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High in the sky: What is really happening?

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Why a plane journey can feel quite overwhelming for nervous flyers

Flying is the safest form of transport. Despite this, there are nervous flyers out there. Some who have been on planes before, and others who have never stepped foot in an airport. The world of aviation can sometimes be a very overwhelming experience due to the sheer amount of complexities that are involved in keeping a plane flying.

white airliner wing on top of sea clouds
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A combination of engineering, safety regulations, routine maintenance, air traffic control, and world class training for cabin crew means that today, it is 19 times more safer to travel in a plane than in a car. According to the International Aviation Trade Association (IATA), the fatality risk in 2018 was 0.17, meaning that a person would have to travel by air daily for 16,581 years to experience a fatal accident.

However, given minor elements such as air turbulence, to more major events such as mid-air emergencies, it is easy to see why some people are nervous about flying today. In this article, I take a look at these fascinating aspects of aviation, in order to provide an accessible bridge between complex engineering and the inner workings of flight.

What does a plane need to fly?

a) Getting off the ground

Every aircraft requires a number of different parts simply to lift off of the ground. Firstly, motion, which is created through thrust generated by engines. In light aircraft these are usually propeller driven, while in airliners they are fan driven. Secondly, the motion needs to be fast enough, and at the same time, the wings of a plane need to allow for fast enough air to flow from high to low pressure, in order to generate lift. That is achieved through a curved upper surface and a flatter lower surface of every wing.

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The third thing a plane needs to fly is an optimum angle-of-attack. This is the angle from the ground to where the wings are pointing. Angle of attack is a critical measure that allows planes to safely take-off from a runway, fly mid-air and then land again. Typically a plane will take-off with an angle of attack of roughly 10-12°. It will then fly at 2-5° and then land with a higher angle of attack that will eliminate lift altogether. If this angle of attack were to exceed 15-20° depending on the airfoil, the pressure of the air would be far too high to maintain a safe flight, and the plane will stall. During landing this is not a problem. Stalling can also be used to a pilot’s advantage during air-show manoeuvres such as a loop.

Image credit: Glenn Research Center – NASA

During take-off, all pilots will calculate take-off weight and use that to determine the correct take-off speed. Take-off weight is determined by the number of passengers, crew, baggage and fuel capacity. From here the pilots work out V1 and V2 speeds.

V1 refers to the speed beyond which the plane cannot abort a take-off safely in the event of engine failure and must proceed. So before the time V1 is reached, pilots must decide whether or not to continue flight if an engine has failed. If the runway length is not sufficient for the plane to abort the take-off it must continue.

On a short runway, V1 is always less than the rotate speed VR, which is the actual speed beyond which the plane can safely climb. On a longer runway, they are both the same. V2 is the speed at which the plane will climb in the event of one engine failure.

b) Moving safely mid-air

A rudder is essential for turning in the air, it works by using a fluid hydraulic system that pushes fluid past the fuselage. This makes the aircraft tilt slightly when turning and is known as yaw. The rudder is connected to the tail-fin which acts as a vertical stabiliser to keep level flight. On the ground, the rudder is the steering mechanism for turning left and right, but it is also used by the auto-pilot to keep the plane on its navigational path. The rudder is operated using left and right pedals.

Image credit: Aero Toolbox

The tailplane acts as a horizontal stabiliser in flight and also controls the pitch of the plane. This allows the nose of the plane to rise or fall. Often after take-off which is manually controlled by pilots, the auto-pilot will control the pitch using elevators, and the plane will continue to climb automatically to its maximum cruising altitude.

Finally, the last requirement for a plane to maintain safe flight is roll, which is controlled using ailerons. The rotation of the object along the direction of motion is called bank. For example, if an aircraft banks to the left, the right wing will rise and the left wing will fall. Ailerons are controlled by a control wheel

The rudder and ailerons are used together to turn the plane during flight. When a passenger looks out a window of an airliner and wonders why the ground is moving away from them or towards them, this is perfectly normal and nothing to worry about.

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All of these systems are operated using the hydraulics, in which fluid is passed along either the roll, yaw or pitch axis from the centre of gravity. If hydraulics fail, there is always a back-up system, and engine thrust difference can help to compensate, although failure is incredibly rare.

Turbulence

Air turbulence is what causes the plane to sometimes shake during mid flight and is one of the primary causes of nervous flying. Turbulence is measured in levels, and all pilots will switch seat-belt signs on if a safe level of turbulence is exceeded. This doesn’t mean the plane is in trouble, but it does mean to avoid things moving around in the cabin very suddenly, it is better to remain seated.

One type of turbulence experienced in planes is wake turbulence. The thrust of a jet engine causes air to collect around the tips of a wing in circular motions called vortices.

Image credit: SimpliFly

The ‘wake’ refers to the air that has been thrust from the back of a plane that is in front of your plane. In order to combat wake turbulence, almost every wing on an airliner has a large rising tip at the end called a winglet, which means the turbulent air can pass without affecting the stability of the flight. Wake turbulence is also why planes sometimes wait on the runway for the previous plane that has taken-off to clear the airspace before they proceed.

No sense of direction

Another cause of nervous flying is simply not having any sense of direction. Being above the clouds, you cannot see anywhere around you that would indicate you need to turn or continue straight. And indeed, early flyers would fly below the clouds and avoid low cloud cover for this reason, when technology such as radar and navigational systems was not as advanced.

Today, you can sit in an airliner and rest easy knowing that the plane is going in the right direction. Before every flight, the pilots program waypoints into the plane’s computer. Think of a waypoint as a random specified geographical coordinate, which in the air would look invisible. Like a dot on a map. Each waypoint has a specified name, some of which are quite funny such as HAMMM BURGER FRYYS towards Lebanon airport in New Hampshire.

