Aircraft

An aircraft is a vehicle or machine that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships (including blimps), gliders, paramotors, and hot air balloons.

The human activity that surrounds aircraft is called aviation. The science of aviation, including designing and building aircraft, is called aeronautics. Crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as lift type, aircraft propulsion, usage and others.



History :

Flying model craft and stories of manned flight go back many centuries; however, the first manned ascent and safe descent in modern times took place by larger hot-air balloons developed in the 18th century. Each of the two World Wars led to great technical advances. Consequently, the history of aircraft can be divided into five eras:

* Pioneers of flight, from the earliest experiments to 1914.
* First World War, 1914 to 1918.
Aviation between the World Wars, 1918 to 1939.
* Second World War, 1939 to 1945.
* Postwar era, also called the Jet Age, 1945 to the present day.


Methods of lift

Lighter than air – aerostats

Aerostats use buoyancy to float in the air in much the same way that ships float on the water. They are characterized by one or more large cells or canopies, filled with a relatively low-density gas such as helium, hydrogen, or hot air, which is less dense than the surrounding air. When the weight of this is added to the weight of the aircraft structure, it adds up to the same weight as the air that the craft displaces.

Small hot-air balloons, called sky lanterns, were first invented in ancient China prior to the 3rd century BC and used primarily in cultural celebrations, and were only the second type of aircraft to fly, the first being kites, which were first invented in ancient China over two thousand years ago.

During World War II, this shape was widely adopted for tethered balloons; in windy weather, this both reduces the strain on the tether and stabilizes the balloon. The nickname blimp was adopted along with the shape. In modern times, any small dirigible or airship is called a blimp, though a blimp may be unpowered as well as powered.

Heavier-than-air – aerodynes :

Heavier-than-air aircraft, such as airplanes, must find some way to push air or gas downwards so that a reaction occurs (by Newton’s laws of motion) to push the aircraft upwards. This dynamic movement through the air is the origin of the term. There are two ways to produce dynamic upthrust aerodynamic lift, and powered lift in the form of engine thrust.

Aerodynamic lift involving wings is the most common, with fixed-wing aircraft being kept in the air by the forward movement of wings, and rotorcraft by spinning wing-shaped rotors sometimes called rotary wings. A wing is a flat, horizontal surface, usually shaped in cross-section as an aerofoil. To fly, air must flow over the wing and generate lift. A flexible wing is a wing made of fabric or thin sheet material, often stretched over a rigid frame. A kite is tethered to the ground and relies on the speed of the wind over its wings, which may be flexible or rigid, fixed, or rotary.

Fixed-wing:

The forerunner of the fixed-wing aircraft is the kite. Whereas a fixed-wing aircraft relies on its forward speed to create airflow over the wings, a kite is tethered to the ground and relies on the wind blowing over its wings to provide lift. Kites were the first kind of aircraft to fly and were invented in China around 500 BC. Much aerodynamic research was done with kites before test aircraft, wind tunnels, and computer modelling programs became available.

The first heavier-than-air craft capable of controlled free-flight were gliders. A glider designed by George Cayley carried out the first true manned, controlled flight in 1853.

The practical, powered, fixed-wing aircraft (the airplane or aeroplane) was invented by Wilbur and Orville Wright

Rotorcraft:

Rotorcraft, or rotary-wing aircraft, use a spinning rotor with aerofoil section blades (a rotary wing) to provide lift. Types include helicopters, autogyros, and various hybrids such as gyrodynes and compound rotorcraft.

Helicopters have a rotor turned by an engine-driven shaft. The rotor pushes air downward to create lift. By tilting the rotor forward, the downward flow is tilted backward, producing thrust for forward flight. Some helicopters have more than one rotor and a few have rotors turned by gas jets at the tips.

Autogyros have unpowered rotors, with a separate power plant to provide thrust. The rotor is tilted backward. As the autogyro moves forward, air blows upward across the rotor, making it spin. This spinning increases the speed of airflow over the rotor, to provide lift. Rotor kites are unpowered autogyros, which are towed to give them forward speed or tethered to a static anchor in high-wind for kited flight.

