Subject to the stresses of aircraft taxiing, taking off and landing, not to mention the ever-present impact of weather, a runway needs regular investment to ensure the safety of passengers, crew and cargo alike. But there are ways to reduce maintenance requirements. Megan Ramsay learns more
Quick off the mark this year, London Southend Airport (LSA) has embarked on a £10 million (US$13.1 million) upgrade to its runway, work having commenced on 7 January.
Glyn Jones, CEO of Stobart Aviation, which owns the gateway, says: “It is essential to maintain a safe runway. The last set of major runway works were in 2011 and were part of the runway extension development. Previous to that, maintenance was carried out in 1994. As part of the strategic plan for continued investment to cater for the growth of the airport … we are enhancing the durability and performance of the runway.”
The airport is using Marshall Asphalt for the runway upgrade, and grooving the new surface to improve drainage. The entire process is expected to take about three months, with most of the work happening between 23.30 and 06.30 (when the airport is closed) to avoid disruption to normal operations.
In the case of a delayed flight arriving out of hours, the airline concerned must divert to another airport. LSA is working closely with all based airlines to ensure any potential flight delays are monitored.
Also in the UK, Dublin Airport recently completed a refurbishment of its main runway. The works included a 150mm structural overlay, upgrade to the airfield ground lighting infrastructure (including the installation of LED lighting), taxiway widening and taxiway structural overlays.
This project took 18 months, with work taking place between 23.30 and 04.30, Monday to Friday inclusive. Dublin Airport head of deliver asset care Ian Devine notes that during this period Dublin’s secondary (crosswind) runway came into service, so normal flight schedules could continue.
Runway maintenance is very much linked to the life of the pavement and as the pavement nears its end of life the cost of maintenance increases significantly.
“Before the structural overlay, which commenced in November 2016, we had a 22mm Thin Porous Friction Course (TPFC) non-structural overlay to the pavement (constructed in 2010 with a six-year design life),” Devine says.
“Towards the end of the life of the TPFC pavement we were carrying out extensive maintenance to ensure the pavement was safe and [serviceable]… Planned interventions were carried out approximately every two months over the last 18 months of life of the pavement and there were, on occasion, unplanned interventions during this period.”
Works included over-banding, joint rehabilitation and patch repairs of the TPFC – some by in-house teams and some by specialist contractors.
The recently laid base, binder and wearing courses are heavily modified polymer grooved Marshall Asphalt pavements, with glass-grid reinforcement between the underlying concrete layers and the base course.
This pavement has a design life of 15 years and Devine would not expect significant pavement defects in the first 10 years – so maintenance interventions will be reduced for some time as a result of the investment.
However: “Given that the runway pavement is a grooved asphalt pavement it is prone to rubber contamination from aircraft landing. At Dublin we anticipate having to carry out rubber removal based on our movements and traffic about six times a year” from much earlier in the life of the surface, he says.
Dublin’s maintenance work benefited from the availability of an alternative runway – but this is not always an option.
Carl Fergusson, CEO of Colas UK (the British subsidiary of Paris-headquartered transport infrastructure construction and maintenance firm Colas Group), recalls that at London Gatwick – the UK’s busiest single-runway airport – the company had a very short window for completing runway maintenance works, making minute-by-minute planning of each night’s tasks essential.
“Materials and equipment also came into that as we had not only to maximise productivity but also de-risk as much as possible, for example by having extra equipment available in case of a breakdown,” he recalls.
Having more than one runway does not guarantee uninterrupted operations, though. Dubai International Airport, for instance, is planning to close its southern runway for 45 days during April and May this year as it is nearing the end of its design life, and is anticipating a reduction in traffic while the upgrade is in progress.
Work will include complete resurfacing and replacement of the airfield ground lighting and supporting infrastructure.
It will occur during a seasonal lull in passenger traffic but Dubai Airports has said that, “During the closure period, airlines will be required to reduce their operations to DXB due to the significant capacity reduction resulting from single runway operations.”
Nearby Dubai World Central Airport will be one possible alternative for affected flights.
Starting afresh
Dublin Airport is currently in the early stages of construction of its new Northern Runway (NR), which is scheduled to become operational in 2021.
With approximately 350,000 square metres of new concrete pavement and an additional 2,000 airfield ground lights, as well as a sizable increase in the grass habitat, there will be an increase in Dublin’s electrical and operational resources for maintenance.
“In relation to additional equipment resources, upon NR becoming operational we shall be increasing the number of vehicles in our snow fleet to cater for the need to clear contamination from our new pavements during winter periods and periods of inclement weather,” Devine says.
“The majority of the maintenance task will be carried out by our in-house expertise with some specialist activities like rubber removal being carried out by a third party,” he confirms.
Devine expects that once live, the new runway will “in many ways simplify our maintenance and more specifically allow us to access areas for maintenance that today can be a challenge”.
As mentioned above, the airport’s crosswind runway (16-34) is used to facilitate operations during maintenance of the main runway (10-28).
“The problem with this is that the thresholds of Runway 28 and 34 are co-located. In order to carry out maintenance works in this busy runway intersection we have to implement a displaced/temporary threshold, which is challenging and is subject to strict weather criteria.”
The new runway will eliminate this difficulty.
Exporting expertise
Colas is also currently building a new runway – in fact, a new airport – in Uganda, following the discovery of oil near Lake Albert.
Fergusson says phase one of Hoima International Airport is intended to service the construction of an oil refinery. “Later it will become Uganda’s new regional airport for tourism and trade, as well as supporting the oil industry there.”
