# NTSB WPR15CA128: Enstrom F28 - C, N5688N, Shelby, MT, March 14, 2015

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Data collection · Final report
- Date: March 13, 2015, 18:00 local (Mar 14, 2015, 00:00 UTC)
- Place: Shelby, MT
- Coordinates: 48.44889, -111.971946
- Nearby events: https://openairdocs.org/map.md?lat=48.4489&lon=-111.9719&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering-low-alt flying: Low altitude operation/event](https://openairdocs.org/ntsb-events/220)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report April 21, 2015
- Report: Approved by Office Director
- NTSB office: Western Pacific Region
- Parties: Federal Aviation Administration
- NTSB case key (mKey): 90888
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR15CA128
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/90888/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=90888
- Page: https://openairdocs.org/ntsb/WPR15CA128

## Probable cause

The pilot's failure to maintain main rotor RPM during a low altitude operation, which resulted in a loss of aircraft control and collision with terrain.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Enstrom F-28C, 5 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=3300407), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md)
- [Performance/control parameters: prop/rotor parameters](https://openairdocs.org/ntsb-findings/01062052): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Enstrom F-28C, 3 cases](https://openairdocs.org/ntsb-findings/01062052/cases.md?model=3300407), [All aircraft, 182 cases](https://openairdocs.org/ntsb-findings/01062052/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Maneuvering-low-alt flying: Low altitude operation/event](https://openairdocs.org/ntsb-events/220) (defining event); cases with it: [Enstrom F-28C, 1 case](https://openairdocs.org/ntsb-events/220/sequence.md?model=3300407), [All aircraft, 780 cases](https://openairdocs.org/ntsb-events/220/sequence.md)
- [Maneuvering-low-alt flying: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Enstrom F-28C, 3 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=3300407), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)

## Analysis

The pilot reported that while maneuvering at a low altitude over a machinery yard, he observed a low rotor rpm condition. When he lifted the collective the rpm continued to bleed off, which resulted in the helicopter yawing to the left. The pilot stated that he managed to get the helicopter back under control, but then entered the low rotor rpm condition a second time. Unable to keep the helicopter flying straight, the aircraft impacted up sloping terrain with its left skid, followed by the main rotor blades striking the ground. The helicopter sustained substantial damage due to the impact with terrain. The pilot reported no preimpact mechanical malfunctions or failures with the helicopter that would have precluded normal operation.

## Factual narrative

The pilot reported that while maneuvering at a low altitude over a machinery yard, he observed a low rotor rpm condition. When he lifted the collective the rpm continued to bleed off, which resulted in the helicopter yawing to the left. The pilot stated that he managed to get the helicopter back under control, but then entered the low rotor rpm condition a second time. Unable to keep the helicopter flying straight, the aircraft impacted up sloping terrain with its left skid, which was followed by the main rotor blades striking the ground. The helicopter sustained substantial damage due to the impact with terrain. The pilot reported no preimpact mechanical malfunctions or failures with the helicopter that would have precluded normal operation.

## Aircraft

- Registration: [N5688N](https://openairdocs.org/deregistered/N5688N-2018-03-05), registration cancelled 2018-03-05, S/N 495-2, built 1980 (OpenAirDocs)
- Reported make and model: ENSTROM F28 - C
- Registry model: [Enstrom F-28C](https://openairdocs.org/model/enstrom-f-28c) (registry code 3300407) (OpenAirDocs)
- Registry engine: [Lycoming HIO-360 series](https://openairdocs.org/engine/lycoming-hio-360-series) (registry code 41524, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 495-2
- Year built: 1980
- Engines: Lycoming HIO-360 reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, April 20, 2014, 1,378 hours before
- Departed: SBX, Shelby, MT
- Destination: SBX, Shelby, MT

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 53; injuries: none; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; last flight review February 17, 2013; seat: left; restraint: lap only; flight hours: 168 total, 112 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 200° at 7 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 64 °F, dew point 48 °F
- Altimeter: 30.15 inHg
- Observed at: CTB, 10 nm away

## 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 20150313002269A](https://openairdocs.org/incident/20150313002269A), Mar 13, 2015: Enstrom F-28C, Shelby, MT, Substantial damage. On March 13, 2015 at 1800 MST, a Enstrom F-28C impacted the ground 10 miles south of Shelby Montana behind a farmers house while hovering. Visual meteorlogical…

## Other investigations on N5688N (1)

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.

- [NTSB LAX82DA283](https://openairdocs.org/ntsb/LAX82DA283), Jul 31, 1982: Enstrom F28C (N5688N), Phoenix, AZ, substantial damage

## Docket (1 files)

The files NTSB released with the investigation on April 16, 2015, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=90888. 3.1 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 3.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40425155&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF

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.

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