WPR14IA297 · Beech B100
Beech B100 · Incident: loss of engine power (total) en route
From Lake Tahoe Airport (KTVL) to McClellan-Palomar Airport (KCRQ)
Event
- NTSB case
- WPR14IA297
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Incident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Beech B100
- Aircraft type
- Beechcraft 100
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N6756P
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Lake Tahoe Airport (KTVL), S. Lake Tahoe, CATo McClellan-Palomar Airport (KCRQ), Carlsbad, CA
- Aircraft age
- About 34 years (built 1980)
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- En route · cruise
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Loss of engine power (total)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Minor
Cause areas
- Aircraft › Aircraft power plant
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot reported that, while in cruise flight, the left engine of the twin turboprop airplane lost power. The pilot secured the left engine and performed an uneventful single-engine landing at an airport. Examination revealed damage to the left nacelle and external damage to the left engine, consistent with an uncontained engine failure. Further examination of the left engine revealed an overload failure of the 2nd-stage turbine wheel. The investigation determined that a repair to a brazed joint on the 2nd-stage main nozzle casting support baffle and outer flange had failed. This baffle directs cooling air to the aft face of the 1st-stage turbine wheel and knife-edge seal ring. Once the baffle failed and cooling air was lost, the temperature of the knife-edge seal ring cavity increased, which precipitated its fracture. Once the seal ring fractured, it sprang open slightly from normal internal stresses, became loose in the cavity, and then migrated axially aft until it contacted the rotating 2nd-stage turbine wheel web and started to machine the web material, weakening it until the overload failure occurred.
According to the engine manufacturer, without the cooling air, metal temperatures of the knife-edge seal ring at the forward and aft ends were estimated to be 1446°F and 1263°F, respectively. Intergranular fractures were initiated after exposure to these high temperatures. The nominal cavity temperature should be 1060°F.
A review of the repair history of the 2nd-stage stator assembly revealed that the forward braze joint had been repaired about 5 years before the accident using a repair process specification that was not applicable for the assembly part being repaired. Further, the engine manufacturer does not consider the part a repairable item and advises that it be removed from service. However, the Federal Aviation Administration designated engineering representative had approved the repair process and did not include technical substantiation.
Probable cause
The failure of the 2nd-stage turbine wheel due to an improper repair of the 2nd-stage stator assembly, which the manufacturer does not consider a repairable item. Contributing to the incident was the designated engineering representative's approval of the repair process.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR14IA297
- Event ID
- 20140718X34015
- Case number
- WPR14IA297
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: local date, investigation status. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 2014-07-17.
- API snapshot SHA-256: 9a087219ecdd1af3b6a6eae3e11e95ba0c0663a1d36c206430f7c72e48eb7227; retrieved 2026-09-16T00:55:59.706Z.