Central Flying Academy Why Is Landing So Hard
Why Is Landing So Hard After Shooting A Perfect ILS?
Two days ago, a 737 slid off the runway at LaGuardia airport. The jet was carrying vice-presidential candidate Mike Pence, as well as a group of campaign staff and media reporters.
Fortunately, everyone was ok. But the incident brings up something that all of us need to be thinking about this time of year: contaminated runways. And it doesn't matter if you're flying a 737, or a 172.
Landing On A Contaminated Runway
While we don't know exactly what happened during the landing, we do know the 737 came to a stop after going through the Engineered Material Arresting System (EMAS) at the end of the runway.
Around the time of the landing, there were overcast ceilings with moderate to heavy rain at LaGuardia.
With rain pounding down, the runway probably looked like a slip-and-slide, and hydroplaning was probably a factor. So how fast do you need to go to hydroplane?
Dynamic hydroplaning happens at about 8.6 times the square root of your tire pressure. For example, a Cessna 172 with 42 PSI tires would hydroplane at about 56 knots. Which, depending on your flap configuration, is very close to your touchdown speed.
Landing From An Approach On A Contaminated Runway
The problem starts on the approach. While jets are typically fully configured on an approach, GA airplanes usually don't use full flaps. Instead, you're usually at an intermediate flap setting.
That alone isn't a problem, but it can lead to one as you approach the runway.
Look at an approach in a Cirrus as an example. Cirrus recommends that you don't change aircraft configuration below 500 feet AGL. If you're shooting an approach in low conditions, you're going to be in IMC at 500', which means your intermediate flap setting is what you're sticking with all the way to the runway.
The recommendation is for a good reason, too. Changing flap settings on an approach can destabilize your approach. And as you're approaching DA/DH, the last thing you want to do is destabilize yourself and have to go missed.
But the flap setting introduces another problem: landing fast. When you have less flaps, you need to touch down faster. And the faster you touch down, the more likely you are to hydroplane on the runway.
When's The Last Time You Practiced Partial-Flap Landings?
The best way to avoid losing control on the runway is practice. When's the last time you practiced a partial-flap and contaminated runway landing?
Practicing partial flap landings is pretty easy. Head up to the pattern, configure your flaps, and practice your touchdowns. After you've done a few, compare them to full-flap landings, so you can get a feel for the difference in speed and touchdown.
And for contaminated runway practice, after touchdown, make sure you're very gentle on the brakes. When you jump hard on the brakes after touchdown, you increase your chances of locking up a tire and starting to skid down the runway.
Also, reducing flaps after touchdown can help with your braking effectiveness. A lot of POHs recommend that you reduce flaps after landing to get more weight on your wheels. And when your have more weight on the wheels, your braking will be a lot more effective.
Keeping It On The Runway This Fall
With more IFR rainy and snowy days on the way, it's a good time to get out and practice for what's to come. By getting yourself ready for partial flap landings on wet or snowy runways, you'll keep it between the white lines on your next touchdown.
This is not an original article. It first appeared on boldmethod.com on 29 October 2016. To read the original article click here.
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