Relentless

A pilot himself, McQuestin flies with Bell as part of the flight operations team. His airborne role sees him undertake demonstration flying on the Bell 429 and Bell 505; both smaller helicopters than the newer 525 – of which McQuestin has already put his hand up to fly once it’s certified.

“We’ve been anticipating it being certified for a while now. It’s obviously a large process certifying an aircraft insofar as getting all the requirements for FAA certification; which become more stringent year on year,” McQuestin says.

“This will be the first commercial certified fly by wire helicopter, so it’s new for FAA as well to go through that process.”

Relentless

Announced at 2012’s Heli-Expo in Dallas, the Bell 525 Relentless is a clean-sheet super-medium twin helicopter. Created to undertake various roles, the 9.3-tonne aircraft is powered by two GE CT7-2F1 engines. It was developed with multi-functional use in mind; providing opportunities for government, military, mining and civil operators.

As a new design, the Bell 525 takes advantage of modern technologies, and incorporates various technological advances into the airframe, its avionics and the various components used throughout.

“The main rotor blade design has swept tips and thin leading edges, and there have been upgrades to engines, APU and aerodynamics,” McQuestin says of some of the design features.

“What you have is the most recent clean sheet design that’s also best in class because it’s the fastest in its class. At its longest ranges, it will be more efficient at doing more work than the heavy class of helicopter that’s actually the class above it. This is what we’re seeing, as the 525 is being considered for tenders and programs and missions around the world.”

Utilising a high degree of composites throughout the airframe, cowlings and fuselage, McQuestin says the helicopter’s design was informed by a Bell advisory panel, that included key operators in the parapublic, commercial and offshore oil and gas sector.

With fly by wire being commonplace across the commercial airline industry, McQuestin says the advisory panel were: “Interested in a fly by wire system that offered the safety and robustness that the airline industry had. They see that as the benchmark for safety – so that’s where Bell went with the 525.”

As such, the Bell 525 will become the first fly by wire helicopter in the commercial market, though the manufacturer is by no means novice to this style of technology.

“Bell is not new to building fly by wire helicopters and tilt rotors. We have fielded aircraft with hundreds of thousands of hours on them which are fly by wire, including the Bell-Boeing V-22 tilt rotor,” McQuestin notes.

It has been a long road to develop and certify the Bell 525. With the aircraft first announced in 2012 and its inaugural flight taking place in mid-2015.

Systems check

As a brand new design, development of the Bell 525 took advantage of modern aeronautical practices that offer proven benefits across fixed wing aviation and military applications.

Fly by wire is perhaps the most notable of these advances, with the technology offering a variety of advantages for operators of the Bell 525.

“When we talk about fly by wire, there’s safety inherent in those systems. It’s not just that the workload is reduced for the pilot, but it’s also a triplex redundant system – it can pick up its own issues as they come along,” McQuestin notes.

“If you think of a duplex system, one system says ‘I’m high’ and the other says ‘I’m low’ – so which one is the actual system that is operating correctly? The triplex system will sit there and see: ‘I’m high’, ‘I’m high’, ‘I’m low’ and it can say: ‘OK, the low one isn’t working, so let’s stop listening to it.’ That’s a basic way of looking at the safety inherent in a triplex system.”

The Bell 525 complements fly by wire systems with a Garmin G5000 glass cockpit. It features large multi function displays that offer aviators a superior visual workspace to analyse systems, diagnostics and troubleshooting.

Of the flight deck, McQuestin says, “It’s controlled by two hand-sized panels in the pedestal. So rather than having an FMS computer where you type things in on a keyboard, you have a Garmin panel touch screen that allows you to navigate through all the features and options and run the Garmin G5000 screen that’s up on the dash.”

The displays are designed to be intuitive, aimed at reducing pilot workload. Wide screen displays were incorporated to allow for detailed diagrams to be accessed, while intuitive colour-coded imagery assists in quick analysis of information.

McQuestin elaborates: “If you want to see the entire hydraulic system you can pull them up on the wide screen and see it in a wide diagram. It shows you what you need to see, if its green you’ll see its working. If they’re not green you’ll know there’s something going on.”

Mechanically, Bell has developed a main rotor gearbox that has a 5,000-hour overhaul time limit, which, McQuestin notes, “Meets the latest requirements for gearbox performance in the event of loss of lubrication.”

“They’ve really done a lot of work on designing that main rotor gearbox so that it has no high-speed items in it, and that Bell has shown more than an hour of ‘run dry’ capability on each of the 525’s gearboxes,” he adds.

Additionally, Bell offers complimentary training with its aircraft sales, giving buyers access to a Level-D full flight simulator at the Bell training academy in Texas.

“I’ll be putting my hand up for that, as soon as we can travel again,” McQuestin adds with a smile.

Target market

Helicopters of different sizes are suited to different roles and missions, with the Bell 525 fitting into the super-medium category. However this aircraft was designed with multi-functional roles in mind.

While designed to hold 16 seats in a standard layout, the aircraft is easily configured for various missions: from transporting passengers or troops to medivac or search and rescue.