Image credit: Reddit

Planes navigate their routes through these waypoints. Every waypoint programmed into the computer means that the auto-pilot can turn the plane in the direction of the next waypoint and ensure the plane stays on track to its destination. Over the Atlantic Ocean, waypoints and tracks are operated in Gander as well as in Shanwick, in North Ayrshire through published North Atlantic Tracks. This method of air traffic control ensures that during busy periods of flights, planes are always at a safe distance apart from each other.

To avoid mid-air collisions, planes now carry a system called TCAS. A transponder for TCAS is found on every single airliner flying commercially. Radio frequencies are sent out within the surrounding airspace and allows the system to warn pilots of a plane that is too close. Within a country’s national airspace, the plane is in close proximity to control towers on airports in that country, such that talking through radio allows the planes to approach safely. Any unidentified aircraft or suspicion can result in interception of the aircraft by a country’s air force.

Some noises

It’s normal to hear a few unfamiliar noises when flying. For example, on all EasyJet planes, you often hear a ‘whirr whirr’ sound similar to the bark of a dog, shortly after the first engine has started up. This is simply the power transfer unit (PTU) that is used to transfer hydraulic pressure from one system to another and allows for the second engine to start up. On a Ryanair plane, you do not hear this noise because the PTU is only used as a standby in the event of a loss of hydraulic pressure when the plane is airborne. Instead the Boeing 737s that make up all of Ryanair’s fleet start their engines up using two independent hydraulic systems.

It is also normal for the plane’s sound pitch to rise slightly just before it starts to move on the ground. The engines need to provide enough thrust to get the plane to move forward. So you’ll often hear a rising pitch when the plane is taxiing, and just before the take-off.

If you have noticed that upon landing, the plane sounds extremely louder than normal, this is noise generated by the reverse thrusters on the engines that are used in conjunction with the brakes and the spoilers.

Usually an airliner is loudest at take-off and landing. The noise itself is caused by interference of sound waves within the engine bypass streams. A higher bypass ratio means that the engine has more space for the air to bypass through the core, and this reduces noise levels.

In fighter jets, the focus is primarily on thrust and airspeed, which means that unstable air has less space to bypass through the engines, and the result is a thunderous noise which can be heard from miles away. Some of these jets also have afterburners which increase the noise even further as the fuel in the engine is being burnt at tremendous speeds, which means more sound wave interference.

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It is also very normal for planes with faster engine thrust to sound louder. A Harrier jump jet would hover in mid-air primarily through nozzles. Even though it doesn’t have an afterburner, these nozzles can force air downwards at extremely fast speeds, and the noise is therefore deafening.

If you’ve ever held your hand under an air dryer in a public bathroom, it tends to sound louder the closer your hands are, as less air is able to bypass. This exact same principle explains why fighter jets are so loud. Because of this, all airliners operate under noise control regulations, while military aircraft tend to train in areas away from large urban centres.

Noise gets even more interesting when you consider supersonic flight, but since that is beyond the scope of this article on safe flying, it won’t be covered here.

What about my baggage?

As soon as a suitcase or large bag that is going into the aircraft hold is checked in at the check-in desk, it enters a completely different world to the one you experience.

Any baggage that is checked in early enters a vast conveyor system that runs through major airports like London Heathrow. Computerised systems allocate the bags into safe storage areas where they will remain until the flight the bags are needed is imminent.

Then the bags are re-entered into the conveyor system, which allocates them according to that particular flight. Baggage handlers receive the bags at their designated checkpoint, and the bags are placed onto an airport vehicle which transports them to the correct aircraft.

Image credit: Amadeo Ascó Signes

Baggage systems are not 100% perfect, and failures do occur. The conveyor system is prone to jamming, which holds up baggage, causing delays. IT malfunctions can also occur, which can stop the conveyor system altogether and cause lengthy delays. Other delays can be caused by adverse weather, particularly if you are making a connecting flight.

A huge lengthy delay can sometimes result in a bag not being loaded onto the aircraft. This is why baggage tags are important, in order for the bag to be traced should it not reach your final destination.

Upon arrival, bags are unloaded from the aircraft hold and transported to the arrivals area. There, they enter the arrival conveyor, which allocates each bag according to what flight it was on. This allows the system to then select the correct arrival conveyor belt, the one that you see when you enter the baggage reclaim area.

Sometimes if it has taken a long time for you to reach the reclaim area, the bags are often removed by an airport worker and set aside in their own collection area. This is just so the conveyor system can move on to the next set of bags from the next flight.

If you encounter a situation where your bag has not showed up on the conveyor belt in the reclaim area, then the responsibility lies on the airline involved to trace it and return it with its full contents. Have a description of contents and bag appearance and brand ready.

woman walking on pathway while strolling luggage
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Some terminology

Pitot tube – measures fluid flow velocity and sends data to the plane’s airspeed indicator and altimeter. It is the small tube that can be found on the nose of the airliner. There is usually more than one.

TCAS – Traffic collision avoidance system.

Slats and flaps – control surfaces, which increase the angle of attack and allow a plane to take-off and land at lower speeds. Slats are the term used on the leading edge of a wing, while flaps are the term used for the trailing edge.

Spoilers – they open up on the wings upon landing and reduce airspeed.

Pylons – they are the spikes you see under the wing when sat by the window – they prevent unwanted disturbance of air flow towards the wing.

APU – auxiliary power unit – used on the ground to supply power to the plane’s avionics when the engines are off.

Feature image credit: Pexels

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