Our Experts on: Aircraft Tyres
While we’re mainly focused on car and truck tyres on CarbonBlack, occasionally something comes along that piques our interest. In this case it was a question posted to our tyre expert David Matthews on aircraft tyres. Here’s David’s response:
The job that aircraft tyres have to do is very simple, but very specialised. They only have to track in a straight line, and operate within a narrow range of speeds. The epitome of this is, of course, a jet aircraft tyre. These have three layers of nylon built into the tread crown to hold the tread on at very high speeds (around 230 knots) – the nylon shrinks when hot, strengthening the hold.
The real issue is the amount of deflection they have to absorb on landing. Around 50% of the tyre section height (the distance between rim and ground) is lost on impact. The tyre flattens out, wears out after around 200-230 landings, (leaving furry bits of nylon protruding) and is retreaded, with the nylon replaced. While taxi-ing, the tyre deflection (percentage of section height lost) is around 30% on a jet, so some airports have limitations on plane weight when it has to taxi a long way in high temperatures.
The qualifying test for an aircraft tyre used to be (I have no recent knowledge, but it wouldn’t be any less today) that the tyre did 50 simulated landings without flaps at one hourly intervals – from memory around 180 knots. This is all done on a machine under controlled conditions.
The tyres operate at about 230 p.s.i on massively strong rims bolted together with massively strong bolts. This is possibly a bit removed from recreational aircraft tyres. What finally brings an aircraft tyre undone after six or seven retreads is fatigue in the lower sidewall, where the massively strong bead wire bundles (3 a side) are tapered into the flexible sidewall. So speed is not what it’s all about- reliability is. Comforting for recreational flyers!