# NTSB CHI98LA292: Bell M74L, N1001N, Grand Forks, ND, July 31, 1998 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 31, 1998, 18:30 local (23:30 UTC) - Place: Grand Forks, ND - Coordinates: 47.909114, -97.069267 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.9091&lon=-97.0693&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report January 28, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 43592 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI98LA292 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/43592/pdf - Page: https://openairdocs.org/ntsb/CHI98LA292 ## Probable cause The worn rotor clutch shoes, and subsequent loss of main rotor rpm. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, approach - vfr pattern - downwind - fuel system,pump - corroded - fuel system,injector - corroded - maintenance,annual inspection - inadequate, other maintenance personnel - Forced landing, descent - emergency - In flight collision with terrain/water, descent - emergency - airspeed - altitude - Roll over, landing - flare/touchdown ## Analysis The pilot refilled the hopper and was in the middle of a swath run when the engine rpm increased and the main rotor rpm decreased. The helicopter impacted the terrain during the forced landing and rolled over. A teardown of the transmission was performed. The inspection revealed that the clutch shoes were worn to the point that there was metal to metal contacted between the clutch shoe and the drum. ## Factual narrative On July 31, 1998, at 1830 central daylight time (cdt), a Bell M74-L (a modified Bell 47), N1001N, registered to Northland Helicopters, Inc., of Stacyville, North Dakota, was substantially damaged during a forced landing. The pilot reported a total loss of main rotor rom with an increase of engine rpm. The loss of rotor rpm occurred during a spray run. The commercial pilot was not injured. The 14 CFR Part 137 aerial application flight was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The flight departed near the accident site. The pilot reported that he was operating the helicopter from a trailer near the accident site. He had just refilled the hopper and was in the middle of a swath run when the engine rpm increased and the main rotor rpm decreased. The helicopter impacted the terrain during the forced landing and rolled over. A teardown of the transmission was performed which was overseen by an inspector from the Federal Aviation Administration Minneapolis, Minnesota, Flight Standards District Office. The inspection revealed that the clutch shoes were worn to the point that there was metal to metal contacted between the clutch shoe and the drum. ## Aircraft - Registration: [N1001N](https://openairdocs.org/deregistered/N1001N-2018-05-30), registration cancelled 2018-05-30, S/N 81-037, built 1981 (OpenAirDocs) - Reported make and model: Bell M74L - Registry model: [Texas Helicopter M74L](https://openairdocs.org/model/texas-helicopter-m74l) (registry code 8930107) (OpenAirDocs) - Registry engine: [Lycoming VO-435 series](https://openairdocs.org/engine/lycoming-vo-435-series) (registry code 41525, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 81-037 - Airframe hours: 3766 - Engines: Lycoming VO-435 265 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Registered owner: Northland Helicopters, Inc. - Airworthiness certificate: Special, Restricted (Special) - Last inspection: 100 hour, December 20, 1997, 107 hours before ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 45; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter; medical: class 2, valid medical--w/ waivers/lim; seat: center; flight hours: 7,000 total, 250 in this make and model, 6,800 as pilot in command, 122 in the last 90 days, 15 in the last 30 days, 6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 140° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: 7,000 ft broken - Temperature: 77 °F, dew point 52 °F - Altimeter: 30.00 inHg - Observed at: GFK ## 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 19980731019139A](https://openairdocs.org/incident/19980731019139A), Jul 31, 1998: Grand Forks, ND, Substantial damage. (-23) On July 31, 1998, at 1930 central daylight time (CDT), a bell 47, N1001N, operated by a commercial pilot, sustained substantial damage during a forced… ## Other investigations on N1001N (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 ERA14FA066](https://openairdocs.org/ntsb/ERA14FA066), Dec 6, 2013: Texas Helicopter M74L (N1001N), Sebring, FL, destroyed, 1 fatal. Probable cause: A partial loss of engine power as a result of contamination of the engine’s fuel supply, and the pilot’s impaired performance due to his use of diphenhydramine, which resulted in his inability to… 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.