Why is it not possible to make the portholes of airplanes round, but not square?

A lot of Peter Pan likes to sit by the window and ......Looking at the endless clouds outside the window, enjoying the masterpiece of nature, it is really refreshing, have you noticed why the portholes of the plane are rounded instead of square? In fact, the original aircraft portholes were not round, but square. In 1952, the Comet jet developed by de Havilland was introduced in a polite way.

I thought I could soar on this plane, but it turned out bad. In just 18 months, from October 1952 to April 1954, a total of 17 "comets" were in flight, six of which were involved in accidents one after another, and 99 passengers and crew members met them.

The tragic accident forced us to speed up the search for the cause, and I don't know why it was in the porthole of the plane! The reason is on the small porthole! Faced with this predicament, British Prime Minister Winston Churchill sent a naval team to find out the truth at all costs.

According to the analysis of the technicians, the cause of the accident is:After multiple takeoffs and landings, metal fatigue cracks appeared at the corners of the portholes, causing the fuselage to disintegrate under the strong external thrust caused by the difference between internal and external pressure.

It turns out that the square window is not suitable for the aircraft! In order to solve the hidden dangers of portholes, scientists have found that the curved design of the portholes has no focus, which can evenly distribute weight and pressure, greatly reducing the possibility of window cracking and cracking.

The evolution of history always comes at a cost. Today's safe travel is also thanks to the continuous exploration and efforts of scientists! Finally, after unremitting exploration and efforts,The porthole of the plane has become today's "chubby" look!

But they can escort you home safely!

I think this is okay, but the round portholes will be softer and more protected.

If it is made round, it can reduce the flight resistance of the aircraft and make it more comfortable for passengers.

Definitely not, the round one can make the most bearable.

In terms of mechanical principles, the circle has superior properties over other shapes, and can withstand tension, compression, shear and other forces greater.

Why are the windows of airplanes round? Is it okay to make a square?

01 The interior of the high-altitude aircraft needs to be pressurized, so there is a huge pressure difference between the inside and outside of the aircraft. If you are making a window with a square shape, then at the four corners of the window, there will be a huge amount of stress, causing the window to break. The structure of the circle is the same in all directions, and the stress will be evenly distributed, and it is very rare for the letter to collapse from a certain point.

When we take a plane, we will find that there is a difference between the windows of the plane and the windows in daily life, the design of the window of the plane is small and round, what is the reason for this?

In the early days, airplanes flew at low altitudes, the cabin did not need to be pressurized, the fuselage had to withstand various stresses, and the windows were sometimes designed to be square.

However, with the increase of aircraft speed, the stress of the aircraft when doing various maneuvers increases, especially the increase of flight altitude leads to the need for pressurization of the cabin to maintain a more comfortable environment, which puts forward higher requirements for the compression resistance of the airframe.

Usually, the opening of the structure is the place where various stresses are concentrated, and it is also the place where the structure is most likely to collapse due to the continuous change of stress. The study found that polygonal (including square) windows are more prone to stress concentration at the corners (70% of the cabin pressure is concentrated in the sharp corners of the windows), and eventually the structure collapses due to material fatigue. The structure of the circle is the same in all directions, and the stress will be evenly distributed, and it is rare for a collapse to occur from a certain point.

The round window is made up of three layers of glass with a clear division of labor: the outer layer is responsible for withstanding the pressure caused by the pressure of the cabin pressurization; The middle layer is an insurance layer designed to prevent the outer layer from breaking, although it is extremely rare for the outer glass to break; The inner layer acts as a drawing board for passengers to smudge as they please.

The small hole under the window is used to ensure that the outer glass can withstand the impact of pressure, and for safety reasons, this small hole is like the "breathing hole" of the aircraft, which is very important. The air in the cabin is pressurized, and the pressure inside and outside the aircraft is different.

With this hole, the higher air pressure in the cabin can act directly on the outermost layer of glass, and when the adjustment effect of the hole reaches its limit, the first glass to break will also be the outermost layer. This ensures that the cabin is still closed and intact so that passengers can continue to breathe.

The windows on the aircraft are relatively small because the airline needs to consider the cost of the aircraft, and the window area of the aircraft basically meets the requirements of economy and appreciation. If the windows of the aircraft are to be larger, the aircraft needs to reduce its flight altitude and flight speed, or use more expensive materials to make the aircraft windows.

This is because the round portholes are able to be evenly compressed by dispersing the pressure.

