Practice Makes Perfect

Any skill you want to create and maintain takes practice. Pilots have many such skills. One of the often neglected skills is gusty and cross-wind landings. In Southern California, we just don’t get that many chances to practice in windy conditions. Strong winds are fairly rare and even the moderate winds generally align with our local runways and crosswind runways that you can use aren’t common (Burbank is an exception). Often when winds are strong, they are TOO strong.

Tomorrow may be a good day for that practice. We’re getting what is locally known as a “Santa Ana”. These are winds that come from the north, rather than our dominant on-shore flow, but they look to be in a range that might work. Take a look at the TAF (terminal area forecast) for Ontario airport

KONT 251730Z 2518/2624 VRB05KT P6SM FEW200 
     FM260300 03008G18KT P6SM SKC WS015/04045KT 
     FM261600 05015G35KT 6SM BLDU SKC 
     FM262100 04015G25KT P6SM SKC

Now, 35 knot winds are not to be trifled with. In a Cessna 172, that starts to push the limits of what you can reliably control when taxiing. You’re at a significant fraction of the stall speed of the airplane, when sitting still on the ground. If that 35 kt winds is a direct crosswind, it is near the max demonstrated crosswind for a Boeing 737!

Knowing that these conditions are coming, I put out the word to pilots I fly with, who want to challenge themselves.and hone their skills. I got some takers – that makes what might have been a bad day for business and potentially turns it into a full day 🙂

Now, I don’t suggest that a pilot who is rusty on cross-wind landings go hop in a plane in these conditions. Get a good instructor (that’s the part where I come in) to go out with you.

I’ll keep an eye on the conditions in the morning to see if winds and other conditions will allow us to safely work. Ideally, what I want to see is fairly mild winds at our home airport and stronger winds at nearby airports that are in the 20-30kt range. That gives us a possible out if conditions are more than we planned for. It also means that windshear and turbulence are very likely, so I’ll also be watching PIREPs (PIlot REPorts) for information on the severity of turbulence.

In the past, Chino (KCNO) has been a good option for cross-wind practice. First, it’s only 5 miles from Ontario, so the TAF at ONT is usually a good indicator for CNO. Second they have two long, wide runways (8/26 L/R) and a third crossing runway (3/21) that usually aligns more with the winds during Santa Ana conditions. On these windy days, there usually are not that many pilots out flying. This means that if runway 3 is too well aligned with the winds, we can often ask for runway 8 and get some more crosswind component.

Cross-wind technique

This is one of those areas that generates a lot of hangar talk. For me, the bottom line is whether you are able to

  1. Keep the direction of motion (momentum) of the plane headed right down the center of the runway. If you do this, you are much less likely to depart the runway sideways.
  2. Align the nose of airplane with the runway and continue to do #1

Doing both of those in crosswind conditions requires some timing and the use of both rudder and aileron in ways that pilots don’t always find comfortable and intuitive.

Crab

When we start with cross-wind landings, this is where I start. Get established on final, trimmed for the appropriate approach speed (adding speed if necessary for gusty conditions), and try to find where the nose of the airplane needs to be pointed in order to maintain motion aligned with the center of the runway. You should find that the nose is pointed towards the cross-wind. Flying such that you are pointed one way and moving in a different direction, but with wings level, is known as crabbing. The strength of the cross-wind (compared to your approach speed) is indicated by the angle between the longitudinal axis (the nose) of the airplane and the centerline of the runway. If the winds are not too gusty or variable, establishing this angle is not that difficult.

However, you would be ill-advised to land the airplane in this configuration, as it would be very tough on the tires and landing gear (possibly to the point of breaking). In a tail-dragger, you would find yourself quickly in a ground loop.

One interesting thing to consider is that if the winds are not gusty and you can’t see outside (think of someone inside a jet in an aisle seat), you will never know you are in a crab. It takes that visual outside reference (or noting the difference between heading and ground track) to tell you that something is odd.

Slip

So, if I can’t land in that crab, what should I do? The next step is to use rudder to try and align the nose with the centerline of the runway. However, if you do that by itself (as is common when learning), you will immediately find yourself moving at that same angle as you were crabbing, except now you are departing the runway at that angle. The astute reader will guess that is not a good idea.

What is needed is some bank (roll/aileron) into the wind. This constant “turning” will help compensate for the cross-wind in the same way that the crab compensated. The challenge is to find the bank angle and rudder pressure to both keep the airplane moving down the centerline and keeping the nose aligned with the centerline. More challenging is to do that as the winds are changing and as the speed of the airplane is changing.

You are now in a condition of one wing down (the one that is into the wind) and the opposite rudder. You’ve generally been taught to avoid this situation. It is called a slip and you can see most definitely if you look at the ball of the turn coordinator, you are not flying coordinated. In this case, that isn’t a problem, it’s a requirement. However, it means that your passenger who can’t see out of the plane can tell something is odd.

How early you transition from crab to slip is a matter of personal taste, skill, and timing. For my early students, I recommend an early entry to the slip, just to get a feeling for the amount of rudder authority you have. More experienced pilots may delay that transition right until they flare for the landing.

Overall, you should think of ailerons as aligning the airplane with the centerline and the rudder as aligning the axis of the airplane with the centerline. If you haven’t got your direction of motion heading down the runway, then I suggest you go around and try again.

If you find that at the limit of rudder movement, you can still not keep the nose aligned and the airplane moving down the runway centerline, then you’ve run into a problem. You’ve found what is usually the limiting factor in those “demonstrated cross-wind component” numbers you read about in the POH or AFM. In many small airplanes, that is in the range of 15-20 knots.

For most pilots, that means the most prudent course of action is to find a different runway to land on (or wait for conditions to improve if you can), especially if the runway is narrow.

Flaps

Flaps are used during landing to both increase the angle of approach during landing without increasing airspeed and to allow landing at lower airspeeds (and hence ground speeds). In windy conditions, a headwind component allows a steeper descent than normal (unless you compensate with power) and will reduce the ground speed at touchdown (even if the airspeed is a little higher than normal). In addition you may find that deployed flaps make the airplane hard to control in cross-wind conditions. For those reasons, when you practice, try out different flap settings to see what works best in your plane. For Cessna 172s, I generally prefer less flaps than normal.

Speed

If the winds are gusting, we are generally given a recommendation to add half the difference to our approach speed. For example, if winds are 15G30, then adding 7.5 knots would be the standard recommendation. This s a good starting point point.

Overall, in gusty and cross-wind conditions, some extra speed will give greater control, as the flow of air over the control surfaces (ailerons and rudder) is greater.

You may also find that full stall, extremely nose-high landings are not the best idea in these conditions. I will often accept slightly higher touch-down speeds and flatter landings to help in control during the flare, while speeding the transition to wheels on the ground, where they can help counteract the cross-wind effects. Like all things, don’t overdue extra speed – it can still result in unintended bounces and loss of control if not managed properly.

Touchdown / Taxi

If cross-winds are strong enough, you will be touching down on the upwind main wheel. In this case, that is desirable (I too often find that pilots think there is something wrong when they touch on only one wheel). In strong winds, you will need to roll ailerons/yoke/stick into the winds as you touch down to counteract the tendency for the wind to want to roll the airplane the opposite direction. As you slow to taxi speed, continue to use ailerons to counteract the wind.

Kick

Now, there are other variations that can allow you to land in greater crosswinds. For that, I recommend Barry Schiff’s excellent Proficient Pilot books

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