Did you know..?

Tim, aged 7

Just about everyone knows or recognises the Lufthansa logo – try it out sometime in a quiet moment, close your eyes and imagine it…what do you see? A bird taking flight within a circle, right? That’s absolutely right.

But why is it a crane, of all things?

More than 90 years ago, the German architect and graphic artist, Otto Firle, laid the foundation for today’s Lufthansa logo and designed a stylised bird in flight. What’s quite funny is that Otto himself actually only had an elegant bird taking flight in mind for the airline – he never defined exactly what kind of bird it was meant to be.

It was only much later that people saw this bird as a crane.
And because, in some cultures, the crane is considered to be a lucky bird and an angel, and also foretells a long life, the bird in the Lufthansa logo remains a crane to this very day.

May, aged 11

You’ve no doubt already heard that it is difficult to breathe at great heights. That’s because the air pressure keeps decreasing the higher you get. Air pressure is virtually the weight of the air above us.

Higher up, there is less air above you and therefore the pressure is lower. However, the oxygen pressure also decreases, and the lungs can take in less oxygen, so breathing becomes more and more difficult. Perhaps you’ve already experienced this when hiking in the mountains?

Nowadays, our aircraft fly at altitudes of more than 10 kilometres (6.2 miles). This means they are flying at a height much greater than that of the highest mountain on earth. So how can we still breathe on the aircraft?

First of all, modern aircraft are equipped with pressurised cabins. These are hermetically sealed chambers in which the pressure can be artificially increased or decreased. At great heights, the pressure for us humans is adjusted so that we can breathe normally. Over time, the air wears out, of course, and the oxygen is used up. New air must therefore be provided and this comes from inside the engines. There are a number of compressors in the engines. These machines press gases together. They ‘compress’ them, so that they take up less space.

In the case of an aircraft, they suck in the thin air from outside and compress it.

Part of this compressed air is “bled off” for the breathable air in the cabin – so it’s also known as ‘bleed air’. As this air is very hot, it is first cooled somewhat and then fed through valves in the air conditioning. In modern aircraft, this is done automatically by a computer. From there the air passes into a mixing chamber, where it is mixed with a portion of the already used cabin air. The finished air mixture is then directed into the cabin and provides the passengers with new oxygen.

By the way: the cabins of larger aircraft are divided into several “climate zones”. The air in the different zones can be adjusted separately. The circulating air from the cabin is repeatedly filtered to keep it clean. For example, the air exchange in an Airbus A340-300 happens every two minutes – which corresponds to 30 times an hour!

Adrian, aged 10

Passenger airliners are some of the biggest and heaviest aircraft around – giants that weigh tonnes and can only take off from the ground with the help of incredibly powerful jet engines. If the pilot turns the jet engines to full power, the aircraft accelerates, achieves 250 km/h in just a few seconds and takes off…but how exactly does that work?

Thanks to lots of metal blades attached to a rotating ring, the fan (1), air is sucked into the inside of the jet engine and heavily compressed (2), thereby increasing its pressure and temperature. From there, the air enters the combustion chamber (3), into which kerosene, i.e. the aircraft fuel, is injected and ignited. The hot combustion gases shoot backwards out of the combustion chamber at great speed (around 1,000 km/h or 600 mph!) and set in motion the turbine (4) behind the chamber. This motion is transferred forward via a shaft and drives both the compressor (2) and the thrust-generating fan (1).

A small proportion of the combustion gases are propelled backward out of the jet engine and also create thrust. On modern jet engines, most of the thrust is generated by the fan (1). This so-called “cold thrust” (blue arrow on the outside) makes up 80% of the jet engine’s power. Only about 20% comes out of the turbine as “hot thrust” at the back.

Maya, aged 10

Have you ever wondered how the toilets on an aircraft actually work? It is really very simple. Normal toilets, such as those in our homes, have a water flush system. Of course, that’s not possible on an aircraft – otherwise huge amounts of water would need to be carried on board for so many passengers. On the one hand, this would take up a lot of space and on the other, the additional weight would considerably increase fuel consumption.

Consequently, so-called ‘vacuum toilets’ are used on aircraft. With the aid of a vacuum, everything is sucked into the toilet, almost like a vacuum cleaner – if you have used a toilet on an aircraft before, you will have certainly heard the loud noise this makes. The toilets are coated with Teflon (as are frying pans, for example) to make sure as little as possible sticks to them. This is why only a little bit of water is needed to rinse the toilet.

The vacuum toilets are part of a ‘closed system’ – this means that everything from the toilets is sucked into a sealed tank inside the aircraft, where it remains until the aircraft lands. Then, special vehicles arrive to empty the tanks and take their contents to a wastewater treatment plant. Very practical, don’t you think?

Daniel, aged 10

When you fly, you will sometimes notice that the aircraft wobbles a little. If the aircraft flies into a so-called ‘air pocket’, it can briefly lose height, for example. It feels as if you are sitting on a roller-coaster. Of course, there aren’t really pockets in the air, like holes in a Swiss cheese, because air is all around us. The term “air pocket” refers to a really fascinating natural phenomenon.

Perhaps you’ve noticed it in summer: whilst it is pleasantly cool on the ground floor of a building, it is hot and sticky on the top floor. There is a simple reason for this: cold air is heavier than warm air. So it flows downwards. The lighter, warm air, in contrast, rises upwards.

