Flying in Dangerous Wind Speeds

flying in dangerous wind speeds -

Flying in Dangerous Wind Speeds

by Ralph Wetterhahn

High winds can ruin a pilot’s day, big time. Crosswind landings can be one of the most stressful piloting experiences, especially if you haven't practiced them lately. Whether you're a student pilot just learning to fly, or a 20-year airline captain who hasn't gotten a lot of practice recently, a little review can go a long way.


It's Not Just the Wind Speed


Every aircraft certified by the FAA has among its notices a “demonstrated crosswind speed,” meaning a pilot can safely land in that wind without requiring exceptional ability or skill. The speed advisory (not a limit) is published either in the Pilot’s Operating Handbook or on a placard.


To exceed that crosswind speed may cause the aircraft to cartwheel on landing or leave the runway out of control. Some assume that this advisory has a safety factor included. Thus, if the crosswind is just over the demonstrated speed, one might choose to press on anyway. The problem with that assumption is that, whenever you are operating in high winds, you will almost always have gusts which can easily exceed any safety factor built into the advisory. Add a wet runway, and you can slide off the pavement even when landing in conditions well below the demonstrated crosswind speed.

It's Dangerous to Get Airborne

Before a pilot can even think about the landing phase, though, the plane needs to get airborne. At startup, use aileron control to keep the upwind wing down (assuming the wind from the front quadrant), and continue throughout taxi to the runway, reversing the control deflection when the wind is from the stern. Delay raising the nose wheel on takeoff to ensure a few extra knots in order to avoid stalling the downwind wing at liftoff.

Crosswinds

Another factor to consider is that it’s not easy to train in high wind conditions. Runways are designed to align with the prevailing winds, such that the opportunity to practice at or near maximum crosswind limits is seldom achieved. When the crosswind is not severe, a pilot can get away with significant errors in pilotage (bounces, long landings, hard landings, etc.).

First, however, a pilot needs to understand the math involved. A “demonstrated crosswind speed” of say, 10 knots, is a wind at 90 degrees to the runway heading. If the wind is a quartering head or tailwind, the pilot must determine the crosswind component, and that involves geometry.

The best sources for wind information are the tower (ATIS) and the airport wind sock. For more detailed data, contact the National Oceanic and Atmospheric Administration, National Climatic Data Center.

Some aircraft have built-in systems to counter effective crosswinds. The Air Force B-52 is able to realign its landing gear in high winds, but most civilian aircraft have no such aids.

How to Navigate Crosswind Conditions

If you ever find yourself in crosswind conditions, using the “wing low and crab” technique is the preferred method.

To accomplish it, the pilot needs to “kill the wind” by crabbing or turning several degrees into the wind to maintain ground track. Then bank in the direction of the crosswind while using opposite rudder to maintain heading. Bank right, rudder left, for example. You cross control with rudder to keep the nose aligned with the direction of the runway.

Increase the bank and rudder as necessary up to a maximum of about 5 degrees bank. When it becomes impossible to keep the plane aligned properly, you have exceeded the aircraft crosswind limit. Go around. Find another runway. Use cross controlling in the suggested manner and hold it all the way to touchdown, such that the upwind main gear contacts the runway first. Then the other main is lowered while rudder and nose wheel steering are used to stay aligned on the concrete

This technique keeps the aircraft from contacting the runway in a sideways drift, which would place considerable stress (shear force) on the gear struts, which are not designed to handle severe side loads. Too much bank and a wingtip or engine nacelle will contact the runway and a cartwheel may spell disaster. Too little and the plane will drift downwind and off the runway. Many airline pilots prefer to crab all the way to the flare, then put in some bank while straightening the fuselage with rudder. This requires real touch, and often the plane will float rather than settle for the landing.

Tips and Techniques

There are numerous hairy crosswind landings shown on YouTube and Facebook. Type in “Dangerous Crosswind Landings” and sit back and enjoy the ride. Almost all flubs involve a late transition in the flare related to over control of the rudder or aileron and a bounce back in the air in gusty wind conditions.

I find it easier with single and multi-engine light aircraft to just set the cross controls early on final, and hold them all the way to touchdown. The bank and rudder deflection should normally decrease as you get close to the runway and the wind lessens, but you will have the right “feel” all the way in. Your approach is more stabilized from final to touchdown. Note that ground effect will try to raise the low wing, so anticipate that and counter the movement. Once all the wheels are safely on the runway, use aileron and rudder as you did on taxi to maintain directional control.

Remember, later at the bar the conversation will never be critical of the pilot who went around but about the pilot who didn’t!

 

References:

  1. https://www.youtube.com/watch?v=-CTFESsA28Q                 
  2. https://www.ivao.aero/training/documentation/books/PP_ADC_Headwind_croswind_calc.pdf
  3. https://www.faa.gov/documentLibrary/media/Advisory_Circular/150_5300_13_part2.pdf       
  4. https://www.boldmethod.com/learn-to-fly/maneuvers/how-to-make-a-perfect-crosswind-landing