What Happened to the Super Puma Helicopter Family?

The Super Puma Family has an interesting reputation. Pilots from across the globe who have flown the type often speak very highly of it.

If you ask offshore workers in Europe however, you might get a very different answer.

The Super Puma has had its technical difficulties, but it still offers a huge amount of benefits compared to the competition. Multiple crashes over the years however, resulted in some reputational damage ⬇️

This caused Airbus to come out with a range of improvements to the helicopter. So does the Super Puma have what it takes to make a comeback? 💡

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An Overview of the Super Puma Family

Helicopters in the Super Puma family have gone through multiple iterations, but the most updated helicopter is the H225. Used in both the civilian and military industry, it is mainly known for its long range, advanced autopilot, and substantial payload.

Here are some technical details on the H225:

This large range and endurance are still hard to find amongst other helicopters, which is one of the reasons the Super Puma was such a compelling choice for a lot of offshore operators. When used offshore, it allowed flights to the furthest rigs with a full load and full fuel, giving more options for diverts and time to deal with any en-route problems.

Many other helicopters have to sacrifice on the amount of passengers, or the amount of fuel (ironically) to get to the furthest rigs (on minimum fuel). The H225 is quite unique because of this benefit!

A Timeline of the Most Recent Accidents due to Technical Problems

So what happened to the Super Puma family over the last 15 or so years that has given it such a challenging time? Here’s a timeline of the most recent accidents that were related to technical problems:

2009: G-REDL – Catastrophic Gearbox Failure

Credit: AAIB

An AS332 L2 Helicopter, G-REDL, took off from the Miller Platform in the North Sea to Aberdeen Airport. While it was cruising at 2000 ft AMSL, about 50 minutes into the flight, the main rotor gearbox had a catastrophic failure.

The helicopter’s main rotor completely separated from the fuselage. This resulted in the helicopter fuselage striking the sea with a very high rate of descend (as you can imagine). The crash was fatal for all 16 on board.

An elaborative and complex investigation showed that the failure of the main rotor gearbox started in 1 of the 8 planetary gears in the epicyclic module of the gearbox.

This planetary gear fractured because of a crack caused by metal fatigue, of which the exact origin was unknown. Analysis of the gearbox showed that the crack was likely to have happened in the loaded area of the planetary gear bearing outer race.

About 36 flying hours before the crash, a metallic particle was discovered on the epicyclic chip detector during maintenance. This was the only indication of an impending failure of the second stage planet gear.

Causal factor

The catastrophic failure of the main rotor gearbox was a result of a fatigue fracture of a second stage planet gear in the epicyclic module.

Contributory factors

1) The identified metallic particle was not recognised as an indication of degradation of the planet gear

2) Existing detection methods did not provide additional indications of any degradation of the second stage planet gear.

3) The ring of magnets installed in the main rotor gearbox reduced the probability of detecting released debris from the epicyclic module.

Safety recommendations

The accident report has 17 safety recommendations, which mainly highlight:

• Additional safety inspections
• Regulatory involvement of the helicopter type
• Reduction on the allowed lifecycle of components
• Additional ways to detect gearbox degradation
• The addition of a warning light that warns flight crew of a chip detector activation in the epicyclic.

2012: G-REDW – Loss of Main Gearbox Oil Pressure

Credit: AAIB

When operating over the North Sea, G-REDW, an EC225 helicopter experienced a loss of main rotor gearbox oil pressure. This resulted in the crew activating the emergency lubrication system.

When this system is activated, glycol and water are injected into the gearbox to provide cooling and lubrication. With this system active, the aircraft should be able to fly for a further 30 minutes.

However, very shortly after the system was activated, a warning light in the cockpit (EMLUB) indicated to the flight crew that this emergency lubrication system had failed. This resulted in a decision by the crew to execute a controlled ditching. There were no serious injuries.

During the investigation it was found that despite the warning light, the emergency lubrication system was in fact working, which would have allowed the aircraft to reach the nearest airport.

The MGB EMLUB caption had illuminated as a result of an incompatibility between the aircraft wiring and the configuration of the pressure switches in both the bleed-air and water/glycol supplies following a modification, giving the crew a false indication.

The primary failure of a loss of oil pressure was caused by a failure of the bevel gear vertical shaft in the main rotor gearbox, which drives the oil pumps. It’s the blue component in this picture:

Credit: AAIB

The failure was the result of a crack caused by fatigue, in the area where parts of the shaft are welded together (see the red arrow):

Credit: AAIB

The crack began due to a corrosion pit located on the countersink of a 4.2 mm manufacturing hole in the weld. A countersink is a conical shaped area next to a hole, that allows a plug or a screw to sit flush with the surface area:

Credit: AAIB

The corrosion pit was the result of moisture in the gap between this countersink and a PTFE plug that sits on it (PTFE stands for Polytetrafluoroethylene, which is a very very long word for a material that is commonly known as Teflon for most of us who can’t even pronounce that!).

