Attitude indicator: Difference between revisions
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This editor is a retired airline pilot and flying instructor. The graphic on this page of the 'soviet' or Russian artificial Horizon (AH) is incorrectly orientated, very wrong in presentation, and therefore confusing and misleading. I do not have the skills to correct the graphic in this page, but could do it on my Mac, but how would I return it to th |
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The Attitude Direction Indicator (ADI), or Flight Director Indicator (FDI), is an AI integrated with a Flight Director System (FDS). The ADI incorporates a computer that receives information from the navigation system, such as the AHRS, and processes this information to provide the pilot with a 3-D flight trajectory cue to maintain a desired path. The cue takes the form of V steering bars. The aircraft is represented by a delta symbol and the pilot flies the aircraft so that the delta symbol is placed within the V steering bars.<ref name=FAA2/>{{rp|5-23,5-24}} |
The Attitude Direction Indicator (ADI), or Flight Director Indicator (FDI), is an AI integrated with a Flight Director System (FDS). The ADI incorporates a computer that receives information from the navigation system, such as the AHRS, and processes this information to provide the pilot with a 3-D flight trajectory cue to maintain a desired path. The cue takes the form of V steering bars. The aircraft is represented by a delta symbol and the pilot flies the aircraft so that the delta symbol is placed within the V steering bars.<ref name=FAA2/>{{rp|5-23,5-24}} |
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[[File:Soviet artificial horizon AGP-2 - shown working.JPG|thumb|Soviet artificial horizon AGP-2, showing the aircraft banked to the right]] |
[[File:Soviet artificial horizon AGP-2 - shown working.JPG|thumb|Soviet artificial horizon AGP-2, showing the aircraft banked to the right. 191126 CAUTION: This graphic is inaccurately presented. A further discussion & correction will be offered when time permits.]] |
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This editor is a retired airline pilot and flying instructor. The graphic on this page of the 'soviet' or Russian artificial Horizon (AH) is incorrectly orientated, very wrong in presentation, and therefore confusing and misleading. |
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I do not have the skills to correct the graphic in this page, but could do it on my Mac, but how would I return it to this page? |
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Basically, the central dark slot which may be observed in the centre of the instrument's glass, is a shielded slot through which the aircraft symbol is raised or lowered on a lever controlled by a gyroscope or other device, to indicate pitch attitude variations of the aircraft. |
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Both the graphic here, and the instrument in the cockpit must be mounted such that the vertical axis of the page, and of the slot in the instrument in the cockpit are all aligned with the vertical. i.e. the slot is rigid & fixed. |
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The aircraft symbol is raised & lowered to reflect pitch, and rotated clockwise viewed by the observer (to indicate a right bank) or anticlockwise (to indicated a left bank,) both motions being driven simultaneously as required. |
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Put another way, if you are a pilot strapped to your seat and looking at the AH, that central instrument slot will be aligned with your backbone. Always. |
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See the discussion at https://aviation.stackexchange.com/questions/51791/how-is-a-confusion-possible-between-western-and-russian-attitude-indicators where initially the web-site builder made the same graphic presentation error. That error is called out further into the article, but the wrongly orientated graphic remains. |
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The graphics all appear to photographs of a WW2 vintage salvaged instrument, and not representative of modern Russian instruments, as all the 'Western' graphics depict. |
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See also: https://commons.wikimedia.org/wiki/File:Soviet_artificial_horizon_AGP-2_-_front_panel.JPG |
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Also see: https://commons.wikimedia.org/wiki/File:Soviet_artificial_horizon_AGP-2_-_whole_view.JPG |
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If the link to the YouTube video is retained, as I guess it would be, I would add a note to be very cautious regarding what is presented in the video - it verges on confusion and hysterical production values. |
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Noted added by JenSee 191126 aka 26 Nov 2019 aka Nov, 26, 2019. Apologies for unprofessional presentation, TLTTOL (Too Late Too Tired Old Lady) |
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==See also== |
==See also== |
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Revision as of 09:11, 26 November 2019
 | The examples and perspective in this article may not represent a worldwide view of the subject. (December 2018) |
The attitude indicator (AI), formerly known as the gyro horizon or artificial horizon, is a flight instrument that informs the pilot of the aircraft orientation relative to Earth's horizon, and gives an immediate indication of the smallest orientation change. The miniature aircraft and horizon bar mimic the relationship of the aircraft relative to the actual horizon.[1][2] It is a primary instrument for flight in instrument meteorological conditions.[3][4]
Attitude is always presented to users in the unit degrees (°). However, inner workings such as sensors, data and calculations may use a mix of degrees and radians, as scientists and engineers may prefer to work with radians.
