Runway Maintenance: How Often Is Safety Checked?

Maintaining airport runways is critical to ensuring the safe takeoff and landing of aircraft. The frequency of maintenance depends on several factors, including runway surface material, climate, aircraft weight, and traffic volume. Typically, maintenance is conducted annually or more frequently, with major resurfacing work occurring every 8 to 12 years for asphalt runways and 20 to 40 years for concrete runways. Regular tasks include removing rubber deposits, cleaning and replacing lights, repainting markings, and checking for foreign objects and structural integrity. Nighttime maintenance is preferred to minimise disruptions, but emergency repairs may require runway closures.

Removing rubber deposits

Rubber deposits are caused by the landing gear wheels starting to rotate as the aircraft touches down. The friction forces peel some rubber off the tyres, and this process continues until the rotation speed of the wheel matches the aircraft speed. This means that the touchdown zone is prone to rubber deposit accumulation. Rubber deposits can have adverse effects, such as obscuring runway markings and becoming slippery when wet, which may contribute to a runway excursion.

There are several methods for removing rubber deposits:

• Chemical solvents: This method involves spraying the contaminated area with a solvent solution, waiting, then washing and sweeping. Different chemical agents are used depending on the surface (e.g. concrete or asphalt). Care should be taken to avoid damaging the surface and surrounding areas.
• High-pressure water blasting: This method uses a jet of water at 2,000-15,000 psi (or ultra-high pressure of up to 40,000 psi) to break the hardened rubber free from the runway surface. Smaller airports may use hand-operated sprays.
• A combination of chemical solvents and high-pressure water blasting: This modern practice involves dissolving rubber deposits with chemical solvents, then flushing with high-pressure water.
• Hot compressed air: This technique uses high-temperature gases to burn away the rubber deposits. The air-gas mixture is fed into a combustion chamber and emitted at approximately 1,200°C directly onto the surface. When used on concrete surfaces, this method produces a small amount of carbon deposit that can be brushed away with a normal tractor- or truck-mounted brush machine.
• High-velocity impact removal: This method involves throwing abrasive particles at high velocity at the runway surface, also known as sandblasting. This can introduce foreign object debris if not contained and cleaned up properly.

The removal of rubber deposits is an important aspect of runway maintenance, and the frequency of this task depends on runway use. For example, the US FAA recommends checking rubber deposits every week for runways with 210 or more daily landings and yearly for runways with less than 15 daily landings.

Runway cleaning schedules

The frequency of runway cleaning depends on several factors, including airport size, weather conditions, and traffic volume. Larger airports with higher traffic volumes tend to have more frequent cleaning schedules and may clean their runways daily or even multiple times a day. Smaller airports with less traffic may have less frequent cleaning schedules.

Removing Debris

Specialised equipment, such as runway sweepers or vacuum trucks, is used to efficiently collect and remove debris, including dirt, leaves, and loose gravel. Manual cleaning crews may also be deployed for larger debris.

Removing Rubber

Rubber deposits from aircraft tyres can be dangerous as they reduce friction between the tyres and the runway, affecting braking performance. Airports use chemicals and high-pressure water to remove rubber.

Cleaning Light Systems

The approach light systems and other visual aids are cleaned using a mix of water and sodium bicarbonate or dry ice.

Weather Conditions

In regions with heavy rainfall or snowfall, runways may require more frequent cleaning to prevent the accumulation of dirt, mud, and excess moisture.

Timing

Cleaning operations are carefully planned to minimise disruptions to flights. They usually take place during quieter periods, such as late at night or early in the morning. In cases of immediate safety concerns, airports may temporarily close runways or restrict operations until cleaning is complete.

Runway maintenance timing

The timing of runway maintenance is critical to ensuring the safety and efficiency of aircraft operations. While the specific maintenance schedule may vary depending on various factors, there are some standard timings and procedures that airports follow to keep their runways in optimal condition.

Regular Maintenance

Airports conduct regular maintenance activities to address normal wear and tear on runways. This includes constant tasks such as filling cracks, repainting runway markings, and removing rubber deposits caused by aircraft tires. Airports may also have dedicated teams and specialised equipment for daily or multiple-times-daily cleaning to remove debris, rubber deposits, and foreign objects. This is particularly common at larger airports with higher traffic volumes.

