WPR09TA277

NTSB accident investigation · Hughes OH-6A · Benson, AZ · June 4, 2009

Accident · No injuriesFinal report
Date
June 4, 2009, 08:50 local (15:50 UTC)
Place
Benson, AZ
Injuries
2 uninjured
Damage
Substantial damage
Phase of flight
Landing
Aircraft
N6641DHughes OH-6A
Defining event
Landing-flare/touchdown: Hard landing
Weather
Visual (VMC) · Day
Status
Completed · report November 9, 2009
Report
Approved by Office Director
NTSB office
Western Pacific Region
Parties
Federal Avitation Administration
FAA report
20090604018059A
Case key
73967

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 under instruction's inadequate autorotation technique and the instructor pilot’s delayed remedial action to arrest the rate of descent of the helicopter while in an autorotation flare.

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.

Action: delayed actionPersonnel issues › Action/decision · Instructor/check pilotHughes OH-6A: 1 caseAll aircraft: 894 casesProbable cause
Use of equip/info: aircraft controlPersonnel issues › Task performance · PilotHughes OH-6A: 3 casesAll aircraft: 9,295 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 instructor pilot reported that they were practicing autorotations to the runway. During a straight-in autorotation at approximately 200 feet above ground level, the instructor called for an increase in throttle to bring rotor rpm into the normal operating range in preparation for landing. Between 200 feet and 100 feet agl, the instructor assisted the flying pilot with the throttle increase when he realized that the pilot had delayed throttle application. The flying pilot then initiated the flare at approximately 50 feet agl. The flying pilot leveled the helicopter and applied collective to slow the descent rate. Upon realizing that the descent rate had not been checked prior to beginning the flare, the instructor joined the flying pilot on the controls. The helicopter landed hard on the runway and bounced, rotated to the left of runway heading as it touched down a second time, resulting in the collapse of the right landing skid. The pilot reported that were no mechanical anomalies with the flight control systems.

Factual narrative

On June 4, 2009, at 0850 mountain standard time (MST), a Hughes OH-6A, N6641D, experienced a hard landing at Benson Municipal Airport, Benson, Arizona. The public-use flight was operated by U.S. Customs and Border Protection as a pilot training flight under the provisions of Title 14 of the Code of Federal Regulations, Part 91. Neither commercial pilot was injured, and the helicopter was substantially damaged. Visual conditions prevailed, and no flight plan had been filed. The flight originated at Tucson International Airport, Tucson, Arizona, at 0715. The instructor pilot reported that they were practicing autorotations to the runway. During a straight in autorotation at approximately 200 feet agl, the instructor called for an increase in throttle to bring rotor rpm into the normal operating range in preparation for landing. Between 200 feet and 100 feet agl the instructor assisted the flying pilot with the throttle increase when he realized that the pilot had delayed throttle application. The flying pilot initiated the flare at approximately 50 feet agl. The flying pilot leveled the helicopter and applied collective to slow the descent rate. Upon realizing that the descent rate had not been checked prior to beginning the flare, the instructor joined the flying pilot on the controls. The helicopter landed hard on the runway and bounced, rotated to the left of runway heading as it touched down a second time, resulting in the collapse of the right landing skid. The helicopter came to rest on the runway heading 150 degrees to the left of runway heading. Examination of the helicopter by a Federal Aviation Administration (FAA) inspector revealed structural damage to the right landing skid and the fuselage of the helicopter. The pilot indicated that there were no mechanical anomalies with the flight control systems prior to the flight. Weather conditions reported at Fort Huachuca, Arizona, at 0755 MST, 24 miles to south of the accident location, indicated that the wind was variable at 1 knot, and visibility was 50 miles with a ceiling of 20,000 feet.

Aircraft

Registration
N6641D
Reported as
Hughes OH-6A
Category
Helicopter
Serial number
66-07855
Airframe hours
6,141
Engine
Allison 250-C20B, 420 horsepower, turbo shaft
Damage
Substantial damage
Flight
Public aircraft - federal · Part 91
Operator
Dept of Homeland Security
Registered owner
Department Of Homeland Security
Last inspection
100 hour · May 6, 2009 · 45 hours before
Departed
KTUS · Tucson, AZ
Destination
E95 · Benson, AZ
Airport
E95 · Benson Municipal Airport, runway 10, 4,000 × 75 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 · 2

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
46
Injuries
None
Certificates
Commercial, Flight instructor
Airplane ratings
Multi-engine land, Single-engine land
Instrument ratings
Helicopter, Airplane
Medical
Class 1, Without waivers/limitations
Last flight review
May 15, 2009
Seat
Left
Flight hours
5,500 total · 990 in this make and model · 3,500 as pilot in command · 141 in the last 90 days · 38 in the last 30 days · 0 in the last 24 hours
Role
Co-pilot
Age
38
Injuries
None
Certificates
Commercial, Flight instructor
Airplane ratings
Single-engine land
Instrument ratings
Airplane, Helicopter
Medical
Class 2, Without waivers/limitations
Last flight review
April 3, 2009
Seat
Right
Flight hours
1,540 total · 208 in this make and model · 1,260 as pilot in command · 144 in the last 90 days · 69 in the last 30 days · 0 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
Variable at 1 knots
Visibility
50 statute miles
Lowest ceiling
200 ft broken
Temperature
84 °F, dew point 16 °F
Altimeter
30.12 inHg
Observed at
KFHU, 24 nm away

Docket · 3

The files NTSB released with the investigation on August 31, 2009, on NTSB’s docket system: statements, records, photos and specialists’ reports. 2.0 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.