“The cabin space is completely open, including the cargo area, and can be quickly reconfigured to any mission. So, you can go from troop transport for the military, to a medevac helicopter really quickly by pulling all the seats out of it and putting in stretchers,” McQuestin says.

“It will have a dual hoist certified for it, to allow for search and rescue; and if you think about the search and rescue aircraft that are used in Europe and around the British Isles, they use large helicopters for off shore search and rescue.”

Additionally, the Bell 525 is expected to be well suited for offshore oil and gas missions, where its large, spacious cabin and roomy seats will offer improved comfort.

“Particularly if you look at the North Sea or southern areas of Australia and New Zealand, the off shore oil and gas workers have to wear large dry suits, so you don’t generally have a lot of room in helicopters flying to and from the oil rigs,” McQuestin notes.

In response, Bell installed larger, comfortable seating, offering extra space per passenger. Large windows reduce any feeling of claustrophobia, while “every aisle is an escape aisle, so the egress of the helicopter is best in class in the event of an emergency”.

Ongoing cost savings will be achieved thanks to a reduced fuel burn, with McQuestin noting: “It’s fuel burn is going to be something like 30 per cent less than the heavy class of aircraft, and the seat per mile will really shine for the 525 in that economic space.”

And performance was a key factor in the aircraft’s development with single engine hover performance being achieved at sea level for the 525 at maximum take-off weight. “It has OEI capability. It is certified Category A, up to max take off weight at sea level. This was driven out of the steering group,” McQuestin adds.

A long road

It has been a long road to develop and certify the Bell 525. With the aircraft first announced in 2012 and its inaugural flight taking place in mid-2015.

In July 2016, the prototype was lost in an incident that took place while simulating a one engine inoperative test. The accident resulted in the deaths of both crewmembers.

The prototype aircraft, N525TA, was at an altitude of 2,000 feet, travelling at around 368km/h when vibrations caused vertical oscillations in the main rotor. As the oscillations worsened, it led to a flapping effect, causing one of the blades to make contact with the tail-boom. As such, the fuselage broke apart.

As a result of the accident, Bell implemented several improvements to the 525s flight control systems, before resuming testing in 2016.

“We’ve been backing the helicopter with Bell research and development funding, post the accident and getting back to a flying start date, they’ve continued to do the certification and the flying at the maximum rate possible to get it flying as soon as possible,” McQuestin notes.

As with all new aircraft types that introduce technologies that are new to the commercial market, certification may be an extended process.

McQuestin adds: “It’s a large process certifying an aircraft insofar as getting all the requirements for FAA certification; which become more stringent year on year. But also, this will be the first commercial certified fly by wire helicopter, so it’s new for FAA as well to go through that process.”

Testing of the Bell 525 isn’t limited to flight tests, with numerous on-ground tests undertaken to push the airframe to its limits. This includes a robust series of stress trials, designed to simulate a lifetime of use.

“When they test the airframe out to its life of type on machines and cradles in the factory, they actually embed flaws into the test airframes,” McQuestin elaborates, adding: “Then they activate the machine to run what looks like the maximum landings and maximum airframe life that the airframe should hold, and make sure that even where the embedded flaws are, that the aircraft doesn’t fail prior to that minimum requirement.”

Counter corrosion

A key feature of the Bell 525 is marinisation. As the term suggests, this marine-centric process sees corrosion proofing implemented throughout the aircraft.

With the Bell 525 expected to attract offshore oil and gas contracts – which operate over seawater up to 90 per cent of the time – the aircraft has been pre-marinised down to an airframe and component level.

Considerations were made when designing and building the helicopter, with components being made from non-corrosive materials.

“They won’t put particular materials next to each other in the airframe because they’re known to cause a corrosion risk, and in general, in modern aircraft as well, composite panels are used that don’t rust like traditional metals,” McQuestin notes.

By pre-marinising the aircraft at the point of manufacture, the Bell 525 should require less ongoing corrosion prevention maintenance than previous-generation helicopters.

“What it does is reduce the ongoing running cost of the helicopter. Maintenance equals time, and time equals money, and then possibly earlier replacement of some components and items that are affected by the salt environment,” McQuestin says.

Ready for take-off?

With the Bell 525 nearing the end of its certification process, all eyes are looking skyward for its introduction into commercial service.

Despite a lengthy development, McQuestin notes that numerous companies and organisations: “Have followed the 525 through the process to certification,” adding: “It is up for consideration in a number of roles globally. It will be a matter of winning competitive tenders.”

Core to its future success is the aircraft’s clean-sheet design and specifications. The fly by wire and glass cockpit will bring modernity to the super medium category, while certification of the type will be achieved to the latest and most robust standards.

McQuestin adds: “In markets where safety is king, you’ve got a brand new helicopter, fly by wire and the latest certification standards. Because it will be the most recently certified helicopter, it will meet the most recent and stringent safety standards.”

This, coupled with marinisation at a component level, fuel savings compared with the heavy-class of helicopter and support from the Bell training academy, should lead to interest in a variety of markets around the world, including Australia – where the aircraft’s search, rescue and offshore oil and gas capabilities are well placed.