Superyacht helicopter deck design solutions
by Dudley Dawson
One of the hot topics in yacht design is the continual updating of something that’s been a feature on superyachts for decades: helipads.
I first encountered one in 1985 with the 36.8 metre motor yacht Buckpasser built at Hitachi-Zosen for an American sportsman. She was one of the earliest yachts to boast a fully functional helicopter landing area. Ogden Phipps used the helicopter in conjunction with his hunting and fishing exploits around the globe, often towing his Merritt sportfishing boat as well.
Even today, Buckpasser remains one of the smallest yachts to incorporate a helideck. The reason is simple: helidecks take a lot of planning, space and money. The sacrifices are often not worth it for a smaller yacht where the trade-offs are proportionally greater. As a yacht grows in size, the costs and compromises become more manageable as part of the overall project.
There are two approaches to helicopter landing aboard yachts. The first, the ‘touch-and-go’ or emergency landing pad, is a spot for the helicopter to land, never shutting down, and take off as soon as its passengers or cargo have embarked or disembarked. There are no set standards for such operations, with the details governing them worked out on a case-by-case basis between the designers, builders and relevant regulators from civil aviation, classification society, flag state and insurer. Note that this is only for non-commercial operation.
The touch-and-go has no real reference, asserts David Nelson, principal aviation consultant at Helidecks Training Solutions, a yacht helipad design consultancy and MCA-accredited training service. ‘However, the owner of a “private helipad” would be foolish not to have equivalence with the standards. Most classification societies have their own minimum firefighting and rescue equipment to satisfy ISM requirements.’
None of this indicates that every non-certified helipad is unsafe. Many comply with the spirit and requirements of the commercial regulations but miss certain dimensions by centimetres. Such is the case with Feadship Lady Christine, built for a certified helicopter pilot.
The second approach, called fully certified or commercially certified, is a lot more comprehensive. For superyachts flying the Red Ensign or its equivalent, particularly those in charter or that intend to charter, the primary regulations governing their design, construction and operation are found in the Maritime and Coastguard Agency’s Large Commercial Yacht Code (LY3) Annex 6.
Between ‘touch-and-go’ and ‘fully compliant’ lies a grey area of compromises for private-use situations that some designers and builders are reluctant to discuss.
‘International aviation regulations mandate that all helicopters engaged in commercial air transport operate to a certified helipad or in this case helideck, which must have been constructed to defined standards and characteristics,’ Nelson says. ‘A private yacht and helicopter owner need not build his helideck to the same standards, nor gain certification, if the use is solely non-commercial. This does have a limitation, however. The owner would not be able to use a charter helicopter service to arrive at his private helideck.’
Even if a Red Ensign yacht complies fully with Annex 6 and is approved by the flag state, its crew, helicopter and pilot are subject to the requirements of the port state as well. Even Annex 6 states, ‘The landing area will be limited to receiving helicopters in the conditions agreed by the Aviation Inspection Body.’ This refers to weather conditions, but it is more broadly applicable. To navigate such a labyrinth of requirements is daunting. Many owners and captains delegate this task to specialised private agencies that assure all is in order before arrival.
‘The length free of obstacles is 1.25 times the length between the tail rotor and the main rotor shaft. Say that distance is 13 metres, then you need 16 metres length free of obstacles. This is a large area, especially on yachts less than 70 metres,’ notes Ronno Schouten, chief designer for De Voogt Naval Architects.
Some builders have developed clever methods for dealing with clearances and ground-plane (airflow) effects. Folding rails are employed in many cases, as is removable safety netting and flush-mounted lighting. In other cases, the structure itself converts during helicopter operations. For instance, the hardtop on the 50 metre Westport Vango hinges up 90 degrees to create additional clearance, and block the airflow interaction between the helicopter’s rotor and the yacht’s mast and satcom domes.
Location, location, location
‘Siting of the helideck is much more likely to be driven by the aesthetics of the yacht design rather than the potential hazards of turbulence and motion,’ says Nelson. A helideck on the top deck is more subject to roll than one on the main deck, for example.
‘The owner’s choice between landing on the foredeck or aft has large implications on the design,’ says Schouten. ‘A pad on the foredeck has less impact on design and enables landing when the aft decks are in use by the guests. However, landing in this location is in general not possible when the boat is moving.’
‘The turbulence generated by the superstructure is greater and more troublesome where there are angular corners and large blocky faces,’ says Nelson. ‘There are ways of designing features that minimise airflow disruption – just look at any modern car. If we are involved with a yacht at the design stage, we always encourage such ideas and the use of computational fluid dynamics (CFD) to avoid problems with turbulence.’
The next thing on the horizon for air tenders will probably be tilt-rotor aircraft and one UK design firm has already begun a yacht design that would land an AW609 aircraft. ‘For something like a tilt rotor, which may be susceptible to turbulence, CFD analysis is a must,’ Nelson says. This is still in the future, however, as certification for the civilian AW609 has moved back to 2017. Of course, for an owner who desires an aircraft that can cruise at 300mph for 852 miles, carry nine passengers and land on his deck, three years is minimal design time.
All helipads, both certified and touch-and-go are designed for a crash load that is 2.5 times the helicopter’s maximum weight. Normally, decks are designed only for sea and human loading, and occasionally for point loads from tender stowage, but when helicopter operations are added, they must be strengthened, with added structure sometimes required from the helideck down to the keel. This adds weight, which increases overall displacement, adversely affecting speed and fuel consumption continually. Except on the largest yachts, helidecks are usually at or near the top of the yacht. This added weight, at such a distance above the keel, also will have a significant negative effect on the yacht’s stability, so added beam and fin stabilisation may be necessary to compensate.
‘It is extremely important designers and ship builders get aviation advice as early as possible to avoid difficulties or costly alterations later. The main objective is to establish at the outset what the owner wants to use his helicopter for, as that drives the design and equipment,’ says Nelson. ‘For example, does the owner want to do ocean transits with his helicopter, which may mean a hangar is required? Does he need to fly at night, which requires a lighting plan? How much flying is intended and does the helicopter require onboard fuel or maintenance capability?’
Builders and designers report that most yachts above 60 metres build in minimal touch-and-go capability, for emergency evacuation if not regular use. Nelson’s database includes 66 yachts over 60 metres with helidecks, including nine that are fully certified. Yet another option for some owners is touch-and-go capability aboard the yacht itself along with MCA Annex 6-compliant landing and stowage aboard a shadow vessel.
Choices in helideck configuration, it seems, are limited by the size of the yacht and the scope of the designer’s imagination in meeting regulatory requirements.
This article originally appeared in Megayachts 2014: Concept – Design – Construction, ShowBoats International magazine’s April 2014 issue, and Boat International magazine’s June 2014 issue. Subscribe here.
Photos and illustrations by Marc Paris; Mark O'Connell