volume. He reported that he removed his left hand from the collective and used it to hold the cyclic so he could use his right hand to adjust the volume on his headset. During this process, he reported that he forgot to increase the friction on the collective prior to removing his left hand. He further reported that the collective "dropped which decreased main rotor pitch causing the engine to overspeed." The pilot reported that the helicopter started to spin to the right; he grabbed the collective, reduced throttle, and then increased the collective pitch. He reported that the helicopter "experienced settling with power," and spun around 8 to 10 times. He further reported that the helicopter landed hard at the top of a ridge and rolled onto its right side. The helicopter sustained substantial damage to the fuselage, main rotor system, tailboom, and tail rotor system. The pilot verified that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation. As a safety recommendation, the pilot stated he "should have increased the collective friction prior to removing his left hand from the collective stick." He also stated that "the problem was made worse because the helicopter was only 300 feet above ground level at 10 miles per hour [8.68 knots]." The Federal Aviation Administration (FAA) has published FAA-H-8083-21 Helicopter Flying Handbook (2012). This handbook discusses the function of the collective and states in part: "An adjustable friction control helps prevent inadvertent collective pitch movement." This handbook also discusses recovery from a settling with power condition and states in part: "When recovering from a settling with power condition, the pilot tends first to try to stop the descent by increasing collective pitch. However, this only results in increasing the stalled area of the rotor, thereby increasing the rate of descent. Since inboard portions of the blades are stalled, cyclic control may be limited. Recovery is accomplished by increasing airspeed, and/or partially lowering collective pitch. In many helicopters, lateral cyclic combined with lateral tail rotor thrust will produce the quickest exit from the hazard assuming that there are no barriers in that direction. In a fully developed vortex ring state, the only recovery may be to enter autorotation to break the vortex ring state." The pilot reported that he utilized a 4-point restraint system installed in the helicopter and sustained minor injuries. He also reported that "I credit the shoulder harness restraint with keeping my injuries from being far worse."

Factual narrative

The helicopter pilot reported that while flying about 300 feet above a ridge with an elevation of 4,900 feet at 10 miles per hour (8.68 knots), he could not hear very well in his headset and needed to adjust the volume. He reported that he removed his left hand from the collective and used it to hold the cyclic so he could use his right hand to adjust the volume on his headset. During this process, he reported that he forgot to increase the friction on the collective prior to removing his left hand. He further reported that the collective "dropped which decreased main rotor pitch causing the engine to overspeed." The pilot reported that the helicopter started to spin to the right; he grabbed the collective, reduced throttle, and then increased the collective pitch. He reported that the helicopter "experienced settling with power," and spun around 8 to 10 times. He further reported that the helicopter landed hard at the top of a ridge and rolled onto its right side. The helicopter sustained substantial damage to the fuselage, main rotor system, tailboom, and tail rotor system. The pilot verified that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation. As a safety recommendation, the pilot stated he "should have increased the collective friction prior to removing his left hand from the collective stick." He also stated that "the problem was made worse because the helicopter was only 300 feet above ground level at 10 miles per hour [8.68 knots]." The Federal Aviation Administration (FAA) has published FAA-H-8083-21 Helicopter Flying Handbook (2012). This handbook discusses the function of the collective and states in part; An adjustable friction control helps prevent inadvertent collective pitch movement. This handbook also discusses recovery from a settling with power condition and states in part; When recovering from a settling with power condition, the pilot tends first to try to stop the descent by increasing collective pitch. However, this only results in increasing the stalled area of the rotor, thereby increasing the rate of descent. Since inboard portions of the blades are stalled, cyclic control may be limited. Recovery is accomplished by increasing airspeed, and/or partially lowering collective pitch. In many helicopters, lateral cyclic combined with lateral tail rotor thrust will produce the quickest exit from the hazard assuming that there are no barriers in that direction. In a fully developed vortex ring state, the only recovery may be to enter autorotation to break the vortex ring state. The pilot reported that he utilized a 4-point restraint system installed in the helicopter and sustained minor injuries. He also reported that "I credit the shoulder harness restraint with keeping my injuries from being far worse."

Aircraft

Registration
N568TB
Reported as
Bell 47 (G2)
Category
Helicopter
Serial number
85
Built
1948
Airframe hours
5,818
Engine
Lycoming VO435A1F, 260 horsepower, reciprocating
Damage
Substantial damage
Flight
Personal · Part 91
Operator
Thomas J. White
Registered owner
Thomas J. White
Airworthiness certificate
Standard, Normal
Last inspection
November 21, 2015
Departed
WJF · Lancaster, CA
Destination
L70 · Agua Dulce, CA
Equipment
None

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
Minor
Certificate
Private
Airplane ratings
Single-engine land
Medical
Class 3, With waivers/limitations
Last flight review
November 24, 2015
Seat
Left
Restraint
4-point
Flight hours
709 total · 137 in this make and model · 585 as pilot in command · 7 in the last 90 days · 1 in the last 30 days · 0.5 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
290° at 13 knots
Visibility
10 statute miles
Lowest ceiling
None
Temperature
75 °F, dew point 18 °F
Altimeter
30.10 inHg
Observed at
KWJF, 11 nm away

Docket · 3

The files NTSB released with the investigation on March 22, 2016, on NTSB’s docket system: statements, records, photos and specialists’ reports. 3.4 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.