Landing a plane is the most delicate part of a flight. It involves turning a flying craft into a ground vehicle, bringing hundreds of tons of mass to earth without incident, while shedding speed along the way. Aircraft will naturally fly all day long. So long as they have sufficient fuel, aerodynamics are designed to keep them moving. To alter this, pilots not only have to reduce engine power, they also must slowly adopt a ‘dirty configuration’, using aerodynamic drag to reduce speed.
The landing procedure begins miles away from the airport. During this time, changes in altitude, speed, direction and overall aircraft setup must be completed. This is mainly conducted in dedicated “step down airspace’ defined by air traffic control. Passengers are told the landing procedure is due to commence, and are instructed to return to their seats and fasten their seat belts.
Furthermore, at night cabin lights are dimmed before the landing procedure commences, and window blinds raised. Why? So, in an incident, passengers will be less disorientated. Dimming the lights reduces glare and means eyes will already be adjusted to dim conditions. It will also let some light into the cabin and allow passengers to spot dangers.
Landing is a two-stage process; the approach to landing, and landing itself – which will only be good if the approach is good. During the approach phase, pilots slow the plane from cruising speed to an approach speed, from which they can descend gently to a landing speed. A stated aim of pilots is to allow the plane to contact the ground with the lowest possible vertical and horizontal speed.
As throttling back is insufficient to fully slow an aircraft, the additional configuration changes are filtered in at defined approach points. These include gradually raising flaps and, later on in the procedure, extending the landing gear. Indeed, such is the drag created in doing this, some engine power must actually be reapplied to compensate.
The pilot’s unquestionable target is to reach the runway at a precise point, and they are able to quickly form a mental picture of the destination landing strip as all runways are given a number from 01-36. This is their heading – where 36 equals 360 degrees, or due north. It enables pilots to quickly visualize the landing direction, and judge how wind conditions may affect this. Runways can have two numbers, for example 34 and 16. They are separated by 18 because it is the same runway operating in two directions.
The final approach procedure is initiated in a 30-50 mile radius. Air traffic controllers (ATCs) on the ground receive ‘their’ approach aircraft from fellow en-route ATCs. The controller’s job is to find a space for the approach aircraft at a safe separation from others entering the centre airspace; they blend all together, with the required separation, into a separate channel for final approach to the runway.
Final approach requires stated clearance from ATC. Sometimes, a landing must be aborted at the last moment, either because of an emergency alert from ATC, or an override by the pilot. This is called a go around: the aircraft will pitch up sharply, full power will be applied, landing gear and flaps will be tucked away and a very steep climb will be felt.
This can be alarming for passengers but it’s a specific procedure for which pilots are trained. It usually occurs either because a plane is still occupying the runway, or the pilots do not have sufficient visual references to land safely. Passengers will be familiar with delays from being kept in a holding pattern. This is for their own safety and ensures the pilot has the time and space to complete their landing procedures – avoiding ‘go around’ emergency calls in the process. Holding patterns are predefined and dictated by ATCs in the control tower.
When it’s busy, ATC will sometimes specify a defined airspeed for pilots to maintain, usually within an accuracy of +/- ten knots. This keeps the aircraft in sequence with those in front and behind – it is how the rate of approach to crowded airports is controlled.
ATC allows two forms of instructions to pilots, which will be stated before the procedure commences. The descent itself can be under specific altitude instructions which pilots must obey -this is to further help in traffic separation. Alternatively, the aircraft is cleared to descend at the pilot’s discretion. This means they themselves decide speed and rate of descent – the only proviso is that once they leave an altitude, they cannot return to it.
On the technical side, landing procedures are managed by an instrument landing system (ILS). This uses radio beacons situated on the ground to precisely guide a plane down with immense accuracy. An ILS follows a specific glide path that helps the plane follow an ideal three-degree angle to the runway.
ILS radar is often supported by an approach lighting system (ALS): lightbars, strobes and so on, which are situated at the start of the runway. They are a major aid for pilots, helping them switch from instrument flight to visual flight – and they can also extend the operating range of the airport because they count as part of a ‘visual approach’. Pilots must be able to see three quarters of a mile to the runway: with a high intensity ALS, this can be reduced to half a mile, or more if the lights extend to parts of the runway.
The final seconds before touchdown is when many passengers hold their breath. Just before an aircraft touches the ground, the nose will be raised up. This is called a ‘flare’, and means the main landing wheels touch the ground first. The perfect landing will see the wheels touch the ground just as lift on the wings completely falls away and the plane ‘stalls’. To feel hundreds of tons of mass controlled in such a precise way is extremely satisfying.
When the rear wheels are on the ground, the pilot does not lower the nose – it drops of its own accord. It does so because as the aircraft loses speed, the flight controls continue to lose effectiveness so gravity can take over. Once all wheels are on the ground, the aircraft is in rollout mode.
Here, the flying machine is turned into a ground machine – and must be stopped before the end of the runway. On large jets, the first method of doing this is to raise more flaps to increase drag, and engage reverse thrust on the jet engines. As forces build, pressure on the landing gear increases.
Once there’s enough mass pressing down on the wheels, the pilot can apply the brakes. Passengers feel this two-stage deceleration in landing – first, the engines will roar, and then there will be a slight jolt as the brakes come on. The length of this rollout process depends on the weight of the plane, the runway’s gradient, condition and elevation, ambient temperature, brake effectiveness and pilot technique.
Autopilot can actually perform the complete procedure right up to touchdown and rollout. What autopilot cannot do is control the ground taxi process; this will always be done by the pilot, using guidance from ground control. On the ground, the aircraft will taxi to its final position, where passengers will disembark.
Instrument landing system explained
An ILS is installed at most important airports, helping land planes accurately, safely and efficiently!
Based on the ground, the instrument landing system is a standardized system that communicates with the aircraft and guides it to ground using radio signals. It uses two components to determine a plane’s path; a localizer, that controls lateral guidance, and a glide path for vertical guidance.
Localizer antennas emit dual signals of different frequencies, either side of the runway. A receiver on the aircraft measures any difference between them and adjusts the approach accordingly. The glide path antennae, situated to one side of the runway, does a similar job for the vertical route.
Landing a plane in an emergency
Pilot passed out? No worries, help is at hand. Just follow these simple steps and a successful emergency landing can be achieved.
Sit in the pilot’s seat; this is the one positioned on the left of the cabin. Before touching anything, check the altitude instrumentation in front of you. The altitude indicator (often referred to as the virtual horizon) is the circular display that shows a W-shaped representation of the plane’s wings in relation to the Earth and sky.
Next check whether the autopilot is engaged. If it is and the plane is level, don’t touch anything. If the wings are not level, adjust any bank or pitch using the yoke (stick).
Now phone-in the emergency on the radio. Air traffic control will guide you to a runway, but you’ll have to make the landing yourself. Pull back on the throttle (handled lever on pilot’s right side) to reduce power, and push down on the yoke to drop the nose. Drop the landing gear and just as you are about to touch down raise the nose so the main wheels touchdown first.
Finally, when on the tarmac engage the reverse thrusters (movable bars behind the throttle), pull the throttle down to its ‘idle’ position and apply pressure to the top of the rudder pedals (down by your feet) to brake.