Takeoffs and landings into the wind are, of course, normal procedure. But there are plenty of times when the opposite happens, or is even desirable. Light-and-variable-wind days often result in a takeoff or landing with a tailwind component, and it’s common practice.
Final instrument approach segments can sometimes require a descent in a tailwind, knowing you’ll circle ’round the other way to land (or perhaps not). In stable weather, these changes are gradual and the wind speeds don’t cause much concern, but anything more than that and things can get dicey.
Then, of course, there are emergencies that could force you to choose between the unappealing options of landing downwind or landing off-airport. Like any nonstandard situation—emergencies not withstanding—knowing the aircraft and how it will behave in various conditions could mean the difference between more options or none.
Emergency or not, common sense dictates that we simply don’t take off or land downwind. But given the common scenarios in which a few knots are acceptable, it’s worth asking the question: “Just where is your limit?”
When It’s “Calm”
Let’s start with the easiest scenario. You’ve just fired up your light twin on the ramp at a non-towered field. It’s a sunny day, so you plan to pick up your clearance in the air. You tune in the AWOS, which reports: “Wind: Calm.” Based on this, you choose the airport’s designated calm-wind Runway, 27, which is 5000 feet long.
As you taxi out, you see that the airport’s only windsock is nearly limp, but it’s picking up a slight breeze from the east. You know from your weather briefing that estimated winds at 3000 feet are easterly at 10 knots, increasing to 15 knots at 6000 feet—no big deal for what you’re planning.
You could take off from Runway 9 to follow what the windsock indicates and get a better climb gradient, but other aircraft are coming and going on 27. In this case, joining the flow of traffic and taking off with a tailwind of what’s estimated to be 3 knots or less is a safe choice for most of us—certainly far safer than departing against traffic.
A calm winds report on AWOS or METAR allows for a few knots of wind blowing at the surface. The National Weather Service defines zero to five mph as “light” or “calm,” which converts to about four knots. So, “calm” doesn’t necessarily mean zero.
Meanwhile, you’ll typically get a few more knots of wind at 100 feet as you depart or approach, a few more at 200 feet, and so on. This is a case in which operational considerations could have you departing with a light tailwind, but it’s important to know where to draw the line, obstacles or terrain notwithstanding. Are you comfortable only when the weather report says it’s calm? Are you OK when you think the windsock is showing three knots? Four? Five?
Note that we fly aircraft. Thus, they at best perform marginally when operating on the ground. Let’s look closely at, say, a five-knot headwind. Assume your normal rotation is at 65 KIAS. Into that five-knot headwind, you’d rotate at 60 knots of groundspeed. But if you departed on the “easy” end of the runway with a tailwind, you’ll be rotating at 70 knots of groundspeed. That 10-knot difference amounts to more than a 15 percent increase in your groundspeed—and potential difficulty handling your aircraft on the ground. Landing can be more difficult
When It’s LIFR
On an IMC day, tailwinds can be, well, interesting. Say your trip for a business meeting in your six-seat single will take you to a Class C airport with 200 feet and 1/2 mile reported. While you’ll enjoy a nice 30-knot tailwind enroute at 8000 feet, winds at your destination are from 230 degrees at 15 gusting to 25 knots.
The ILS 36 is the only precision approach there, giving you an estimated 19-knot crosswind component at peak gusts on top of a 16-knot tailwind. You’re comfortable with only 5 knots of tailwind for a 5000-foot runway, so it’s time for plan B. There’s an alternate 20 miles away, also with an ILS available, and you can rent a car to get to the meeting.
The alternate offers ILS 33, and according to the latest report, winds are from the same direction, but a bit lighter at 18 knots. You can expect a significant crosswind with a 3-knot tailwind component. This is far more appealing than the original destination, but you’ll have to beef up your contingency plans if conditions worsen. You’ll also want to monitor that near-your-limit crosswind.
Higher ceilings can give you the option of flying the approach you need and then circling to land on the most suitable runway. This is normal life for those based at airports with one published approach (or only one you’re equipped to fly). Outages can also require a downwind approach and landing on another runway.
