# NTSB SEA01LA003: Enstrom F-28F, N223RS, Twin Falls, ID, October 10, 2000 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: October 10, 2000, 08:30 local (14:30 UTC) - Place: Twin Falls, ID - Coordinates: 42.410942, -114.589126 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.4109&lon=-114.5891&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report May 18, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 50429 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA01LA003 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/50429/pdf - Page: https://openairdocs.org/ntsb/SEA01LA003 ## Probable cause The pilot's failure to maintain adequate rotor rpm. Unsuitable terrain was selected for the maintenance test flight operation. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight collision with terrain/water, landing - rotor rpm - not maintained, pilot in command (cause) - unsuitable terrain or takeoff/landing/taxi area - selected, pilot in command (contributing factor) ## Analysis The pilot reported that during a maintenance test flight to check controls, collective pitch position, throttle positioning, and rpm correlation control entering an autorotation, he entered the autorotation with low rpm. When the pilot corrected with collective pitch, the correlator over responded, resulting in an rpm overspeed. The pilot closed the throttle and increased the collective, however, the rpm dropped and the pilot had to complete the autorotation to touch down on rough terrain. So as not to have any forward speed at touch down, and fearing that the helicopter might roll over, the pilot anticipated a hard flare to stop the forward speed. Just prior to touch down, the tailrotor contacted the ground, and the tailrotor gearbox separated from the tail boom. The helicopter yawed to the right about 150 degrees before the pilot was able to level the helicopter, arrest the yaw and land without further incident. ## Factual narrative On October 10, 2000, about 0830 mountain daylight time, an Enstrom F-28F, N223RS, registered to and operated by Reeder & Haye Aircraft as a 14 CFR Part 91 maintenance test flight, landed hard in a field located about five miles southeast of Twin Falls, Idaho. Visual meteorological conditions prevailed at the time and no flight plan was filed for the local flight. The commercial pilot and passenger were not injured. The flight originated from Twin Falls about 30 minutes prior to the accident. During a telephone interview and subsequent written statement, the pilot reported that this was a maintenance test flight to check controls, collective pitch position, throttle positioning, and rpm correlation control entering an autorotation. The pilot stated that during the first autorotation, the rpm was high and the correlator wanted to overspeed. During the second autorotation, the rpm was low and when the pilot corrected with collective pitch, the correlator over responded, resulting in an rpm overspeed. The pilot closed the throttle and increased the collective, however, the rpm dropped and the pilot had to complete the autorotation to touch down on rough terrain. So as not to have any forward speed at touch down, and fearing that the helicopter might roll over, the pilot anticipated a hard flare to stop the forward speed. Just prior to touch down, the tailrotor contacted the ground, and the tailrotor gearbox separated from the tail boom. The helicopter yawed to the right about 150 degrees before the pilot was able to level the helicopter, stop the yaw and land without further incident. ## Aircraft - Registration: [N223RS](https://openairdocs.org/aircraft/N223RS), registered now, S/N 748, built 1987 (OpenAirDocs) - Reported make and model: Enstrom F-28F - Registry model: [Enstrom F-28F](https://openairdocs.org/model/enstrom-f-28f) (registry code 3300412) (OpenAirDocs) - Registry engine: [Lycoming HIO-360 series](https://openairdocs.org/engine/lycoming-hio-360-series) (registry code 41524, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 748 - Airframe hours: 2949 - Engines: Lycoming HIO-360 225 horsepower reciprocating - Damage: Substantial damage - Flight: Part 91 - Registered owner: Reeder & Haye Aircraft - Airworthiness certificate: Standard, Normal - Last inspection: Annual, October 5, 2000, 2 hours before - Departed: TWF, TWIN FALLS, ID ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 40; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 1,599 total, 196 in this make and model, 1,398 as pilot in command, 132 in the last 90 days, 70 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 360° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: 10,000 ft broken - Temperature: 46 °F, dew point 46 °F - Altimeter: 29.00 inHg - Observed at: TWF, 5 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 20001010018969A](https://openairdocs.org/incident/20001010018969A), Oct 10, 2000: Enstrm F28F, Twin Falls, ID, No damage. (-23)These flights were maintenance test flights. During the third auto-rotation of N233RS, when the collective was dropped. The engine throttle rolled off too… 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.