Why are portholes round? Why are portholes round and not square?

Jet aircraft manufacturing was just beginning in the 1950s. The first airliner was the Comet, the brainchild of de Havilland.

It was an ultra-modern jet passenger aircraft with technical characteristics unique for that time and a pressurized cabin. Unfortunately, in 1954, two Comets broke up mid-flight, killing a total of 56 people.

The reason is ridiculously simple:

Square portholes.

This was one of those annoying little things that are easy to miss when designing; but as soon as something happens, they become obvious even to a child.

Here's a chocolate bar. Where do you think it will break if you press on it?

That's right, along these notches.

So, a square window consists of four 90-degree recesses, which means it has four weak points. If there was pressure on your house, the crack would certainly go through the corner of some window:

Have you noticed that the windows on all planes are round? This is not done for beauty - the round shape does not allow the plane to be torn into pieces. The pressure is distributed along the entire curve, instead of cracking at the corners (as it turned out) and tearing the plane to shreds.

Believe me, it wasn't easy to find out. Experts had no idea why the plane's structure was falling apart until they tested the structure by repeatedly simulating cabin pressure. Of course, the fuselage eventually burst, and the rupture began precisely from these notorious corners.

Since then, all aircraft have only round windows.(odnaknopka)(jcomments on)

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Cause:

Square portholes!

The designers of the Comet did not even think about such a small thing as the shape of the windows. Imagine a bar of chocolate. If you press on it, where will it break?

If you put pressure on the house, the crack will certainly go through the corner of some window:

Because a square window consisting of four 90-degree recesses has four weak points at once.

With round windows, the pressure on the plane is distributed evenly, and the circular shape prevents the plane from being torn to pieces. The Comet designers were able to establish this pattern after many months of testing the cockpit for strength. The fuselage invariably began to burst from these very corners. Since then, airplanes have only round windows and no other ones.

Why on an aircraft carrier runway strip Is it located at an angle?

Landing on an aircraft carrier requires the highest level of skill from pilots. Not only is the runway short and crowded with other planes, but the ship itself rocks on the waves.

The first aircraft carriers had a straight runway.

What else could it be if not straight? On one side of the deck there are planes, on the other side you are trying to land. If you fail to catch the brake cable, you crash into a bunch of other planes. Armageddon is guaranteed. Designers installed special nets on aircraft carriers designed to catch planes that missed the brake cable, but landing planes still managed to either break through the net or jump over it. How to secure a landing? The idea turned out to be brilliantly simple:

The runway must be at an angle of 9 degrees!
A plane that does not catch the cable simply takes off again and tries to land again. The rest of the planes are located off the runway out of harm's way.

Why should partitions be connected by solid columns?

The owners of the Hyatt Regency hotel in Kansas City decided to redesign it with several galleries attached to the ceiling. At one party, the ceilings collapsed, burying more than 100 people.

The main drawback of the project was the fact that when constructing galleries, one above the other, instead of one solid long rod attached to the ceiling

The builders secured the structure with two short rods. Like this:

This small change killed 114 people, maimed 216 and cost the company $140 million.

As can be seen from the diagram, tragedy was inevitable, because the top nut had to bear the weight of two galleries. However, none of the engineers and builders noticed this error until, during a disco, the supporting nut gave way and both galleries collapsed.

Why do doors have to open outwards?

Long before Lame Horse, in 1942, a fire broke out at the Cocoanut Grove nightclub in Boston, killing 492 people. The waiter was looking for an outlet, lighting his space with matches, and accidentally set fire to some flammable interior detail. The fire instantly spread to dry pine needles and other decorations imitating a tropical forest. The fire spread so quickly that some of the dead were left sitting with glasses in their hands.

Firefighters calculated that if all the doors in the nightclub opened outward, there would be four times fewer casualties. Because leaving a room urgently if the doors open outward is much faster than leaving a room where the doors open inward.

Why are there so many “holes” in bridges?

One of the largest in the USA suspension bridges The Tacoma Narrows once collapsed into the strait of the same name. Fortunately, at that moment there was only one car on the bridge, the owner of which managed to jump out and take a video camera with him:

Cause of the collapse: the bridge was solid, without “holes”. Compare - modern bridges literally shine through:

The main purpose of the holes is not to save metal, but to allow air to pass through. The designers of the Tacoma Narrows decided that there was already enough room for the wind:

One day, a gust of wind coincided with the vibration frequency of the bridge and the central span, convulsing, collapsed into the water.

This is what the same bridge looks like now.

Learn mathematics, the queen of sciences.

