Airplanes have become one of the common means of transportation, bringing great convenience to people's travel. But with the seemingly commonplace rules and common sense on board, do you really know the mystery behind them?

1. Where does the air we breathe in the cabin come from?

There is a set of equipment on the aircraft. During the flight, the aircraft can suck in the outside low-temperature and low-pressure air, pressurize it, warm it, filter it, and then force it into the cabin through special pipes. In addition, the air circulation system of the aircraft has been strictly designed to filter out harmful microorganisms in the air.

2. Why are all aircraft portholes oval?

The portholes of commercial airliners have evolved from square to oval shapes for the safety of passengers. As the flight altitude increases, the cabin needs to be pressurized to maintain a more comfortable environment, and the high pressure inside the cabin will act on the portholes.

Studies have found that polygonal (including square) windows are less stable and take on more pressure at the corners, eventually causing structural problems due to metal fatigue.

Round shapes, on the other hand, have the same structure in all directions, so the pressure is evenly distributed and rarely collapses from a single point. This is why the portholes of the aircraft cabin are in the oval shape seen today.

3. Why can the plane turn in the air?

The airframe is free to tilt in the air, and if the pilot stick is turned to the right, the airplane is also tilted to the right. The gravity of the plane is perpendicular to the ground, but the lift on the wings is perpendicular to the wings.

At this moment, the lift force is no longer pointing directly above the ground, but rather pointing diagonally upward. Since the direction of gravity and lift are different, they no longer balance each other, and a force perpendicular to the fuselage pointing to the right is created.

Under this force, the aircraft turns to the right along a circular arc, which is similar to the experience of a person riding a bicycle. If the cyclist's body is tilted to one side, the bicycle will tilt and automatically turn in the tilt direction without turning the handlebars.

4. When landing at night, why do you dim the cabin lights?

Weak lights are intended for evacuating passengers, not for sleeping. When the aircraft is ready to land at night, the lights inside the aircraft will be dimmed. This way, after landing, passengers' eyes can easily adapt to the light intensity outside at night when they get off the plane, and they can see things outside more clearly.

5. Why should the plane wait on the runway for a while before takeoff?

There are many reasons for waiting for takeoff. Just as an airplane may need to wait before landing, an airplane waits before taking off. It may be due to air traffic. The tower is letting the planes take off in order or letting those landing planes land first.

Of course, it could also be a meteorological reason, the tower let the aircraft stand by on the taxiway, and then take off when the weather meets the takeoff and landing requirements.

6. Why say the weather can not fly?

When it comes to flight delays, the reason many people often hear is the weather. But seeing that the weather is clear in front of you and the weather at your destination is also clear, you will inevitably wonder if you have been fooled by the airline.

In fact, weather reasons include many kinds of situations: weather conditions at the departure airport are not suitable for takeoff; weather conditions at the destination airport are not suitable for landing; weather conditions on the flight path are not suitable for flying over, etc.

In a long-established route, as long as a place with abnormal weather conditions, the aircraft may be stopped in place due to weather. Therefore, clear does not mean normal weather in the sense of flight.

Do you understand all these little airplane facts?