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INTRODUCTION
Airport runways can rightly be called “the arteries” of airport operations given their roles in seamless movement of aircrafts and connecting the world. However, from this essential service of aircraft landing on the runway surface comes the unique challenge of Rubber Deposits. And given its direct bearing on the safety and efficiency of air travel, the importance of rubber deposits removal from airport runways cannot be downplayed but should rather be taken seriously.
RUNWAY RUBBER DEPOSITS EXPLAINED
If you have witnessed aircrafts touching down or have seen video clips of it, you surely would have noticed that there is a puff of smoke as soon as the wheels make contact with the runway. This occurs because the wheels are static, unlike the aircraft moving through the air. The sudden contact with the ground causes friction and heat, creating a chain reaction that allows rubber from the tires to polymerize and adhere to the runway’s surface. Those peeled-off rubbers from the aircraft tyres, that are left on the runway during aircraft touchdown, are what we refer to as Rubber Deposits.
It has been estimated that whenever an aircraft lands, each tyre leaves up to 1.5 lbs of rubber on the runway. Or, as posited by Alex Groom (a business development manager at Jetting Systems, a UK-based firm that manufactures high-pressure water jet cleaning machines for rubber removal), “every time a plane lands on a runway, up to 14kg of rubber can be deposited – especially in the touchdown zone.” Now, just consider that an Airbus – A380 has 22 tyres, and the magnitude of the challenge or hazard posed by rubber deposits on the runway becomes clearer!
EFFECTS OF RUBBER DEPOSITS ON THE RUNWAY
A build-up of rubber on the runway poses a significant risk to aircraft and passenger safety. As aircrafts touch down on the runway and tyres heat up to leave behind thin layers of rubber, they over time accumulate and reduce the friction coefficient of the runway surface.
This buildup poses several challenges, among which are:
- Obliteration of runway markings;
- Creating of an extremely slick area on the runway surface when wet;
- Making the runway surface too smooth (the smoother the runway, the lower the friction);
- Making stoppage and control of aircrafts on the runway more difficult;
- Distortion of vision on the runway as lines are harder to see; and
- Creating an increased risk of Foreign Object Debris (FOD).
Runway Friction Testing
Runway friction testing is carried out to measure the runway grip under worst case, wet conditions, and provide operators with essential data to determine whether maintenance is required. When carried out before rubber removal, it ascertains the extent of the build-up and the impact on runway safety. After removal, it confirms that the runway’s friction levels have been restored to optimal standards, ensuring that the surface is ready for safe operations.
In any case, Runway Friction Test must meet strict regulatory standards set by aviation authorities, such as the International Civil Aviation Organization (ICAO). To ensure compliance, friction testing is conducted regularly using advanced equipment, such as Continuous Friction Measuring Devices (CFMEs).
METHODS FOR REMOVING RUBBER DEPOSITS
Various methods or techniques are employed to combat rubber buildup on airport runways, each designed to efficiently restore friction and maintain a safe operating environment. Some of these methods include:
- Mechanical Abrasion: This is the use of equipment such as runway sweepers, brooms, or brushes that physically scrub away the rubber deposits. These machines may use water or specialized cleaning agents to enhance their effectiveness.
- High-Pressure Water Blasting: This technique employs high-pressure water jets to dislodge and remove rubber deposits. The force of the water effectively breaks down the rubber, leaving the runway surface clean and restored. Also known as Hydroblasting, this technique is arguably the most cost-effective and environmentally friendly way of removing runway rubber marks.
- Chemical Cleaning: This method involves using specialized chemicals that break down the rubber deposits on the contaminated area, waiting for a specified period of time to make the rubber deposits easier to remove, washing with high-pressure water jets, and using mechanical scrubbers to clean the treated areas. While this approach is quite effective, it requires careful consideration of environmental impacts because of the aggressive nature of the cleaning compound. For example, if the chemical in use is allowed to remain on the runway surface for too long, the paint and possibly the pavement surface could be damaged. Or, if not properly diluted, the washed-off water could harm the surrounding vegetation, drainage system, wildlife, or pollute nearby streams.
- Hot compressed air. This technique involves the use of high temperature gases to burn away the rubber deposits. The gases soften and shear off the rubber particles. However, caution should be exercised and the condition of the pavement should be closely monitored when using this technique on asphaltic concrete runways.
CONCLUSION
In the dynamic world of aviation, maintaining the integrity of airport runways is paramount for ensuring the safety and efficiency of air travel, the reason for which airports worldwide invest in cutting-edge techniques to address this challenge. As technology continues to advance, the aviation industry will likely witness the development of even more innovative and sustainable solutions to keep these “arteries” of the industry clear and safe for the countless take-offs and landings that connect the world.
REFERENCES
- ICAO Doc 9137 – Airport Services Manual Part 2, Chapter 8: Removal of Rubber,
- Kirstie Pickering (Airport Industry Review – AIR): Why Airports Need to Clean Rubber From Runways
- ROADGRIP: Runway Rubber: Why It Builds Up and How To Remove It Safely
- THB: The Crucial Role of Rubber Removal on Airport Runways
