# NTSB DEN99LA173: Enstrom 280C, N84DH, Longmont, CO, September 30, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 29, 1999, 18:40 local (Sep 30, 1999, 00:40 UTC) - Place: Longmont, CO - Coordinates: 40.169178, -105.109924 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.1692&lon=-105.1099&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report June 22, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 47476 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN99LA173 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/47476/pdf - Page: https://openairdocs.org/ntsb/DEN99LA173 ## Probable cause An inaccurate touchdown during a full autorotation, which resulted in main rotor flex which cut off the tail boom. Factors were the pilot's lack of total experience in helicopters and high density altitude. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power, approach - reason for occurrence undetermined - Forced landing, descent - emergency - weather condition - high density altitude (contributing factor) - autorotation - performed, pilot in command - touchdown - inaccurate, pilot in command (cause) - lack of total experience in kind of aircraft, pilot in command (contributing factor) ## Analysis While practicing autorotations, the pilot, who was a commercial pilot in single and multiengine aircraft but a student pilot in helicopters, experienced a loss of engine power for unknown reasons. During the full autorotation, which was necessitated by the power loss, the landing was hard and resulted in main rotor flex, which cut off the tail boom. Density altitude at the time was 9,000 feet. ## Factual narrative On September 29, 1999, at 1840 mountain daylight time, an Enstrom 280C helicopter, N84DH, sustained substantial damage during a hard landing, after a practice autorotation, at Vance Brand Airport, Longmont, Colorado. The non-helicopter rated commercial pilot and sole occupant was not injured. The flight was a local solo instructional flight operating under Title 14 CFR Part 91 and no flight plan was filed. Visual meteorological conditions prevailed. According to the pilot, he was practicing autorotations and the engine lost power while in an autorotation. During the ensuing hard landing, the main rotor flexed and cut of the tail boom. Density altitude at the time was 9,000 feet. The pilot reported that he had 40 hours flight experience in helicopters and that all his helicopter experience was in the Enstrom 280C. He said he had 11 hours of helicopter experience in the 30 days prior to the accident, and 40 hours in the preceding 90 days. No evidence was developed during the investigation as to the reason for the power loss. ## Aircraft - Registration: [N84DH](https://openairdocs.org/aircraft/N84DH), registered now, S/N 1055, built 1976 (OpenAirDocs) - Reported make and model: Enstrom 280C - Registry model: [Enstrom Helicopter 280C](https://openairdocs.org/model/enstrom-helicopter-280c) (registry code 3300505) (OpenAirDocs) - Registry engine: [Lycoming HI0-360 series](https://openairdocs.org/engine/lycoming-hi0-360-series) (registry code 41553, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 1055 - Airframe hours: 688 - Engines: Lycoming HIO-360-E1AD 205 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Jeffery J. Sands - Registered owner: Mile High Skydivers, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, April 5, 1999, 12 hours before - Departed: 2V2 - Airport: 2V2, Vance Brand, runway 29, 4,800 × 75 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 2,127 total, 40 in this make and model, 2,004 as pilot in command, 91 in the last 90 days, 30 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 250° at 6 knots - Visibility: 40 statute miles - Lowest ceiling: none - Temperature: 97 °F, dew point 86 °F - Altimeter: 30.00 inHg - Observed at: BJC, 15 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 19990929047519A](https://openairdocs.org/incident/19990929047519A), Sep 29, 1999: Enstrm 280C, Longmont, CO, Substantial damage. (.4) While practicing autorotations, the pilot, who was a commercial pilot in single and multiengine aircraft but a student pilot in helicopters, experienced a… 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.