Inspections

Runways are subject to regular inspections to identify any issues that may impact safety. These inspections are typically conducted visually and with specialised equipment, such as runway friction testers, to assess the condition of the runway surface. Some airports, like Finavia's airports in Finland, conduct inspections as frequently as hourly.

Short Maintenance Operations

To minimise disruptions to flight operations, airports try to perform as many short maintenance operations as possible during periods of low traffic, such as between 11 pm and 5 am. Some tasks, such as replacing a slab of concrete on the runway, can be divided into several perfectly timed operations conducted during these nightly windows.

Resurfacing

The timing of runway resurfacing depends on several factors, including the runway material (asphalt or concrete), climate, weight and frequency of aircraft, and traffic volume. Asphalt runways typically last 20-25 years, while concrete runways can last 30-40 years or more, assuming proper annual or more frequent crack sealing and joint repairs. Airports in regions with extreme weather conditions, such as freezing winters and hot summers, may need to resurface their runways more frequently, typically between eight and twelve years.

Emergency Maintenance

In addition to scheduled maintenance, emergency maintenance may be required in response to unexpected issues. For example, if a runway surface starts to deteriorate more than 30%, immediate repairs or replacement may be necessary to prevent further damage.

Runway deformation

Causes of Runway Deformation

• Aircraft weight: Larger and heavier aircraft can exert more pressure on runways, causing deformation over time.
• Climate and weather conditions: Extreme temperatures, such as freezing winters and hot summers, can cause the asphalt to contract and expand, leading to cracking.
• Frequency of usage: Busier runways may experience more rapid deterioration due to increased stress and wear.

Preventing Runway Deformation

To prevent deformation, airports implement regular maintenance schedules, which may include:

• Crack sealing: Using hot pour rubberized crack fillers can help close cracks and increase runway durability.
• Asphalt sealing: Applying a commercial-grade asphalt sealer can protect against oxidation, drying, and cracking. It also repels water and staining agents like oil and gasoline.
• Foreign object checks: Regularly checking for and removing foreign objects like debris, grass, and pebbles helps maintain runway surface integrity.
• Rubber removal: Skid marks from aircraft tires leave rubber on the runway, reducing adherence. High-pressure water removal helps restore stopping distances.

Repairing Runway Deformation

When deformation is detected, repairs may be conducted immediately or scheduled as part of the runway's life cycle management. Repairs can include:

• Resurfacing: This involves replacing slabs of concrete or conducting full-length resurfacing of the runway.
• Crack repair: Patching and filling cracks can help prevent them from enlarging and becoming potholes.
• Light system maintenance: Cleaning and replacing approach light systems and visual aids ensure safe operations during takeoff and landing.
• Marking repainting: Runway markings, such as lines and stencils, need to be repainted periodically for visibility.

Runway life cycle

The life cycle of a runway depends on various factors, such as the weight of the aircraft using it, the climate, and the frequency of usage. Generally, a runway's life cycle is between eight and twelve years, after which it needs to be resurfaced. However, with proper maintenance, a runway can last up to 30 years.

Maintenance

Maintenance of runways is a continuous process. Maintenance crews are constantly filling in cracks, repainting runway markings, and removing rubber deposits left by aircraft tires. This rubber build-up is dangerous as it can cause planes to skid when the runway is wet. To remove the rubber, chemicals and high-pressure water are used.

Inspections

Regular inspections are crucial to ensure the safety and structural integrity of the runway. These inspections are carried out by qualified personnel and may be conducted visually or using specialised equipment, such as runway friction testers. Inspections are often conducted daily, and some airports even conduct hourly inspections.

Cleaning

The frequency of cleaning depends on factors such as airport size, weather conditions, and traffic volume. Larger airports with higher traffic volumes may clean their runways daily or even multiple times a day to remove debris, rubber deposits, and foreign objects. Weather conditions also play a crucial role, with runways in regions of heavy rainfall or snow requiring more frequent cleaning.

Resurfacing

Every eight to twelve years, a runway needs to be resurfaced. The timing depends on the factors mentioned above, such as climate and aircraft weight. Airports like Heathrow, which handle large aircraft like the Boeing 777 and Airbus A380, will need to resurface more frequently than smaller airports with lighter aircraft.

End of life cycle

As a runway nears the end of its life cycle, maintenance regimes become even more important for safe operations. Regular checks and general maintenance are conducted as per a fixed schedule or as and when needed. This includes repairs to any signs of deformation or deterioration, such as slipperiness of the surface.

Frequently asked questions