Monday, December 7, 2020

AEROBATICS - It's pretty amazing that anyone can fly an airplane in the first place. But for an elite cadre of exceptionally skilled and extremely nervy aviators, plain old straightforward flight isn't thrilling enough. Instead, in the parlance of test pilots, these aviators push the envelope, doing exotic midair maneuvers -- loops, rolls, spins, abrupt changes of direction, and even flying straight up like a rocket. These tricks are so gravity-defying that even birds would be envious. This type of flying is called aerobatics, and it's almost as old as the airplane itself. In fact, the very first aerobatic flyers were Orville and Wilbur Wright, the two men who invented the airplane itself. In September 1904, only nine months after their first-ever heavier-than-air powered flight, the Wrights successfully performed the first aerobatic maneuver, a 360-degree banked turn. The feat was more amazing than you might think because ailerons, the hinged panels that go up and down to tilt a fixed-wing aircraft to the left or right, hadn't yet been invented. Instead, the brothers utilized a cumbersome system that actually tilted the entire wing. Aerobatics soon morphed into hair-raising, daredevil entertainment for spectators at county fairs and air shows. And it's now evolved into an established international sport, with rules and regulations and records. Aerobatics tricks often have exotic names, like the Pugachev's Cobra -- names that are puzzling to all but those who are steeped in the sport. The possibility of injury or death performing a stunt is something a stunt pilot learns to live with and respect. Aerobatics isn't a sport for milquetoasts, or fools.

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Aerobatics

How Aerobatics Works

By PATRICK J. KIGER


 

It's pretty amazing that anyone can fly an airplane in the first place.

But for an elite cadre of exceptionally skilled and extremely nervy aviators, plain old straightforward flight isn't thrilling enough.

Instead, in the parlance of test pilots, these aviators push the envelope, doing exotic midair maneuvers -- loops, rolls, spins, abrupt changes of direction, and even flying straight up like a rocket.

These tricks are so gravity-defying that even birds would be envious.

This type of flying is called aerobatics, and it's almost as old as the airplane itself.

In fact, the very first aerobatic flyers were Orville and Wilbur Wright, the two men who invented the airplane itself.

In September 1904, only nine months after their first-ever heavier-than-air powered flight, the Wrights successfully performed the first aerobatic maneuver, a 360-degree banked turn.

The feat was more amazing than you might think because ailerons, the hinged panels that go up and down to tilt a fixed-wing aircraft to the left or right, hadn't yet been invented.

Instead, the brothers utilized a cumbersome system that actually tilted the entire wing.

Aerobatics soon morphed into hair-raising, daredevil entertainment for spectators at county fairs and air shows.

And it's now evolved into an established international sport, with rules and regulations and records.

In this article, we'll look at the types of tricks aerobatics pilots perform, and how they manage to pull them off safely and land in one piece -- or not.

But first, let's take a closer look at the history of aerobatics and the sport's true pioneers.

Aerobatics Inventors

Orville and Wilbur Wright may have been the first to perform an aerobatic move, but the real aerobatic pioneers were the barnstorming American and European pilots who performed exhibitions for paying audiences at fairs and air meets in the 1910s and 1920s. Spectators grew bored with mundane, everyday airplane maneuvers, so the entertainers began attempting increasingly fancy stunts. The scarier the stunts, the better.

One of the great showmen of that era was American pilot Lincoln Beachley who startled crowds with his "death dip," in which he flew to 5,000 feet (1,524 meters), turned off the engine, and then dove straight down at the ground, only to pull up at the last second.

At times he added to the difficulty by flying under telegraph wires or through a grove of trees.

After Russian military flyer Petr Nikolaevich Nestoy invented the loop in 1913, Beachley had aviation designer Glenn Curtis create a special plane made for the maneuver.

He began performing the trick at shows, charging a fee of $500 for the first loop and $200 for each one afterward.

After World War I, many returning fighter pilots, who used aerobatic maneuvers to win dogfights, began second careers as air show performers.

