Ensuring safe landings in hostile environments

Anthony Gaffney
Tuesday, December 15, 2009

Landing a helicopter on a fixed platform can be testing at the best of times, but landing on a floating vessel with changing vessel motion and significant weather variations throughout the day quite another matter. Fugro’s Anthony Gaffney discusses how a sophisticated helideck monitoring system on BP’s Schiehallion FPSO has measured up to the demands of its hostile West of Shetland location.

Safety and cost are keywords in all offshore helicopter operations. They become all the more critical when assessing the criteria for safe landing after long flights to and from floating production or drilling units.

In such cases reliable information on weather and helideck motion needs to be supplied at the very outset of, and continually during, a flight to give maximum opportunity for the flight to be completed safely and efficiently.

The CAP437-rated helideck monitoring system on BP’s Schiehallion FPSO in the environmentally challenging West of Shetland region can now determine rate of heave and is being further upgraded to include new parameters such as cloud cover and visibility.

Landing a helicopter on a fixed platform can be testing at the best of times; but landing on a floating vessel with changing vessel motion and significant weather variations throughout the day to be taken into consideration requires not only skill but, importantly, accurate data on wind, visibility and vessel motion. Helideck systems require input of heave, pitch and roll to calculate landing conditions which are also affected by other factors including seastate, the vessel response characteristics, vessel draft and heading.

With the safety of their personnel and loss of manhours in mind, BP commissioned Fugro GEOS in 2004 to equip the Schiehallion FPSO, located 100 miles west of the Shetland Islands – 180 miles from Aberdeen – with its CAP437-rated Helideck Monitoring System (HMS) for a trial period. BP took this a step further by providing live helideck data from Schiehallion at the pilot briefing room in Aberdeen, updated every minute.

Anthony Gaffney is a metocean specialist with over 20 years’ experience of installing and supporting offshore metocean systems globally. He manages the Fugro GEOS offshore systems division worldwide.

The helideck monitoring system on the Schiehallion has provided a full range of benefits to BP. These include an increase of 20% in successful helicopter flights. Before they had the system there were high incidents of delays.

Helicopters would fly out but not land resulting in a serious knock-on effect on other flights for the operator.

TOP: Fugro GEOS helideck real time monitoring display from Schiehallion and (ABOVE) the company’s new MSI (motion severity index) web display.

‘So it is fair to say that we have seen extensive cost benefits including savings on flights that are unable to land; flights that are booked and don’t fly; and unexpected personnel costs,’ explains BP’s Steve Smith. ‘The system ensures that we can now plan with greater efficiency and with confidence. There is another very important benefit – increased staff morale. Thanks to the system they are no longer delayed unnecessarily on the vessel waiting to go home.

Comparison of measured and forecast data for FPSO Schiehallion, West of Shetland.

‘Five years from its initial installation, the system is still playing a reliable role and handling at least five BP 11/2 hour flights a week,’ he notes. ‘We rely on Bond, which provides the safety guidelines, to advise optimum flying times and conditions. The helideck monitoring system has provided Bond with more confidence and also helped improve the relationship between us and them by providing both companies with data that they can now view themselves, anytime on the web. Public live data provides pilots with more confidence and BP management with the credibility that substantiates their decisions.

‘Following advice from Bond, the HMS is now being upgraded to include higher specification sensors delivering higher accuracy and new parameters including acceleration, cloud cover and visibility,’ he adds.

Capt Tony Duff of Bond Offshore Helicopters takes up the story: ‘The helideck system provides a much safer environment for the landing of helicopters on the deck. With the new upgrade the parameters are not limited to just pitch, roll and heave, but are now be able to determine the all-important rate of heave. The old system relied on the pilot’s judgment as to whether he thought he could land on the vessel, although the vessel’s heave was possibly 5m (moving up and down) they could not always assess the helideck’s speed of movement.

