# NTSB FTW97LA206: Piper PA-31-350, N491SC, Greeley, CO, May 28, 1997 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: May 27, 1997, 19:00 local (May 28, 1997, 01:00 UTC) - Place: Greeley, CO - Coordinates: 40.440624, -104.670257 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.4406&lon=-104.6703&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report September 30, 1997 - Report: Approved by Office Director - NTSB case key (mKey): 20232 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW97LA206 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/20232/pdf - Page: https://openairdocs.org/ntsb/FTW97LA206 ## Probable cause unlatching of the left outboard engine cowling latches for undetermined reason(s), which allowed the left engine cowling to separate inflight and strike the vertical stabilizer. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - normal - reason for occurrence undetermined (cause) - nacelle/pylon - unlatched - nacelle/pylon - separation ## Analysis The pilot said that while in cruise flight, he observed the left front portion of the left engine cowling starting to come loose. After receiving clearance from air traffic control, he started to divert to the nearest suitable airport. Shortly thereafter, the left cowling completely separated from the aircraft and struck the vertical stabilizer. Postaccident inspection disclosed the outboard cowling latches were in the UNLOCKED position, and the inboard latches were in the LOCKED position. A portion of the cowling remained attached via the inboard latches. The pilot said he checked the cowling latches during his preflight inspection and they were all in the LOCKED position. Orange stripes had been painted across the latches to visually indicate LOCKED and UNLOCKED positions. ## Factual narrative On May 27, 1997, approximately 1900 mountain daylight time, a Piper PA-31-350, N491SC, operated by Sundance Air, Inc., as flight 6416, nonscheduled domestic cargo service, was substantially damaged when the left engine cowling separated inflight and struck the vertical stabilizer about 30 miles north of Greeley, Colorado. The commercial pilot was not injured. Visual meteorological conditions prevailed and an IFR flight plan had been filed. The airplane was being operated under Title 14 CFR Part 135. The flight departed at 1630 from Scottsbluff, Nebraska, and was en route to Colorado Springs, Colorado. According to the pilot, he was in cruise flight when he observed the left front portion of the left engine cowling starting to come loose. After obtaining clearance from air traffic control, he diverted to the Greeley/Weld County Airport. Shortly thereafter, the left cowling completely separated from the aircraft and struck the vertical stabilizer. The pilot reported no change in aircraft performance, but noted oil leaking from a cracked oil filler neck. He then made a normal and uneventful approach and landing at Greeley. Postaccident inspection disclosed substantial damage to the vertical stabilizer. The outboard cowling latches were found in the UNLOCKED position, and the inboard latches were in the LOCKED position. A portion of the cowling remained attached via the inboard latches. The pilot said he checked the cowling latches during his preflight inspection and they were all in the LOCKED position. Orange stripes had been painted across the latches to visually indicate LOCKED and UNLOCKED positions. ## Aircraft - Registration: [N491SC](https://openairdocs.org/deregistered/N491SC-2013-08-23), registration cancelled 2013-08-23, S/N 31-7405225, built 1974 (OpenAirDocs) - Reported make and model: Piper PA-31-350 - Registry model: [Piper PA-31-350](https://openairdocs.org/model/piper-pa-31-350) (registry code 7103110) (OpenAirDocs) - Registry engine: [Lycoming TI0-540 series](https://openairdocs.org/engine/lycoming-ti0-540-series) (registry code 41533, turbo-prop) (OpenAirDocs) - Category: Airplane - Airframe hours: 15061 - Engines: Lycoming T10-540-32BD 300 horsepower reciprocating - Damage: Substantial damage - Flight: Part 135 - Registered owner: Sundance Air - Airworthiness certificate: Standard, Normal - Last inspection: Annual, May 14, 1997, 12 hours before - Departed: BFF, SCOTTSBLUFF, NE - Destination: COS, COLO SPRINGS, CO - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 28; airline transport, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 2,250 total, 600 in this make and model, 2,100 as pilot in command, 200 in the last 90 days, 80 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Dusk ## 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 19970527047389A](https://openairdocs.org/incident/19970527047389A), May 27, 1997: Piper PA31350, Greeley, CO, Substantial damage. (-16) Inspection of the aircraft revealed multiple unairworthy and unsafe conditions.[privacy data omitted] 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.