Other methods of lift:

A lifting body is an aircraft body shaped to produce lift. If there are any wings, they are too small to provide significant lift and are used only for stability and control. Lifting bodies are not efficient: they suffer from high drag, and must also travel at high speed to generate enough lift to fly. Many of the research prototypes, such as the Martin Marietta X-24, which led up to the Space Shuttle, were lifting bodies, though the Space Shuttle is not, and some supersonic missiles obtain lift from the airflow over a tubular body.
Powered lift types rely on engine-derived lift for vertical takeoff and landing (VTOL). Most types transition to fixed-wing lift for horizontal flight. Classes of powered lift types include VTOL jet aircraft (such as the Harrier Jump Jet) and tiltrotors, such as the Bell Boeing V-22 Osprey, among others.

Size :
The smallest aircraft are toys/recreational items, and nano aircraft.

The largest aircraft by dimensions and volume (as of 2016) is the 302 ft (92 m) long British Airlander 10, a hybrid blimp, with helicopter and fixed-wing features, and reportedly capable of speeds up to 90 mph (140 km/h; 78 kn), and an airborne endurance of two weeks with a payload of up to 22,050 lb (10,000 kg).

The largest aircraft by weight and largest regular fixed-wing aircraft ever built, as of 2016, is the Antonov An-225 Mriya. That Ukrainian-built six-engine Russian transport of the 1980s is 84 m (276 ft) long, with an 88 m (289 ft) wingspan. It holds the world payload record, after transporting 428,834 lb (194,516 kg) of goods, and has recently flown 100 t (220,000 lb) loads commercially. With a maximum loaded weight of 550–700 t (1,210,000–1,540,000 lb), it is also the heaviest aircraft built to date. It can cruise at 500 mph (800 km/h; 430 kn).

The largest military airplanes are the Ukrainian Antonov An-124 Ruslan (world’s second-largest airplane, also used as a civilian transport), and American Lockheed C-5 Galaxy transport, weighing, loaded, over 380 t (840,000 lb). The 8-engine, piston/propeller Hughes H-4 Hercules “Spruce Goose” an American World War II wooden flying boat transport with a greater wingspan (94m/260ft) than any current aircraft and a tail height equal to the tallest (Airbus A380-800 at 24.1m/78ft) — flew only one short hop in the late 1940s and never flew out of ground effect.

The largest civilian airplanes, apart from the above-noted An-225 and An-124, are the Airbus Beluga cargo transport derivative of the Airbus A300 jet airliner, the Boeing Dreamlifter cargo transport derivative of the Boeing 747 jet airliner/transport (the 747-200B was, at its creation in the 1960s, the heaviest aircraft ever built, with a maximum weight of over 400 t (880,000 lb)),and the double-decker Airbus A380 “super-jumbo” jet airliner

Size and speed extremes:

Speeds :
The fastest recorded powered aircraft flight and fastest recorded aircraft flight of an air-breathing powered aircraft was of the NASA X-43A Pegasus, a scramjet-powered, hypersonic, lifting body experimental research aircraft, at Mach 9.6, exactly 3,292.8 m/s (11,854 km/h; 6,400.7 kn; 7,366 mph). The X-43A set that new mark, and broke its own world record of Mach 6.3, exactly 2,160.9 m/s (7,779 km/h; 4,200.5 kn; 4,834 mph), set in March 2004, on its third and final flight on 16 November 2004.

Prior to the X-43A, the fastest recorded powered airplane flight (and still the record for the fastest manned, powered airplane / fastest manned, non-spacecraft aircraft) was of the North American X-15A-2, rocket-powered airplane at Mach 6.72, or 2,304.96 m/s (8,297.9 km/h; 4,480.48 kn; 5,156.0 mph), on 3 October 1967. On one flight it reached an altitude of 354,300 ft (108,000 m).

The fastest known, production aircraft (other than rockets and missiles) currently or formerly operational (as of 2016) are:

The fastest fixed-wing aircraft, and fastest glider, is the Space Shuttle, a rocket-glider hybrid, which has re-entered the atmosphere as a fixed-wing glider at more than Mach 25, equal to 8,575 m/s (30,870 km/h; 16,668 kn; 19,180 mph).
The fastest military airplane ever built: Lockheed SR-71 Blackbird, a U.S. reconnaissance jet fixed-wing aircraft, known to fly beyond Mach 3.3, equal to 1,131.9 m/s (4,075 km/h; 2,200.2 kn; 2,532 mph). On 28 July 1976, an SR-71 set the record for the fastest and highest-flying operational aircraft with an absolute speed record of 2,193 mph (3,529 km/h; 1,906 kn; 980 m/s) and an absolute altitude record of 85,068 ft (25,929 m).

