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Rotor Hub, - August-September 2011 -- Manufacturers of helicopters and related subsystems have long been focused on the requirements of the oil and gas sector, developing technologies to ensure safe offshore operations.

 

At the heavy end of the field, arguably the two most important transport helicopters in this industry are the Eurocopter EC225 and Sikorsky S-92.

 

The importance and demanding nature of offshore operations is evident in the time and money that has been invested in evolving the capabilities of both these aircraft. While the EC225 and S-92 generally utilise more advanced equipment than their lighter industry counterparts, much of the technology developed specifically for the oil and gas sector could filter into others.

 

Unique capabilities
The EC225 was derived from the AS322 Super Puma and, according to Eurocopter, features significant advances in man-machine interface, decision-making and piloting aids, offering improved performance, including range and endurance. Mickael Melaye, senior operational marketing manager for oil and gas applications at the company, said that there is a specific set of equipment often requested by offshore operators.

 

These include Eurocopter’s four-axis digital AFCS, a de-icing system, HUMS, a helicopter terrain awareness and warning system, TCAS II and flight data monitoring programs.

 

‘The AFCS provides automatic hover flight capacity without any wind limitation, and is the only one on the market permitting automatic take-off and landing when pilots have no visual reference,’ said Melaye.

 

He added that the EC225 was designed with the capability to maintain flight in ice-accretion conditions, and is ‘perfectly adapted’ to missions occurring in such severe weather. He also said that Eurocopter had upgraded the standard configuration of the aircraft with advanced safety equipment.

 

These included: new advanced radio and intercom systems; an Automatic Dependent Surveillance – Broadcast (ADS-B)-capable transponder; the coupling of the TCAS with the AFCS and Advanced Helicopter Cockpit Avionics System; and the upgrading of the AFCS with enhanced command laws (ground speed mode and distance-to-stop assessment).

 

In addition, the inclusion of basic wiring for hoist, searchlight and dual flight management systems will simplify the aircraft’s conversion for SAR operations.

 

Gilles Bruniaux, VP of operational fleet safety at Eurocopter, noted that his company was now able to integrate data from the Wide Area Augmentation System (WAAS) air navigation network into an existing helicopter display system following EASA approval in July 2010. ‘With incorporation of WAAS data, landing on oil rigs or sites not equipped with ground navigation aids will be easier, especially in poor weather conditions,’ he explained.

 

Extra strength
Meanwhile, the S-92 uses systems similar to those of the EC225, but also comes with some unique capabilities. Sikorsky highlights its spacious, high-visibility cockpit, as well as modern avionics with large NVG-compatible displays, a flight management system with GPS and a Multi-Mission Management System, high-intensity radiated field protection, HUMS, enhanced ground proximity warning system and TCAS I. In addition, sponsons have been utilised to keep fuel away from passengers, while a suction system prevents hazardous fuel spray.

 

Other survivability features include energyabsorbing landing gear, built-in corrosion resistance, bird and lightning strike protection, high-energy turbine burst protection, an optional rotor ice-protection system, an electronic location transmitter (ELT), upper and lower anti-collision lights, crashworthy seats, jettisonable cabin windows, three cabin emergency hatches, an emergency flotation and life raft system and emergency exit lighting.

 

A strengthened main transmission housing developed for the higher gross weight military H-92 is being offered on new S-92s and is also available as a retrofit. Sikorsky has also indicated that it could introduce future H-92 technologies on its civil models.

 

In March, the company announced that the S-92 had been approved by the FAA to execute ‘Category A’ vertical take-offs and landings from ground helipads, noting that this required the ability to safely land or continue to fly from the helipad after a single engine failure.

 

Finding the way
Industry has also been seeking to improve oil and gas helicopter navigation through developing technologies such as ADS-B, multilateration, precision landing and helideck lighting technology.

 

According to industry association Oil and Gas UK, the new North Sea Wide Area Multilateration (WAM) helicopter tracking system, which became operational in December 2010, enables both rotary- and fixed-wing aircraft positions to be shown in real time on ATC displays without actually using radar.

 

The system uses signal transmitters and receivers on 16 oil and gas platforms (in four four-platform ‘clusters’) in the central North Sea, and covers an area of 25,000 square miles. Oil and Gas UK noted that, while previous shore-based radars only tracked helicopters up to 80 miles from land, the new system follows flights all the way from runway to platform.

 

The responsible contractor, Sensis, says that the system employs the same standards and procedures as a traditional radar network, but with a higher update rate and greater positional accuracy. It can track flights using transponder modes S, A/C or ADS-B.

 

The transponder of a helicopter departing from the shore-based radar zone receives an interrogation signal from a platform, which it re-transmits. Receivers on each of the four platforms in a cluster detect this signal and send the data to the control tower at Aberdeen airport. While three received signals allow the position of the helicopter to be determined, the fourth improves accuracy and provides redundancy.

 

‘Installing a WAM system on oil and gas platforms posed similar challenges that a number of such installations typically face – power and communications constraints and a harsh physical operating environment,’ said Rob Conrad, a spokesman for Sensis. ‘In addition, the platforms have limited available space for equipment.’

 

One of the sensors is located on a moored production ship, with positional changes of up to 100m. He identified this as a unique aspect of the North Sea system, noting that the ‘sensor must continually correct its position as the ship moves, making it the industry’s first deployment of a moving multilateration sensor’.

