So what are all these then and how should we deal with these things?

First, remember that mother nature has a mind of her own, and doesn’t distinguish between any of these things. It’s only us humans that try to cram things mother nature does into neat little boxes with titles like "Windshear, Turbulence and Gusts".

It’s not just the winter that bring these topics closer to home for pilots, although it always seems worse in the darker months.

For the non-pilot on the ground these things bring “entertainment”. Just take a look at YouTube to find out how sweating, tense pilots seem to make YouTube audiences expand rapidly.

As instructors (and indeed other pilots), we always watch with a keen interest on the performance of our fellow aviators dealing with challenging landings! So what tips and tricks should we make use of to make our task of a controlled crash into the ground a little easier?

Windshear
Gusts
Turbulence
Crosswinds

Windshear

Windshear is defined as a sudden change in wind speed, or wind direction. Caused by lots of things (including turbulence and gusts), it’s basically going to affect the airspeed of the aircraft i.e. the amount of lift the wings produce! Worst case windshear results in a sudden loss of airspeed and consequent sudden increase in rate of descent. Not something you really want when you’re on final approach at low level! Additionally, when you’re just about to round out and flare, you don’t really want a sudden increase in airspeed causing a huge “balloon” taking place that may well mean you no longer have enough runway left to land safely.

So how to deal with it?

Advance notice of windshear is key, and it’s a pilots (mandatory) responsibility to report windshear when experienced, so others can be warned! If windshear is caused by turbulence, then there’s some techniques to try and avoid it (see Turbulence below). Bottom line is “be prepared”. Hand on throttle at all times, and take immediate action if windshear is experienced – including adding FULL power if on an approach and sink is experienced. Depending on other factors such as runway length, landing with less than full flap will also help the aircraft to accelerate more quickly if full power is needed on the approach to arrest that sink.

Back to Contents

Gusts

Wind gusts are only forecast where a temporary increase in the speed of the wind is at least 10KT more than the ambient wind speed. So a reading of 24010G30KT means the wind speed is generally 10KT, with gusts of 30KT (i.e. a gust factor of an extra 20KT). That little bit of information is important to remember. If we are on an approach with gusts present, we should add a little bit extra to our normal approach speed. But how much? In fact you should only add HALF of the gust FACTOR. For the example above we would add 10KT (half of the 20KT gust factor). Again, be ready with hand on the throttle, and be prepared to use more runway than expected if you’re carrying the extra speed and no gust materialises! Take it from someone who’s been around the “weather block” so to speak; if the gust factor is more than 20 to 25 KT, just don’t bother going flying. You’ll be in for a rough ride and an exciting time when close to the ground (take-off and landing).

Back to Contents

Turbulence

This can be caused by a whole host of mother nature events, but can also be caused by man-made objects, and even pilots themselves (pilot induced turbulence – but that’s different story).

Turbulence can be especually awkward on the latter stages of the approach to a runway due to buildings or trees up-wind of the runway. Even if the wind is aligned with the runway, turbulence can be experience on the approach if there are obstacles in the vicinity of the threshold. This can produce some especially unwelcome turbulance on short final as well as up the approach path.

So how to deal with this one then?

This type of turbulence is confined to low level, so to give your passengers a smoother ride the pilot should consider performing a STEEPER approach to the runway. This means that the turbulence is encountered for a much shorter time-period. Normally, final approach is performed at slow speed which also means control effectiveness is reduced; so don’t be afraid (or surprised) to have to use FULL control deflection BRIEFLY. The other thing to remember is that generally speaking, when you get really close to the ground (i.e. round out) the turbulence gets less (more manageable). There are of course limits to how effective aircraft controls can be – so take heed of pilots who have experienced turbulence going before you. Remember you never HAVE to get anywhere when flying – you are not in the realms of the commercial world – there is always another day to fly.

Back to Contents

Crosswinds

In the good old days, crosswinds didn’t exist. Crosswinds are a human invention. Crosswinds came about when some “smart Alec” decided to use something called a “runway” instead of letting aircraft use any direction on a very large piece of grass.

Firstly then, not all aircraft are equal, and nor are pilots. There will be a maximum crosswind an aircraft can cope with (check the aircraft POH), and also a maximum crosswind a pilot can cope with (skill). When an aircraft touches down, the wheels need to be in line with the runway, otherwise the ground crew get excited and start a costume change, also the pilots wallet declares itself open for underpant purchase!

The technique for crosswind landing is actually quite a simple affair if you split it into its two constituent parts; it’s not a black art – it’s not guesswork – its measured and definable. First, the aircraft will be crabbed coming down the approach with the nose pointing into the crosswind. It’s really important that the aircraft tracks down the runway (in other words, the pilot’s backside tracks the runway direction). We don’t want to arrive at the threshold at an angle else we have just introduced another complication. That aircraft nose direction is maintained at the round-out where we transition from a descent to level flight just above the runway.

The pilots task is to now get the wheels in line with the runway – so to do that we use rudder. Look out of the front of the aircraft and use just enough rudder to keep the nose in line down the runway. If we don’t do anything else, the crosswind will move (blow) the aircraft sideways. To counter that, we introduce just enough AILERON (into wind) to stop that sideways movement. We end up cross-controlled – e.g. right rudder and left aileron. Too much aileron and the aircraft drifts too much into wind. Too little, and the wind blows the aircraft too much the other way. The objective is to use enough aileron to keep the aircraft positioned (left/right) over the centre line of the runway. Yes, you can even land like this (one wing low) providing you take into account the clearance between your wing tip and the ground (and hence one of the factors that determines the aircraft crosswind limit).

Once on the ground, into wind aileron must be used progressively more as the aircraft slows down. If you ever get to fly a seaplane or a tail dragger you will find out very quickly why this is the case – but that’s’ another lesson for another day. There’s so much more I could say on this subject – but my tea is getting cold, so that’s it for now.

Remember that in all of the things you have read about above, you ALWAYS have a get out of jail free card – GO AROUND.

If you’d like to learn more about these topics and techniques, then take the opportunity to go flying with an instructor on a suitably “turbulent/crosswindy” day to see what it’s like and practice those skills in the safe comfort that your instructor is there to save your embarrassment (well let's hope so anyway).

Back to Flybyte Articles