In 1927, the first international aerobatics competition was held in Zurich, and trick flying gradually morphed into a sport with rules and standards.

Aerobatics has continued to evolve over the years.

After World War II, the aircrafts' increased speed and other capabilities actually made some of the early pilots' maneuvers too dangerous to perform anymore.

But clever pilots soon developed other moves to take their places.

In the 1950s, Czech aerobatics flyers, for example, invented a maneuver called the lomcovak, a series of bizarre gyroscope twists during which the plane rotated on all three axes.

Aerobatics pilots also have developed the ability to fly in nearly perfect circles and accurate figure eights, and to do maneuvers in formations so close that their wings almost appear to be touching.

Next, we'll take a look at some of the tricks aerobatics pilots perform.

Aerobatics Maneuvers

Aerobatics tricks often have exotic names, like the Pugachev's Cobra -- names that are puzzling to all but those who are steeped in the sport.

But listed below are some of the more familiar maneuvers. If the descriptions are too hard to visualize, check out the Web site of Sunrise Aviation, an aerobatics school, which provides animated graphics that illustrate most of these maneuvers.

Chandelle: This is a combination of a vertical climb and a turn. It's actually a basic flying fundamental, rather than a true aerobatic move. But you'll see stunt pilots do it as part of more complicated maneuvers.

Dive: This one's just like it sounds. The plane's nose is turned downward, though the plane is not necessarily completely perpendicular to the ground. Diving causes an increase in air speed, which the pilot can use to pull up at the right moment.

Loop: A loop is when an aircraft flies upward and then, at the top of its arc, begins to slow down, so that it turns down and completes the circle. You can do an inward or outward loop.

Roll: A roll is a 360-degree revolution along the plane's longitudinal axis.

Barrel roll: A barrel roll is a combination of a loop and a roll. The flight path is the shape of a corkscrew.

Wingover: A wingover is a left or right 180-degree tight turn at the top of an upward quarter loop.

Hammerhead or stall turn: Contrary to its name, this maneuver doesn't actually involve stalling. The plane soars upward and then abruptly turns 180 degrees and descends.

Cuban eight: The plane does five-eighths of a loop to the 45 degree line, a half-roll, another five-eighths of a loop back to the 45 degree line again, another half roll, and then three-eighths of a loop to level out. If that's too complicated to picture, imagine a Hot Wheels car doing a figure eight on one of those loop-de-loop tracks. The variations include the Half Cuban Eight and the Reverse Half Cuban Eight.

These maneuvers sound pretty dangerous, and we'll cover that topic on the next page.

Aerobatics Dangers

So how do stunt pilots do those maneuvers without spinning out of control -- or worse, crashing and being killed? Sometimes they can't.

Some of the most illustrious early aerobatics pioneers, like Lincoln Beachley, for example, ended up buying the farm via aerobatics.

The possibility of injury or death performing a stunt is something a stunt pilot learns to live with and respect. Aerobatics isn't a sport for milquetoasts, or fools.

As explained in Geza Szurovy's and Mike Goulian's how-to textbook "Basic Aerobatics," one secret of staying alive and looking good in the process is to adeptly calculate and manage the amount of kinetic energy -- that is, airspeed -- used in a maneuver.

If you don't go fast enough, the aircraft won't have enough kinetic energy to perform the stunt properly.

On the other hand, if you're going too fast, you'll overstress the physical limits of the plane's structure and components. And the result can be very, very bad.

Adept stunt pilots are masters of conserving energy by balancing the plane's air speed-kinetic energy against the potential energy in its altitude.

During a typical aerobatic maneuver, an increase in air speed is balanced by a decrease in altitude, or vice versa.

If that's a bit too abstract for you, here's an example.

When an aerobatic pilot pulls up into an inside loop, he or she is converting kinetic energy (air speed) into potential energy (altitude).

As the aircraft floats at the top of the loop, the potential energy is at its maximum, but the aircraft is slowing down, so that its kinetic energy is at the lowest point.

As the aircraft descends, the potential energy decreases and the kinetic energy increases again.

