# NTSB SEA99LA016: McDonnell Douglas MD-900, N977LF, Idaho City, ID, November 30, 1998 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: November 29, 1998, 17:56 local (Nov 30, 1998, 00:56 UTC) - Place: Idaho City, ID - Coordinates: 43.869174, -115.640373 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=43.8692&lon=-115.6404&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 4 uninjured - Status: Completed, report January 11, 2000 - Report: Approved by Office Director - NTSB case key (mKey): 45449 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA99LA016 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/45449/pdf - Page: https://openairdocs.org/ntsb/SEA99LA016 ## Probable cause The pilot-in-command's not obtaining/maintaining clearance with the unmarked transmission lines. Contributing factors were environmental (dusk) conditions, the transmission lines, and both the pilot-in-command and the ground personnel not identifying the existence of the hazardous condition (high wires). ## Analysis The McDonnell Douglas MD-900 medevac helicopter was dispatched to a car accident at a site characterized by high terrain and high trees. Prior to landing, the pilot requested information about wires and was advised by ground personnel that 'there were none.' Subsequent to landing, the pilot examined the landing site and proposed departure route for wires, and reportedly observed none. The departure from the site was conducted under dusk to dark night conditions. While climbing out vertically due to the narrow canyon conditions at the site, the helicopter struck unmarked transmission lines approximately 150 feet above ground. The pilot then determined that the helicopter was controllable and displayed no unusual flight characteristics, and chose to proceed to his destination. Post-flight examination revealed crazing of the windscreen and damage to four of the five main rotor blades requiring major repair/replacement. ## Factual narrative On November 29, 1998, approximately 1756 mountain standard time, a McDonnell Douglas MD-900 helicopter, N977LF, registered to Alvac, Inc., operated by Idaho Helicopters, Inc., and being flown by a commercial pilot, sustained substantial damage when it collided with unmarked transmission lines. The collision occurred during the initial climb immediately following takeoff approximately eight miles south-southwest of Idaho City, Idaho (refer to CHART I). The pilot, nurse, EMT, and patient were uninjured. Visual meteorological dusk to dark night conditions prevailed, and a company flight plan was in effect. The flight, which was an unscheduled medevac pickup of a car accident victim, was to have been operated under 14CFR135, and was destined for the St. Alphonsus hospital heliport, Boise, Idaho. The pilot reported that the helicopter was dispatched to the accident site and "prior to landing the ground crew was asked about wires and the[y] said there were none" and "no wires were observed by the front passenger crew member, pilot or ground personnel." He also reported that the approach to the landing site was steep with high trees and terrain, and that after landing he "took [a] flashlight and surveyed obstructions and looked for wires ahead in [the] direction of takeoff" with "none seen other than trees." He further reported that he "elected to do a vertical takeoff since due to the narrowness of the canyon" and that "the vertical takeoff was initiated and at approximately 150' I rotated forward and at approx[imately] 20 kts a loud noise similar to equipment falling in the back and a bright white light flashed." The pilot assessed the controllability of the helicopter and determined that there were no unusual vibrations or instrument readings, and an onboard crew member reported that "he had seen or thought we had hit wires." "Due to no adverse flight characteristics and all instruments reading normal and no safe landing area available" the pilot elected to continue to his destination. Post-flight examination revealed crazing of the windscreen and damage to four of the five main rotor blades requiring major repair/replacement. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight collision with object, climb - to cruise - light condition - dusk (contributing factor) - object - wire,transmission (contributing factor) - unsafe/hazardous condition warning - not identified, pilot in command (contributing factor) - terrain condition - high terrain - unsafe/hazardous condition warning - not identified, ground personnel (contributing factor) - object - tree(s) - clearance - not obtained/maintained, pilot in command (cause) ## Aircraft - Registration: N977LF (not matched to a registry record) - Reported make and model: McDonnell Douglas MD-900 - Category: Helicopter - Serial number: 900-00027 - Airframe hours: 1752 - Engines: P&W 206A 629 horsepower turbo shaft - Damage: Substantial damage - Flight: Part 135 - Operator: Idaho Helicopters, Inc. - Registered owner: Alvac, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Continuous airworthiness, November 16, 1998, 22 hours before - Destination: U56, BOISE, ID - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 63; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: right; flight hours: 19,275 total, 498 in this make and model, 19,000 as pilot in command, 105 in the last 90 days, 29 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Dusk - Wind: 100° at 14 knots - Visibility: 10 statute miles - Temperature: 43 °F, dew point 39 °F - Altimeter: 29.00 inHg - Observed at: BOI ## 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 19981129032899A](https://openairdocs.org/incident/19981129032899A), Nov 29, 1998: Doug MD900, Boise, ID, Substantial damage. (.19) On November 29, 1998, approximately 1830 mountain standard time, a Mcdonnell Douglas MD-900 helicopter, N977LF, registered to alvac, inc., operated by… 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.