Use
The essential components of the AI include a symbolic miniature aircraft mounted so that it appears to be flying relative to the horizon. An adjustment knob, to account for the pilot's line of vision, moves the aircraft up and down to align it against the horizon bar. The top half of the instrument is blue to represent the sky, while the bottom half is brown to represent the ground. The bank index at the top shows the aircraft angle of bank. Reference lines in the middle indicate the degree of pitch, up or down, relative to the horizon.[2][1]
Most Russian-built aircraft have a somewhat different design. The background display is colored as in a Western instrument, but moves up and down only to indicate pitch. A symbol representing the aircraft (which is fixed in a Western instrument) rolls left or right to indicate bank angle.[5] A proposed hybrid version of the Western and Russian systems that would be more intuitive, never caught on.[6]
Operation
The heart of the AI is a gyroscope (gyro) that spins at high speed, from either an electric motor, or through the action of a stream of air pushing on rotor vanes placed along its periphery. The stream of air is provided by a vacuum system, driven by a vacuum pump, or a venturi. Air passing through the narrowest portion of a venturi has lower air pressure through Bernoulli's Principle. The gyro is mounted in a double gimbal, which allows the aircraft to pitch and roll as the gyro stays vertically upright. A self-erecting mechanism, actuated by gravity, counteracts any precession due to bearing friction. It may take a few minutes for the erecting mechanism to bring the gyros to a vertical upright position after the aircraft engine is first powered up.[2][1][7]
Attitude indicators have mechanisms that keep the instrument level with respect to the direction of gravity.[8] The instrument may develop small errors, in pitch or bank during extended periods of acceleration, deceleration, turns, or due to the earth curving underneath the plane on long trips. To start with, they often have slightly more weight in the bottom, so that when the aircraft is resting on the ground they will hang level and therefore they will be level when started. But once they are started, that pendulous weight in the bottom will not pull them level if they are out of level, but instead its pull will cause the gyro to precess. In order to let the gyro very slowly orient itself to the direction of gravity while in operation, the typical vacuum powered gyro has small pendulums on the rotor casing that partially cover air holes. When the gyro is out of level with respect to the direction of gravity, the pendulums will swing in the direction of gravity and either uncover or cover the holes, such that air is allowed or prevented from jetting out of the holes, and thereby applying a small force to orient the gyro towards the direction of gravity. Electric powered gyros may have different mechanisms to achieve a similar effect.[9]
Older AIs were limited in the amount of pitch or roll that they would tolerate. Exceeding these limits would cause the gyro to tumble as the gyro housing contacted the gimbals, causing a precession force. Preventing this required a caging mechanism to lock the gyro if the pitch exceed 60° and the roll exceeded 100°. Modern AIs don't have this limitation and don't require a caging mechanism.[2][1]
Flight Director Attitude Indicator
Attitude indicators are also used on manned spacecraft and are called Flight Director Attitude Indicators (FDAI), where they indicate the craft's yaw angle (nose left or right), pitch (nose up or down), roll, and orbit relative to a fixed-space inertial reference frame from an Inertial Measurement Unit (IMU).[10] The FDAI can be configured to use known positions relative to Earth or the stars, so that the engineers, scientists and astronauts can communicate the relative position, attitude, and orbit of the craft. [11][12]
Attitude and Heading Reference Systems
Attitude and Heading Reference Systems (AHRS) are able to provide three-axis information based on ring laser gyroscopes, that can be shared with multiple devices in the aircraft, such as "glass cockpit" primary flight displays (PFDs). Rather than using a spinning gyroscope, modern AHRS use solid-state electronics, low-cost inertial sensors, rate gyros, and magnetometers.[2]: 8–20 [1]: 5–22
