NTSB CAROL · Event
Event DEN00IA075
Aircraft involved
Probable cause & findings
The fatigue failure of the #6 cylinder connecting rod cap.
Factual narrative
On November 9, 1999, approximately 1100 mountain standard time, a Beech A60, N457DA, received minor damage when the left engine failed during descent near Boulder, Colorado. The commercial pilot, the sole occupant in the airplane, was not injured. The airplane was being operated on a public use flight by the Boulder County Sheriff's Department under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the cross-country flight that originated from Centennial Airport, Englewood, Colorado, approximately 20 minutes before the accident. The pilot had not filed a flight plan. The pilot said that as he descended to 6,500 feet mean sea level, the engine failed. The pilot landed the airplane without further incident. The engine had 23.5 hours on it since major overhaul. An engine teardown revealed that the #6 connecting rod had failed. Postaccident examination of the #6 cylinder parts, by the National Transportation Safety Board's (NTSB) Materials Laboratory, found preexisting fractures on both the rod cap and the connecting rod. The fatigue features displayed on the rod cap are suggestive of lower stress propagation than those stress propagation marks on the connecting rod. The NTSB's Materials Laboratory found that the two halves of the 2 separated rod bolts from the #6 cylinder (see attached report figures 7, 8, 9, and 10) exhibited surface separation features that were consistent with overstress separations. Additionally, the head portions of these two bolts both displayed bending deformation in an outward direction from the center of the connecting rod and rod cap. The pilot said that as he descended to 6,500 feet mean sea level, the left engine of the twin-engine airplane failed. The pilot landed the airplane without further incident. The engine had 23.5 hours on it since major overhaul. An engine teardown revealed that the #6 connecting rod had failed. Examination of the #6 cylinder parts found preexisting fractures on both the rod cap and the connecting rod. The fatigue features displayed on the rod cap are suggestive of lower stress propagation than those stress propagation marks on the connecting rod. It appeared that the engine failure-initiating event was the failure of the rod cap. Examination of the #6 connecting rod bolts indicated that they fractured as a result of overstress. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12
Verbatim from NTSB's published report. Source file
NTSB_1999_DEN00IA075.txt.
Findings + structured fields enriched from FAA avall.mdb.
Full investigation docket on
data.ntsb.gov ↗.
Beyond the agency record
Search this event elsewhere.
Pre-filled searches into the sources where news + community discussion of aviation events lives. External sources are reported, not agency. Treat them as signal that something happened, not as fact about what happened.
Entity-clustered aviation events in the press — last 24 hr + 30-day archive.
Official agency record + docket.
Investigative docket: factual reports, photos, transcripts.
Long-running aviation incident database (Flight Safety Foundation).
Community NTSB synthesis blog — often has photos and witness reports.
Gold-standard aviation incident blog.
Aviation industry news search.
GA pilot forum — informed but rumor-prone.
GA pilot subreddit search.
Tail-number page — flight history (free tier limited).
AOPA Air Safety Institute search.
Mainstream press coverage. Recent events only.
Privacy-preserving news search.
External links open in a new tab. We don't ingest their content; we deep-link search queries.
Related research
What the literature says.
Academic papers and agency reports matching this event's aircraft type or causal vocabulary (engine failure). Sourced from NASA NTRS, NTSB Safety Studies, FAA CAMI, AOPA Air Safety Institute, Embry-Riddle Scholarly Commons, arXiv, and the Semantic Scholar academic graph.
- arXiv 2022 · arXiv preprint
Multi-level Adaptation for Automatic Landing with Engine Failure under Turbulent Weather
This paper addresses efficient feasibility evaluation of possible emergency landing sites, online navigation, and path following for automatic landing under engine-out failure subject to turbulent wea…
- NASA NTRS 2019 · Conference Paper
Simulation of Liquid Rocket Engine Failure Propagation Using Self-Evolving Scenarios
Traditional probabilistic risk assessment approaches often require failure scenarios to be explicitly defined through event sequences that are then quantified as part of the integrated analysis.
- NASA NTRS 2019 · Conference Paper
Rocket engine failure detection using system identification techiques
The theoretical foundation and application of two univariate failure detection algorithms to Space Shuttle Main Engine (SSME) test firing data is presented.
- NASA NTRS 2019 · Conference Paper
Rocket engine failure detection using system identification techniques
The theoretical foundation and application of two univariate failure detection algorithms to Space Shuttle Main Engine (SSME) test firing data is presented.
- NASA NTRS 2019 · Technical Memorandum (TM)
A simulator investigation of engine failure compensation for powered-lift STOL aircraft
A piloted simulator investigation of various engine failure compensation concepts for powered-lift STOL aircraft was carried out at the Ames Research Center.
- Semantic Scholar 2019 · Article (AIAA Scitech 2019 Forum)
Impact of Engine Failure Constraints on the Initial Sizing of Hybrid-Electric GA Aircraft
Potential advantages of hybrid-electric aircraft are fuel savings, lower emissions, and reduced noise. Since these aircraft generally apply multiple power sources, they can also be designed to sustain…
Browse the full corpus — academia portal ↗