CEN22LA146 · Hughes (MD Helicopters) 369 D
Winco Hughes (MD Helicopters) 369 D · Accident: loss of engine power (partial) while maneuvering
Event
- NTSB case
- CEN22LA146
- 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
- 0
- 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
Hughes (MD Helicopters) 369 D
- Aircraft type
- Hughes (MD Helicopters) 369
- 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
- N500MZ
- Operator
- Winco
- Onboard fatalities
- Unknown
- Route
- From not recordedTo not recorded
- Aircraft age
- About 45 years (built 1977)
- 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 133: Rotorcraft Ext. Load
- 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
- Maneuvering · low-altitude flying
- 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 (partial)
- 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 › Action/decision
- Personnel issues › Psychological
- Personnel issues › Task performance
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
During longline operations, and while flying to a structure, the helicopter sustained a partial loss of engine power. The helicopter was at 90ft above ground level and about 30 kts airspeed, when the pilot lowered the collective to attempt an autorotation. There was insufficient altitude and airspeed to increase main rotor rotation, and the helicopter impacted a muddy grass hill. The helicopter came to rest on its right side. After the helicopter came to rest, the pilot noticed the engine was still, “at a slow run, less than idle.”
The helicopter sustained substantial damage to the fuselage, the main rotor system, and the tail rotor system. During the recovery of the helicopter from the field, it was noticed by the operator that the compressor discharge pressure (Pc) line B-nut connection at the fuel control unit (FCU) was not attached. It appeared the B-nut had backed off the FCU fitting. A postaccident examination was performed on the airframe with no anomalies noted. The engine was removed from the airframe and an engine test run was performed with no anomalies noted after the Pc line B-nut was properly torqued. During the Pc line B nut torquing process, a “squeeze out” of pink paint, consistent with torque stripe paint, was observed emanating from the remaining threads on the line. On the day before the accident, the fuel control unit (FCU) was installed on the helicopter’s turboshaft engine. A calibrated torque wrench was used by the mechanic to tighten the various FCU B-nuts. The mechanic tightened and torqued each B-nut, one at a time, when completing the task. Another mechanic inspected the work after it was completed and found no issues. After the B-nuts were torqued, pink torque stripe paint was applied. Following the FCU installation, the fuel system was purged of air, and a leak check was performed with the helicopter running, an acceptable practice per the engine manufacturer, with no issues noted. It is likely that the mechanic failed to properly torque the B-nut that secures the Pc line to the FCU, which resulted in a partial loss of engine power due to the Pc line separation. Based on the available evidence, it was undetermined as to why the mechanic failed to properly torque the B-nut.
Probable cause
The mechanic’s failure to properly torque a fuel control unit B-nut, which resulted in a partial loss of engine power, an attempted autorotation, and an impact with terrain.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CEN22LA146
- Event ID
- 20220318104795
- Case number
- CEN22LA146
- 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, cause areas. 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: 172457bfc6f09366ad62ef7146859ac1180437e3c422eb6eba57e424a1af7f97; retrieved 2026-09-16T15:02:57.163Z.