CEN21LA173

NTSB accident investigation · Robinson Helicopter R44 II · Dustin, OK · March 26, 2021

Accident · Serious injuriesClass 3 · LimitedFinal report
Date
March 26, 2021, 15:15 local (20:15 UTC)
Place
Dustin, OK
Injuries
2 serious, 2 minor
Damage
Substantial damage
Phase of flight
Maneuvering
Aircraft
N178DFRobinson Helicopter R44 II
Defining event
Maneuvering-low-alt flying: Loss of control in flight
Weather
Visual (VMC) · Day
Status
Completed
Report
Approved by Office Director
Investigation class
Class 3
NTSB office
Central Region
Parties
Federal Aviation Administration; Will Rogers Flight Standards District Office
FAA report
20210326005769A
Case key
102855

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 insufficient monitoring of the helicopter’s power while flying at low altitude and at low airspeed, which resulted in the loss of rotor rpm and impact with a tree and terrain.

Findings · 3

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.

Performance/control parameters: airspeedAircraft › Aircraft oper/perf/capability · Not attained/maintainedRobinson Helicopter R44 II: 6 casesAll aircraft: 1,681 casesProbable cause
Object/animal/substance: tree(s)Environmental issues › Physical environment · Effect on equipmentRobinson Helicopter R44 II: 9 casesAll aircraft: 933 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 of the helicopter stated that, while maneuvering “low and slow” with three passengers onboard, he noticed “insufficient power” and shortly thereafter, the low rotor rpm warning annunciated. He applied full throttle and attempted to regain rotor rpm but was unsuccessful. The pilot stated that he was forced to land immediately, during which the helicopter impacted a tree then terrain, resulting in substantial damage. The pilot reported that there were no mechanical malfunctions or failures of the helicopter and recommended operating “at a lower gross weight.” Postacccident examination of the helicopter revealed no anomalies that would have precluded normal operation.

Factual narrative

On March 26, 2021, about 1515 central daylight time, a Robinson Helicopter Company R44 II, N178DF, was substantially damaged when it was involved in an accident near Dustin, Oklahoma. The private pilot and one passenger received serious injuries, and two passengers received minor injuries. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 aerial observation flight. The pilot stated that while maneuvering “low and slow” with three passengers onboard, he noticed “insufficient power” and shortly thereafter, the low rotor rpm warning annunciated. He applied full throttle and attempted to regain rotor rpm but was unsuccessful. The pilot stated that he was forced to land the helicopter immediately, during which the helicopter impacted a tree then terrain, resulting in substantial damage that included damage to the main rotor, fuselage, and tailboom. The pilot reported that there were no mechanical malfunctions or failures with the helicopter, and recommended operating “at a lower gross weight.” Postacccident examination of the helicopter revealed no anomalies that would have precluded normal operation.

Aircraft

Registration
N178DF
Reported as
Robinson Helicopter R44 II
Category
Helicopter
Serial number
11969
Built
2007
Airframe hours
2,347
Engine
Lycoming IO-540-AE1A5, 290 hp, reciprocating
Damage
Substantial damage
Flight
Aerial observation · Part 91
Operator
Brush Popper Aviation LLC
Registered owner
Brush Popper Aviation LLC
Airworthiness certificate
Standard, Normal
Last inspection
Annual · January 18, 2021
Departed
F10 · Henryetta, OK
Equipment
Electronic flight bag or handheld device

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
59
Injuries
Serious
Certificate
Private
Airplane ratings
Single-engine land
Instrument ratings
Helicopter
Medical
Class 2, Without waivers/limitations
Last flight review
June 3, 2020
Seat
Right
Restraint
4-point
Flight hours
3,687 total · 1,447 in this make and model · 3,552 as pilot in command · 124 in the last 90 days · 82 in the last 30 days · 3 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
150° at 14 knots, gusting 21
Visibility
10 statute miles
Lowest ceiling
None
Temperature
75 °F, dew point 45 °F
Altimeter
29.89 inHg
Observed at
OKM, 90 nm away

Docket · 5

The files NTSB released with the investigation on July 29, 2022, on NTSB’s docket system: statements, records, photos and specialists’ reports. 159 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.