GAA19CA063

NTSB accident investigation · Robinson R44 · Knox City, TX · November 18, 2018

Accident · No injuriesData collectionFinal report
Date
November 18, 2018, 08:30 local (14:30 UTC)
Place
Knox City, TX
Injuries
4 uninjured
Damage
Substantial damage
Phase of flight
Maneuvering
Aircraft
N4167YRobinson R44
Defining event
Maneuvering-low-alt flying: Loss of control in flight
Weather
Visual (VMC) · Day
Status
Completed · report September 26, 2019
Report
Approved by Office Director
NTSB office
General Aviation Accidents
Parties
FAA
FAA report
20181118022739A
Case key
98654

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 maintain adequate airspeed with a tailwind, which resulted in the helicopter settling with power, and his subsequent incorrect collective application while attempting to recover, which resulted in a loss of helicopter control due to a loss of tail rotor effectiveness.

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.

Performance/control parameters: airspeedAircraft › Aircraft oper/perf/capability · Not attained/maintainedRobinson Helicopter R44: 3 casesAll aircraft: 1,682 casesProbable cause
Performance/control parameters: prop/rotor parametersAircraft › Aircraft oper/perf/capability · Not attained/maintainedRobinson Helicopter R44: 15 casesAll aircraft: 182 casesProbable cause
Wind: tailwindEnvironmental issues › Conditions/weather/phenomena · Effect on operationRobinson Helicopter R44: 6 casesAll aircraft: 594 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 conducting a photography flight about 70 ft above ground level, the helicopter's heading was 190°, and the airspeed was less than 9 knots. With a 10-knot tailwind, the helicopter began to settle with power. The pilot increased the collective and applied forward cyclic to increase the airspeed, but the helicopter continued to settle and impacted the ground hard. The helicopter sustained substantial damage to the main rotor system and fuselage. The pilot reported that there were no mechanical malfunctions or failures with the helicopter that would have precluded normal operation. The pilot reported that the wind about the time of the accident was from the north at 10 knots. According to the Helicopter Flying Handbook, Chapter 11, page 11-10 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 tailrotor 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.

Factual narrative

The helicopter pilot reported that while conducting a photography flight about 70ft AGL, the helicopter's heading was 190° and the airspeed was less than 9 knots. With a 14-knot tailwind the helicopter began to settle with power. He increased collective and applied forward cyclic to increase the airspeed, but the helicopter impacted the ground. The helicopter sustained substantial damage to the main rotor system and the fuselage. The pilot reported that the wind about the time of the accident was from the north at 14 knots. The pilot reported that there were no mechanical malfunctions or failures with the helicopter that would have precluded normal operation. According to the Helicopter Flying Handbook, Chapter 11, page 11-10: 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 tailrotor 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.

Aircraft

Registration
N4167Y
Reported as
Robinson R44 (Undesignat)
Category
Helicopter
Serial number
1889
Built
2008
Airframe hours
2,087.5
Engine
Lycoming O-540-F1B5, 235 horsepower, reciprocating
Damage
Substantial damage
Flight
Aerial observation · Part 91
Airworthiness certificate
Standard, Normal
Last inspection
100 hour · July 10, 2018
Departed
F75 · Knox City, TX
Destination
F75 · Knox City, TX
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
34
Injuries
None
Certificate
Commercial
Instrument ratings
Helicopter
Medical
Class 2, Without waivers/limitations
Last flight review
September 28, 2018
Seat
Right
Restraint
3-point
Flight hours
302.8 total · 302.8 in this make and model · 224.8 as pilot in command · 35.2 in the last 90 days · 30.8 in the last 30 days

Weather

Conditions
Visual (VMC) · Day
Wind
350° at 10 knots
Visibility
10 statute miles
Lowest ceiling
3,300 ft overcast
Temperature
30 °F, dew point 23 °F
Altimeter
30.37 inHg
Observed at
KCDS, 57 nm away

Docket · 2

The files NTSB released with the investigation on June 27, 2019, on NTSB’s docket system: statements, records, photos and specialists’ reports. 3.6 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.