How pilots land planes throughout 100 mph wind situations and storms

The United Kingdom was rocked by storms and severe wind during the Christmas and New Year’s holidays, causing a spree of flight cancellations and delays. But amid all of this chaos, spare a thought for the pilots left to grapple with the elements to safely land their flights.

Just as we saw two years ago with Storm Eunice, hundreds of thousands of people were once again gripped by Big Jet TV and its coverage of various commercial airliners landing at London’s Heathrow Airport (LHR) as winds reached almost 100 mph.

Here, pilot Charlie Page explains what it’s like attempting to land during extreme weather conditions.

Sets of steps can blow over, baggage containers can move and other small objects, such as cones, steps, etc., can blow onto taxiways and runways. As a result, the ground staff must follow set procedures to ensure that these items do not become a threat to them or the aircraft.

Such procedures normally include adding extra chocks to the aircraft to ensure that it doesn’t move, removing safety cones from around the aircraft and ensuring that there is no foreign object debris left around the aircraft. They will also tie down baggage containers and apply brakes to baggage trolleys.

As the forecast windspeed increases, more steps have to be taken. These could include moving all ground equipment into a building and stopping the use of steps and high lifts. All aircraft types also have a wind limit on the operation of the doors, both cabin and cargo. On the 787, this is 40 knots (46 mph). Beyond this, the doors should not be operated as it risks damaging the movement mechanism.

The result of all this could mean that the ground servicing of an aircraft is severely restricted and quite possibly stopped altogether. Aircraft may arrive at the gate but not be able to open the doors to unload baggage, and catering trucks may not be able to access the cabin to restock the galleys for the next flight.

All this can ultimately lead to delays.

Like a sailor continually assessing the ocean, a pilot always assesses the weather: seeing how the wind is behaving, what clouds are forming and how this could affect their flight. The commute to work is a good way to get a feel for the conditions. We’ll take note of the wind direction and strength, how gusty that wind is, how much moisture there is on the ground and how the cloud cover is around the airport.

Many staff parking lots provide a good view of the runways so we can see how the weather conditions affect aircraft as they take off and land. Are they experiencing any sudden gusts on landing? How are the flight conditions just after takeoff? All the while, we are building up our mental model of how the weather will affect our flight in a couple of hours.

Crosswind takeoffs

The design of major international airports is not by mistake. Knowing the prevailing wind direction, runways are constructed in a direction that will result in the wind blowing close to straight down the runway most days a year. Not only does this help with the performance of the aircraft, but it also makes life a little easier for the pilots.

However, the wind is rarely straight down the runway when winter storms hit the U.K. The more the wind blows across the runway, the more it affects how the aircraft handles the takeoff run.

The aircraft’s vertical tail is a key component in keeping the aircraft stable in the air. Without the tail, the aircraft would wobble about laterally as it flew, making it difficult for the pilots to control and incredibly uncomfortable for the passengers. The tail acts like the keel of a boat, keeping it stable in the air.

However, an element of this stability is the length of the fuselage. The longer the fuselage in relation to its width, the more stable the aircraft is. Conversely, the shorter the fuselage compared to its width, the more unstable it is. As a result, an aircraft such as the A340 — with a long and thin fuselage — has a relatively short tail, but the A380, with a short, fat body, has a particularly large tail.

While the bigger tail brings more stability, it also acts as a huge weathercock in crosswind conditions.

As the wind hits the tail, it pushes it across the runway, causing the nose to turn in the opposite direction. To counter this, pilots must use the pedals under their feet to control the tail rudder. This counteracts the effects of the wind.

However, this input also creates a secondary effect.

As the input of the rudder, in effect, drives the windward wing (the left wing in the image below) into the air more quickly, it generates more lift than the other wing. Left uncorrected, this could cause the right wing to drop just as the aircraft lifts off, striking the engine or wingtip on the ground.

How this is countered depends on the aircraft type, and each manufacturer details the best way for pilots to fly the aircraft in these conditions.

On Boeing aircraft types like the 787, pilots must gradually turn the control wheel toward the side the wind is coming from as we accelerate down the runway. This deflects the wing’s control surfaces, countering the extra lift’s effect.

Once airborne, we release the input on the rudder and allow the aircraft to fly “side-on” in a position known as “crabbing.” This entails pointing the nose toward the wind to ensure we fly the correct track over the ground.