The cost and logistical challenges of bringing in materials to the remote site mean that the company will use materials available locally.
Slated for completion in late 2021, Hoima International Airport is financed by UK Export Finance (UKEF) and also involves locally based experts from SBI International.
Colas has experience of working in remote places. For instance, in 2010 it resurfaced the runways and taxiways, and upgraded the airfield ground lighting and electrical installations, at RAF Mount Pleasant airfield in the Falkland Islands.
Fergusson remembers: “It was logistically challenging – all the plant and materials were brought over from the UK by ship, while people were flown in via Ascension Island. We were working with an 8,000km supply line. If you needed something else brought in you had to wait for the next ship – which could take a month, and might be fully booked anyway, in which case you might need to consider flying things in.”
Meticulous planning was a must for this challenging project.
In 2015-16, Colas won a new contract with Interserve Defence to repair specific areas of the runway at RAF Mount Pleasant and to construct a taxiway strip to the southern side of the western access taxiway, as well as carrying out concrete repairs, joint sealing, and over 100,000 square metres of Addagrip surface treatment on an aircraft servicing platform.
Overall, this project involved shipping over 100 containers of plant, equipment and materials to the Falkland Islands, including a mobile asphalt plant and mobile laboratory to guarantee a supply of Marshall Asphalt for the job.
Last year, Colas secured a contract to upgrade Hawarden Aerodrome in Chester, Wales. Operated by Airbus UK and the location of Airbus’ Broughton factory, the site is used to assemble and test wings for a variety of Airbus aircraft.
The purpose of the project was to facilitate the movement of larger aircraft at the aerodrome.
Besides resurfacing the full length of Runway 04/22, the contract included the grooving of existing and new pavements, the construction of asphalt fillets between the taxiways and aprons to change the available turning circle for aircraft, and the installation of airfield ground lighting and associated chases and cabling on Runway 04/22 and Taxiway Bravo. This latter task was carried out in conjunction with Colas’s subsidiary, Allied Infrastructure.
Right now, Colas is resurfacing a runway at RAF Cranwell in Lincolnshire in the UK, Fergusson says.
Innovation
Back in Dublin, Devine informs: “Over the last 10 years or so we have installed new pavement wearing courses including TPFC, SMA [Stone Mastic Asphalt] and moved away from conventional tried and tested materials. Furthermore we have trialled asphalt rejuvenation products that are now being used more extensively globally to extend the life of asphalt pavements.”
One of the more recent developments in runway materials is the introduction of Béton Bitumineux pour chaussées Aéronautiques (BBA) to the UK. According to Fergusson, this represented a “step change” in the country. While BBA had been in use for some time in France, it had not caught on across the Channel.
He explains: “Until we introduced BBA into the UK, the only option (for at least the last 40 years) was Marshall Asphalt. Our first project using BBA was at East Midlands Airport in 2016. It was a new material here so people were cautious, because of course we are working in a high-risk environment. But we were able to show that it works elsewhere.”
BBA offers several advantages over more traditional materials. For instance, it is less susceptible to rutting and cracking, and less sensitive to weather. Aircraft can use the BBA binder course as a temporary operating surface during works. It is also quicker to lay, and being very coarse, does not need to be grooved to improve wet friction and aid run-off.
“You get better productivity and less risk for airports, which are able to get back to normal operations more quickly,” Fergusson points out, adding that there has been “a big upswing” in the use of BBA in the UK.
There were other aspects of the East Midlands Airport runway resurfacing project besides the use of BBA that made this an innovative operation. Done traditionally, it would have involved months of night-time closures, but Colas reduced this to five weekends of closure using techniques that its parent company had found to be successful at other airports, such as Toulouse. It brought in three mobile asphalt plants, for instance, to provide a continuous supply of BBA.
Plus: “We used echelon paving, with five pavers side by side at the same time rather than using one to go up and down the runway. This is quicker, and you also get better joints because you are working hot on hot,” Fergusson sums up.
Sustainability
Colas manufactures bitumen products and chemicals that vary the workability of asphalt depending on each job. Modified materials that set quickly are more suitable in hot conditions, while in a cold climate it is necessary to make the material stay workable for longer before it sets.
There are also additives that enable the manufacture of asphalt at a lower temperature.
Fergusson explains: “Asphalt is made at a variety of temperatures, but let’s say for instance you have some that is made at 175°C. With the right additives you can bring the mixing temperature down by 40°C.
“This improves sustainability because you need less energy to heat the asphalt, and you also have a greater window of opportunity because it doesn’t need to cool down so much – it has a 40°C head start, as it were.”
The Colas Group tests bitumen and aggregates at its research and development centre near Paris. The Campus for Science and Techniques (CST) is currently busy with a “cutting-edge” surfacing product that uses vegetable oil instead of bitumen to eliminate hydrocarbons, Fergusson says.
“We are also working on an epoxy asphalt that can extend the life of the product from, say, 20 years to at least 40 years, reducing maintenance interventions,” he adds.
Rubber removal
Dublin Airport’s Devine says that during busy summer days the gateway averages around 730 aircraft movements per day.
“This volume of traffic results in significant rubber build-up on the trafficked touchdown zones that, if not removed, can reduce significantly the coefficient of friction,” he continues, noting that this can have a negative impact on the safety of aircraft operations.
“It can be challenging juggling essential maintenance with the operational demands of our customers and airlines; that said, safety is fundamental and to the forefront of how we manage the business. We endeavour to plan our maintenance activities to ensure we minimise impact to our airlines and customers.”
