How do you build an Antarctic runway?
8 February 2006
How do you build a runway in Antarctica, many kilometres from the nearest station, with construction materials of ice and snow?
AAD staff are exercising their ingenuity and expertise to construct a blue ice runway topped with a snow pavement high on the inland plateau of the Upper Peterson Glacier, 70 km from Casey.This season a hardy team of five runway construction crew, with considerable input from many others on station, has constructed a trial snow pavement, separate from the proposed main runway at Wilkins. Although its size, a mere 200 m by 30 m, is but a fraction of the finished runway (4000 m by 100 m), it has exceeded all expectations in terms of success. One of two key objectives for the season was to validate the construction process for the main runway for intercontinental air transport from Australia to Antarctica.
Blue ice runways have been used many times in Antarctica, but during the summer, these surfaces can quickly become unusable. Even in temperatures which never rise above 0 degrees Celsius, the deep blue ice absorbs heat from the sun and warms up, causing melts and pitted surfaces which rapidly become unsafe for landing aircraft. This is particularly the case in the lower latitudes of the AAT coastline.
A protective white snow pavement bonded to a blue ice glacier will deflect the sun's rays, remain colder and so is less to prone to breaking up and melting than blue ice. It is also infinitely repairable. Wilkins runway is being constructed high on the plateau 70 km inland from Casey so that the temperatures will remain cool enough for the technique to work throughout the summer.
Although the runway is sited to face into the katabatic winds, cross winds do occur which can make it dangerous to land an aircraft. The snow pavement has the additional benefit of creating a higher friction co-efficient which will allow aircraft to operate more safely in these conditions.
The science of snow paving depends on understanding variables such as temperature, moisture content, and grain size of the snow. New snow has a larger grain size and so bonds more easily. AAD staff have learnt a great deal about the process of pavement rolling from ongoing US technical support, whose expertise was gained at the Pegasus runway at McMurdo. However, the trial at Wilkins runway was in a location at which the variables were largely unknown.
As it is essential to compact every square centimetre of the runway surface to ensure bonding and a smooth level surface, each section of the trial area had to be passed over with special rollers seven times with varying weights, speed and tyre pressures. Each rolling process comprised 20 passes with the machine, with a consolidation period of 24 hours between each complete roll.
This would be a time consuming and painstaking process at the best of times, but in Antarctic conditions of high winds, below freezing temperatures and often poor visibility and whiteout, it was an outstanding feat!
The new runway construction machinery which was recently shipped from Hobart has now arrived at Casey on the Vasiliy Golovnin, and will soon be in operation at the runway site. The range of new machinery, in particular the new rollers, will reduce the number of passes from 20 to just five, and so will greatly expedite the process.
As Runway Construction Supervisor Matt F commented, It is as if we now have a well stocked toolbox, whereas before we were working with just a hammer!
Now that the variables of the conditions and situation are better understood, and with the outstanding success of the trial snow pavement process behind them, AAD staff will now work to validate the site location by the end of the season. They will use the newly arrived machinery to clear the snow off the main runway site and conduct a proof roll along the 4000 m. If all goes well, work will continue on the main runway next season, with a possible trial flight scheduled for early December 2006.
Written by Annie Rushton