Credit: AAIB

So in summary, the moisture between the plug and the countersink allowed corrosion to form, which lead to the crack.

Causal Factors

The investigation concludes there are 2 main causal factors:

1) A 360 degree circumferential high cycle fatigue crack resulted in a failure of the main gearbox bevel gear vertical shaft, which caused the oil pump to no longer be driven.

2) An incompatibility between the aircraft wiring and the internal configuration of the pressure switches that were installed in the bleed-air and water/glycol supplies. This resulted in the illumination of the MGB EMLUB caption, which required an immediate landing (in this case a ditching).

Contributing Factors

In regards to contributing factors, the AAIB mentions:

1) The helicopter manufacturer’s Finite Element Model (a mathmatical model that is used to support fatigue behaviour for specific components) underestimated the maximum stress in the area of the vertical shaft’s weld.

2) Residual stresses that are caused by welding operations were not fully taken into account when the vertical shaft was designed.

3) The presence of corrosion pits.

2012: G-CHCN – Loss of Main Gearbox Oil Pressure

Credit: AAIB

This accident, which happened to another EC225 over the North Sea, was so similar to the G-REDW one that the AAIB decided to address them in the same investigation report.

The helicopter departed Aberdeen at 1322 hrs on their way to the West Phoenix platform, which is North West of Sumburgh. About 60 minutes into the flight, whilst in the cruise at 140 kts and 3,000 ft AMSL and with approximately 81% total torque applied, the crew were alerted by various cautions and warnings that the gearbox had experienced a total loss of oil pressure.

It happened several months after the previously discussed accident. The same part caused the same failure, with the emergency lubrication system then again showing as failed. This resulted in the same flight crew decision: another ditching. There were also no serious injuries.

The only main difference between the 2 accidents was the origin of the crack forming in the bevel gear vertical shaft. For this accident, it was the result of a corrosion pit on a shaft called the inner radius, rather than on the countersink of the 4.2 mm hole.

Credit: AAIB

However, the crack still passed through part of the the 4.2 mm hole, which is a similar area to the crack on G-REDW. A small piece of debris that contained iron oxide and moisture became trapped on the inner radius, which led to the formation of corrosion. This particular shaft had a high amount of flying hours logged: 3845 hours. This was a lot more than any other EC225 LP shaft.

Credit: AAIB

As with G-REDW, examination of G-CHCN’s MGB found that despite the warning light, the emergency lubrication system had worked. There was no visual evidence of heat damage or imminent failure of the gearbox.

Safety Recommendations based on both accidents

The AAIB made various recommendations after these accidents, the main ones were:

• EASA to require Eurocopter (at the time) to review the design of the main gearbox emergency lubrication system
• EASA to commission research into the impact of scratches and corrosion pits on fatigue strength of components
• Post crash improvements such as life raft deployment reliability (G-REDW passengers reported the life rafts as deploying slowly. On G-CHCN the mooring lines and rescue pack lines became entangled on the left-hand life raft and constrained it to the sponson, preventing it’s initial use. Once untangled the raft was then usable).

2016: LN-OJF – Catastrophic Gearbox Failure

Credit: AIBN

An EC225, LN-OJF, took off at 1005 hours from Flesland (Bergen Airport, Norway), for its second round trip that day. Its destination was Gullfaks B (ENQG Helideck) where it remained rotors running while the passengers disembarked. 11 passengers then boarded for the inbound flight.

Based on Flight Data Recorder information, the helicopter maintained 3000 ft AMSL in the cruise until shortly before reaching the Norwegian coast. It then descended to a cleared altitude of 2000 ft AMSL while flying at 140 kts for about 1 minute.

Suddenly, the engine torque dropped and the main rotor started to tilt erratically. The helicopter climbed about 120 ft before the main rotor detached, and the helicopter started a ballistic descent towards the ground.

Without the main rotor, the fuselage rolled right near 360 degrees while yawing to the right. It then slowly started to roll left while the helicopter nose ended up pointing at the ground. It hit Storeskitholmen island at 1155 hours. The force of the impact destroyed the helicopter before most of the wreckage continued into the sea.

Credit: AIBN

The fuel vapour made a cloud above the accident site, and ignited. This started a fire on the island. Meanwhile, the main rotor had continued to fly on its own in a wide erratic descending left hand turn towards Storskora island and made impact there. The crash was fatal for all 13 on board.

