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The term Runway Maintenance is usually used to refer to activity required to keep the runway in a safe condition for aircraft use. Whilst this self evidently means making sure that the integrity of the top surface is absolute, it is also defined in terms of minimum surface friction.
Runway Occupancy for Surface Maintenance Purposes
The necessary occupancy for runway maintenance activity is achieved by access when a runway is scheduled for closure anyway such as overnight, or for longer periods during which part or all of a runway is taken out of service. If a runway is going to be unavailable when an airport is open then a Notice To Airmen must be used to advise accordingly. Whilst such NOTAMS are available in Airport Flight Briefing facilities and, increasingly, online, many larger aircraft operators take responsibility for making their flight crew aware of relevant NOTAMS through their own directly-provided procedure or an equivalent sub contract service provision.
The Maintenance Process
The integrity of runway surfaces is assured by regular inspections. Pavement maintenance requires periodic renewal of the top or wearing surface. The interval between surface re-making will vary according to the type of surface. The most commonly used hard surface types are concrete and asphalt. To aid surface water dispersal, the former is frequently grooved laterally to allow surface water to drain in the grooves and the latter employ a porous top layer, which allows surface water to run off below the surface rather than across it. Certain types of asphalt can also be grooved. Minor repairs such as joint re-sealing, crack stopping and the removal of rubber deposits from the TDZ may need relatively little continuous occupancy time but major works will either involve complete or partial runway closure for a continuous period of several weeks or a carefully managed programme of night closures during which a complex resurfacing programme can be progressively accomplished. In such cases, the friction characteristics of various parts of the available surface may vary on a daily basis which will invite very careful pre flight attention to NOTAM information, especially if adverse weather conditions may occur.
Risk Management and Runway Maintenance
There is a long history of accidents and serious Runway Excursion incidents which have especially occurred during take off or attempted take off as a result of a lack of flight crew awareness of the temporary closure of part of all of a runway to facilitate runway maintenance. It demonstrates that the lessons of proper pre flight briefing on runway availability and on positive Runway Identification have still to be learned.
- Examples of accidents and serious incidents arising from a lack of awareness of runway maintenance or its effects include the Accident to a Singapore Airlines Boeing 747-400 at Taipei, Taiwan in 2000 when it attempted to take off from a completely closed runway in poor visibility and Serious Incidents involving an XL Airways Boeing 737-800 at Manchester in 2003 and a Gulf Air Airbus 340-300 at Singapore in 2007 which both involved take offs in which a reduced runway length, because of surface maintenance, was not appreciated by the crews who were obliged to conduct premature rotations to avoid/minimise collision with obstructions ahead.
- The Assessment of Runway Surface Friction UK CAA CAP 683 (2010)
- ICAO Runway Excursion Risk Reduction Toolkit - Aerodrome Best Practice (2nd edition)
- ACRP Synthesis 11: Impact of Airport Rubber Removal Techniques on Runways, Transportation Research Board, 2008.