Environmental impact of Hovercraft

For any vehicle to operate economically the drag, or resistance to motion, must be kept to a minimum.  The majority of drag arises from the motion of the vessels hull through the water, therefore we can reduce drag and consequentially propulsive power by minimizing hull contact.  The hovercraft achieves this by using low-pressure air to form an air cushion beneath it, thus actually lifting the hull clear of the water/ surface.  In addition, by using air propulsion to generate forward movement, the hovercraft becomes amphibious, and able to traverse land, soft terrain / mud flats or water. The main point here is that because the hovercraft does not pierce the surface over which it is traveling the advantage is two-fold, 
a) less friction = less fuel burnt to move, 
b) less friction or interruption to the surface = less disturbance of the environment. 

Therefore Hovercraft can be used to best advantage in shallow water and drying areas, these areas often being remote and environmentally sensitive. Most of these areas are wetlands, swamps, and river delta. They are not only the feeding ground for a lot of different species of birds but as well very often used from marine live for hiding from predators. In these sensitive areas are nearly no transportation means available. Hovercraft are able to operate in these areas in an environmentally friendly way. 

Being amphibious the hovercraft can use direct routes across sand banks, marshes and flats, with no loss of speed or comfort. Channel dredging becomes unnecessary as well as the problem of dreged material disposal, whilst rivers and tidal estuaries present no problem for the passage of the vessel.

Previously inaccessible areas may be accessed economically with little or no impact on their environment. If this area is a future wetland where nobody could proof that it is a wetland or not -since it was not accessible by traditional transportation means, or a very shallow bay where you need to download your data from your instrument platform. With the Hovercraft you can reach destinations which where before not accessible for research and studies. And not only travel though these areas - but as well take samples and collect data.

Damage to the shore environment, such as beaches, mud flats and vegetation is virtually nil because of the hovercraft’s low pressure "footprint".   For example, the average human being when standing on a beach exerts a pressure of some 3lbs per square inch underfoot, rising locally to 25lbs per square inch when walking.  The average hovercraft by comparison, exerts a pressure of only 0.33lb per square inch on the surface regardless of speed.  This "footprint" pressure is less than that of a  seagull standing on one leg! 

All advanced  Hovercraft are fully amphibious and create virtually no under water noise, just atmospheric noise levels which would be typical of a truck or bus.  The fact that there are no underwater protrusions eliminates the usual thrashing noise signature associated with conventional propeller driven craft, as well as negating any possible sea bed erosion when operating in shallow waters.  It therefore becomes obvious that fish and other marine life are in no way affected.  This has been confirmed by independent scientific tests.   The major noise factor with any hovercraft is the air-propeller noise, which in any case is largely directional in characteristic and more apparent to above surface creatures like humans. To minimize this effect advanced  hovercraft propulsion propellers have been designed with low tip speed to minimize atmospheric noise as well as most modern Hovercraft have a fully ducted thrust propeller which creats a more or less directional noise field aft of teh duct. It is not  possible to move air for the purpose of creating thrust without making some noise. What must be attempted is to keep the noise within tolerable limits and we believe that we have gone a long way towards this. The remaining propeller noise can not be eliminated - just dirceted with ducts - as such it is of the utmost importance for a future Hovercraft operator to select his course in a manner that he is flying parallel to the shoreline and not 90 degree  away from it - while approaching a shore line you can take the most efficent approach as the propeller noise is 80% aft of the craft while in motion - a little planing can help your tour operations reduce future problems.

Another important factor is that, by necessity, the hovercraft hull is a 'sealed unit'.  Any accidental discharges and leaks are fully contained within the hull structure, remaining there to be pumped out at an appropriate shore facility.  There is no exhaust discharge into the water as with most conventional water craft, thus eliminating the pollution of the marine environment by oil and fuel particles, particularly prevalent with two stroke outboard motor usage. These engines operate at a mixing range of 1 : 50 = 1 part oil : 50 parts gasoline where the unburned oil and fuel particles get discharged over the lower unit of the engine - basically oil injecting the environment you navigate in. Atmospheric pollution is also considerably less because of the inherent fuel efficiency of the modern four stroke machinery utilized, as opposed to the very large percentage of marine propulsion units which still utilize the two stroke principle.  In addition, the hovercraft is in itself a fuel efficient mode of transport, thus lessening the pollution of the atmosphere even more.  For example a fully loaded six-person hovercraft burns less fuel per hour than a typical Jet Ski, it does not pollute the water and does not disturb the bottom in shallow areas which many fish rely upon for food and breeding. The lower hull of a Hovercraft is not in water contact under way and very seldom at stand. This eliminates an anti fouling coating like on all common boat hulls. These anti fouling paints have just one purpose - slowly come off your hull with whatever marine live adheres to it. On an average 30' boat hull you have to apply all two years a new bottom coat - besides the expenses of haul out - you will apply between 1 gal - 1 1/2 gal of bottom paint to your hull. Bottom paint which tries to have a very high copper contend to work effectively ( 50% to 75% ). Copper is just not the best stuff for our marine environment - but we do our best to supply on a continuos basis till we find a better solution ... when?  If the last fish is dead? 

The wake created by the passage of a hovercraft is minimal, ensuring that river bank erosion and damage to foreshore by the waves created is virtually nil.  A recent study in the United Kingdom concluded that the passage of hovercraft over inter tidal areas caused no damage to sea grasses or invertebrates.  It was also noted that bird life rapidly adjusted to the presence of hovercraft.  This has been confirmed on the Gold Coast (Australia) where a commercial operator passed over the same area of beach many times a day for more than three years without any affect to the Yabby population (a Yabbies live just below the surface of the wet sand) on the actual operating launch ramp. The air pressure exerted by the hovercraft is considerably less than the normal pressure variations due to natural tidal movements. Commercial operators in other areas around Australia have had similar experiences. 

Last not least - Hovercraft need minimal base requirements. 

 Hovercraft do not require, docks, piers or dredged channels and can operate off many beach sites. Road access to the maintenance base is desirable but not essential. Hovercraft can work in areas and leave without the need for environmentally damaging construction projects to support the operation.

Summary
In conclusion, hovercraft have a negligible impact on the environment. In virtually all areas they have a significantly lower impact than any other watercraft currently opperating.

Joint script of Airlift Hovercraft Au. and 4wings Hovercraft development.

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