Causal Factors

The main causal factor identified by the investigation was the structural degradation of a second stage planet gear. Subsurface cracks had developed undetected, and lead to a catastrophic fatigue failure.

Credit: AIBN

It initiated from a surface micro-pit in the upper outer race of the bearing. It eventually turned towards the gear teeth, and fractured the rim of the gear.

Credit: AIBN

The crack in the planet gear then caused cracks in the gearbox, which lead to the separation of the main rotor. The investigation also found that the combination of material properties, surface treatment, design, operational loading, and debris caused a failure mode that was not anticipated or assessed.

Contributing Factors

Airbus further elaborated on the potential contributing factors that lead to the planet gear failure:

• Very limited spalling (a degradation of bearings over time), and an insufficient detection accuracy for this
• Metal fatigue, and a maximum operating time that wasn’t limited enough
• The design of the planet gear was not identical between each individual gear, even if it matched the technical specification. The differences were based on which manufacturer made the gear to be used in the main gearbox. One planet gear introduced greater contact pressure between other components
• Contamination of the gearbox by impurities that entered the main gearbox during maintenance

What Improvements Were Made by Airbus?

Airbus has made numerous improvements to the main rotor gearbox and other areas, as announced in this video from Airbus:

It highlights the main improvements made by Airbus themselves, which are:

• A review of quality and safety processes for all Airbus helicopters
• Traceability on handling and tracking components
• Reassessment of the stress analysis for all their aircraft
• Removal of the problematic planet gear type, and the only planet gear now used has registered over 22 million flight hours without any outer race spoiling in normal conditions
• The launch of a research program on how to analyse vibrations more accurately using leading universities
• Applying vibration sensing techniques to epicyclic gear trains as a way to detect damage
• Improved metal particle detection in the gearbox by using new magnetic plugs, and a reduction of allowable collected particle size
• A reduction in maximum operating time of the planet gear by a factor of 4
• Additional measures to make sure the gearbox is protected during maintenance, to avoid contamination of parts

In addition to this list, Airbus announced that they have improved the H225 in ways that don’t just revolve around the main rotor gearbox:

Credit: Airbus Helicopters

In addition to this, remember the 4.2 mm hole we discussed for the 2012 ditching? Airbus improved various items for this after those accidents happened, including:

• New tooling to comply with increased tolerances
• A final polishing operation to remove corrosion
• More thorough and frequent inspections
• Introduction of a sealant to fill the gap between the PTFE plug and countersink
• New serial numbers for the shafts that comply with the new improvements
• Recall of all in-service shafts that didn’t
• Introduction of 5 µm acceptance criteria specifically for specific shafts

So that’s a summary of the technical improvements, but how has this impacted overall perception of the type?

Has the Super Puma Reputation Been Restored?

It is safe to say that Airbus has done a lot to address the reliability and reputation of the Super Puma family. When the 2016 crash happened, the reputation of the H225 in the North Sea took a serious hit. A lot of offshore workers came forward to discuss the future of offshore helicopter travel.

One of the offshore unions, Unite, threatened to strike if the helicopter continued to be used for passenger flights in the North Sea. A petition that was circulated by North Sea oil workers and their families to ban the Super Puma, received more than 27,000 signatures. In addition to this, a 2017 survey conducted by Airbus that asked over 5000 people, found that 62% of respondents would not fly on it again.

In the same year, the National Secretary for the Union RMT, Steve Todd, said:

But all of this happened right after the crash, so what is the perspective now? Well, as reported by Vertical Mag at the start of 2024:

And:

And:

So, the question is: where does this leave the future of the Super Puma family? While offshore companies in Europe appear to be focussed on other types, the H225 is still used across the globe in lots of different industries.

Pilots who have flown the type still speak very highly of it, and while the type has had its difficulties, there is no denying it offers a lot of different benefits that are hard to find at the competition.

Resources

Accident Report for G-REDL

Accident Report for G-REDW and G-CHCN

Accident Report for LN-OJF

Conclusion

The Super Puma helicopter family has faced significant challenges over the years due to technical issues and accidents, which have led to damage to the type’s reputation. However, Airbus has taken various measures to address the root causes of these incidents and implement improvements.

There are still many areas in the world where the H225 and previous versions still fly successfully, and pilots still speak highly of it. However, for the helicopter to make a full comeback, it will depend on the trust offshore workers have in the type in the coming years, and how the competition will ramp up their efforts to enter the offshore market.

We don’t publish all our Notes from the Cockpit (like this one) publicly, some are shared only by email. Get the next one sent straight to your inbox ⤵️