Of course, that's just one greatly oversimplified version of the scores of complex, delicate physics equations that a pilot must make while he or she is doing hair-raising tricks thousands of feet above the ground.

He or she also must deal with other hazards, like the effect of acceleration and the resulting G forces on the human body.

Too many Gs and the blood can be shunted away from the brain, causing a blackout. Inducing negative Gs, on the other hand, can pump too much blood into the brain, interfering with vision and hearing.

For more on airplanes and flying, visit the links on the next page.

Aerobatics: Author’s Note

I've flown as a passenger in small aircraft and helicopters enough times to understand how precarious flight actually is.

So it's utterly amazing to me that some pilots have the nerves and skill to attempt hair-raising stunts in the air.

It was interesting to learn about the long history of stunt flying and that it dates back practically to the invention of the airplane itself.

Those early aerobatics pioneers really had to have a lot of courage, since the aircraft they flew were far less sophisticated than the planes used for stunts today.

It was also fascinating to learn that what appears to be random craziness in the air actually is an elaborately structured sport, with rules and standard maneuvers.

Aerobatics: Cheat Sheet

Stuff you need to know:

·      Aerobatics is a type of flying in which pilots demonstrate their skill by performing exotic midair maneuvers, including loops, rolls, spins, abrupt changes of direction and even flying straight up like a rocket.

·      Aerobatics is practically as old as flying itself, and the first aerobatic maneuver -- a 360-degree banked turn -- actually was performed by the Wright brothers in 1904.

·      Since the late 1920s, when the first international aerobatics competition was held in Zurich, aerobatics gradually evolved into a sport with rules and standards.

·      Standard aerobatics maneuvers include Chandelles, dives, loops, rolls, wingovers, stall turns and Cuban eights.

·      To keep from crashing, aerobatics pilots must carefully calculate and manage the amount of kinetic energy used in a maneuver.

·      Some aerobatics pilots are so skilled that they can fly in formation so close together that their wings appear to be touching.

Patrick J. Kiger has written for HowStuffWorks since 2008 covering a wide array of topics, from history and politics to pop culture and technology. He worked as a newspaper reporter for the Pittsburgh Press, and the Orange County Register in California, where he covered one of the biggest serial murder cases in U.S. history, and also as a staff writer at Baltimore Magazine. As a freelancer, Patrick has written for print publications such as GQ, Mother Jones and the Los Angeles Times, and on the web for National Geographic Channel, Discovery News, Science Channel and Fast Company, among others. In recent years, he's become increasingly interested in how technological advances are altering urban life and the design of cities, and has written extensively on that subject for Urban Land magazine. In his spare time, Patrick is a longtime martial arts student and a fan of crime fiction, punk rock and classic Hollywood films.

https://science.howstuffworks.com/transport/flight/future/aerobatics.htm



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BAMBOO FOR REINFORCED CONCRETE CONSTRUCTION - The steel as a reinforcing material is a demand that is increasing day by day in most of the developing countries. There are situations when the production is not found enough to face the demand for steel. Hence it is essential to have an alternative that is worth compared to steel. Bamboo is found in abundance. They are resilient and hence these can face the demand as a reinforcing material and become an ideal replacement for steel. The tensile strength property which is the main requirement of a reinforcing material is seen appreciable for bamboo, compared with other materials including steel. The structure of bamboo from its origin gives this property. The hollow tubular structure has high resistance against wind forces when it is in natural habitat. Working on the weak points of bamboo and bringing up an innovation of bamboo as a structural steel replacement, would be a great alternative. Advantages of Bamboo in Reinforcement: Bamboo is extremely strong natural fiber. It has high tensile strength. Due to its hollow structure, it is highly flexible. Lightweight compared to steel. Low cost and environment-friendly. It has great shock absorbing capacity. Employ bamboo having an evident brown color. This shows the age of bamboo to be at least 3 years. Diameter – Use the one with long large culms. Among 1500 species of bamboo, the best one must be checked, tested to satisfy the requirement as a reinforcing material.

