Aviane Air Ambulance MBB BO-105S accident
MBB BO-105S · Accident: partial loss of engine power (mechanical failure) during initial climb
From Ponce, PR to San Juan, PR
Event
- NTSB case
- MIA06LA044
- 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
- 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
MBB BO-105S
- Aircraft type
- MBB BO-105
- 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
- N495LF
- Operator
- Aviane Air Ambulance
- Onboard fatalities
- Unknown
- Route
- From Ponce, PRTo San Juan, PR
- 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
- Initial climb
- 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
- Hydraulic system › Low pressure
- Pneumatic system › Leak
- Rotorcraft flight control system › Locked
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
After the patient was placed aboard the helicopter, the pilot started the engines and performed a hover check. He then moved the helicopter forward to gain airspeed and initiated a climb to cruise altitude. After reaching an altitude of about 100 feet, the main rotor rpm light and audio warning system activated, and the number 2 engine N1 rpm and torque began to decay. The pilot attempted to regain normal engine parameters, but was unable to regain engine rpm. The pilot maneuvered to avoid several light poles as he attempted to land in a parking lot. By this time, main rotor rpm had bled off sufficiently to prevent the hydraulic pumps from pressurizing the hydraulic system, and all flight controls locked is a slight right banked attitude. This prevented the helicopter from reaching the parking lot. The helicopter impacted a construction area in a right bank, nose down attitude. An on-site and later follow-up investigation by FAA and Rolls-Royce investigators revealed a B-nut on the Pc line connecting the power turbine governor (PTGOV) to the fuel control unit (FCU) had become loose at the T-fitting end. It was partially torqued and could be moved with the fingers. The female end was threaded onto the male end three-quarters of a turn. There was no cross-threading. The torque stripe was broken. According to Rolls-Royce Allison, "This line serves a critical function to the engine control system and when leakage occurs will cause the engine to roll back to an idle or near idle condition."
Probable cause
A loose B-nut on the PC line connecting the power turbine governor (PTGOV) to the fuel control unit (FCU) that created a leak and caused the engine to roll back to an idle condition, causing a low hydraulic system pressure and subsequent control lock. A contributing factor was the unsuitable terrain (construction area) on which to make a forced landing.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record MIA06LA044
- Event ID
- 20060118X00085
- Case number
- MIA06LA044
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (5)
- 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: e1da4020a671148d910422bf4756e4ce5d16e24d04544a62598be69d91cac83e; retrieved 2026-09-18T14:55:59.543Z.
- The NTSB's operator name is blank for N495LF; the operator shown is the name the NTSB records it doing business as.