Airbus Helicopters H225
The H225, formerly the Eurocopter EC225 Super Puma, is a long-range heavy-lift helicopter developed for the offshore oil and gas industry and search and rescue operations. Its safety record has been defined by critical mechanical failures within the main rotor gearbox (MGB) and power transmission systems, leading to significant grounding periods and major redesigns.
Fleet Safety Record
260Fleet statistics include both EC225 LP and H225 variants; excludes the military H225M/EC725.
In BlackBoxWiki Archive
Design Evolution and Transmission Architecture
The H225 is an evolution of the AS332 Super Puma, featuring a five-blade composite main rotor and an upgraded Makila 2A engine. The primary engineering focus was increased payload and range for offshore transport. Central to its design is the Main Rotor Gearbox (MGB), which utilizes two stages of epicyclic reduction to manage high torque loads from the twin-engine configuration.
Epicyclic Gear Failure and Fatigue
The type's operational history is marked by two distinct failure modes within the MGB. The first involved the failure of the bevel gear vertical shaft due to corrosion-fatigue cracking. The second, more critical failure mode involved the second-stage planet gear, where sub-surface fatigue cracks led to catastrophic structural failure of the gear teeth and subsequent detachment of the main rotor head.
Operational Shift and Market Impact
Following the 2016 Turøy accident, the H225 faced a prolonged grounding by EASA and the UK CAA. While technical fixes involving the replacement of the planet gear type (moving from the 'Type A' to 'Type B' design) and enhanced vibration monitoring were implemented, the type saw a significant migration from offshore passenger transport to utility, heavy-lift, and search and rescue (SAR) roles.
Notable Accidents
- Bond Offshore G-REDW (Ditching)· 2012Controlled ditching in the North Sea following a failure of the MGB bevel gear vertical shaft.
- CHC Scotia G-CHCN (Ditching)· 2012Second ditching involving a bevel gear shaft failure, leading to a temporary fleet-wide grounding.
- CHC Helikopter Service LN-OJF· 2016Catastrophic inflight separation of the main rotor near Turøy, Norway, caused by fatigue failure of a second-stage planet gear.
Recurring Causal Patterns
- Sub-surface fatigue cracking in the MGB epicyclic planet gears
- Corrosion-fatigue cracking in the MGB bevel gear vertical shaft
- Inadequacy of Health and Usage Monitoring Systems (HUMS) to detect sub-surface gear degradation
- Contact stress concentrations exceeding material fatigue limits under specific load conditions
Regulatory & Industry Response
- EASA Emergency Airworthiness Directive (EAD) 2016-0089-E (Grounding)
- Mandatory replacement of Type A planet gears with Type B gears
- Reduction of service life limits on MGB internal components
- Enhanced magnetic plug inspection protocols and oil debris monitoring requirements
Verdict
The H225 is a high-performance heavy-lift platform whose reputation was compromised by fundamental fatigue vulnerabilities in its power transmission system. While engineering modifications and rigorous inspection regimes have addressed the root causes of MGB failure, the type has largely transitioned out of the North Sea oil and gas sector in favor of utility and governmental roles.