# NTSB CEN13LA463: Bell 47G-3B-1, N83702, Vinton, IA, August 6, 2013 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 6, 2013, 10:30 local (15:30 UTC) - Place: Vinton, IA - Coordinates: 42.176666, -91.980834 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.1767&lon=-91.9808&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report January 30, 2014 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Scott's Helicopter Services, FAA - NTSB case key (mKey): 87697 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN13LA463 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/87697/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=87697 - Page: https://openairdocs.org/ntsb/CEN13LA463 ## Probable cause The pilot's operation of the helicopter at high gross weight and high density altitude while still in ground effect, which reduced the efficiency of the rotor system and the amount of lift produced, which resulted in a collision with terrain. Contributing to the accident was the pilot's decision to continue the flight after the first indication of reduced performance. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Aircraft](https://openairdocs.org/ntsb-findings/01060000): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Bell 47G-3B-1, 1 case](https://openairdocs.org/ntsb-findings/01060000/cases.md?model=1181028), [All aircraft, 63 cases](https://openairdocs.org/ntsb-findings/01060000/cases.md) - [Action: incorrect action performance](https://openairdocs.org/ntsb-findings/02041015): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Bell 47G-3B-1, 2 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md?model=1181028), [All aircraft, 1,386 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md) - [Info processing/decision: decision making/judgment](https://openairdocs.org/ntsb-findings/02041520): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Bell 47G-3B-1, 2 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md?model=1181028), [All aircraft, 3,098 cases](https://openairdocs.org/ntsb-findings/02041520/cases.md) - [Performance/control parameters](https://openairdocs.org/ntsb-findings/01062000): Aircraft › Aircraft oper/perf/capability · Capability exceeded (probable cause); cases with it: [Bell 47G-3B-1, 3 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md?model=1181028), [All aircraft, 1,269 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Takeoff: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Bell 47G-3B-1, 5 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=1181028), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Takeoff: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Bell 47G-3B-1, 10 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1181028), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis After reloading the helicopter with agricultural spray product, the pilot flew the helicopter off of the loading truck bed for the aerial application flight. Shortly after takeoff, while operating the helicopter at an altitude of about 10 feet above the ground, the pilot noted a decrease in rotor rpm and made a precautionary landing in tall grass. When he noted no anomalies after the landing, the pilot decided to continue the flight. He took off in the helicopter again and flew for about 100 yards before he again noted a decrease in rotor rpm. The helicopter descended and struck the ground with the tail low, which resulted in substantial damage to the tail rotor and tailboom. An examination of the airframe and engine did not reveal any mechanical malfunctions or failures that would have precluded normal operation. The helicopter was operating above tall grass and crops while still in ground effect, which likely reduced the efficiency of the rotor system and decreased the amount of lift produced as compared to operating over bare ground. In addition, the helicopter was loaded to within 16 pounds of its maximum gross weight and was operating at a density altitude of about 2,800 feet, which likely also contributed to the decreased performance of the helicopter. ## Factual narrative Video Footage The flight was being recorded by a hand held recording device. A review of the video footage revealed that the pilot flew the helicopter off of the truck bed, flew about 50 yards while maintaining an altitude of about 10 feet above the ground (AGL), and then landed in tall grass. Shortly after, the helicopter lifted off again and flew over a bean field for about 100 yards. The helicopter descended and the pilot executed a forced landing straight ahead in the bean field. The helicopter struck the ground with the tail low, which resulted in damage to the tail boom and tail rotor. The video footage was reviewed by a representative of Scott's Helicopter Services, the helicopter's type-certificate holder and a party to the investigation. He noted that when the helicopter first settled in the grass, the pilot should have assessed the weight and balance and possibly off-loaded applicant. The flight path of the second attempt, the pilot did not fly along the road, but chose a flight path over standing crops. The engine sounds were normal during the takeoff but then sounded as though the engine was "lugged down" as the takeoff continued. Weight and Balance and Density Altitude Calculations According the responding Federal Aviation Administration (FAA) inspector, the weight and balance calculations revealed that the helicopter was loaded 16 pounds under the maximum gross weight. The density altitude at the time of the accident was calculated about 2,800 feet. Helicopter Flying Handbook – FAA-H-8083-21A Chapter 2 "Aerodynamics" defines "In Ground Effect (IGE)" as the increased efficiency of the rotor system caused by interference of the airflow when near the ground. The air pressure or density is increased, which acts to decrease the downward velocity of air. Ground effect permits relative wind to be more horizontal, lift vector to be more vertical, and induced drag to be reduced. These conditions allow the rotor system to be more efficient. Maximum ground effect is achieved when hovering over smooth hard surfaces. When hovering over surfaces as tall grass, trees, bushes, rough terrain, and water, maximum ground effect is reduced. Rotor efficiency is increased by ground effect to a height of about one rotor diameter (measured from the ground to the rotor disk) for most helicopters. An excerpt from Chapter 7 "Helicopter Performance" states: As density altitude increases, more power is required to hover. At some point, the power required is equal to the power available. This establishes the hovering ceiling under the existing conditions. Any adjustment to the gross weight by varying fuel, payload, or both, affects the hovering ceiling. The heavier the gross weight, the lower the hovering ceiling. The Bell 47G-3B-1 four-seat, single