How pilots stop airplanes from hydroplaning on wet runways?
In: 385
Large airplanes have anti-skid systems that function much like anti-lock brakes in passenger cars. However, you can’t fight the physics of standing water.
Airplanes require significantly more distance to stop on wet runways, and can easily hydroplane over standing water.
Above 60 knots of airspeed, much of an airplane’s braking acton is aerodynamic, and from engine thrust reversers (if equipped with them).
Spoilers add some drag, but their main effect is to kill lift to maximize friction between the wheels and the runway.
On a wet runway, pilots sometimes intentionally touch down harder to get better traction for the tire.
Having multiple wheels does help as the preceding wheel displaces the water for the following wheel.
Then there’s the a very good antiskid system.
Then you gonna anticipate the problem and plan to use a lot more thrust Reverser than normal.
There’s some pilot skill also, some plane require some pilot input to make the plane weigh more on the nose wheel to preserve steering authority.
Then there’s weight. Less weight, less braking effort. You can purposely take off lighter or you can burn all the reserve fuel before landing. Both of this will ease the braking.
The biggest factor is math. You land only if the math checks out. If not, divert to another place.
the tires treads are designed with channels for water to run through to make it easier for the tire to make contact with the ground
On top of the answers that focus on the airplane specifically, runways are not smooth asphalt like a highway. Runways are usually grooved to facilitate draining rain water.
[safety grooves](https://aviationoiloutlet.com/blog/safety-grooving/)
One other thing that you don’t see so commonly anymore because propeller planes have gone out of favor commercially is some of them had a thing called “beta” which was reverse pitch on the blades. The pilot effectively is using the propeller(s) as a massive powered brake at that point instead of the tires.
What can you say on ELI5 that isn’t taken down for being concise and to the point?
Airplanes are designed to be controlled absent contact with the ground and contact with the ground does not obviate those controls such as rudder, flaps and ailerons. In short, it doesn’t matter as much in a plane if it does hydroplane because it has two system of control.
TLDR: They don’t
I once had a pilot explain it to me thus: “We land harder to break through the water”
I feel like that’s about as clear an ELI5 as there is.
Just a question to people who know more than me; could a high-pressure air hose be mounted in front of the wheels to blow the water away?
They use NASA developed technology to minimize hydroplaning on wet runways. Have you ever seen grooved roadways? Nasa design. Langley Research Center (NASA) has a [Aircraft Landing Dynamics Facility](https://www.nasa.gov/vision/earth/improvingflight/aldf_demonstration.html) where aircraft tires and runway surfaces can be tested at race-car velocity. It was called Landing Loads Test Facility in the ’80s when I worked on their instrumentation. They were testing Space Shuttle tire designs while I was there.
Latest Answers