Uses for aircraft:

Aircraft are produced in several different types optimized for various uses; military aircraft, which includes not just combat types but many types of supporting aircraft, and civil aircraft, which include all non-military types, experimental and model.

Military:

A military aircraft is any aircraft that is operated by a legal or insurrectionary armed service of any type.] Military aircraft can be either combat or non-combat:

Combat aircraft are aircraft designed to destroy enemy equipment using its own armament.Combat aircraft divide broadly into fighters and bombers, with several in-between types, such as fighter-bombers and attack aircraft, including attack helicopters.
Non-combat aircraft are not designed for combat as their primary function, but may carry weapons for self-defense. Non-combat roles include search and rescue, reconnaissance, observation, transport, training, and aerial refueling. These aircraft are often variants of civil aircraft.

Civil:

Civil aircraft divide into commercial and general types, however there are some overlaps.

Commercial aircraft include types designed for scheduled and charter airline flights, carrying passengers, mail and other cargo. The larger passenger-carrying types are the airliners, the largest of which are wide-body aircraft. Some of the smaller types are also used in general aviation, and some of the larger types are used as VIP aircraft.

General aviation is a catch-all covering other kinds of private (where the pilot is not paid for time or expenses) and commercial use, and involving a wide range of aircraft types such as business jets (bizjets), trainers, homebuilt, gliders, warbirds and hot air balloons to name a few. The vast majority of aircraft today are general aviation types.

Model:

A model aircraft is a small unmanned type made to fly for fun, for static display, for aerodynamic research or for other purposes. A scale model is a replica of some larger design.

The end…

Top Technical Screening Tools

What is a technical skills screening tool?

A technical skills screening tool is software that contains a rich library of technical assessment tests, including questions and answers for recruiters to screen and evaluate candidates.

The assessments created on these platforms are used to evaluate candidates before employment by technical recruiters and/or hiring managers.

How do skill assessments compare to other screening methods?

Skill assessments are not the only type of evaluation used by the hiring teams – job simulation resumes, and reference checks are all common screening methods. The trouble with resumes and reference checks is that they don’t reveal the whole picture. A candidate and often their references will attempt to present the applicant in the best positive light. Unfortunately, this may not be the most accurate portrayal of the candidate’s skills and abilities. 

Job simulations, also known as work simulations, require candidates to perform tasks that the role requires in the workplace. These simulations are an effective evaluation tactic to understand how the candidate will perform in the real work environment.

Structured interviews are also an effective evaluation method, and they include a scoring system similar to that of skill assessments. The common denominator between the two methods is that they are both quantitative and can thus be reliably compared and contrasted. Moreover, recruiters can extract useful insights from the collected data.

Screen developers at scale with accurate, custom programming tests that evaluate technical skills hyper-relevant to the role.

  • Library of coding tasks for roles at all levels 
  • High-scale plagiarism detection and fraud prevention 
  • Top-rated candidate experience with fair scoring methodology

Skill assessments have the added benefit of providing recruiters with the opportunity to reliably screen out candidates pre-interview. Thus, when it comes to tech hiring, skill tests take the cake to justify reliability, efficiency, and cost-effectiveness.

The 5 best technical screening tools

While skill tests are great, we mentioned earlier that you need the right kind of assessment to guarantee fair evaluation and the best results. Therefore, the ideal technical screening tool should offer:

  • The ability to measure modern as well as legacy developer skills
  • Automation to minimize manual grading – through auto-evaluators and industry-leading compilers
  • Exceptional candidate experiences and custom branding opportunities for companies
  • Tests specifically tailored to various jobs and roles
  • Efficient qualitative score analysis
  • Seamless integrations with other hiring solutions
  • Unmatched data security for your candidate data
  • Video interviews with pair programming abilities
  • Comprehensive data insights, analytics, and reporting

Of course, not every tool will have all these features. So let’s take a look at the best technical screening tools for tech recruiters and hiring managers and see which one wins out.

