# NTSB CHI90DCD02: Bell 47G-2, N90529, Wall Lake, IA, August 26, 1990 - Type: NTSB accident investigation - Classification: Accident · No injuries · Final report - Date: August 25, 1990, 19:40 local (Aug 26, 1990, 00:40 UTC) - Place: Wall Lake, IA - Coordinates: 42.260021, -95.090148 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.2600&lon=-95.0901&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 14, 1992 - Report: Approved by Office Director - NTSB case key (mKey): 14437 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI90DCD02 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/14437/pdf - Page: https://openairdocs.org/ntsb/CHI90DCD02 ## Probable cause THE FAILURE OF THE PILOT TO MAINTAIN ROTOR RPM DURING TAKEOFF. THE HIGH DENSITY ALTITUDE AND UPHILL TERRAIN WERE FACTORS. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight collision with terrain/water, takeoff - weather condition - high density altitude (contributing factor) - terrain condition - rising (contributing factor) - object - fence - rotor rpm - not maintained, pilot in command (cause) ## Analysis AFTER REFUELING & RELOADING THE HELICOPTER WITH A SPRAY SOLUTION AT A FIELD SITE, A TAKEOFF WAS INITIATED IN CALM WIND CONDITIONS. THE PLT RPRTD THAT THE LOCATION REQUIRED HIM TO TAKE OFF UPSLOPE. HE STATED THAT THE RPM DROPPED SLIGHTLY, BUT REMAINED IN THE GREEN ARC DURING THE UPSLOPE PORTION OF THE TAKEOFF. AS THE HELICOPTER CROSSED A FENCE & THE TERRAIN STARTED SLOPING DOWNHILL, THE HELICOPTER FLEW OUT OF GROUND EFFECT. THE PLT RPRTD HE LEVELED THE HELICOPTER, THEN BEGAN A SLIGHT DSCNT TO INCREASE RPM & AIRSPEED. HOWEVER, THE ROTOR RPM DECAYED & JUST BEFORE TOUCHDOWN, THE HELICOPTER YAWED 90 DEG TO THE RIGHT. AFTER TOUCHDOWN, THE HELICOPTER ROLLED OVER. DENSITY ALT WAS ESTD TO BE 3216 FT. ## Aircraft - Registration: [N90529](https://openairdocs.org/aircraft/N90529), registered now, S/N NT1958-1, built 1974 (OpenAirDocs) - Reported make and model: BELL 47G-2 - Registry model: [Bell-Tellijohn 47G-2](https://openairdocs.org/model/bell-tellijohn-47g-2) (registry code 1181013) (OpenAirDocs) - Registry engine: [Lycoming 0-435A2-KSER](https://openairdocs.org/engine/lycoming-0-435a2-kser) (registry code 41518, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: NT1958-1 - Airframe hours: 1061 - Engines: LYCOMING VO-435-A1F 270 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Registered owner: Northland Helicopters, Inc. - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, December 18, 1989, 142 hours before - Departed: NONE ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 44; commercial; airplane ratings: single-engine land, single-engine sea; instrument ratings: helicopter; medical: class 2, valid medical--w/ waivers/lim; seat: front; flight hours: 2,000 total, 75 in this make and model, 1,500 as pilot in command, 75 in the last 90 days, 30 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 1 statute miles - Temperature: 86 °F, dew point 77 °F - Altimeter: 29.00 inHg - Observed at: FOD, 41 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 19900825036029A](https://openairdocs.org/incident/19900825036029A), Aug 25, 1990: Bell 47G2, Wall Lake, IA, Substantial damage. Took off up hill then lost lift on downslope leaving ground effect. ## Other investigations on N90529 (3) 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 CEN17LA232](https://openairdocs.org/ntsb/CEN17LA232), Jun 15, 2017: Bell-Tellijohn 47G (N90529), Hastings, MN, substantial damage. Probable cause: The pilot's failure to maintain helicopter control for reasons that could not be determined because postaccident examination of the helicopter did not reveal any preimpact mechanical malfunctions or… - [NTSB CHI98LA291](https://openairdocs.org/ntsb/CHI98LA291), Jul 30, 1998: Bell 47G-2 (N90529), Plainview, MN, substantial damage. Probable cause: The pilot's not achieving the proper descent rate prior to touchdown. A factor related to the accident was fuel starvation due to a low fuel level. - [NTSB MKC76FCD31](https://openairdocs.org/ntsb/MKC76FCD31), Mar 17, 1976: Bell 47G-2 (N90529), Dows, IA, destroyed 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.