# NTSB CHI95LA003: Bell 47G2, N5193B, Decatur, IL, October 3, 1994 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: October 3, 1994, 15:20 local (20:20 UTC) - Place: Decatur, IL - Location: 39.8403° N, 88.9548° W: Placed by OpenAirDocs: center of Decatur, IL, within about 6 miles (OpenAirDocs) - Nearby events: https://openairdocs.org/map.md?lat=39.8403&lon=-88.9548&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 2 minor - Status: Completed, report June 19, 1995 - Report: Approved by Office Director - NTSB case key (mKey): 9770 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI95LA003 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/9770/pdf - Page: https://openairdocs.org/ntsb/CHI95LA003 ## Probable cause the failure of the roller springs in the freewheeling unit of the transmission which caused the unit to disengage. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, climb - rotor drive system,freewheeling sprag unit - disengaged (cause) - rotor drive system,freewheeling sprag unit - failure (cause) - Forced landing, descent - emergency - Hard landing, landing - flare/touchdown ## Analysis THE PILOT STATED THAT AFTER COMPLETING A LINE PATROL, HE MADE A CLIMBING LEFT TURN TO RETURN TO THE AIRPORT. AT APPROXIMATELY 50 TO 75 FEET ABOVE THE GROUND, THE PILOT HEARD A STRANGE SOUND, THE ENGINE BEGAN TO OVERSPEED, AND THE HELICOPTER BEGAN TO DESCEND. HE LOWERED THE COLLECTIVE AND PLACED THE HELICOPTER INTO AN AUTOROTATION TO MAKE A FORCED LANDING ON A ROAD. THE HELICOPTER TOUCHED DOWN HARD AND WAS DAMAGED. A POSTACCIDENT INVESTIGATION REVEALED 13 OF 32 ROLLER SPRINGS INSIDE THE FREEWHEELING UNIT OF THE TRANSMISSION WERE BROKEN CAUSING THE UNIT TO BECOME DISENGAGED. ## Factual narrative On October 3, 1994, at 1520 central daylight time, a Bell 47G2, N5193B, sustained substantial damage following a loss of engine power and subsequent forced landing on a road near Decatur, Illinois. The commercial pilot and passenger reported minor injuries. The local 14 CFR Part 91 flight operated in visual meteorological conditions without a flight plan. The pilot stated he began a climbing left turn to return to Decatur Airport after completing a line patrol. At approximately 50 to 75 feet above the ground, the pilot stated he heard a strange sound, the engine began to overspeed, and the helicopter began to descend. He lowered the collective and placed the helicopter into an autorotation to make a forced landing. The helicopter landed hard on a road. The helicopter logbook shows the last inspection was a 100 hour inspection performed on September 23, 1994. The helicopter has logged 33 hours since the inspection. A postaccident examination of the engine and transmission revealed 13 of the 32 roller springs were broken inside the freewheeling unit of the transmission. Eight of the 13 broken springs were located in the 270 degree to 360 degree quadrant; a total of 10 were located in the 180 degree to 360 degree quadrant; and the remaining three were dispersed throughout the one degree to 180 degree quadrant. All pieces of the broken springs were self-contained within the freewheeling unit. There were no discrepancies noted to any other component. ## Aircraft - Registration: [N5193B](https://openairdocs.org/deregistered/N5193B-2008-03-03), registration cancelled 2008-03-03, S/N 2174, built 1958 (OpenAirDocs) - Reported make and model: BELL 47G2 - Registry model: [Bell 47G-2](https://openairdocs.org/model/bell-47g-2) (registry code 1181008) (OpenAirDocs) - Registry engine: [Lycoming VO-435 series](https://openairdocs.org/engine/lycoming-vo-435-series) (registry code 41525, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 2174 - Airframe hours: 6413 - Engines: LYCOMING VO-435-A1F 150 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial observation, Part 91 - Registered owner: Fostaire Helicopters - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, September 23, 1994, 33 hours before - Departed: DEC, IL ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 30; commercial, flight instructor; instrument ratings: helicopter; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 3,500 total, 3,450 as pilot in command, 100 in the last 90 days, 40 in the last 30 days, 5 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 80° at 11 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 70 °F ## 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 19941003032719A](https://openairdocs.org/incident/19941003032719A), Oct 3, 1994: Bell 47G2, Decatur, IL, Substantial damage. Lost power en route. Crash landed. No further info. Cause power loss not addressed. Damage indicates low rotor RPM. ## Other investigations on N5193B (6) 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 FTW02LA264](https://openairdocs.org/ntsb/FTW02LA264), Sep 25, 2002: Bell 47G-2 (N5193B), Edmondson, AR, destroyed, 1 fatal. Probable cause: The pilot's failure to maintain clearance from the high voltage power lines. - [NTSB NYC70DFM16](https://openairdocs.org/ntsb/NYC70DFM16), Jun 8, 1970: Bell 47G2 (N5193B), Danbury, CT, substantial damage - [NTSB LAX70F0025](https://openairdocs.org/ntsb/LAX70F0025), Sep 4, 1968: Bell 47G-2 (N5193B), Hollywood, CA, destroyed, 2 fatal - [NTSB LAX68A0022](https://openairdocs.org/ntsb/LAX68A0022), Aug 18, 1967: Bell 47G-2 (N5193B), Camarillo, CA, substantial damage - [NTSB UNK64X4172](https://openairdocs.org/ntsb/UNK64X4172), Sep 26, 1964: Bell 47G2 (N5193B), Pomona, CA, substantial damage - [NTSB UNK64X1672](https://openairdocs.org/ntsb/UNK64X1672), May 8, 1964: Bell 47G2 (N5193B), Glendora, CA, substantial damage 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.