EASA studies satellite approaches to bolster offshore helo safety

 - August 28, 2009, 7:48 AM

The recent spate of accidents in helicopter offshore oil operations has thrown safety research programs–many of which have long been under way–into the spotlight. The European Aviation Safety Agency (EASA) is working on improving the safety of offshore helicopter operations through research into satellite-guided approaches–which would rely on Egnos, Europe’s Waas counterpart–and, in case of ditching, a side-floating concept.

Instrument landing systems (ILS), which provide highly precise landing guidance at many airports worldwide, are deemed generally unsuitable for oil and gas platforms.

According to an EASA expert, the presence of metallic masses, such as neighboring platforms and ships, generates electromagnetic interference with the accuracy required of ILS. Moreover, precise calibration would be difficult, if not impossible, on rigs that move with wave swells. Finally, the cost of installing an ILS on each platform would be prohibitive.

EASA is therefore discussing instrument approach (rather than landing) systems that would not require rig-based equipment. The European Commission has already funded two research programs: Giant (GNSS introduction into the aviation sector) and Hedge (helicopters deploy GNSS in Europe). Only “a more or less ordinary GPS/Egnos receiver and some additional avionics are required in the cockpit for such approaches,” the EASA expert said. A prerequisite, however, is the certification of Egnos’s safety-of-life signal. This is expected next year.

The approach procedure will “basically [be] an IFR letdown to a missed approach point [MAP],” an expert explained. The MAP will be offset 30 degrees from the rig at a distance of 0.5 to 0.75 nm and 200 feet above the helideck. The procedure will thus resemble current airborne radar approaches, which use the helicopter’s weather radar but are less precise. “To what extent additional guidance can be provided to the flight crew for the last visual part of the approach [between the MAP and the helideck] will have to be investigated,” the expert added.

The EASA is also looking for ways to improve survivability in case of ditching or uncontrolled water impact. Under the side-floating concept, the helicopter would have additional flotation bags “high up on the side of the cabin,” another specialist explained to AIN. The idea is to prevent total capsize. If the aircraft lies on its side, some airspace is retained within the cabin. Occupants then have more time to escape, and egress is easier when some doors and windows remain above the water surface.

“Most fatalities in ditching/water impact events are due to drowning, so preventing inversion and maintaining a survival environment inside the cabin is key to enhanced safety,” the EASA specialist emphasized.

Existing requirements for ditching are minimum Sea State 4 (moderate), although some helicopters have higher standards.

In some parts of the world, including the North Sea and the North Atlantic, such conditions are regularly exceeded. When that happens, or if adverse wave types are present (such as breaking waves) or if there is damage to the flotation system, the helicopter is highly likely to capsize if equipped solely with standard floats. This is due
to the helicopter’s inherent instability and high center of gravity. Adding upper flotation bags would also enhance redundancy.

According to the specialist, testing and analysis have already shown the concept is feasible. One outcome of the study, which was conducted by Eurocopter and equipment manufacturer Aerazur, was the cost for retrofitting an EC 225, roughly €300,000 ($400,000). Development costs would be close to