 

Trial separation
In June 2011, Sensis announced that it had been selected by Avinor, a Norwegian air navigation service provider, to deploy an ADS-B system for the surveillance of oil and gas helicopter traffic in the part of the North Sea adjacent to that country. This will comprise onand offshore ground stations, and will allow a minimum separation of 5nm between aircraft. US helicopter operator PHi has already introduced ADS-B technology to oil and gas operations in the Gulf of Mexico on S-92s.

 

The helicopters automatically transmit position and other flight information to land-based receivers, which is then relayed to the FAA ATC centre in Houston, Texas, allowing it to maintain a consistent less-than-5nm separation between the helicopters, a fourfold improvement over the previous system.

 

In terms of precision landing, consultancy firm Helios, in conjunction with the UK CAA, has been developing and validating the new Satellite-Based Augmentation System (SBAS) Offshore Approach Procedure (SOAP).

 

In January 2011, a Super Puma conducted SOAP flight tests at the Beatrice oil platform in the North Sea using Helios’s flexible, portable Rotorcraft Experimental Avionics Package. This processes global navigation satellite system data from the European Geostationary Navigation Overlay Service SBAS, combines it with data from the aircraft’s sensors and provides guidance to a primary flight display (PFD) and navigation display.

 

PFD modes comprise ‘raw guidance’, ‘flight director guidance’ and ‘tunnels in the sky’. According to Helios, pilots found the approaches precise and comfortable to operate compared to traditional ones.

 

Seeing the light
Advances are similarly being made in helideck lighting systems, with AGI and Orga currently testing a new product on a North Sea platform, while a further pilot is being installed on the Centrica CPC-1 platform in the Irish Sea.

 

The former system includes touchdown circle lighting, which comprises light units positioned at the mean radius of the painted circle on the helideck, spaced to provide a minimum of 50% coverage. The light units contain high-power yellow LEDs that are narrow-beamed in order to minimise vertical light emissions and avoid dazzling the pilot.

 

The system also includes a helideck identification marking comprising similar light units, but with green LEDs assembled into a 4x3m ‘H’. AGI expects that the CAA publication ‘CAP 437: Offshore Helicopter Landing Areas – Guidance on Standards’ will be updated to include the requirement of replacing traditional helideck floodlighting with an illuminated touchdown circle and ‘H’ identification marking.

 

Meanwhile, Daniel Powell, business development manager at Orga Offshore, said that his company expects the system to become commercially available in the fourth quarter of 2011.

 

Orga has also developed the L425EX ‘explosion-proof’ LED helideck status (wave-off) light. It says that the system meets the latest CAP 437 requirements – the ability to provide 360° of visibility around the structure with 120 flashes per minute, fully automatically and operated by a control panel that interfaces with the platform’s fire and gas detection system – and can be used in all environmental conditions. Powell indicated that commercial deliveries should begin in July 2011.

 

‘The introduction of LED technology has meant that both the circle and H, and the status light have now become viable to be placed directly on the helideck, and has also led to greatly reduced power consumption and [improved] reliability,’ he said.

 

A smarter choice
Recently, one technology developed for the event of a helicopter ditching has been found to be ‘too’ advanced. ‘Smart’ emergency beacons – ELTs and portable locator beacons (PLBs) – have been designed to deactivate on detection of another beacon signal within a certain radius, simplifying SAR operations by ensuring that only one high-powered beacon is transmitting at a time.

 

However, in an offshore helicopter ditching in February 2009, smart long-range beacons on the aircraft and life rafts detected (non-smart) lower-powered passenger PLBs and deactivated. PLBs were withdrawn from service on oil and gas helicopter flights the following month.

 

Oil and Gas UK’s Helicopter Task Group (HTG) determined that before PLBs could be reintroduced, the smart ELTs on helicopter life rafts needed to be replaced with non-smart technology, and PLBs had to be proven to not inadvertently activate during normal operations or interfere with aircraft equipment.

 

The second requirement involved testing the PLBs and analysing how they interfaced with aircraft types in service. The two requirements were met, and the HTG achieved the reintroduction of PLBs into service in February 2010.

 

Oil and Gas UK confirmed to RotorHub that the Sea Marshall AU9-HT and Rhotheta RT-B77 were the only PLBs tested, and are the only ones available for use. The former transmits a 100mW signal at 121.5MHz and can be tracked by a high-altitude SAR aircraft more than 50km away – five to eight kilometres by boat – and the latter transmits a 2W signal on 121.5 or 243MHz.

Of all the technologies considered, arguably the most ambitious is one that directly confronts the situation of a helicopter ditching – the Aero Sekur helicopter crash landing protection (floatation/shock attenuation) system. It measures vertical velocities of the helicopter fuselage through algorithms that the company developed for the ExoMars lander airbag.

 

Giacomo Giovangrossi, chief engineer at Aero Sekur, said that ensuring controlled touchdown has been one of the most significant technical challenges, requiring development of a shock attenuation system that controls g-forces to manage descent.

 

‘Additionally, we have had to ensure that the aircraft is maintained in an upright position at all times,’ he explained. ‘Sensors are key to preventing helicopter roll. Movement, orientation and details of the landing surface are monitored, and this data is used to control valves, which in turn deflate airbag compartments in the required sequence to keep the craft upright. Tailoring is at the heart of the concept, and this will ensure that the system precisely meets manufacturer needs. This is not an off-the-shelf product – each order will require individual attention.’ RH

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