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Bamboo for Reinforced Concrete Construction

by Kathir 

Civil Snapshot 

 

The steel as a reinforcing material is a demand that is increasing day by day in most of the developing countries.

There are situations when the production is not found enough to face the demand for steel.

Hence it is essential to have an alternative that is worth compared to steel.

Bamboo is found in abundance.

They are resilient and hence these can face the demand as a reinforcing material and become an ideal replacement for steel.

The tensile strength property which is the main requirement of a reinforcing material is seen appreciable for bamboo, compared with other materials including steel.

The structure of bamboo from its origin gives this property.

The hollow tubular structure has high resistance against wind forces when it is in natural habitat. Working on the weak points of bamboo and bringing up an innovation of bamboo as a structural steel replacement, would be a great alternative.

Advantages of Bamboo in Reinforcement:

1.    Bamboo is extremely strong natural fiber.

2.    It has high tensile strength.

3.    Due to its hollow structure, it is highly flexible.

4.    Lightweight compared to steel.

5.    Low cost and environment-friendly.

6.    It has great shock absorbing capacity.

Disadvantages of Bamboo in Reinforcement:

The biggest part which discourages the use of bamboo as reinforcement is its disadvantages.

1.    Less durable than steel, cannot be used in permanent structure.

2.    Shrinking problems.

3.    More prone to environmental degradation and insect attack.

4.    Cannot be used in cold climate.

5.    It does not have longer life compared to steel.

6.    Low modulus of elasticity, poor adherence to concrete mix.

7.    Due to lower modulus of elasticity, it can crack and deflect more than steel reinforcement.

Selection of Bamboo for Reinforced Concrete Construction

Selection of bamboo for reinforcement can be done based on these factors

Color and Age – Employ bamboo having an evident brown color. This shows the age of bamboo to be at least 3 years.

Diameter – Use the one with long large culms.

Harvesting – Try to avoid those bamboos that are cut either during spring or summer seasons.

Species – Among 1500 species of bamboo, the best one must be checked, tested to satisfy the requirement as a reinforcing material.

Civil Snapshot is a learning site for all the Civil Engineers and Students around the world. Our mission is educate with trusted source of knowledge everything related to Civil Engineering.

If you want more details about civil engineering follow us:

Youtube Channel: https://www.youtube.com/channel/UCrq9YEOQmmLP4b5o_PbQeqg

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https://civilsnapshot.com/bamboo-for-reinforced-concrete-construction/


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Sunday, December 6, 2020

AGGREGATES - Aggregates are coarse particulate rock-like material consisting of a collection of particles ranging in size from < 0.1 mm to > 50 mm. It includes gravel, crushed rock, sand, recycled concrete, slag, and synthetic aggregate. Aggregate is a granular material, such as sand, gravel, crushed stone, crushed hydraulic-cement concrete, or iron blast-furnace slag, used with a hydraulic cementing medium to produce either concrete or mortar. Types of aggregates include Coarse aggregate and fine aggregate. The aggregate of each type is further sub-divided into many types and classification based on its size. The technique of Sieve Analysis is used for gradation of aggregate for use in concrete and for other applications. Aggregate is called bound material when it is mixed with cement or binding materials and referred to as unbound material when used without cement or binding materials. Aggregates are commonly obtained by crushing naturally occurring rock. The properties of aggregates depend on the parent rock which can be igneous, sedimentary, or metamorphic. Aggregates are evaluated through tests to determine their suitability for various applications. Mineralogy, grain size and texture, and petrographic description of rock samples are also used to evaluate suitability. Coarse-grained aggregates will not pass through a sieve with 4.75 mm openings (No. 4).

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Aggregates

By: Haseeb Jamal


 

Aggregates Definition:

Aggregates are coarse particulate rock-like material consisting of a collection of particles ranging in size from < 0.1 mm to > 50 mm.

It includes gravel, crushed rock, sand, recycled concrete, slag, and synthetic aggregate.

Aggregate is a granular material, such as sand, gravel, crushed stone, crushed hydraulic-cement concrete, or iron blast-furnace slag, used with a hydraulic cementing medium to produce either concrete or mortar.

