Great Lakes Aviation Flight 1555
Embraer 120 · Incident: airframe, component or system failure en route
From Raleigh-Durham International Airport (RDU) to Wilmington International Airport (ILM)
Event
- NTSB case
- ATL96IA053
- 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
- Incident
- 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
- Charter & commuter
- 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
Embraer 120
- Aircraft type
- Embraer 120
- Category
- Airplane
- 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
- N129AM
- Operator
- Great Lakes Aviation
- Onboard fatalities
- Unknown
- Route
- From Raleigh-Durham International Airport (RDU)To Wilmington International Airport (ILM), Wilmington, NC
- 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 135: Air Taxi & Commuter
- 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
- En route · climb to cruise
- 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
- Airframe, component or system failure
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- None
Cause areas
- Company/operator management › Maintenance, aaip/progressive program, inadequate
- Fluid, hydraulic › Contamination, other than water
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
According to the flightcrew, during the initial climb after takeoff, an uncommanded right rudder pedal hardover occurred, during which the right rudder pedal moved to the fully depressed position. The hydraulic system was deenergized and an uneventful landing was made at the departure airport. A postincident examination of the airplane's rudder control system did not reveal any discrepancies. However, hydraulic system fluid samples were obtained and analyzed, along with an inspection, testing, and disassembly of the rudder hydraulic power control unit and the rudder actuators. As a result of the testing, contamination was found in the fluid samples from the airplane's hydraulic reservoirs and the power control unit that exceeded the maximum levels established by the airplane manufacturer's maintenance manual. The operator's FAA accepted general operating manual requires compliance with the manufacturer's maintenance manual. Additionally, the operator did not have an established procedure for periodically sampling and analyzing hydraulic fluid from airplane systems.
Probable cause
The operator's inadequate progressive inspection program that did not require periodic analysis of airplane hydraulic system fluid; and the failure of the operator to comply with the airplane manufacturer's maintenance manual resulting in contamination of the airplane's hydraulic system that exceeded the maximum contamination level.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ATL96IA053
- Event ID
- 20001208X05210
- Case number
- ATL96IA053
- 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, damage. 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: a06ba66c6e6e13979bab19b80666ecdf04af43a33868cb830f36f36ed1f82d44; retrieved 2026-09-18T17:53:29.810Z.