Why Do Airplane Tires Screech?

A common question passengers often ponder during the landing process is why do airplane tires screech or emit a loud chirping sound as they make contact with the runway. This phenomenon is a result of the rapid acceleration of the tires from a state of rest to the high speeds required for touchdown.

Understanding the Science Behind It

Before the aircraft lands, the wheels and tires are not rotating. Upon touchdown, the tires hit the runway and must spin up to their high rotation speed in an incredibly short period of time, typically a second or less. This rapid increase in speed causes the tires to momentarily skid on the runway surface, resulting in the characteristic screeching sound and the visual effect of rubber being scrubbed off the runway.

How Car Tires Screech for Similar Reasons

This situation is analogous to what happens with car tires. When drivers accelerate from a stop, particularly when flooring the accelerator, the tires begin to spin rapidly to match the speeds required by the vehicle's engine. In the same way, airplane tires suddenly spin up to match the aircraft's high speeds upon touchdown. This skidding is similar to what you might observe with a drag racer flooring the gas pedal from an idle state. The tires rotate as if the vehicle is suddenly decelerating to a stop, similar to a car making an emergency stop and the tires locking up, causing them to skid and leave smoke trails on the road.

Similarity to Top Fuel Dragsters

For a more vivid illustration, think of the sound and appearance of a Top Fuel dragster. From a stationary start, these cars can accelerate to over 150 mph in a fraction of the time it takes them to even begin to skid. The rubber tires of a dragster screech and smoke, leaving visible trails of rubber on the track. The same physical principle applies to airplane tires during landing. Despite the massive power of jet engines, the transition from stationary to moving at 150 mph instantaneously is akin to a dragster's start. The tires, in essence, 'burn out' as they rapidly increase their rotation, just like the tires of a dragster.

What Happens to the Rubber?

The rubber that is scrubbed off the runway during this skidding process is similar to the rubber left behind by a dragster. This material is the part of the tire that has been in contact with the runway surface during this moment of high-speed acceleration. It can be seen as a dark smear or streak on the runway's end. This phenomenon is not only visually interesting but also helps to explain the sound and smoke often observed during landing.

Conclusion

The screeching and smoke from airplane tires during landing are a fascinating example of the physics of motion. These phenomena are a result of the rapid acceleration required to match the aircraft's speed with that of the runway. Whether on a tense landing or during a world-record-breaking drag race, the science of stopping and starting at such high speeds is consistent across various modes of transportation. Understanding this can help in better preparing for landings and appreciating the engineering involved in modern aviation.