Naturally, this requires careful planning and knowing what you can handle. If you arrive and find the winds aren’t as advertised and exceed your comfort, treat the situation like any other operation: abort sooner rather than later, use an alternate, or buy some time from ATC with a hold or extra vectors.
Temperature inversions and intense frontal activity can present strong, varying winds close to the ground, especially when mixed with mechanical turbulence. With accompanying wind shear, it could mean that as you’re fighting your way down to your desired landing spot, you’ll get a tailwind component blowing you further down the runway.
Say you’re flying an RNAV 18 approach in a Cessna 210 to an 8000-foot runway in unstable conditions. Your initial leg begins with 50 knots of quartering tailwind on an eight-mile final, then shears to a west-northwest wind further down, presenting a gusty surface wind with a steep crosswind expected on the surface. You’re at your desired airspeed of 120 knots, but see that as you descend to the final leg at 2000 feet, your tailwind is sticking around and the resulting groundspeed is still 150 knots. You think, “This would be great if I were about 4000 feet higher.”
You’ve already made it a point to complete pre-landing checks early. The tower was still reporting the southwest wind you were so looking forward to, but the direction varied all the way down. Even after you broke out at 700 feet, your groundspeed was a little over 120 knots. If you see that you can touch down at or prior to your pre-planned abort point 3000 feet down, you’ll continue because you’ve given yourself 5000 feet to stop. If in doubt, you’ll take the missed.
When Things Go Wrong
Avoiding any and all tailwinds for takeoffs and landings is a great policy to have as you’ll never have to make that call. But what if an emergency requires considering a downwind landing? It never hurts to examine the particulars of your aircraft and know what to expect if you ever had to make such a choice.
Take the circle-to-land example. If you have an engine failure while in IMC on an approach that was supposed to allow you to circle for landing, you might not have the time or space to break out of the clouds, get your bearings and make the intended runway. This could be a case when you’ll have to land straight in. All things being equal, it would be nice to have some idea how much runway you’d need and what a six-knot quartering tailwind feels like in your aircraft.
If you’re having an icing or fuel emergency, your options are to burn precious minutes to set up an approach into the wind or fly straight in to the nearest available runway, even if it means landing downwind. Again, already knowing there’s a tailwind you can accept, you might have two options rather than one.
Handle With Care
Obviously, a surface tailwind of any significance will require careful consideration for a departure or approach. Deciding whether it will work for you and your aircraft requires calculating performance (see sidebar), being aware of the variables, and building some experience under controlled conditions.
Achieving the latter is like getting into any other unfamiliar operation—have a goal, study the particulars, and get with a trusted instructor to be your safety pilot. If you need to brush up on any standard IFR operation or crosswind takeoffs and landings, now’s the time. Then, set the parameters and get out there when conditions are right.
If you’re fairly new to the airplane you’re flying and haven’t had a chance to experience significant tailwinds on approach, or if you (thankfully) haven’t had to deal with such conditions for a long time, the first step would be to try things out at altitude, such as in a localizer intercept several miles from the runway with a quartering tailwind.
An instrument approach with which you’re quite familiar—and one that’s obstacle-free—would be a good place to practice, as you already know the stepdowns and the airport environment. Now, you can see what it’s like to descend on a typical three-degree profile with a 20-knot tailwind and transition to a circle-to-land. If landing isn’t practical, have a safe cutoff/go-around point planned so you can climb back out to a comfortable altitude.
For tailwind takeoffs and landings, it’s the same deal. Set the limits, whether it’s a varying crosswind or a five-knot tailwind, and work them into your operations. Keep in mind that you also want to emphasize missed approaches, so you know what to expect when in these conditions.
No one wants to deal with tailwinds on or near the ground, but some situations can be managed with proper planning. Getting a handle on the various scenarios you might encounter can give you more options when the wind isn’t going the right way.
Elaine Kauh is a CFII in eastern Wisconsin, where tailwinds are best served cold above 5000 feet.