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This ERJ-145 Accident Could Happen To Anyone. Here's How To Avoid It.

What Happened Here?

Crash Transport Safety Board of Canada

This wasn't the result of an emergency or a mechanical failure, it was caused by hydroplaning. With spring rain on the way, hydroplaning is something you need to consider.

So, what happened here?

Hint: It has to do with this...

Tire Transport Safety Board of Canada

On September 4th, 2011, a Trans States EMB-145 operating as United Express Flight 3363 made its approach into Ottawa, Ontario during heavy rain showers.

ILS In Heavy Rain

The crew chose to fly an ILS to Runway 32. Tower reported the winds from 310 degrees at 10 knots. As the crew descended through 1000' AGL, tower called the winds from 320 degrees gusting to 20 knots. The crew increased their approach speed by 7 knots to compensate for the gusts.

As the crew crossed the runway threshold, the rain showers increased in intensity, and the crew switched the windshield wipers to high.

Sink Rate!

Just before touchdown, the showers became a heavy downpour - giving the crew the illusion that their sink rate was rapidly increasing. The captain applied maximum thrust for 7 seconds to counter the sink.

Fast Touchdown And Bounce

The aircraft touched down 2700 feet past the runway threshold, but the airspeed was increasing and the Embraer lifted back off. It settled back down 3037 feet past the threshold, still increasing in speed.

After the nose wheel touched down, the captain applied maximum braking, but the aircraft began to skid. He asked the first officer to apply brakes - but nothing changed.

Hydroplaning Down The Runway

Suddenly, brake pressure increased to maximum and the aircraft skidded to the left. The captain applied full right rudder - without effect. A spray of water from the wheels rose 22 feet above the runway, 300 feet past the aircraft. The captain applied the emergency brake, but stowed it after it had no effect.

At 7500 feet, the aircraft had turned nearly perpendicular to the runway and was skidding sideways. At 8120 feet, the nose wheel left the runway, followed by the main gear. The aircraft stopped on a heading of 211 degrees, with the main gear collapsed.

Findings

Lots happened here, and the Transportation Safety Board of Canada details the entire chain events in their report. Their findings focus on several important factors:

  1. Heavy rain contaminated the runway with 4-6mm of water
  2. The aircraft's approach speed was fast
  3. The crew didn't execute a go-around when their speed exceeded company standards
  4. The aircraft touched down fast
  5. The combination of a less-than-firm landing and under-inflated tires caused the aircraft to hydroplane
  6. The captain applied the emergency/parking brake, disabling the anti-skid system and prolonging the skid
  7. The aircraft lost directional control while hydroplaning and veered off the runway

These findings apply to any pilot - whether you're flying a Cessna 172 or an Embraer EMB-145. And, with spring rain coming up - it's time to think about hydroplaning.

Hydroplaning - What Is It?

You're familiar with the term, and you may have had the chance to try it out during drivers-ed. But did you know that there are three kinds of hydroplaning?

Dynamic Hydroplaning - A Wedge Of Water

You're probably familiar with "dynamic hydroplaning" - when water lifts your wheels off of the pavement. But, why does it happen?

Dynamic Hydroplaning

In general, you need one-tenth of an inch of water to start dynamic hydroplaning. As your wheel travels across the pavement, a wedge of water builds up in front of - and under - the wheel. Once the pressure from the wedge of water equals the weight of the airplane, the wedge lifts your plane off the pavement. Now you're water-skiing.

How fast do you need be going to start hydroplaning? It's about 8.6 times the square root of your tire pressure. So, if you're flying a Cessna 172S with the main tires inflated to the recommended 42.0 PSI, you're looking at about 56 knots.

Under-Inflated Tires = Trouble

But, if your tires are under-inflated, the risk of hydroplaning increases and can happen at a lower speed. Why? Under-inflated tires can deflect inwards, raising the center of the tire and trapping water.

Under Inflated

Reverted Rubber - From Bad To Worse

Reverted rubber hydroplaning, also known as "steam hydroplaning," often follows dynamic hydroplaning - but it can happen on its own, as well.

Revert Rubber

If a wheel locks and begins to skid, the friction heats up the surface of the tire. The tire begins to melt, forming a seal between the pavement and the tire. Any water underneath the tire becomes steam, lifting the tire off of the runway.

You may not even know it's happening - especially if it follows dynamic hydroplaning.

If your wheels lock up, release the brakes and allow the wheels to begin rolling. Then apply moderate braking.

Viscous Hydroplaning

Water is viscous. On a smooth surface, like an asphalt runway, it can easily form an inpenetrable layer of liquid. Even a tiny amount of water - 1/1000 of an inch - can cause hydroplaning.

Viscous Hydroplaning

Grease or accumulated rubber on the pavement increases the chance of viscous hydroplaning - and has the same amount of friction as wet ice. That's slick.

Things That Can Help

Grooved runways make a big difference. Not only do the grooves help water drain off the runway, they provide an "escape route" for water trapped underneath your tire.

Grooved / Smooth Bill Abbott

Check your Airport/Facility Directory - you'll see "GRVD" after the runway length for a grooved runway. At Centennial Airport, Runways 17L/35R and 17R/35L are both grooved. Runway 10/28 isn't.

AFD

Keep your tires inflated. Under-inflated tires add to the problem. Don't land fast on a wet runway - make sure you hit your touchdown speed or go-around and set up again. And, use back pressure and aerodynamic braking to slow down. Use moderate braking after the nose wheel touches down, but release the brakes if your wheels start to lock up.

And finally, any lesson on hydroplaning is not complete without a demo - so here's a Super Cub to help us out...

NASA cut this video back in 1963 - and while the music's a little corny now, the info still applies.

Aleks Udris

Aleks is a Boldmethod co-founder and technical director. He's worked in safety and operations in the airline industry, and was a flight instructor and course manager for the University of North Dakota. You can reach him at aleks@boldmethod.com.

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