#1 WeCP | We Create Problems

WeCreateProblems has the largest repository of technical interview questions & tests. Where other platforms average a few thousand to generously over 10,000 questions, WeCP has over 0.2 million+ technical questions in the bank. The question bank contains skill test questions for every tech role, whether it’s frontend or full-stack development, data science, DevOps, or something else. 

Tech recruiters can generate custom tests on-demand with WeCP to evaluate over 2000 different technical skills. Need morecustomization with the test questions and design? WeCP’s team is on standby to help you out there too.

Aside from the impressive size of the question bank and the high quality of the questions themselves, WeCP sets itself apart from the competition in another big way – the evaluation process. WeCP uses SkillMaps for scientifically evaluating candidates, guaranteeing accuracy, and all the tests in the repository have been thoroughly vetted. Moreover, WeCP’s technical screening is made cheat-proof through:

  • Constant addition of new tests
  • Internal patrol 
  • Dynamic rotation
  • Advanced plagiarism checker
  • AI-based video proctoring

WeCP’s questions are thoroughly scrutinized for difficulty, guaranteeing candidates can’t just Google the answers or prepare for them beforehand. Whether you design a custom test or use a pre-built one, WeCP guarantees unique, challenging, skill-mapped assessments to help you track down the best candidate.

#2 Codility

Codility is a powerful tech screening solution and remote hiring tool tailored for engineering teams. The recruitment platform has been around since 2009 and provides employers with powerful screening and interviewing tools. 

Codility has a diverse knowledge base and includes skill tests for various roles – you can use the tool to evaluate potential candidates for frontend and backend developer positions, data science, language skills, and more. However, one drawback of using this tool is that it lacks AI-powered video proctoring and web proctoring features, which may lead to cheating.

One of Codility’s most appreciated features is its ‘candidate feedback’ option. If you enable this feature, Codility provides candidates with a breakdown of their score immediately after submission of the skill test. Enabling automated candidate feedback helps recruiters be more transparent about the hiring process.

#3 CodeSignal

CodeSignal is a popular technical screening tool for tech recruiters with a decent repository of questions, web proctoring, on-demand custom questions, and even video interviews.

CodeSignal is a relatively young recruitment platform, having popped up in 2015, but it has since made a good name for itself. The tool helps recruiters generate custom tests for a wide variety of programming languages and developer skills.

Pedigree is a poor proxy for programming skills. Broaden your candidate pool and qualify individuals based on their coding skills. Measuring developer skills accurately and at scale is easy with CodeSignal.

Some candidates have expressed concern regarding CodeSignal’s existing questions, citing them to be verbose and difficult to comprehend. On the whole, though, CodeSignal is a reliable tool. It has helped many tech companies evolve past using resumes for evaluation into the more reliable realm of coding skill tests.

#4 HackerRank

HackerRank is a popular developer screening tool. The platform offers assessment tests for a variety of skills, including tests for full-stack development skills and database skills.

From simple coding challenges to full-stack engineering scenarios, allow developers to demonstrate their design, development, and communication skills in a real-time pair programming environment, complete with a virtual whiteboard. Add projects that provide insight into the quality of work candidates will perform at your company.

HackerRank has been around since 2012 and has since grown its client list to over 2000. The tool provides framework support and helps recruiters assess up to 44 skills with its rich repository of questions. After designing your custom assessment with HackerRank, you can opt for the automated scoring system or manually score the tests.

#5 HackerEarth

HackerEarth has the makings of a solid technical screening tool – it has a decent question bank (sporting over 15000 questions), has tests for all relevant skills, and has features like video interviews that some of its competitors lack. However, it does miss out on the whiteboarding features that WeCP offers.

HackerEarth lets you engage or source top developers with hackathons, while also enabling you to assess, interview and upskill them with ease.

Like HackerRank, HackerEarth was founded in 2012 and has since catered to over a thousand clients. The platform supports proctoring and helps recruiters screen and short-list top-performing candidates thanks to reliable coding assessments and an integrated scoring system.