The term “offshore operations” is used to describe situations where not only a part of the flight takes place over large bodies of water but when most of the flight, including the main objectives, are to be completed away from dry land. Because of their VTOL and hover capabilities, the use of helicopters in offshore operations has increased greatly. In this post, my guest author, Wg Cdr Vikram Mahajan (Retd) will tell us about helicopter offshore operations, their complexities and safety risks.
Crude oil and natural gas are invaluable natural resources for every nation. A large proportion of these are found offshore under the sea bed at varying depths. India as a nation too possesses both oil and natural gas on both the eastern and the western coast. Ability to harness these reserves allows the country to save significantly on the crude import bill.
The difference between the Western and Eastern coast is significant in terms of sea bed depth. On the West coast, the shelf is shallow and the depth increases very gradually. So much so that even at 100 miles plus distance from the coastline at Mumbai, the depth is just about 80-100 meters. On the Eastern coast though the depth increases rapidly and reaches more than 1000 meters at just 10-15 miles from the coast.
Helicopters play a very important and significant role in support of the oil and gas sector performing a large number of flights daily. Before I go on to describe the types of flights, it is important to understand the general layout of an oil field.
OIL FIELD
An offshore oil field is generally an area of sea with defined dimensions and contains a large number of oil wells. Each of these wellheads has a small platform on top with a helideck. Each oil field has a processing platform. All the wells within the field are connected to the processing platform through pipelines at the seabed. The processing platform is a relatively large fixed setup of heavy machinery where some initial processing of the oil is done and then it is pumped via pipelines to onshore facilities. The individual wells are always unmanned and men work on it on a need basis for routine maintenance or in case of other contingencies. The Platforms on the other hand house a large number of crew who work in shifts 24X7. Additionally, it houses administrative and logistic support staff to cater to the boarding and lodging needs of the crew. Just as an example, there are more than 2000 personnel at BOMBAY HIGH as a whole every night.
In addition to the wellheads and the processing platforms, an oilfield at any given time generally contains a few oil rigs operating and also some support vessels. I will cover the oil rigs subsequently.
OIL RIGS.
These are large floating structures capable of undertaking a variety of offshore activities including drilling/ prospecting for fresh oil and maintenance of existing wells/pipelines. They mostly do not have self-propulsion capability and need to be towed around by tugs. They are owned by various private companies or many times by the Govt/PSU. Many of us in our school days were taught about Sagar Samrat in our geography classes. Incidentally, Sagar Samrat was an oil rig owned and operated by ONGC and was retired about a decade ago. Each oil rig houses a set of crew required to undertake the specific job for which the rig is built and operated. All oil rigs too have a helideck located on them to allow for transport of men and material by helicopter. Shallow waters are suitable for rigs that have metallic legs which can be dug into the seabed for operations. Deep waters require semi-submersible rigs. Pics of these two types are attached. Just as an additional information cost of hiring of oil rigs runs into a couple of crores per day.
FPSO.
FPSO stands for Fuel Processing & Storage Offshore. These are large offshore vessels/ships which are modified to undertake limited processing and storage of crude oil. These are used in places where initial drilling has been done and laying of pipelines is not yet completed or at times where it is more economical not to lay pipelines. FPSOs are accordingly positioned in such areas and are connected to the offshore oil wells directly placed below them or within a very short distance from their anchor position. FPSOs generally have a large helideck capable of accommodating medium-sized helicopters.
TYPES OF HELICOPTER OFFSHORE OPERATIONS
Offshore operations by helicopter can broadly be categorised into the following types :-
(a) Routine Crew Change Flights These flights are performed for transporting offshore crew from onshore locations to offshore locations and vice versa. Offshore crew work routinely on a work schedule of 2 Weeks ON and 2 Weeks OFF. Therefore, on a daily basis, a large number of crew are being rotated between onshore and Offshore locations. The crew change helicopter flights are flown from Onshore Base to Oil Platforms, Oil Rigs, FPSos and to Floater vessels. The daily requirements are collated and sorties are planned accordingly.
(b) Production Flying The extremely harsh saline environment at offshore locations necessitates a lot of preventive maintenance in addition to the response to technical contingencies. Therefore, on a daily basis, a large number of crew are deployed from Oil platforms to oil well heads within the field. Helicopter flights to deploy these crew, reposition and to subsequently retrieve them by the evening are called production flights. Production flying involves doing a large number of landings (up to 60 in a 24 hr period) and is therefore extremely fatiguing.
(c) Medical Evacuation Flights These flights are flown on as and when required basis. The helicopter is positioned in the evening at an offshore location to undertake these flights and provides cover to all the oil fields in the area. At some places, the helicopter is kept on stand by at an onshore location to undertake these flights.
HELICOPTER PERFORMANCE
All helicopters undertaking offshore operations are mandated to be capable of Performance Class 1. Operating under Performance Class 1 gives the helicopter the capability to continue the take-off in case of loss of an engine at or after TDP (Take off Decision Point) and in case of loss of an engine before TDP to execute a safe landing back at the helideck. This, therefore, introduces a large degree of safety in these operations. It also implies that all comercial offshore opeartions are undertaken only by Multi Engine helicopters.
