# NTSB ANC09LA098: Robinson Helicopter R44 II, N4186Y, Central, AK, September 7, 2009 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 6, 2009, 17:35 local (Sep 7, 2009, 01:35 UTC) - Place: Central, AK - Coordinates: 65.57389, -144.780838 - Nearby events: https://openairdocs.org/map.md?lat=65.5739&lon=-144.7808&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-VFR go-around: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: No injuries - Injuries: 3 uninjured - Status: Completed, report June 17, 2010 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: Federal Aviation Administration (Operations) - NTSB case key (mKey): 74733 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC09LA098 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74733/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74733 - Page: https://openairdocs.org/ntsb/ANC09LA098 ## Probable cause The pilot’s failure to maintain control of the helicopter after an in-flight encounter with a downdraft while landing. Contributing to the accident was the pilot’s inadequate evaluation of wind conditions. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Aircraft capability: climb capability](https://openairdocs.org/ntsb-findings/01061010): Aircraft › Aircraft oper/perf/capability · Capability exceeded (probable cause); cases with it: [Robinson Helicopter R44 II, 5 cases](https://openairdocs.org/ntsb-findings/01061010/cases.md?model=7640122), [All aircraft, 183 cases](https://openairdocs.org/ntsb-findings/01061010/cases.md) - [Planning/preparation](https://openairdocs.org/ntsb-findings/02061000): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Robinson Helicopter R44 II, 3 cases](https://openairdocs.org/ntsb-findings/02061000/cases.md?model=7640122), [All aircraft, 113 cases](https://openairdocs.org/ntsb-findings/02061000/cases.md) - [Wind: downdraft](https://openairdocs.org/ntsb-findings/03034035): Environmental issues › Conditions/weather/phenomena · Effect on operation; cases with it: [Robinson Helicopter R44 II, 4 cases](https://openairdocs.org/ntsb-findings/03034035/cases.md?model=7640122), [All aircraft, 178 cases](https://openairdocs.org/ntsb-findings/03034035/cases.md) - [Wind](https://openairdocs.org/ntsb-findings/03034000): Environmental issues › Conditions/weather/phenomena · Awareness of condition (probable cause); cases with it: [Robinson Helicopter R44 II, 2 cases](https://openairdocs.org/ntsb-findings/03034000/cases.md?model=7640122), [All aircraft, 110 cases](https://openairdocs.org/ntsb-findings/03034000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach: Other weather encounter](https://openairdocs.org/ntsb-events/400); cases with it: [Robinson Helicopter R44 II, 14 cases](https://openairdocs.org/ntsb-events/400/sequence.md?model=7640122), [All aircraft, 1,127 cases](https://openairdocs.org/ntsb-events/400/sequence.md) - [Approach-VFR go-around: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Robinson Helicopter R44 II, 74 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=7640122), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Uncontrolled descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Robinson Helicopter R44 II, 95 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=7640122), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The airline transport helicopter pilot reported that he was on a Title 14, CFR Part 135 passenger flight and was approaching a mountain ridge to drop off two technicians at a radio repeater site. Before beginning his approach, the pilot circled the site to determine the wind conditions, and then began his approach into a 10 knot wind. During the approach to the 5,657 foot level site, the pilot said he encountered a downdraft as the helicopter approached the site, and the helicopter descended below his anticipated approach path. He initiated a go-around, but the helicopter continued to descend, and landed hard, about 150 feet short and down slope of his intended touchdown point. During touchdown, the toes of the helicopter’s skids broke, and the helicopter rocked forward and aft, sustaining substantial damage to the right side of the tail boom. The pilot reported wind conditions on the ground as variable, gusting between 10 and 20 knots. In the pilot’s written statement to the NTSB, he reported that there were no preaccident mechanical problems with the helicopter. ## Factual narrative On September 6, 2009, about 1735 Alaska daylight time, a Robinson R44 II helicopter, N4186Y, sustained substantial damage during a hard landing while on approach to a mountain ridge, about 38 miles southeast of Central, Alaska. The helicopter was being operated by Alpine Air Alaska, Inc., Girdwood, Alaska, as a visual flight rules (VFR) on-demand charter flight, under the provisions of Title 14 Code of Federal Regulations (CFR) Part 135. The airline transport pilot and the two passengers were not injured. Visual meteorological conditions prevailed, and company flight following procedures were in effect. The flight departed the Fairbanks International Airport, Fairbanks, Alaska, about 1400, en route to various communication sites near Central. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on September 15, the pilot reported that the purpose of the flight was to transport two maintenance technicians to various mountaintop radio repeater sites in the area. He said that before beginning his approach to the 5,657 feet msl site, he circled the area to determine the wind conditions, and then planned his approach into a 10 knot headwind. During the approach to the treeless, tundra and rock-covered site, the pilot said he encountered a strong downdraft, and the helicopter began to descend below his anticipated approach path. He initiated a go-around, but the helicopter continued to descend, and it landed hard, about 150 feet short and down slope of his intended touchdown point. During touchdown, the toes of the helicopter’s skids broke, and the helicopter rocked forward and aft. The helicopter sustained substantial damage to the right side of the tail boom. The pilot characterized wind conditions on the ground as variable, gusting between 10 and 20 knots. In the pilot’s written statement to the NTSB he indicated that there were no preaccident mechanical problems with the helicopter. Additionally, he recommended relocating the landing site to an area above the ridge to minimize the exposure to downdrafts, and to install a functioning windsock. During a telephone conversation with the NTSB IIC on April 2, 2010, a representative from Alpine Air reported that the owner of the remote radio repeater site recently installed a new windsock, and is considering relocating the existing landing site. ## Aircraft - Registration: [N4186Y](https://openairdocs.org/aircraft/N4186Y), registered now, S/N 12533, built 2008 (OpenAirDocs) - Reported make and model: ROBINSON HELICOPTER COMPANY R44 II - Registry model: [Robinson Helicopter R44 II](https://openairdocs.org/model/robinson-helicopter-r44-ii) (registry code 7640122) (OpenAirDocs) - Registry engine: [Lycoming IO-540-AE1A5](https://openairdocs.org/engine/lycoming-io-540-ae1a5) (registry code 41899, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 12533 - Airframe hours: 487 - Engines: LYCOMING IO-540-AE1A5 260 horsepower reciprocating - Damage: Substantial damage - Flight: Part 135 - Operator: Alpine Air Alaska Inc - Registered owner: Alpine Air Alaska Inc - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, August 9, 2009, 41 hours before - Departed: FAI, Fairbanks, AK - Destination: Central, AK - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 40; injuries: none; airline transport, flight instructor; airplane ratings: single-engine land, single-engine sea, multi-engine land; instrument ratings: helicopter, airplane; medical: class 1, without waivers/limitations; seat: right; flight hours: 2,408 total, 892 in this make and model, 169 in the last 90 days, 38 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 10 knots, gusting 20 - Visibility: 20 statute miles - Lowest ceiling: 2,000 ft broken - Temperature: 41 °F - Altimeter: 29.60 inHg ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20090906049319A](https://openairdocs.org/incident/20090906049319A), Sep 6, 2009: Robinson He R44 II, Central, AK, Substantial damage. Airman stated that on short final to a remote landing area he encountered low level windshear. He initially attempted a go-around but due to the tail wind… ## Docket (1 files) The files NTSB released with the investigation on April 15, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74733. 1.0 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40328519&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.