Aerospace Engineering

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Aerospace engineering is the primary branch of engineering concerned with the design, construction, and science of aircraft and spacecraft. It is divided into two major and overlapping branches: aeronautical engineering and astronautical engineering. The former deals with craft that stay within Earth’s atmosphere, and the latter with craft that operate outside it. Aerospace Engineering deals with the design, construction, and study of the science behind the forces and physical properties of aircraft, rockets, flying craft, and spacecraft. The field also covers their aerodynamic characteristics and behaviors, airfoil, control surfaces, lift, drag, and other properties. Aerospace engineering is not to be confused with the various other fields of engineering that go into designing elements of these complex craft. For example, the design of aircraft avionics, while certainly part of the system as a whole, would rather be considered electrical engineering, or perhaps computer engineering. Or an aircraft’s landing gear system may be considered primarily the field of mechanical engineering. There is typically a combination of many disciplines that make up aerospace engineering. While aeronautical engineering was the original term, the broader “aerospace” has superseded it in usage, as flight technology advanced to include craft operating in outer space. Aerospace engineering, particularly the astronautics branch, is referred to colloquially as “rocket science”.

A fighter jet engine undergoing testing. The tunnel behind the engine muffles noise and allows exhaust to escape.

Flight Simulator

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A flight simulator is a device that artificially re-creates aircraft flight and various aspects of the flight environment. This includes the equations that govern how aircraft fly, how they react to applications of their controls and other aircraft systems, and how they react to external environmental factors such as air density, turbulence, cloud, precipitation, etc. Flight simulation is used for a variety of reasons, including flight training (mainly of pilots), the design and development of the aircraft itself, and research into aircraft characteristics and control handling qualities.

Depending on their purpose, flight simulations employ various types of hardware, modeling detail and realism. They can range from PC laptop-based models of aircraft systems to simple replica cockpits for familiarisation purposes to more complex cockpit simulations with some working controls and systems to highly detailed cockpit replications with all controls and aircraft systems and wide-field outside-world visual systems, all mounted on six degrees-of-freedom (DOF) motion platforms which move in response to pilot control movements and external aerodynamic factors.

Modern high-end flight simulators

High-end commercial and military flight simulators have large field-of-view (FoV) image generation and display systems of high resolution. All civil Full Flight Simulators (FFS) and many military simulators for large aircraft and helicopters also have motion platforms for cues of real motion. Platform motions complement the visual cues and are particularly important when visual cues are poor such as at night or in reduced visibility or, in cloud, non-existent. The majority of simulators with motion platforms use variants of the six-cylinder Stewart platform to generate cues of initial acceleration. These platforms are also known as Hexapods (literally “six feet”) and use an operating principle known as Acceleration onset cueing (which see). Motion bases using modern hexapod platforms can provide about +/- 35 degrees of the three rotations pitch, roll and yaw, and about one metre of the three linear movements heave, sway and surge.

The NASA Ames Research Center in “Silicon Valley” south of San Francisco operates the Vertical Motion Simulator. This has a very large-throw motion system with 60 feet (+/- 30 ft) of vertical movement (heave). The heave system supports a horizontal beam on which are mounted rails of length 40 feet, allowing lateral movement of a simulator cab of +/- 20 feet. A conventional 6-degree of freedom hexapod platform is mounted on the 40 ft beam, and an interchangeable cabin is mounted on the hexapod platform. This design permits quick switching of different aircraft cabins. Simulations have ranged from blimps, commercial and military aircraft to the Space Shuttle. In the case of the Space Shuttle, the large Vertical Motion Simulator was used to investigate a longitudinal pilot-induced oscillation (PIO) that occurred on an early Shuttle flight just before landing. After identification of the problem on the VMS, it was used to try different longitudinal control algorithms and recommend the best for use in the Shuttle programme. After this exercise, no similar Shuttle PIO has occurred. The ability to simulate realistic motion cues was considered important in reproducing the PIO and attempts on a non-motion simulator were not successful (a similar pattern exists in simulating the roll-upset accidents to a number of early Boeing 737 aircraft, where a motion-based simulator is needed to replicate the conditions).

AMST Systemtechnik (Austria) and TNO Human Factors (the Netherlands) have developed the Desdemona flight simulation system for the Netherlands-based research organisation TNO. This large scale simulator provides unlimited rotation via a gimballed cockpit. The gimbal sub-system is supported by a framework which adds vertical motion. Furthermore, this framework is mounted on a large rotating platform with an adjustable radius. The Desdemona simulator is designed to provide sustainable g-force simulation with unlimited rotational freedom.

 

Flight Instruments

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Altimeter

The altimeter shows the aircraft’s altitude above sea-level by measuring the difference between the pressure in a stack of aneroid  capsules inside the altimeter and the atmospheric pressure obtained through the static system. It is adjustable for local  barometric pressure which must be set correctly to obtain accurate altitude readings. As the aircraft ascends, the capsules  expand as the static pressure drops therefore causing the altimeter to indicate a higher altitude. The opposite occurs when  descending.

Attitude indicator

The attitude indicator (also known as an artificial horizon) shows the aircraft’s attitude relative to the horizon. From this the pilot  can tell whether the wings are level and if the aircraft nose is pointing above or below the horizon. This is a primary instrument for  instrument flight and is also useful in conditions of poor visibility. Pilots are trained to use other instruments in combination  should this instrument or its power fail.

