Let’s pick this up right where the runway surface gets truly hostile — Page 289, Lesson 360

Let’s pick this up right where the runway surface gets truly hostile. I want to walk you through a phenomenon called reverted rubber hydroplaning — and I’ll be precise, because this is a classic exam trap and a real operational hazard. First, the name. “Reverted rubber” refers to what happens to the tyre material itself. The term “reverted” means the rubber is changed back — reverted — into a different physical state. So the full definition: reverted rubber hydroplaning requires three things to be present simultaneously. A prolonged, locked wheel skid. Reverted rubber — that is, the tyre material that has already undergone the change. And a wet runway surface. All three must exist together. Now, the mechanism. When the wheels lock, they stop rotating. But the aircraft is still moving forward, so the locked tyres are dragged along the runway. That dragging creates friction, and friction generates heat — enough heat, in this case, to vaporize the underlying water film. The water turns to steam. That steam forms a cushion that physically lifts the tyre off the runway surface. So the tyre is no longer in contact with the runway at all — it’s riding on steam. That eliminates tyre-to-surface contact entirely, which means the braking force is gone. Here’s where the “reverted” part comes in. The heat from that steam is so intense that it reverts the rubber — it changes the tyre rubber into a black, gummy deposit that gets left behind on the runway. That’s the reverted rubber you’d see as a skid mark. Now the critical operational characteristics. Once reverted rubber skidding starts, it will persist down to very low speeds — virtually until the aircraft comes to rest. It does not stop at some moderate speed; it keeps going almost to a full stop. And during that entire skid, two things are true. You have no steering capability — the nosewheel or main wheels that are locked can’t steer you. And the braking effect is almost nil — essentially zero deceleration from the brakes. So you’re sliding, not stopping. The good news, and this is a key point for modern operations: reverted rubber hydroplaning is greatly reduced in modern aeroplanes. Why? Because of the standardization of advanced anti-skid braking systems. These systems prevent wheel lock-up. If the wheel never locks, you never get that prolonged locked-wheel skid, so you never generate the heat that creates the steam cushion. That’s the direct cause-and-effect chain: anti-skid prevents lock-up, lock-up is required for the heat, the heat is required for the steam, and the steam is what lifts the tyre. Now let’s move to the practical side — the landing technique on slippery runways. This is the guidance for landing on contaminated runways, and it’s a sequence of actions. First, check the current weather and the runway conditions, using the most accurate information possible. That’s your starting point — you need to know what you’re dealing with. Second, once you have that information, completely reassess the landing performance data. You don’t just glance at it — you redo the calculation to ensure satisfactory compliance with the regulations. The landing distance you planned on a dry runway is not valid on a contaminated one, so you must verify the new numbers still meet the regulatory requirements. Third, the approach itself. Ensure you are at VREF at the landing screen height. VREF is the reference landing speed — the target speed you fly on final approach. And the landing screen height is the point, typically 50 feet, where you’re committed to the landing. So you want to be at VREF exactly when you cross that height. Fourth, prepare to land the aircraft in the touchdown zone, within the 1000 ft target of the airborne segment. The touchdown zone is the designated area of the runway where you should touch down, and the 1000 ft target refers to the aiming point — the first 1000 feet of the runway from the threshold. So you’re aiming to touch down within that zone. Finally, the actual touchdown technique: land on the centre line, with minimal lateral drift, and without excess speed. Centre line keeps you on the prepared surface, minimal drift keeps the load even, and no excess speed means you’re not carrying extra energy into a landing where braking is already compromised. So the whole picture: understand the physics of reverted rubber hydroplaning — locked wheel, heat, steam, loss of contact — then apply the disciplined technique: check conditions, reassess performance, fly VREF at screen height, aim for the touchdown zone, and touch down cleanly on the centre line. That’s the complete picture from this passage.