ERA14LA405 · Hiller UH 12E
Cape May County Mosquito Hiller UH 12E · Accident: powerplant system/component malfunction/failure en route
From H309 · Cape May CH, NJ to H309 · Cape May CH, NJ
Event
- NTSB case
- ERA14LA405
- 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
- Accident
- 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
- Government
- 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
Hiller UH 12E
- Aircraft type
- Hiller UH-12
- Category
- Helicopter
- 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
- N4035A
- Operator
- Cape May County Mosquito
- Onboard fatalities
- Unknown
- Route
- From H309 · Cape May CH, NJTo H309 · Cape May CH, NJ
- Aircraft age
- About 32 years (built 1982)
- 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
- Public Aircraft
- 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 · climb to 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
- Powerplant system/component malfunction/failure
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Aircraft › Aircraft power plant
- Personnel issues › Task performance
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot reported that, at 300 ft above the ground while climbing the helicopter out of a marshy area during mosquito control operations, he heard a loud, metallic "bang" and then felt an "immediate significant rhythmic vibration." He immediately performed an autorotation to the nearest clear area. The helicopter collided with trees and then the ground and came to rest on its right side.
A postaccident examination of the engine revealed that the engine's antivibration snubbers were fractured. Subsequent examination of the snubbers revealed that the vibration reported by the pilot was likely due to a fracture of the lateral snubber assembly's vibration mount outboard of the mounting plate. The location of the fracture combined with the deformed outboard edge of the circumferential band indicate that the lateral snubber assembly moved both outboard and inboard relative to the mounting plate and, thus, that the fracture likely did not result from motion in one direction when the helicopter came to rest on its side. Additionally, dark red oxide was found on the steel surfaces that should have been encapsulated by elastomer, which indicates that relatively long-term oxidation of the surfaces had occurred due to environmental exposure. Further, areas of the lateral snubber vibration mount were separated from the elastomer, and only a little elastomer was adhered to the surface. The oxidation and lack of adhered elastomer suggest that preexisting cracks were present at or near the interface between the elastomer and the mounting plate. Circumferential cracks with a slight opening displacement were also observed at the inboard face of the elastomer, indicating that the elastomer was degraded.
According to the helicopter manufacturer, specific inspections of the vibration mount assemblies are required at 50- and 100-hour intervals. An annual/100-hour inspection of the airframe and engine was completed about 6 weeks before the accident; the engine had operated about 18 hours since the inspection. The mechanic who performed the inspection stated that the snubber assemblies appeared airworthy at the time of the inspection. However, given the condition of the lateral snubber vibration mount, the mechanic should have been able to detect the wear on the mount and then replaced the vibration mount assembly.
Probable cause
The mechanic’s failure to detect excessive wear on the engine’s lateral snubber vibration mount during the latest annual inspection, which resulted in an in-flight engine failure and a subsequent forced landing.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ERA14LA405
- Event ID
- 20140825X61141
- Case number
- ERA14LA405
- 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: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: ee84c35386a8a8f819d8fe0fa3e973bba11b86283d46b245c2e16993b6701b65; retrieved 2026-09-16T01:40:53.024Z.