MIA04LA122 · Robinson R-22
Robinson R-22 · Accident: partial loss of engine power (mechanical failure) while maneuvering
From Palm Beach County Park Airport (KLNA) to an unrecorded destination
Event
- NTSB case
- MIA04LA122
- 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
Robinson R-22
- Aircraft type
- Robinson R-22
- 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
- N4062X
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Palm Beach County Park Airport (KLNA), West Plam Beach, FLTo 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
- Maneuvering
- 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, cylinder › Low compression
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
According to the flight instructor, the student pilot was practicing autorotations with the instructor at an indicated altitude from about 1,500 to 500 feet. The flight instructor decided to fly back to their departure airport, and while doing so the flight instructor idled the helicopter engine to simulate an engine out for the student pilot. When the student pilot went to recover from the simulated engine out, the helicopter engine did not respond to any power inputs. The flight instructor heard a low RPM horn, and took over the flight controls of the helicopter. The instructor proceeded to re-enter autorotation, flared, leveled the helicopter, and landed in an uneven field. The helicopter came to rest on its side. The helicopter engine was removed from the airframe and taken to a certified engine overhaul facility with NTSB and FAA oversight. The engine operated through several parameters, engine start, magneto check, and a series of several rapid throttle advancements from idle, to full engine power. No abnormalities were noted with the test. A differential compression check was conducted and the following compressions were recorded: Cylinder one, 15/80 PSI, cylinder two, 15/80 PSI, cylinder three, 20/80 PSI, cylinder four, 15/80 PSI. The cylinders were removed, and sent to ECI, Engine Components Inc., for further examination of the pistons and cylinders, with FAA oversight. Pistons, pistons pins, and combustion chambers of all four cylinders displayed discoloration, consistent with of high engine temperature operation.
Probable cause
The partial loss of engine power due to low cylinder compression during recovery from a practice autorotation resulting in a hard landing and damage to the helicopter.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record MIA04LA122
- Event ID
- 20040908X01365
- Case number
- MIA04LA122
- 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: b18170439417dbf598c59929f2d4b23f49fb4d4ee8bff317694751caf16bb99a; retrieved 2026-09-21T19:09:30.749Z.