The grass taxiways at my local aerodrome are sometimes crossed by hard surfaces. Where they cross, the levels don't quite match, so there's a bump as you cross: not quite a pavement kerb, but still a sudden change in surface height.

What's the best way to cross these safely? Crossing straight-on carries the risk that the mainwheels will both stick against the ledge, lifting your tail and in extreme cases maybe causing a prop strike; like trying to cycle up a kerb and going over the handlebars. Crossing at an angle makes sticking less likely, but it rolls the aircraft slightly, and in a low-wing airplane you risk touching a wing-tip.

What's the best way to balance these risks and safely cross the kerb?

  • 1
    $\begingroup$ Is it possible to put some kind of support to make level difference less? Maybe a sand bag or some pipe so the cross is lower or less vertical? $\endgroup$
    – vasin1987
    Jun 26 '16 at 13:18
  • 3
    $\begingroup$ Opinion: Taxi diagonally to minimize nose-over risk, if the wing tips are too close to ground, don't taxi there. Pull the plane straight over the step manually in this case, tail first. $\endgroup$
    – Wirewrap
    Jun 26 '16 at 13:53

The rule I was always taught is to cross any 'step' - up or down - at an angle with the elevator full back:

  • It minimizes the chance of a prop strike, which is much more expensive than a wingtip strike
  • When going 'up', you avoid having both wheels up against the step at the same time, which usually means you need a burst of power to get over it, which could lead to sudden acceleration and sharp braking
  • When going 'down' you avoid the aircraft dropping down suddenly, with the same risks of strikes or an increase in speed
  • Lifting the elevator reduces the chance of it striking

There may be some differences for specific aircraft types, but I've always followed that advice and never had a problem. I've also never seen an aircraft get close to a wingtip strike doing this, but I suppose it could happen if the step is large enough. Although in that case you might want to just find another taxi route.

  • 4
    $\begingroup$ This is true of both tricycle and taildraggers. $\endgroup$
    – GdD
    Jun 27 '16 at 7:56

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