Boundary layer turbulence

Once airborne, the fun is still not over, as it is here where you can feel the real effects of the wind. During the takeoff run, passengers may well feel the aircraft jolting and swinging as gusts of wind hit the aircraft, requiring the pilots to adjust their control. It can feel quite dramatic if you’re seated at the back of the aircraft.

However, once airborne, another element comes into play: the boundary layer.

The air around us behaves like a liquid. It will flow from an area of high pressure to an area of low pressure, and this is what we experience as wind. When the pressure differences are very high over a short geographical distance, the airflow (windspeed) is high — very much like a river flowing down a mountainside.

When the water flowing in a river hits obstacles, such as rocks, bridges and stray tree branches, the flow is disrupted, and it becomes turbulent. The same happens with the wind.

Up in the atmosphere, the wind flows unimpeded, and so the air, for the most part, is smooth. However, the closer to the ground it gets, the more obstacles there are, such as hills, office blocks, houses and trees. This is known as the boundary layer. As the air hits these obstructions, it becomes turbulent and the stronger the wind, the more turbulent that air becomes.

The turbulence created in the boundary layer can be extreme. Fortunately, this is never dangerous, only uncomfortable. The aircraft is more than capable of dealing with the worst of this turbulence, no matter how bad it may feel.

We will normally instruct the cabin crew to stay in their seats until we tell them it is safe to move around. If possible, we will try to climb to a higher altitude more quickly to escape the effects of the boundary layer.

Once up in the air and away from the boundary layer, conditions start to smooth out. However, what about aircraft landing in strong winds?

As mentioned above, with strong winds often come delays. With that in mind, time in hand is always our friend, so these are not days to take the minimum required amount of fuel for the flight.

Delays due to strong winds occur for a whole host of reasons. Parking stands may get backlogged as aircraft cannot depart due to ground restrictions. Without parking spaces on the ground for arriving aircraft, they must wait in the air until there is space.

The rate at which aircraft can land is also reduced during strong winds. On a normal day, an airport like Heathrow may land around 45 flights an hour. This relies on the aircraft maintaining a certain speed over the ground during the approach.

However, with strong winds, this can be severely affected. Why?

Aircraft fly because of the air flowing over the wings. It is why the engines merely provide the forward thrust to drive the wing through the air, creating lift. In this example, let’s assume that an aircraft needs to have 180 mph of airflow over the wings to fly. On a day without wind, the aircraft will have to fly through the air at 180 mph to generate that lift. By virtue of this, its speed over the ground is also 180 mph.

However, if the aircraft is flying into an 80 mph head wind, it will only need to be moving forward at 100 mph to create the same lift, meaning that it is only flying over the ground at 100 mph. This means it will take longer to travel the same distance down the approach, resulting in fewer aircraft landing per hour.

This creates a backlog in the sky, requiring us to carry more fuel while waiting for our turn to land.

That said, Heathrow now uses a system called time-based separation that can reduce these delays by up to 60%, saving around 15,000 tons of fuel.

Go-arounds and diversions

Strong winds go hand in hand with the increased likelihood of a go-around or rejected landing. Touching down safely in strong winds can be particularly challenging, so we never back ourselves into a corner. We always ensure that we have an “escape” plan, and this is via a go-around or rejected landing.

If, at any point during the approach, the pilots are not happy with how things are going, they can apply full power to the engines and go back up to a safe altitude before deciding on what their next steps will be. It is far safer to do this than to continue with a landing that may result in the aircraft touching down in an unsafe manner.

Even if the aircraft has touched down, until the reverse thrust has been engaged, the pilots can still go back up into the air with a slightly different maneuver called a rejected landing, as demonstrated perfectly in the video below.

The footage may look dramatic, but the aircraft (particularly the landing gear) is built to withstand such impacts, and the crew executed the perfect rejected landing after a gust of wind caught the aircraft at the last moment before touchdown.

Once back up in the safety of the air, the pilots then have time to decide on what to do next. The more fuel they have at this point, the more time and options they will have available.

Ultimately, if the weather conditions do not improve, they may have to divert to an airport where the weather is more favorable — something that they will have thought about many hours previously when they decided how much fuel to carry for the trip.