A stress concentration is the accumulation of stress in the body due to a sudden change in the geometry of an object. When the geometry of the body changes abruptly due to the decrease of the crack tip, hole and cross-section area of the crack, the local stress near the crack tip and hole increases, and the cross-sectional area decreases.

The monolithic structure tends to be destroyed where these pressures are more concentrated. Therefore, in order to prevent the structure from being damaged, pressure concentrations should be avoided or reduced.

The study found that due to the square shape of the windows and window frames, the stress concentration was higher. The abrupt change in the angle is the geometry that destroys the stress flow, unlike the modern round window. Due to the high stress at the corners, there is often a chance of crack initiation at the incision of the structure.

During the flight, the aircraft structure is subjected to various loads, all of which are not equal in equal quantities, but circular. This leads to fatigue loads. Fatigue loads cause cracks to propagate over large cycles.

However, due to the lack of understanding of fracture mechanics in 1954, the crack propagation theory was not considered in the design of the aircraft.

The failure of the pressure chamber was caused by the growth of fatigue cracks, which were most likely due to defects in the structure of the aircraft, which did not arise as a problem in earlier aircraft designs because of the lower pressure required in the cabin.

The rigorous tests carried out by de Havilland did not reveal this problem, probably due to a set of imperfections in the order in which the tests were conducted, which was difficult to anticipate at the time.

First flight:

In 1903, the Wright brothers made the first human flight, but it wasn't until 1952 that the first jetliner made its first maiden flight. The de Havilland DH106 Comet was a great success for a manned airliner, as its pressurized cabin allowed it to fly to an altitude of 35,000 feet (10,668 meters).

The higher the flight altitude, the lower the density of the air, which reduces the drag on the structure, which in turn increases the speed of the aircraft. At that time the aircraft was considered a feat of a British engineering company. Even Queen Elizabeth made a special flight on June 30, 1953, but the conversation didn't last long.

Squire. Two DH106 Comet airliners disintegrated in mid-air, killing 56 people: Boak Flight 781 crashed into the Mediterranean Sea after decompression, killing all 35 people on board, and South African Airways Flight 201 disintegrated at an altitude of 35,000 feet (11,000 meters), killing all 21 people on board.

The above content reference: Encyclopedia - Stress Concentration.

Why the windows of the plane are round has aroused the curiosity of many people. In fact, the shape of the airplane windows is not designed for accident or aesthetic reasons. It depends on a number of factors that the aircraft is subjected to while flying.

First of all, the round design can bring higher strength and can withstand more pressure. The pressure is distributed around the window, which ensures the integrity of the window without cracking or cracking, ensuring a safe flight.

Secondly, the circular design can eliminate optical distortion. The curvature and thickness of the round window are uniform, which means that it does not distort the view like other shapes, providing a clearer and more natural view.

In addition, round windows can reduce wind resistance, helping to reduce air resistance and improve fuel efficiency. Aircraft are exposed to extremely high wind resistance when flying at high altitudes, and by reducing the resistance of the windows, the load on the fuselage can be reduced.

In summary, the design of a round window is not a simple choice of style, but a decision based on many considerations. The contours and sizes of the windows have been carefully calculated to ensure that they optimize the aircraft and the flight experience.

The windows on the aircraft are all round, in order to make the force around the windows of the aircraft more balanced, without stress concentration, mainly to protect the aircraft. The aircraft is under greater pressure in the air, and the force balance of all parts of the fuselage must be considered, so that the force concentration does not occur, so that the aircraft is protected.

This is to reduce the stress concentration and improve the fatigue strength of the body, so it is round or designed with large rounded corners.

The earliest jetliner "Comet" has several accidents that have been destroyed and killed, the reason is that every time it takes off and lands, the pressurized cabin has a load on the square porthole, which becomes a low-cycle load, and takes off and lands many times, causing metal fatigue, and fatigue cracks first appear at the sharp corners of the porthole, which eventually leads to the disintegration of the aircraft in the air. The future portholes are all rounded.

The round shape is the most material-saving under the same area.

And spacecraft should be as light as possible.

The force of the circle is uniform, and the installation of the round window is convenient, which can refer to the window of the ship.

In the early days, the flight altitude of the aircraft was low, the cabin did not need to be pressurized, and at the same time, the fuselage needed to withstand various stresses was relatively small, so the windows were sometimes designed to be square.

The windows at home are square, but why are airplanes round?