What’s the Big Deal about Tailwind Landings?
From the moment you start learning to fly, you’re taught to take off and land into the wind. I often phrase it as “Like flying a kite in the park, always run into the wind so that you don’t have to run as fast to get it to fly.” There’s no doubt that while you can land with a tailwind, it increases your risk of things going wrong.
So, what’s the big deal with tailwinds? The first two major factors, performance and controllability, are easy to understand as they are just physics scenarios. The third factor (which is often the immediate precursor to the accident) is the psycho / physiological response to an uncomfortable situation.
Tailwinds and Landing Distance
A 10 kt tailwind is a significant change from a 10 kt headwind when you are flying an aircraft that lands at around 50 kts. This is a 50% increase in ground speed (60 kt v 40 kt). In practice this results in more than double the runway length being used up.
That’s a big performance penalty. But that’s not the only problem. In a loss of control situation, the kinetic energy in the crash is proportional to the square of the speed (1/2 Mass V2). Your aircraft at 60 kts has 2.25 times the energy it would have at 40 kts.
Tailwind Post-Touchdown Controllability
Controllability after touchdown is another issue. When you’re landing with a tailwind, you have a higher ground speed on touchdown. When pilots land with a higher ground speed, they have a tendency of braking more aggressively than usual.
In tricycle gear planes, most of the aircraft’s weight is on the main gear. But that all changes when you land and hit the brakes. Your brakes are trying to slow you down, but your aircraft wants to keep moving forward.
You feel it in the cockpit when it happens. When you brake aggressively, you get thrown forward against your shoulder harness. When you aggressively brake, a lot of the aircraft’s weight is ‘transferred’ to the nose gear.
When you combine that load transfer with the crosswind component of a quartering tailwind, you could put yourself in a situation where one of your main gear has little or no weight on it, affecting your ability to keep the plane under control and on the runway.
All of the above assumes that you haven’t over cooked the flare and landing.
Pilot Induced Oscillations
If you haven’t intentionally chosen a downwind runway but have arrived at final with a tailwind by mistake, inattention or habit, you are in for a surprise. How long it takes for this reality to dawn on you is entirely up to you. Rather that actively monitoring during approach many pilots become overloaded and become fixated on the upcoming landing. The windsock should be checked a couple of times on final with the intention of estimating the headwind, crosswind and tailwind components. When you check the windsock, you need to counter your internal confirmation bias which lets you see what you want to see instead of critically evaluating the actual conditions in front of you.
If you haven’t picked the tailwind on approach you will start to feel uncomfortable as you approach the runway and it just doesn’t feel right as world wizzes by. Then you encounter an overshoot windshear as you cross the threshold and enter the slower air closer to the ground. This results in an increase in airspeed at the point in your landing that you would normally have a decrease in airspeed.
Now your psycho / physiological response to an uncomfortable situation will kick in and your grip on the controls will become overly firm with the white-knuckle ride about to start. Over controlling while being out of sync with the aircrafts motion will lead to the aircraft porpoising down the runway.
Pilot induced oscillation crashes are typical fare for YouTube, but a timely go-around decision needs to be made before the magnitude of the oscillation develops to the stage of a prop strike or gear collapse.
As a general rule you should go around after the second bounce if not before. Don’t attempt to analyse the situation then and there, instead, just get out of Dodge.
Better Decision Making and Situational Awareness
There are many factors which can get you in an uncomfortable or dangerous situation, but there is often a chain of missed opportunities to be informed…
- Is your destination typically subject to adiabatic, katabatic, land-breezes or sea breezes at your planned time of arrival?
- What is the forecast for your planned time of arrival?
- What are the forecast winds aloft?
- What are your aircraft limits? What are your personal limits?
- Does your destination have an ATIS or AWIS? What is it saying?
- Is there any other traffic using the airfield? Which runway are they using?
- All of the above must be confirmed or repudiated by your own observations when you fly overhead the airfield at 1500’ AGL. What is the windsock showing? Again, when you check the windsock, you need to counter your internal confirmation bias which lets you see what you want to see instead of critically evaluating the actual conditions in front of you. If you skip this vital step you are asking for trouble.
- If ATC offer you a runway other than the most in to wind runway you do not have to accept it.
- The windsock should be checked a couple of times on final for the purpose of estimating the headwind, crosswind and tailwind components.
If in doubt, go-around.