29.01.2018, 10:01

Many people wonder: why are the windows on an airplane rounded, and not square like regular windows or, for example, not triangular?

The answer is elementary simple. The very shape of the aircraft without corners, the rounded shape of the windows, as well as hatches and doors, is necessary for safety. Roundness allows you to evenly distribute the load from the difference in temperature and pressure, which prevents the occurrence of cracks, and subsequently the depressurization of the cabin and the tearing of the aircraft into pieces.

To explain it in more scientific terms, it looks like this: when a plane gains altitude, the external pressure drops faster than the internal pressure - this creates a pressure difference between the inside and outside of the plane, causing the body to expand.

When the material of the housing changes its shape, tension is created in it. The material expands due to the fact that the stress constantly increases, eventually the stress reaches the limit that the material can collapse.

On airplanes, the shape of the windows greatly affects the voltage level. Tension easily passes through the material without damage, if there are no obstacles such as a window in its path, in a given place it needs to change direction, and this causes an increase in pressure. This is called stress concentration.

By comparing the effect of round and square windows on stress concentration, you can see that square windows create a greater barrier to stress passage. This means that tension is created at the corners of square windows.

An extreme increase in stress concentration causes the formation of housing cracks in these places. Such cracks led to tragic disasters until studies of destroyed aircraft made it possible to study the nature of the occurrence of stress in materials. That is, based on this, it becomes obvious why the windows on airplanes today are round, as well as all the load-bearing parts of the body, hatches, and doors are rounded. It’s good that the designers came to such a solution, and the passengers are now safe.

Round windows to provide access to light, built into the sides of airplanes and ships, are a common sight. It is difficult to imagine that they did not always have such outlines. So why are the portholes round? There are a number of explanations for this.

Portholes on ships

The windows built into the sides of ship hulls were not always round in shape. In historical photographs you can see ships with square and rectangular windows that look like regular vents.

The rounder shape that is more familiar to us is due to higher strength parameters. Roundness makes it possible to evenly distribute the load created by differences in pressure and temperature. This “negates” the risk of cracks and, as a result, rupture of the ship’s hull. For the same reason, all load-bearing parts of ship hulls, as well as doors and hatches, are rounded.

The second reason for the widespread use of round windows is ease of manufacture.

Previously, window frames were made from cast brass blanks, followed by processing on lathes. The round pieces were much easier to make. In addition, during installation it was easier to seal them, protecting them from leaks.

Modern round portholes on ships are completely waterproof. As additional protection in severe weather or rough seas water element portholes are equipped with storm covers made of metal or removable shields.

Windows on airplanes

Even before the middle of the last century, square windows were installed on passenger planes. Airplanes such as the Caravel even had triangular windows.

The turning point was the tragedy that occurred in 1953. In those years, the jet aircraft industry was actively developing. One of the first to enter the world market was a supersonic airliner called Comet. By technical specifications in those days he had no equal. But contemporaries remembered the supersonic airliner for the reason that it crashed at the moment of takeoff. 56 passengers died. Over the next year, two more similar disasters occurred. "De Havilland Comed" was removed from flights, discontinued and the causes of the accidents began to be investigated.

As it turned out later, the key cause of the tragedies was the depressurization of the aircraft body due to microcracks that appeared in the corners of the windows. To understand, as the plane climbed to altitude, there was a rapid drop in external pressure, while the pressure inside the plane remained more stable. The pressure difference provoked the expansion of the housing. As a result, tension was created in the body material, and it began to gradually change its shape. The square window acted as a kind of obstacle to the distribution of stress, forcing it to change its direction and thereby causing an increase in pressure. Peak stress points formed at the corners of the square windows, causing cracks to form in these areas.

After this, the windows on the plane are made exclusively round or oval. They distribute pressure along the entire curve, minimizing the risk of deformation.

Essentially the portholes of modern passenger aircraft, such as the wide-body twin-engine Boeing Dreamliner, are more likely not to have a round shape, but rather a rectangular one with beveled and rounded corners. This engineering solution allows you to “bypass” places where fatigue stresses are concentrated.

It is noteworthy that according to the instructions, the window curtains must remain open during takeoff or landing of the aircraft. This precaution allows you to solve two problems at once: it allows passengers to more easily and quickly adapt to the natural light outside, and crew members at any time, with a quick glance, visually assess the condition of the aircraft and, if necessary, take appropriate measures in a timely manner.

In addition, the polymer curtains should be pulled back for the reason that if emergency situations at the moment of mechanical damage, do not injure nearby passengers.