 Airspeed indicator

The airspeed indicator shows the aircraft’s speed (usually in knots ) relative to the surrounding air. It works by measuring the  ram-air pressure in the aircraft’s pitot tube. The indicated airspeed must be corrected for air density (which varies with  altitude,  temperature and humidity) in order to obtain the true airspeed, and for wind conditions in order to obtain the  speed over the  ground.

Magnetic compass

The compass shows the aircraft’s heading relative to magnetic north. While reliable in steady level flight it can give confusing indications when turning, climbing, descending, or accelerating due to the inclination of the Earth’s magnetic field. For this reason, the heading indicator is also used for aircraft operation. For purposes of navigation it may be necessary to correct the direction indicated (which points to a magnetic pole) in order to obtain direction of true north or south (which points to the Earth’s axis of rotation).

Heading indicator

The heading indicator (also known as the directional gyro, or DG; sometimes also called the gyrocompass, though usually  not in aviation applications) displays the aircraft’s heading with respect to magnetic north. Principle of operation is a  spinning gyroscope, and is therefore subject to drift errors (called precession) which must be periodically corrected by  calibrating the instrument to the magnetic compass. In many advanced aircraft (including almost all jet aircraft), the  heading indicator is replaced by a Horizontal Situation Indicator (HSI) which provides the same heading information, but  also assists with navigation

Turn indicator

The turn indicator (also known as turn and slip) displays direction of turn and rate of turn. Internally mounted inclinometer displays ‘quality’ of turn, i.e. whether the turn is correctly coordinated, as opposed to an uncoordinated turn, wherein the aircraft would be in either a slip or a skid. The original turn and bank indicator was replaced in the late 1960s and early ’70s by the newer turn coordinator, which is responsive to roll as well as rate of turn. The turn and bank indicator is seen typically in aircraft manufactured only prior to that time, or in gliders manufactured in Europe.

 Vertical speed indicator

The VSI (also sometimes called a variometer). Senses changing air pressure, and displays that information to the pilot as a rate of climb or descent in feet per minute, meters per second or knots.

Additional panel instruments that may not be found in smaller aircraft

Course deviation indicator

The CDI is an avionics instrument used in aircraft navigation to determine an aircraft’s lateral position in relation to a track, which can be provided by a VOR or an Instrument Landing System.

This instrument can also be integrated with the heading indicator in a horizontal situation indicator.

Radio Magnetic Indicator

An RMI is generally coupled to an automatic direction finder (ADF), which provides bearing for a tuned Non-directional beacon (NDB). While simple ADF displays may have only one needle, a typical RMI has two, coupled to different ADF receivers, allowing for position fixing using one instrument.

IAI Heron

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The IAI Heron (Machatz-1) is a Medium-altitude long-endurance unmanned aerial vehicle (UAV) developed by the Malat (UAV) division of Israel Aerospace Industries. It is capable of Medium Altitude Long Endurance (MALE) operations of up to 52 hours’ duration at up to 35,000 feet. It has demonstrated 52 hours of continuous flight, but the effective operational maximal flight duration is less, due to payload and flight profile. There is a new version, Heron TP, also known as IAI Eitan.

On 11 September 2005, it was announced that the Israel Defence Forces purchased US$50 million worth of Heron systems.

 Heron navigates using an internal GPS receiver, and either a pre-programmed flight profile (in which case the system is fully autonomous from takeoff to landing), manual override from a ground control station, or a combination of both. It can autonomously return to base and land in case of lost communication with the ground station. The system has fully automatic launch and recovery (ALR) and all-weather capabilities.

Heron can carry an array of sensors, including infra-red and visible-light surveillance, intelligence systems (COMINT and ELINT) and various radar systems, totaling up to 250 kg (550 lb). Heron is also capable of target acquisition and artillery adjustment.

The payload sensors communicate with the ground control station in real-time, using either direct line of sight data link, or via an airborne/satellite relay. Like the navigation system, the payload can also be used in either a fully pre-programmed autonomous mode, or manual real-time remote operation, or a combination of both.

Autogyro

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An autogyro (from Spanish autogiro), also known as gyroplane, gyrocopter, or rotaplane, is a type of rotorcraft which uses an unpowered rotor in autorotation to develop lift, and an engine-powered propeller, similar to that of a fixed-wing aircraft, to provide thrust. While similar to a helicopter rotor in appearance, the autogyro’s rotor must have air flowing through the rotor disc in order to generate rotation. Invented by the Spanish engineer Juan de la Cierva to create an aircraft that could safely fly at slow speeds, the autogyro was first flown on 9 January 1923, at Cuatro Vientos Airfield in Madrid. De la Cierva’s aircraft resembled the fixed-wing aircraft of the day, with a front-mounted engine and propeller in a tractor configuration to pull the aircraft through the air. Under license from Cierva in the 1920s and 1930s, the Pitcairn & Kellett companies made further innovations. Late-model autogyros patterned after Dr. Igor Bensen’s designs feature a rear-mounted engine and propeller in a pusher configuration. The term Autogiro was a trademark of the Cierva Autogiro Company, and the term Gyrocopter was used by E. Burke Wilford who developed the Reiseler Kreiser feathering rotor equipped gyroplane in the first half of the twentieth century. The latter term was later adopted as a trademark by Bensen Aircraft.

Flettner Airplane

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A flettner or rotor airplane is an airplane that has no wings but instead uses the Magnus effect to create lift. Thus it is similar to the Flettner rotor used in a Rotor ship. Such airplanes were first built by Anton Flettner.

Although at least one aircraft was constructed, there is no record of them ever having flown.