I've now seen several landing strips up close and there are lots of tire tracks from planes' landing wheels. I wonder if it somehow modifies the properties of landing strips to make for poorer landing conditions.
Do landing strips suffer from lots of tire tracks?
It does indeed degrade performance, and runways (and their lights) have to be routinely cleaned of rubber. The FAA specifies safe friction levels.
Wikipedia has this to say:
The build up of rubber affects the level of friction of the runway, most noticeably as a reduction in braking and ground handling performance. This can lead to incidents such as runway overrun or a lateral slide off the runway.
Some runways are particularly poor:
The Runway friction level is affected by accumulation of rubber deposits (in the touchdown zone) on the runway. Periodic removal of the deposits is needed to maintain the highest possible friction level. On busy runways rubber deposit accumulation if inevitable, runway maintenance needs to address this. When the actual runway friction level is below the minimum friction level, a 'slippery when wet' NOTAM is devised or another runway is designated.
Detailed information about friction, measurement and contamination can be found here.
As a side note: next to rubber deposits the paint used for markings on runways and taxiways contains a certain amount of sand to increase its friction.
Oh yeah it certainly does as I learned one rainy day.
The A7-E Corsair is a single seat jet attack plane for the Navy. They were deployed aboard carriers in the mid 1980's. It needs at least 10,000 feet of runway to land. On a wet runway the pilot is required to take the wire, or divert to another field because it won't stop in time.
I always found the stopping distance of the A7-E to be remarkable. The brake system on the A7-E incorporated anti-skid, however they were undersized for the aircraft and therefore the necessity for long roll-outs.
I was flying in to NAS Sigonella in Italy with the carrier air-wing close behind. There were over 20 planes headed for the field. As I came in to the runway it was raining off and on, and the air temperature was hot. Going VFR at the initial, below the clouds, I did a touch and go, and rolled out looking over the runway surface. It was relatively dry with no standing water, and so opted not to take the gear on the runway. I assumed that it was the heat of the runway that evaporated most of the water.
The arresting gear was laid across the runway at the both ends and if an aircraft required it, they lowered their tail hook on the approach, and snagged it as the ran over the wire. Taking the gear took some consideration though since it took at least 15 minutes to reset if personnel are well trained. In Sigonella's case not many planes take the wire and so it might take 30 minutes to reset. For one plane! And there are another 20 plus coming soon.
I came back around and landed. After slowing down I tested the braking, still having time to go around. It was good. I relaxed and coasted toward the end at around 60 knots. When I got into the tire marks it was time to slow down for the turn off, and it was like being on ice. Nothing! I turned the nose gear with the rudder and the aircraft indeed turned, but kept sliding straight down the runway. Disconcerting to say the least. After the rain, the oil had risen to the surface of the skid marks, forming a film there.
Entered the area were the skid marks disappeared and the plane came to a stop. Wow, that was a surprise.