Most operations involve flying at the limits of AUW and therefore require a higher degree of skill on the part of the pilots. Additionally, this also leaves very little room for error.
CHALLENGES
Offshore helicopter operations bring with them a unique set of challenges. Some of the important ones are enumerated in the succeeding paragraphs:-
(a) Environment. The offshore environment is deemed extremely hostile both on the fronts of Operations and Maintenance. There are very few helidecks which are suitable for carrying out a landing with an emergency on board. Loss of an engine dictates a diversion back to an onshore location/Runway. Landing with FIRE on board is forbidden on oil platforms as it can lead to fire hazard for the platform, Therefore, just imagine the plight of a pilot if God forbid he has an engine fire and it doesn’t get extinguished. I will leave it to the imagination of the readers to contemplate what would go on in the mind of that offshore pilot. Certain conditions allow for landing on small helidecks in case of contingencies. The subsequent retrieval of the helicopter from those decks is a nightmare for maintenance personnel. On the maintenance front, the saline environment causes rapid corrosion both on the engine and the airframe and necessitates preventive maintenance on a daily basis in the form of Engine compressor wash and washing of the airframe with fresh water. It also increases the frequency of maintenance checks required thus increasing the workload substantially.
(b) Weather. As with all other flying, weather presents a significant challenge in offshore operations. The paucity of suitable areas to carry out a precautionary landing due to weather makes it all the more significant. To add to the issue is the fact that there is not much leeway in terms for additional fuel carriage in case of helicopters. And in commercial operations, as every additional pound carried means additional revenue, very little margin is left at the discretion of the pilot in terms of additional fuel uplift. Therefore, the pilots have to exercise their skills, both mental and flying during adverse weather conditions to ensure the safety of operations.
(c) Winds / Obstructions The oil platforms vary significantly in shape and size and each has its unique set of obstructions which present a hazard to helicopter operations. The orientation of runways is decided by the overall wind patterns. In the case of helideck location on an oil platform while the general wind pattern is taken into consideration but multiple other technical factors from the standpoint of oil and gas extraction assume more significance. The net result is that at many locations, the sighting of the helideck is not ideal from the operations standpoint and thus ends up presenting significant challenges on approach and take off. Wind direction and strength and helicopter control in crosswinds can add/reduce the misery of the pilots.
(d) Floater Ops Floater operations are carried out to helidecks on board sea going vessels which are equipped with a helideck. They come with additional restrictions and challenges. The helicopter operations to floating vessels are limited by values of ROLL, PITCH and HEAVE and are defined by the OEM for each type of helicopter. For Example for a Bell 412, the limitations are 4 deg Roll/4 deg Pitch and 2 metres Heave. These values are reported by the floater vessels and are many times misreported. Thus, while the reported values are within limits the pilot finds himself at all odds trying to safely put down the helicopter on the deck of a vessel during rough sea. Floater landing during rough sea leads to many accidents/ incidents every year.
UNIQUE ASPECTS OF AN OFFSHORE APPROACH
The helicopter offshore approach to a helideck has some unique aspects worth enumerating. The obstructions around the helideck and winds at a given time strictly dictate the direction of approach. This also in most cases dictates as to which pilot i.e left seat or the right seat is ideally suited for executing the approach. This havine been decided, that pilot takes over as PF and flies the approach. The offshore approach is steeper with an appraoch angle close to 5 deg. The intersting part happens at about 300 ft from the deck. At this point on a correct approach the PM loses sight of the deck and gets to see helideck only when the helicopter is below 50 ft or so and is entering the helideck. So from 300 ft onwards, it is an act of faith in the other pilot making the approach. If both pilots can see the deck, it implies that the helicopter is below the correct profile. The judgement of high approach by the PM comes with the experience of taking cues from other visual indiactors around the deck. This is in total contrast to fixed-wing operations where both pilots can see the exact same thing on an approach and are in a position to advise each other in case of significant deviations.
CONCLUSION
It, therefore, becomes amply clear that offshore helicopter operations are significantly different in complexity vis a vis onshore operations. They come with their unique set of challenges which need to be adequately compensated for to ensure safe operations. They are though a significant Force Multiplier in realms of the oil and gas sector and offer substantial time and cost benefits. Last but not the least, their contribution to morale-building of the offshore crew is immeasurable. They always have and will continue to bring cheer to personnel working offshore all around the world.
About the Author
Wg Cdr Vikram Mahajan (Retd) was commissioned in Indian Air Force on 16 Jun 1990. He trained on the HPT-32 and HJT-16 Mk II aircraft in the pre-commissioning training. He joined the helicopter stream and flew Alouette, Mi-8, Mi-17 and the Mi-26 helicopters with the IAF. He took premature retirement in Sep 2012 and worked in the offshore helicopter industry for 5 years flying the Bell 412 helicopter. He is qualified on both helicopters and aeroplanes and holds both ATPL(Aeroplane) and ATPL(Helicopters). He has a total experience of 7200 hrs accident/incident free flying over 31 yrs. He is currently flying Bombardier Dash 8 Q400 aircraft with SpiceJet.
