GAA19CA279

NTSB accident investigation · Guimbal Cabri · St. Louis, IL · May 23, 2019

Accident · No injuriesData collectionFinal report
Date
May 23, 2019, 14:10 local (19:10 UTC)
Place
St. Louis, IL
Injuries
2 uninjured
Damage
Substantial damage
Phase of flight
Landing
Aircraft
N369PAGuimbal Cabri
Defining event
Landing-aborted after touchdown: Loss of control on ground
Weather
Visual (VMC) · Day
Status
Completed · report April 13, 2020
Report
Approved by Office Director
NTSB office
General Aviation Accidents
Parties
FAA
FAA report
20190523005059A
Case key
99479

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 flight instructor's improper emergency procedure instruction to the student pilot, which resulted in the student improperly using the throttle to correct the loss of yaw control, which resulted in ground impact and a dynamic rollover.

Findings · 4

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: directional controlAircraft › Aircraft oper/perf/capability · Not attained/maintainedHelicopteres Guimbal CABRI G2: 3 casesAll aircraft: 3,958 casesProbable cause
Use of equip/info: aircraft controlPersonnel issues › Task performance · Student/instructed pilotHelicopteres Guimbal CABRI G2: 11 casesAll aircraft: 9,295 casesProbable cause
Use of equip/info: aircraft controlPersonnel issues › Task performance · Instructor/check pilotHelicopteres Guimbal CABRI G2: 11 casesAll aircraft: 9,295 casesProbable cause
Terrain: wet/muddy terrainEnvironmental issues › Physical environment · Effect on operationHelicopteres Guimbal CABRI G2: 1 caseAll aircraft: 110 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 flight instructor reported that, during a training flight in the helicopter, he briefed the student pilot on the procedures required to land with a simulated stuck left pedal. The student began a descent to enter a shallower-than-normal glidepath to the runway surface, and he completed his final checks for the maneuver and continued the approach. During the approach the flight instructor directed the student pilot to use "throttle manipulation to control the yaw caused by a fixed input on the anti-torque system." Upon contacting the runway, the helicopter veered left, and the instructor chose to abort the landing. As the helicopter lifted off, it began to rapidly yaw left while drifting left of the runway. Recognizing that the helicopter was in a spin, they attempted to correct by leveling the helicopter long enough to regain tail rotor authority. The helicopter's left skid impacted mud on the left side of the runway, and the helicopter rolled onto its left side. The helicopter sustained substantial damage to the main rotor, fuselage, and tailboom. The instructor reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation. A manufacturer's service letter, SL 19-002 A, stated, "During in-flight tail rotor control failure simulation, pilots should never use the twist grip to control yaw." Therefore, the flight instructor's direction to the student to use the throttle to correct the yaw was incorrect and led to ground impact and a dynamic rollover.

Factual narrative

The helicopter flight instructor reported that, during a training flight, he briefed the student pilot on the procedures required to land with a simulated stuck left pedal. The student began a descent to enter a shallower-than-normal glide path to the runway surface, and he completed his final checks for the maneuver and continued the approach. Upon contacting the runway, the helicopter veered to the left, and the instructor elected to abort the landing. As the helicopter lifted off, it began to yaw to the left at a rapid rate, while drifting to the left of the runway. Recognizing the helicopter was in a spin, they attempted to correct by leveling the helicopter "long enough for the aircraft to regain tail-rotor authority." The helicopter's left skid impacted the mud on the left side of the runway and the helicopter rolled onto its left side. The Federal Aviation Administration's Helicopter Flying Handbook, FAA-H-8083-21A, provides information and guidance in a section titled "Landing – Stuck Neutral or Right Pedal" which stated in part: The landing profile for a stuck neutral or a stuck right pedal is a low-power approach terminating with a running or roll-on landing. The approach profile can best be described as a shallow to normal approach angle to arrive approximately 2–3 feet landing gear height above the intended landing area with a minimum airspeed for directional control. During the approach the flight instructor directed the student pilot to "utilize throttle manipulation to control the yaw caused by a fixed input on the anti-torque system." The manufactures service letter, SL 19-002 A, states, "During in-flight tail rotor control failure simulation, pilots should never use the twist grip to control yaw." The helicopter sustained substantial damage to the main rotor, fuselage and tail-boom. The flight instructor reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation. The automated weather observation station located on the airport reported that, about the time of the accident, the wind was variable at 4 knots.

Aircraft

Registration
N369PA
Reported as
Guimbal Cabri (G2)
Category
Helicopter
Serial number
1109
Built
2015
Airframe hours
1,839.8
Engine
Lycoming O-360-J2A, 145 horsepower, reciprocating
Damage
Substantial damage
Flight
Instructional · Part 91
Operator
D H Helicopter Inc
Registered owner
D H Helicopter Inc
Airworthiness certificate
Standard, Normal
Last inspection
100 hour · May 8, 2019
Departed
CPS · St Louis, IL
Destination
CPS · St. Louis, IL
Airport
CPS · St Louis Downtown, runway 30R, 5,301 × 75 ft, concrete
Equipment
Electronic multifunction display, Electronic primary flight display, ADS-B

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 · 2

As NTSB recorded them. NTSB leaves out names.

Role
Flight instructor
Age
32
Injuries
None
Certificates
Flight instructor, Commercial
Instrument ratings
Helicopter
Medical
Class 2, Without waivers/limitations
Last flight review
August 27, 2018
Seat
Left
Flight hours
653 total · 425 in this make and model · 545 as pilot in command · 135 in the last 90 days · 32 in the last 30 days · 1 in the last 24 hours
Role
Student pilot
Age
27
Injuries
None
Certificate
Student
Medical
Class 2, Without waivers/limitations
Seat
Right
Flight hours
62 total · 62 in this make and model · 11 as pilot in command

Weather

Conditions
Visual (VMC) · Day
Visibility
10 statute miles
Temperature
79 °F, dew point 70 °F
Altimeter
30.05 inHg
Observed at
KCPS

Docket · 3

The files NTSB released with the investigation on July 18, 2019, on NTSB’s docket system: statements, records, photos and specialists’ reports. 1.5 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.