Types of aggregates include Coarse aggregate and fine aggregate.

The aggregate of each type is further sub-divided into many types and classification based on its size.

The technique of Sieve Analysis is used for gradation of aggregate for use in concrete and for other applications.

Aggregate is called bound material when it is mixed with cement or binding materials and referred to as unbound material when used without cement or binding materials.

Aggregate Origin and Geology

Aggregates are commonly obtained by crushing naturally occurring rock.

The properties of aggregates depend on the parent rock which can be igneous, sedimentary, or metamorphic.

Aggregates are evaluated through tests to determine their suitability for various applications.

Mineralogy, grain size and texture, and petrographic description of rock samples are also used to evaluate suitability.

Types of Aggregates

Coarse Aggregate

Coarse-grained aggregates will not pass through a sieve with 4.75 mm openings (No. 4).

Those particles that are predominantly retained on the 4.75 mm (No. 4) sieve and will pass through 3 inch screen, are called coarse aggregate. 

The coarser the aggregate, the more economical the mix.

Larger pieces offer less surface area of the particles than an equivalent volume of small pieces.

Use of the largest permissible maximum size of coarse aggregate permits a reduction in cement and water requirements.

Using aggregates larger than the maximum size of coarse aggregates permitted can result in interlock and form arches or obstructions within a concrete form.

That allows the area below to become a void, or at best, to become filled with finer particles of sand and cement only and results in a weakened area.

For Coarse Aggregates in Roads following properties are desirable:

1.        Strength

2.        Hardness

3.        Toughness

4.        Durability

5.        Shape of aggregates

6.        Adhesion with bitumen

Fine Aggregate

The other type of aggregates are those particles passing the 9.5 mm (3/8 in.) sieve, almost entirely passing the 4.75 mm (No. 4) sieve, and predominantly retained on the 75 µm (No. 200) sieve are called fine aggregate.

For increased workability and for economy as reflected by use of less cement, the fine aggregate should have a rounded shape.

The purpose of the fine aggregate is to fill the voids in the coarse aggregate and to act as a workability agent.

Properties of Aggregates also has effect on resulting concrete. e.g. variation in size, grading, texture, shape and strength of aggregates means variation in the properties of resulting concrete. 

Purpose & Uses of Aggregates

In concrete, an aggregate is used for its economy factor, to reduce any cracks and most importantly to provide strength to the structure.

1.    Aggregates are used as the base, subbase, and/or surface of roads in several forms

2.    In roads and railway ballast, it is used to help distribute the load and assist in ground water running off the road.

3.    Increases the volume of concrete, thus reduces the cost. Aggregates account for 60-75% of the volume of concrete and 79-85% weight of PCC

4.    Provide dimensional stability

5.    Influence hardness, abrasion resistance, elastic modulus and other properties of concrete to make it more durable, strong and cheaper.

6.    Other uses include fills, backfills, and drainage and filtration applications.

Haseeb Jamal

I am a Civil Engineer, graduated from University of Engineering and Technology, PeshawarPakistan in 2010. I also have a PG-Diploma in Disaster Management and MS in Urban Infrastructure Engineering (In Progress). My expertise include civil related softwares like AutoCAD, SAP2000, MS Project, Primavera, MS Office and GIS. My technical skills include project management, monitoring and evaluation, structural assessment, disaster risk management, Quantity survey, land survey, material testing, site management and technical writing. I am trained in writing project progress reports as well as proposals and concept papers. I have also received advanced training on surveying, proposal writing, Monitoring and Evaluation of projects as well as organizations.

I have worked as Project Engineer at National Research and Development Foundation, Peshawar and CENCON Associates. I also worked with Spectra Engineering Solutions as Senior Civil Engineer in monitoring of World Bank and UNDP funded projects all over Khyber Pakhtunkhwa and FATA. Currently, I am working as Deputy Manager Development at NayaTel, Peshawar.

https://www.aboutcivil.org/aggregates-types-uses-definition.html