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Performance & Navigation 5.

Runway Operations:
Tyre Cornering Force

An important function of tyre/ground friction is to produce cornering forces. Tyre cornering forces are the primary means of controlling runway tracking on the ground-even on very slippery runways. On slippery

runways a tyre develops its maximum cornering force at about 5 degrees of yaw; beyond this point the sideforce decreases rapidly. A high vertical load (i.e.: weight on the tyres) and no tyre skidding also increase the cornering force available.

Whereas a certain amount of tyre rotational slip is necessary to produce a braking force, that same slip reduces the tyre cornering force.

Braking and skidding, reduce tyre cornering force. A locked tyre produces no cornering force at all, so spinning up all the tyres as they touchdown is essential to maintain runway tracking capability.
As the pilot you can NOT change the available friction on the runway, but you can increase the vertical load on the tyres by lowering the nose, which will reduce lift. Promptly lowering the nosewheel onto the runway will also greatly increase the patch area available for cornering, and will assist in keeping the aircraft straight.
If a side slide should develop, release the brakes momentarily. This will increase the cornering force of the tyres and get the aircraft straightened up quickly. Do NOT stay on the brakes ! Side slides can occur when there is significant cross winds. These not only blow the aircraft onto the downwind side of the runway, but also weathercock the aircraft so that the nose swings into wind (i.e.: pointing back toward the runway centre).

Improving runway surface

  • Some runways have a very noticeable camber. This allows any water present to flow off the runway. Roads also have a marked camber (ie: rise up from gutter to the centreline), for this purpose.
  • Some runways are porous, and/or have grooves running across them. Both features assist in clearing water off the runway, and the grooves also help in keeping the tyre rotating.


  • Smooth, flat runways with poor drainage, rubber deposits and painted surface markings are the worst.
  • Runways that are porous, grooved and have a marked crest toward the centreline are best.
  • Do NOT attempt a “greaser” landing on a runway with significant water on it.
  • Lower the nosewheel as soon as possible after the main wheels touch down.
  • Use thrust reverse if available. Spoilers and reverse thrust together contribute about 70% of the total braking action during the high speed portion of the landing roll on a slippery runway. They are less effective at low speed, where wheel braking effort has a greater contribution to total deceleration.
  • Ensure the speed is safe before turning off the runway.
  • Remember that greatest tyre cornering effort occurs when braking is NOT used.
  • On slippery runways, antiskid or individual brake failures may limit the takeoff weight, due to the reduced braking effort available should an abort be required.
  • Tyre condition is important. Carefully inspect the tyres for tread depth, cuts and flat spots.
  • Avoid landing too far into a slippery runway. Remember runway behind you is of no use to you.

I hope this mini-editorial assists you.

Happy flying !

Rob Avery

ATPL Lecturer

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Marty says ... "Goodbye to GA".

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