engine, agricultural equipped helicopter was manufactured in 1966. A review of the maintenance logbooks revealed that an annual inspection was completed on July 17, 2013. According to the pilot, the helicopteraccumulated 77 hours of total flight time and 41 hours since the last annual inspection. The helicopter had a maximum gross weight of 2,850 pounds. On August 6, 2013, about 1030 central daylight time, a Bell 47G-3B-1 helicopter, N83702, made a forced landing after experiencing a decrease in engine performance near Vinton, Iowa. The commercial pilot, who was the sole occupant, was not injured. The helicopter sustained substantial damage. The helicopter was registered to Benedict Fluke and operated by Speas Aviation Inc., under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed for the flight which operated without a flight plan. The local flight was departing at the time of the accident. In a statement provided by the pilot, the helicopter was loaded with 60 gallons of spray product. When the helicopter lifted off of the truck bed, the pilot noted that the rotor rpm decreased so he landed. The pilot then decided to lift off from the ground and did not detect any anomalies with the helicopter. He flew the helicopter forward at 20 feet AGL and 20-25 miles per hour groundspeed over a bean field. The rotor rpm decreased again so the pilot elected to land in the field. The helicopter struck the ground with the tail low, which resulted in damage to the tail rotor and tail boom. At 1035, an automated weather report at the Vinton Veterens Memorial Airpark, which was about 10 miles northeast of the accident, reported wind from 240 degrees at 3 knots, 10 miles visibility, clear skies, temperature 27 degrees Celsius (C), dew point 22 degrees C, and a barometric pressure of 29.89 inches of mercury. The pilot reported that the wind was variable and favoring 180 degrees at 3 to 5 knots. The pilot, age 46, held a commercial pilot certificate for a helicopter and an instrument helicopter rating. He also held a flight instructor certificate for helicopters. The pilot reported having accumulated 1,352 total flight hours, of which 1,315 hours were in a helicopter, and 210 hours were in the make and model of the accident helicopter. He had accumulated 41 hours in the accident helicopter in the preceding 30 days. The helicopter came to rest upright in a bean field. The main rotor blades and tail rotor blades impacted the ground and sustained damage. The tail boom was separated from the helicopter. A postaccident examination was conducted by the FAA inspector. The examination did not reveal any mechanical malfunctions or failures with the airframe or engine that would have precluded normal operation. ## Aircraft - Registration: [N83702](https://openairdocs.org/deregistered/N83702-2017-12-01), registration cancelled 2017-12-01, S/N 66-8093, built 1966 (OpenAirDocs) - Reported make and model: BELL 47G-3B-1 - Registry model: [Bell 47G-3B-1](https://openairdocs.org/model/bell-47g-3b-1) (registry code 1181028) (OpenAirDocs) - Registry engine: [Lycoming TVO-435-B1A](https://openairdocs.org/engine/lycoming-tvo-435-b1a) (registry code 41938, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 66-8093 - Year built: 1966 - Airframe hours: 77 - Engines: LYCOMING TVO-435-B1A 270 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Speas Aviation Inc - Registered owner: Benedict Fluke - Airworthiness certificate: Special, Restricted (Special) - Departed: Vinton, IA - Destination: Vinton, IA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; injuries: none; flight instructor, commercial; instrument ratings: helicopter; medical: class 2, with waivers/limitations; last flight review April 16, 2013; seat: left; restraint: lap only; flight hours: 1,347 total, 210 in this make and model, 548 as pilot in command, 41 in the last 90 days, 41 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 230° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 81 °F, dew point 70 °F - Altimeter: 29.88 inHg - Observed at: KVTI, 10 nm away ## 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 20130806019749A](https://openairdocs.org/incident/20130806019749A), Aug 6, 2013: Bell 47G-3B-1, Vinton, IA, Substantial damage. Pilot was attempting takeoff for aerial application when aircraft started to settle back to ground and pilot made emergency landing in bean field hitting tail… ## Other investigations on N83702 (1) 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. - [NTSB DEN04LA047](https://openairdocs.org/ntsb/DEN04LA047), Feb 13, 2004: Bell 47G-3B-1 (N83702), Kremmling, CO, substantial damage. Probable cause: the pilot's failure to attain landing flare and maintain adequate rotor rpm. ## Docket (10 files) The files NTSB released with the investigation on December 18, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=87697. 8.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 810 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399273&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Reports from Parties to the Investigation (item 2, .PDF, 205 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40402340&FileExtension=.PDF&FileName=Reports%20from%20Parties%20to%20the%20Investigation-Redacted.PDF - Other Pertinent Forms and Reports - Weight and Balance (item 3, .PDF, 11 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399267&FileExtension=.PDF&FileName=Other%20Pertinent%20Forms%20and%20Reports%20-%20Weight%20and%20Balance-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 4, .PDF, 289 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399274&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 5, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40403371&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - Weather Reports and Records (item 6, .PDF, 24 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40399268&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records-Master.PDF - Video Still Shots - Entire Accident Sequence (item 7, .PDF, 993 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40403379&FileExtension=.PDF&FileName=Video%20Still%20Shots%20-%20Entire%20Accident%20Sequence-Master.PDF - Photo 1: Helicopter in bean field (item 8, .PDF, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40403372&FileExtension=.PDF&FileName=Photo%201%3A%20Helicopter%20in%20bean%20field-Master.PDF - Photo 2: Damaged tail rotor (item 9, .PDF, 2.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40403373&FileExtension=.PDF&FileName=Photo%202%3A%20Damaged%20tail%20rotor-Master.PDF - FAA-H-8083-21A - Helicopter Flying Handbook Excerpts (item 10, .PDF, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40403381&FileExtension=.PDF&FileName=FAA-H-8083-21A%20-%20Helicopter%20Flying%20Handbook%20Excerpts-Master.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.