CHI04CA237 · Enstrom F-28A
P & N Enstrom F-28A · Accident: partial loss of engine power (mechanical failure) during takeoff
From Leroy, MN to an unrecorded destination
Event
- NTSB case
- CHI04CA237
- 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
- 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
Enstrom F-28A
- Aircraft type
- Enstrom F-28
- 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
- N9573
- Operator
- P & N
- Onboard fatalities
- Unknown
- Route
- From Leroy, MNTo not recorded
- Aircraft age
- Not recorded
- 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
- Takeoff
- First occurrenceThe 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
- Partial loss of engine power (mechanical 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
- Engine assembly, other › Missing
- Engine assembly, other › Undertorqued
- Other maintenance personnel › Maintenance, installation, inadequate
- Pilot in command › Run on landing, improper
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
The helicopter sustained substantial damage when it impacted terrain and rolled over after a loss of engine power during takeoff. The pilot reported that the engine was producing 3,000 rpm's when he brought the helicopter into a hover. He transitioned into forward flight and cleared a fence, and then the engine lost power. He reported that he thought that an exhaust valve was stuck. He attempted to do a run on landing to a field. The helicopter touched down on its left skid two times but the helicopter was not straight. He reported that the third time the helicopter touched down on its left skid, the helicopter was not straight and the rpm's were low. He reported that he ran out of tail rotor authority. The helicopter rolled over on its left side. The engine was inspected and an engine run was conducted. The engine was run at 1,800 to 2,000 rpm, and then at 1,110 to 1,200 rpm; but the engine popped and ran unevenly. A re-inspection of the engine revealed that the 1/8-27 NPT Allen plug to the number four cylinder was missing. Once the hole was plugged, the engine ran smoothly.
Probable cause
The partial loss of engine power due to the missing 1/8-27 NPT Allen plug as a result of other maintenance personnel undertorquing the plug. Additionally, the pilot improperly excecuted a run on landing. A factor was the loss of tail rotor effectiveness.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI04CA237
- Event ID
- 20040913X01409
- Case number
- CHI04CA237
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
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, coordinates. 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: 76ba05c416adf88ab6546f9ad01ca48b46993f002e170bb21d69e91a2292069d; retrieved 2026-09-21T09:13:47.614Z.