‘Now they need not worry about how high it goes but whether it can land on the deck in a controlled fashion. If we set the limits on the deck of 1.3m/s, that’s just 250-260ft/min that it is actually moving, so it is a controlled movement up and down.

‘The Norwegian authorities who have been using the rate of heave for over 10 years, are working with the UK Civil Aviation Authority (CAA) in trying to establish a MSI/WSI (motion severity index and wind severity index) standard across the North Sea, with the cooperation of the operators,’ he explains.

Having run trials for two years on the Schiehallion with BP, Bond has now passed on the helideck system data to Atkins which, with the CAA, has been developing a MSI/WSI standard and is currently running trials. This standard is an extension of rate of heave, but it also includes wind which has a side effect on the helicopter potentially forcing it to roll over.

‘The West of Shetland can often see wave heights that make the Schiehallion FPSO exceed the current limit in amplitude,’ explains Capt Duff. ‘Hence it has led the way in the UK sector in many aspects – one being the helideck system. Together with BP, Bond made sure that from the start the system had high specs and it certainly has helped improve the rate of landing in the challenging West of Shetland area. Safety is paramount – it isthe key, and this system enhances safety, and thus efficiency.

‘Being able to view the data online provides a lot more confidence because one is aware of what is happening and it reinforces a lot of expectations, eventually the aim will be to view this data in the cockpit.

‘We ensured the system had the capability of providing trends over the previous 12 hours – it gives the offshore installation manager the capability to establish if there is a downward trend predicted, so if they are likely to be out of limits at that point in time, he is then able to reasonably forecast whether it will be within limits by the time the helicopter reaches its destination. They work on a 2-3 hour lead time and they expect that using the data they can determine whether it will be within limits once it reaches the deck. This means they can make maximum use of the window of opportunity and thus prevent delays that can cause serious backlogs to other scheduled flights,’ says Capt Duff, adding that Bond has always been proactive in looking at how to improve the situation and taking it forward in a positive and safe way.

Fugro also lays claim to being the first commercial company to have its helideck system certified by the Norwegian Civil Aviation Authority. With the new upgrade BP leads the way by incorporating both the proven Norwegian standard and CAP437 standards for the UK.

Another feature that has been added to the Fugro system is forecast data that allows the operator to compare the measured data with forecast conditions, providing Bond and BP management with the ability to predict more accurately and plan their operations. The integrated display is available at the heliport for pilot briefing. Direct comparison of the forecast performance with measured data in real-time provides additional guidance on forecast confidence.

Looking at the technicalities

Fugro engineers have worked for many years in helping to provide useful information for helicopter operators. The Fugro software and system design has proven to be ideal in integrating differing inputs form a wide range of sources and managing data to suit a vast range of applications.

Clear software displays show and provide online access to the data that are needed for operational decision making and pre-flight planning. They allow the vessel motion, wind and wave trends to be examined for expected conditions on arrival. Any adverse weather working policy thresholds can be added to the display or used to trigger alarms.

Measured parameters displayed include: heave, pitch, roll, surge, sway and yaw; heave rate, heave acceleration; helideck inclination; motion and wind severity index; barometric pressure (QNH, QFE); wind speed and direction; and air temperature and relative humidity.

Optional parameters can include: sea water temperature; waves (directional/non-directional); sea currents; visibility and cloud height; precipitation; and lightning monitoring.

The software is designed to meet the latest regulations and certification standards required by helideck monitoring systems for offshore FPSOs such as Schiehallion and floating vessels. These include specific ‘Standard Measuring Equipment for Helideck Monitoring System (HMS) and Weather Data guidelines’ issued by CHC Helicopter Service and the Norsk Helikopter Service.

The HMS software has been proven operationally under extreme conditions for over a decade in the North Sea, and has been installed in over 400 sites around the world meeting stringent regulations and requirements in different countries and regions such as Norway, Canada and Brazil as well as the on the UKCS.

‘It’s a good system, we embrace the addition of rate of heave – it works well,’ concludes Capt Duff. OE

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