Introduce to Air Data Instruments
11 Pages2402 Words291 Views
Added on 2020-04-13
Introduce to Air Data Instruments
Added on 2020-04-13
ShareRelated Documents
SOLUTIONS 1.Comparison of how 2 Air data instruments compensate for the principle changes in the atmosphere. Due to changes in barometric pressure, input errors would arise as aircraft maneuvers in the air stream. The air data has the true and indicated airspeed, pressure, altitude, ambient air temperature, angles of attack and rate of climb among othersNow, the earth’s atmosphere is stratified into various zones; notably, the one in which most aircrafts are flown is the troposphere. Other divisions include: chemosphere, ionosphere, exosphere and ozonosphere. Temperature changes are fairly uniform in the troposphere (Wiolland, 2005).). The air data system mainly comprises the primary air data instruments, and pitot-statictube; The primary air data instruments include : altimeter, vertical speed indicator and air speedNotably, the ground-based radar are normally used to establish the exact position and velocity of the plane. However, the optical trackers can also be used in this case. GPS receiver then determines the time, position and velocity minus drift errors. Additionally, the euler angles are mostly measured using mutltiple GPS receiver. The rate gyroscope is used in measuring angular acceleration rates and linear accelerations. However, in steady flight, linear accelerators are used to measure pitch and roll attitude. Notaly, therefore, airdata instruments are useful in maintenance of the plane stability hence contributing to safety, navigation and control by the pilot Figure 1: Air speed indicator (courtesy of USA aerospace.com)
2.Selection of a Pitot-static system to be fitted into a modern aircraft (Provide the design considerations, construction and operation that would influence the choice of the system)Design considerations Error-free: The system must be able to minimize the effects of error on the indicated readings; too much exaggerated final readings may be risky as pilot receives wrong information that could pose danger to aircraft maneuvers as the pilot is often informed through the readings. Besides, factors such as resolution, accuracy, cost and maintenance and size of aircraft requirements are critical in the integration of the system. The system must be able to repeatedly give the same value in the same condition of performance (FAA, no year).). However, practically, errors would often arise hence accuracy needs to be within a small range that is allowable. Besides, it should be responsive in functionalitysuch that parameters like attitude and barometric pressure changes must be captured in real-time and displayed for the pilot to make informed decision. The construction and operation The Pitot-static system is mainly composed of the pitot-static tube, airspeed indicator altimeter and vertical speed are all connected to a static port such that air introduced into the system via the port as the airplane climbs, the altitude changes so is air pressure. The pressure changes are recorded by this system.The air speed indicator measures speed of air by getting the static difference between the static pressure and the ram air pressure. The display is usually done in a mach number in knob units. Notably, the air speed indicator is constituted with an expandable diaphragm such that airrushes in, it is filled and expanded while ram air pressure is increased. The altimeter measures air pressure; the calibration is normally in height. It indicates the static pressure as altitude. The air speed indicator will indicate difference between pilot static pressure and pitot pressure. The vertical speed gives an indication as to the rate at which static pressure changes with either climbing or descending. In the altimeter, the air pressure increases as airplane descends and decreases as the airplane climbs. The vertical speed indicator indicates the rate of climb or descends of the aircraft; calibration is done in feet per minute. There is a needle connected to the wafer such that it rotates as wafer expands and contracts to indicate the rate of climb or descend of aircraft.
Figure 2: The Pitot-static tube (courtesy of NASA.gov)3.Comparison of an analogue to digital air data computer and how they are integrated into an aircraft. Discuss the advantages and disadvantagesAnalogue air data computer Digital air data computer This is the traditional air data computer thatwas used. It mainly comprised of airspeed indicator and altimeter in which primitive pneumatically driven instruments was performed and a nonlinear computation done via a spring mechanismThe digital remote sensing is normally separated from the display featureServo-driven cams would compute the parameters like speed, altitude and mach numbers. Flat panel computer screens are used for display of output information The sensing and display functions are driven in a single unit. Special digital data buses are used to carry information signals Conveying of sensor information is done via wires and pneumatic lines and cams profiles. Numerous display gauges are It normally maintains optimum performance of aircraft
often used to show the outputAttitude capsule was the main airdata sensing used ; it had a simple aneroid to operate itIt provides additional information to the aircrafts system Varying accuracy at different altitudesIt provides accurate and realtime sensing and computation capabilitiesIt failed to maintain pressure rates hence system failure was common Has self-correcting mechanism which can adjust as conditions and altitude change viathe static source error correction4.Construction and Operation of a typical flight director systemThis is normally an embedded system within the flight control system in which it provides real-time guidance to the pilot or autopilot along a flight path by selection and computation of various commands. It is linked with an ADC from which it receives the input signal and flight data computer performs computation and supplies data such as attitude, air speed, and flux and air temperature. These signals are then sent and displayedin the altitude indicator (All Star Network, 2000). Notably, in the absence of the autopilot, the FD should still be functional with manual maneuvers. In the manual mode, the pilot directly instructs the FD to carry out the said functions and the system responds by controlling the listed parameters. The FD therefore provides a set of commands which are fed from the flight control computer while in steering mode using a command bar located on the altitude director indicator (Bombarider, no year). There are about three status modes, namely: vertical, transfer and lateral modes which are selected accordingly. The steering commands are in charge of providing visual guidance to pilot as she manually operates the aircraft maneuvers. Therefore, in a nutshell, according to FAA (no year) the FDS provides command options to perform selection of a desired altitude, maintain altitude pressure and ensure aircraft stays at a vertical speed, holds a mach number and ceases a preselected barometric altitude; a part from maintaining the trim options and wing-level (All Star Network, 2000).Construction Now, the FD is composed of flight director indicator, horizontal situation indicator, modeselector and a flight director computer. The flight director computer comprises features such as altitude, indicator, glide slope, slip indicator, wearing flag for gyro, pitch and bank command and fixed aircraft symbol. The HSI normally facilitates selection and operation navigation aids while both outbound and inbound tracking is made possible. The FDC receives input signals from the radar altimeter, sensors (barometric), and compass and altitude gyro. Certainly, the FDC computes and provides steering
End of preview
Want to access all the pages? Upload your documents or become a member.