Whether for tourism or business trips, flying has become an indispensable part of modern life.

While enjoying the high-altitude scenery and the convenience of air travel, one might become curious about the workings of airplanes.

Today, we will uncover some lesser-known "cold knowledge" about airplanes to provide a deeper understanding of this modern mode of transportation.

Firstly, the white trails often seen at the tail of an aircraft are known as contrails. Contrails form when the high-temperature exhaust gases emitted by the aircraft engine encounter cold, thin air at high altitudes, causing the moisture in the exhaust gases to condense into visible clouds.

This phenomenon is akin to the way hot breath turns into white fog in cold weather. However, the shape and persistence of contrails are not uniform and are closely related to factors such as flight altitude and air humidity. At lower altitudes, contrails are less likely to appear due to variations in air humidity.

Next, the cost of emergency slides is often a topic of concern. Emergency slides, typically installed above cabin doors and wings, are folded into compact packages and can be rapidly deployed in an emergency. The high cost of these slides arises from several factors.

Firstly, emergency slides are made from high-strength, flame-retardant, and airtight polyurethane nylon. They must function reliably in any environment, necessitating stringent production and installation standards. Additionally, maintaining these slides is expensive.

Although it takes only seconds to deploy a slide, if it is damaged during use, it must be discarded. Even if undamaged, it requires a professional team about 20 days to repackage it. The associated labor and equipment costs are significant.

Moreover, the deployment of the slide can lead to indirect losses such as flight delays, rescheduling of aircraft, and passenger relocation. Civil Aviation Security Regulations prohibit the unauthorized movement of lifesaving equipment on aircraft to ensure safety.

Another interesting aspect is the aircraft toilet system. Early pressurized civil airliners used a large amount of blue sanitary liquid for flushing waste. This liquid not only took up valuable payload space but also had a tendency to leak, complicating maintenance.

In 1975, James Kemper invented the modern vacuum toilet, revolutionizing waste treatment in aircraft. Contemporary aircraft use high-pressure air pumps to transport waste into a closed wastewater tank located away from the cabin.

The waste travels through pipes at speeds of up to 200 kilometers per hour. Upon landing, a specialized sewage truck connects to the aircraft's waste tank to collect and disinfect the waste.

Additionally, many people may have noticed a small hole in the aircraft window, known as a vent. Aircraft windows are composed of three layers of glass, with the vent located at the bottom of the middle layer.

This vent allows excess pressure in the cabin to escape from the middle layer to the outer layer, thereby reducing the pressure on the middle window and minimizing the pressure differential between the inside and outside. The vent also helps prevent fogging and ice formation on the windows, ensuring a clear view.

Finally, many modern aircraft feature raised sections at the wing tips, known as winglets or wingtip sails. These winglets primarily function to manage wingtip vortices and reduce the loss of lift caused by circumferential flow, thereby improving the lift-to-drag ratio.

Winglets enhance lift, reduce drag, and contribute to lower fuel consumption, increased range, and reduced noise during takeoff. Winglets are not only used in aviation but are also prevalent in racing to enhance performance.

As the civil aviation industry continues to advance, airplanes are no longer shrouded in mystery but have become an integral part of daily life. May every flight offer a pleasant experience. Fly safely and have a smooth and enjoyable journey!