MIA98TA215 · Hughes TH-55A
Hughes TH-55A · Accident: loss of engine power while maneuvering
Event
- NTSB case
- MIA98TA215
- 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 TH-55A
- Aircraft type
- Hughes TH-55
- 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
- N998MC
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From not recordedTo 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 · aerial application
- 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
- Loss of engine power
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Reason for occurrence undetermined
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
According to the pilot this was the second flight on that day. The first flight lasted 1.3 hours with 'no discrepancies noted.' The pilot said the second flight was 'normal' for the first 1/2 hour of flight. He completed five passes, and on the last pass at 40 feet above ground level [field elevation 25 feet msl], with right hand quartering headwind, he reported, '...an engine partial power loss.' He said the '...symptoms were main rotor started to droop below 490 RPM (2900 engine RPM).' He lowered the collective, rolled in full throttle, and raised the collective to stop the decent. He said the rotor RPM 'continued to droop.' The pilot tried to maneuver the helicopter past trees, and a mound of dirt to a flat area on the far side of a ditch. He could not maintain enough altitude or rotor RPM to clear the ditch, and contacted the far side of ditch with the left side of the helicopter. The pilot told investigators, that the helicopter was functioning properly before the accident, and he had no explanation for the loss of rotor RPM. An engine run revealed no discrepancies. A compression check, while the engine was hot, reveled low compression on cylinders No. 1 and 3. Both cylinders were removed, and both cylinders were found to have exhaust valves that were not seated completely. The calculated density altitude, based on a temperature of 31 degrees C (88F), altitude 65 feet msl, and an altimeter setting of 30.05 inches of mercury, all obtained from the Savannah 0953 weather observation, was 1868 feet. The pilot stated that the weight of the helicopter was '...1590 [pounds] at the time of the accident.' The maximum gross weight of the helicopter was 1670 pounds.
Probable cause
The loss of engine power for an undetermined reason, resulting in a forced landing, and an in-flight collision with a ditch. A factor in this accident was a high density altitude.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record MIA98TA215
- Event ID
- 20001211X10669
- Case number
- MIA98TA215
- 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. 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: 72344541d7cd8c626972ee64900921ba778a44871857282d0cff00f9fe799de2; retrieved 2026-09-22T17:16:52.599Z.