Air is therefore constantly moving, even at very high altitudes where aircraft fly. Vertical movements of air are also referred to as updrafts and downdrafts. So, when warm air flows upwards (updraft), the cold air has to escape downwards at the same time (downdraft). If an aircraft flies through an area where cold and warm air meet, not only does the cold air suddenly rush downwards, but the aircraft is pushed down too.

As a passenger, you then feel as if the aircraft is falling into a hole or (air) pocket. The pilot then only has to accelerate a little and the aircraft returns to its previous altitude.

Peter, aged 10

The white stripes, which you must have seen in the sky, are condensation trails, more commonly known as ‘vapour trails’. To condense means that a substance turns from being gaseous to being liquid. Aircraft exhaust emissions contain hot water vapour and soot particles. When the hot exhaust gases leave the jet engines, they mix with the cold air and condense into tiny droplets. If the air is cold enough, i.e. at least minus 40 degrees Celsius, these droplets freeze into small ice crystals. When these crystals clump together we see them from the ground as white stripes in the sky. Because they are made up of the frozen, condensed exhaust gases, we call them condensation or vapour trails.

If there is no wind, you can see that the vapour trails stay in the sky for a very long time. If an aircraft doesn’t leave any vapour trails in the sky, it is because there is not enough humidity: if the air is dry, the water condenses quickly and the ice crystals cannot form. Why not grab a pair of binoculars and take a closer look at vapour trails. You’ll notice that they never start right behind the aircraft. That’s because to become visible to us, lots of ice crystals first have to clump together. That can take a little while.

Johanna, aged 9

Have you ever sat next to the window on an aircraft? If so, you might perhaps have noticed that at the bottom of the pane there is a tiny hole – but why?
Aircraft are fascinating … but also incredibly complicated! To ensure that they can carry passengers around the world safely, every single tiny detail like this is hugely important.

That’s why aircraft also have special windowpanes.

Normal windowpanes, like those you have at home, would not be able to withstand the air pressure above the clouds – if an aircraft equipped with such windowpanes were to fly into the air, the glass would break, because the air pressure around the aircraft drops.

For this reason, the windows in most airliners have three panes in total – an inside one, a middle one, and, of course, an outside one. The inner pane that you can touch is there solely to prevent contact with the outer pane, because above the clouds, the air (and thus also the pane) is very cold: up to minus 60 degrees Celsius!

But why is there that tiny hole?

For two reasons: firstly, flying wouldn’t be half as wonderful if you didn’t have such an amazing view, would it? The small hole allows the moisture that forms between the two panes to escape, so the windows don’t steam up.

But the second reason is much more important: the hole is there to equalize the air pressure. Once an aircraft climbs high, the air pressure around it decreases. In the cabin, however, the air pressure stays almost the same. The outer pane is the thickest and therefore the strongest of the three panes and must maintain the pressure in the cabin. The small hole ensures that air can circulate between the two outer panes and the cabin pressure is only borne by the strongest pane.

Alex, aged 8

In some cultures, the number 13 is considered unlucky. You have probably heard that before, right? That is why there is no 13th row in aircraft, because airlines respect this superstition. It means that no one who believes that the number 13 is unlucky has to sit in row 13.

But in a lot of Lufthansa aircraft you will notice that the 17th seat row is also missing. That is because in some countries, for example Italy and Brazil, the typical unlucky number is 17 and not 13. And since Lufthansa welcomes many international passengers on board, we observe as many of these cultural beliefs as possible. So all Lufthansa passengers can feel comfortable when they fly with us.

Tom, aged 9

Do you know that feeling? During take-off and landing you suddenly feel an unpleasant pressure in your ears. They pop and you can’t hear very well, sometimes it even hurts. Why is that?

An aircraft flies at an altitude of up to 12,000 metres (39,370 ft). That is higher than the highest mountains on earth! The higher it flies, the lower the air pressure outside the aircraft. To compensate for this, the pressure in the cabin is increased. We have already explained how that works in our “Kid’s Question”: “How can you breathe in an aircraft at an altitude of several thousand metres?”

If the cabin pressure changes, your ears must adapt to this pressure. But that’s not quite so simple at such a height. The eardrum in your ear is a strong membrane that ‘seals off’ your ear canal, making it water and airtight. If an aircraft increases its altitude, for example, the pressure drops. The pressure in your middle ear, however, remains the same and overpressure results on the ear. The Eustachian tube is responsible for the pressure balance in your ear. This is a tubular connection between the middle ear and the nasopharynx. It is normally closed, but when you yawn or swallow it opens slightly.

So if you chew something during take-off or landing, or simply give a few big yawns, the Eustachian tube opens and balances the pressure in your ears. Or, you can pinch your nose shut and firmly press the air to the front. That will also make sure the uncomfortable pressure in your ears vanishes.

Marie, aged 10

This is not actually a fixed regulation, but it is considered to be a so-called “unwritten rule”. Although the pilots and co-pilots are not obliged to, they always try to follow the rule and eat different meals before the flight.

The reasoning behind this is quite simple: if there is something wrong with one of the meals, only one of the two pilots will have eaten it. If one of the pilots then becomes ill with food poisoning, the other one can take over the controls in an emergency. Sounds logical, doesn’t it?