# NTSB DEN99LA062: Sly RV-6A, N80287, Payson, UT, April 2, 1999 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: April 1, 1999, 17:00 local (Apr 2, 1999, 00:00 UTC) - Place: Payson, UT - Coordinates: 39.960784, -111.719757 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.9608&lon=-111.7198&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report May 8, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 46085 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN99LA062 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/46085/pdf - Page: https://openairdocs.org/ntsb/DEN99LA062 ## Probable cause The development of carburetor ice resulting in a loss of engine power, and the inadequate carburetor heat shroud. Factors were the carburetor icing weather conditions, the kit manufacturer's inadequate carburetor heat shroud design, the FAA's inadequate certification of the aircraft, the snow covered, unsuitable terrain on which to perform a forced landing, and the fence post. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - nonmechanical, cruise - weather condition - carburetor icing conditions (contributing factor) - fuel system,carburetor - ice (cause) - carburetor heat,shroud - inadequate (cause) - acft/equip,inadequate design, kit manufacturer (contributing factor) - inadequate certification/approval,aircraft, faa(organization) (contributing factor) - Forced landing, emergency descent/landing - terrain condition - snow covered (contributing factor) - terrain condition - none suitable (contributing factor) - On ground/water collision with object, emergency landing - object - fence post (contributing factor) ## Analysis After being airborne for 15 minutes, the aircraft's engine began to lose power. The pilot initiated an emergency landing along a county road but switched to another road to avoid power lines. Upon touchdown, the aircraft departed the side of the road and struck a fence post. The engine was examined and test run, and no discrepancies were observed. The pilot stated that 'other pilots at the scene agreed the conditions could cause carburetor icing.' According to the FAA inspector present at the accident scene, 'the conditions were a classic setup for carburetor icing.' The Van's Aircraft construction and operating manual states that one method of building the carburetor heat system is to 'run a 2-inch air hose from a heat muff and position it to feed into the alternative air inlet of the carb[uretor] air box,' which is the method by which the pilot constructed the airplane. According to the inspector, the 2-inch hose is not large enough to adequately supply enough heat to the carburetor to sufficiently melt the ice. The aircraft was issued an airworthiness certificate by the FAA on August 24, 1995. ## Factual narrative On April 1, 1999, approximately 1700 mountain standard time, a Sly RV-6A homebuilt aircraft, N80287, owned and operated by the pilot, was substantially damaged after impacting terrain following a loss of engine power while in cruise flight near Payson, Utah. The airline transport rated pilot and one passenger were not injured. The local area personal flight was being operated under Title 14 CFR Part 91, and no flight plan was filed. The flight originated from the Spanish Fork-Springville Airport, Spanish Fork, Utah, at 1645. Visual meteorological conditions prevailed. According to the pilot, after being airborne for approximately 15 minutes, the aircraft's engine began to lose power. He stated that he applied carburetor heat and switched the fuel tanks, but observed no change in power. The loss of engine power was gradual, with no sudden stoppage, backfiring or surging. Unable to restore power to the engine, he initiated an emergency landing along a county road 6 miles south of the airport. During landing, he switched to another road to avoid power lines. Upon touchdown, the aircraft departed the side of the road and struck a fence post, damaging the nose gear, ailerons and rudder. At the request and in the presence of a Federal Aviation Administration (FAA) inspector, the engine was examined and test run at the Spanish Fork Flying Service on April 16, 1999. During the inspection, the fuel was clear and free of contaminates. The engine ran with and without the fuel pump turned on, and no discrepancies were noted. The pilot stated in his accident report that "other pilots at the scene agreed the conditions could cause carburetor icing." According to the FAA inspector present at the accident scene, weather conditions were partly cloudy and cold with calm wind. According to the inspector, "the conditions were a classic setup for carburetor icing." According to the Van's Aircraft construction and operating manual, one method of building the internal carburetor heat system is to "run a 2-inch air hose from a heat muff and position it to feed into the alternative air inlet of the carb[uretor] air box without being attached and closed." According to the FAA inspector who examined the aircraft following the accident, this is the method by which the pilot constructed the airplane. According to the inspector, the 2-inch hose is not large enough to adequately supply enough heat to the carburetor to sufficiently melt the ice. The aircraft was issued an airworthiness certificate by the FAA on August 24, 1995. ## Aircraft - Registration: [N80287](https://openairdocs.org/aircraft/N80287), registered now, S/N 22902 (OpenAirDocs) - Reported make and model: Sly RV-6A - Registry model: [SLY Russell M RV-6A](https://openairdocs.org/model/sly-russell-m-rv-6a) (registry code 05626TV) (OpenAirDocs) - Registry engine: [Lycoming O&VO-360 series](https://openairdocs.org/engine/lycoming-o-vo-360-series) (registry code 41514, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 22902 - Airframe hours: 198 - Engines: Lycoming O-360-A1A 180 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Russell M. Sly - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Annual, September 22, 1998, 8 hours before - Departed: U77, SPANISH FORK, UT ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 61; airline transport, commercial, military, flight engineer; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; seat: left; flight hours: 9,183 total, 198 in this make and model ## Weather - Conditions: Visual (VMC), Day - Visibility: 30 statute miles - Lowest ceiling: none - Temperature: 39 °F - Altimeter: 29.00 inHg ## 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 19990401003029A](https://openairdocs.org/incident/19990401003029A), Apr 1, 1999: Amtr RV6A, Spanish Fork, UT, Substantial damage. (.19) On April 1, 1999, approximately 1730 mountain standard time, a sly RV-6A homebuilt, N80287, owned and operated by the pilot, was substantially damaged… 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.