How does grass keep aircraft safe?
Even relatively small airports can have several hundred acres of grass. It must all be mown regularly and maintained without getting in the way of aircraft or affecting the airport’s operation. Its not simple. This requires specially certificated personnel who maintain the grass to official standards. These are set out by the UK’s Civil Aviation Authority (CAA) and can be fairly costly – even by aviation standards.
Why go to all this expense? What about paving over the grassed areas?
To begin with, if the airfield were just one big expanse of concrete, it would be difficult for pilots to distinguish the runway and taxiways from the surrounding areas. Particularly when visibility is poor at sunrise and sunset. In addition, grassed areas absorb water. Standing water can affect pilots’ control of the aircraft particularly where the planes are taxiing or taking off .
Patches of turf will also keep the air temperature cooler than paving. Whilst not such an issue in the UK this can give benefits in terms of additional lift for aeroplanes.
As with all vegetation, grass also has benefits of absorbing CO2 from the atmosphere. However, more importantly grass helps airports deal with noise. The irregular surface an area of turf provides helps absorb the sounds from aircraft engines during take-off and landing; especially compared to concrete. Good news for those living nearby.
How does grass keep aircraft safe – managing wildlife
However, many runways are built in areas where the surrounding land is unused, or near wetlands and other bodies of water. These can also be very effective sound dampeners.
But, this creates an additional problem for operating aircraft as these are habitats that attract birds. Bird strikes. In 2013 there were over 1500 confirmed collisions between birds and aircraft. Though usually without consequence, they can force aircraft to make emergency landings or even crash. In serious cases birds may be ingested into the engines or affect important controls. It isn’t difficult to see why – a plane hitting a goose at 150mph has the equivalent force of a 1000lb weight being dropped on the plane from 10 feet.
Let the grass grow..
Since geese eat grass, it might seem strange for airports to be cultivating acres of food for these birds which are so hazardous.
Leaving the ground as bare soil isn’t an option for airports. Jet blast from creates problems with dust. While this would remove the attraction for geese, other birds which feed on worms and other insects in the soil would be attracted in their place.
The solution to this is simple. By letting the grass grow longer, the attraction for geese and other similar birds is removed. Its harder to move about and its easier for predators to find cover. This is good news for airports. But predators can also be food for and therefore attract other types of birds lime buzzards.
Airports must strike a balance between keeping grass long enough to repel some birds and short enough so as not to attract others – this length turns out to be about six inches. Making sure grass is free from weeds is also important since these can flower attracting insects and, with them, birds.
Research into grass varieties has come up with innovative solutions for airports
However, a New Zealand company seems to have come up with the best solution yet. The state-owned agricultural research company has developed a variety of grass which contains a particular fungus which makes the grass unpleasant for birds and insects to eat without harming them. In trials at Auckland Airport, the grass was found to reduce the number of birds on the airfield by 95%.
And so grass has become the solution to many of the challenges faced by airports in order to make the aviation industry around the world safer.