With most AHRS systems, if an aircraft's AIs have failed there will be a standby AI located in the center of the instrument panel, where other standby basic instruments such as the airspeed indicator and altimeter are also available. These mostly mechanical standby instruments may be available even if the electronic flight instruments fail, though the standby attitude indicator may be electrically driven and will, after a short time, fail if its electrical power fails.[13]
Attitude Direction Indicator
The Attitude Direction Indicator (ADI), or Flight Director Indicator (FDI), is an AI integrated with a Flight Director System (FDS). The ADI incorporates a computer that receives information from the navigation system, such as the AHRS, and processes this information to provide the pilot with a 3-D flight trajectory cue to maintain a desired path. The cue takes the form of V steering bars. The aircraft is represented by a delta symbol and the pilot flies the aircraft so that the delta symbol is placed within the V steering bars.[1]: 5–23, 5–24
This editor is a retired airline pilot and flying instructor. The graphic on this page of the 'soviet' or Russian artificial Horizon (AH) is incorrectly orientated, very wrong in presentation, and therefore confusing and misleading.
I do not have the skills to correct the graphic in this page, but could do it on my Mac, but how would I return it to this page?
Basically, the central dark slot which may be observed in the centre of the instrument's glass, is a shielded slot through which the aircraft symbol is raised or lowered on a lever controlled by a gyroscope or other device, to indicate pitch attitude variations of the aircraft.
Both the graphic here, and the instrument in the cockpit must be mounted such that the vertical axis of the page, and of the slot in the instrument in the cockpit are all aligned with the vertical. i.e. the slot is rigid & fixed.
The aircraft symbol is raised & lowered to reflect pitch, and rotated clockwise viewed by the observer (to indicate a right bank) or anticlockwise (to indicated a left bank,) both motions being driven simultaneously as required.
Put another way, if you are a pilot strapped to your seat and looking at the AH, that central instrument slot will be aligned with your backbone. Always.
See the discussion at https://aviation.stackexchange.com/questions/51791/how-is-a-confusion-possible-between-western-and-russian-attitude-indicators where initially the web-site builder made the same graphic presentation error. That error is called out further into the article, but the wrongly orientated graphic remains. The graphics all appear to photographs of a WW2 vintage salvaged instrument, and not representative of modern Russian instruments, as all the 'Western' graphics depict. See also: https://commons.wikimedia.org/wiki/File:Soviet_artificial_horizon_AGP-2_-_front_panel.JPG Also see: https://commons.wikimedia.org/wiki/File:Soviet_artificial_horizon_AGP-2_-_whole_view.JPG
If the link to the YouTube video is retained, as I guess it would be, I would add a note to be very cautious regarding what is presented in the video - it verges on confusion and hysterical production values.
Noted added by JenSee 191126 aka 26 Nov 2019 aka Nov, 26, 2019. Apologies for unprofessional presentation, TLTTOL (Too Late Too Tired Old Lady)
See also
- Acronyms and abbreviations in avionics
- Air India Flight 855
- Korean Air Cargo Flight 8509
- Peripheral vision horizon display (PVHD)
- Turn and slip indicator
References
- ^ a b c d e f Instrument Flying Handbook, FAA-H-8083-15B (PDF). U.S. Dept. of Transportation, FAA. 2012. p. 5-17,5-19.
- ^ a b c d e Pilot's Handbook of Aeronautical Knowledge, FAA-H-8083-25B (PDF). U.S. Dept. of Transportation, FAA. 2016. p. 8-16,8-18,8-19.
- ^ Jeppesen, A Boeing Company (2007). Guided Flight Discovery Private PilotJe. Jeppesen. pp. 2–66. ISBN 978-0-88487-429-4.
- ^ https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/ AMT Handbook - Aircraft Instrument Systems page 10-56
- ^ Learmount, David (2009-02-09), "Which way is up for Eastern and Western artificial horizons?", flightglobal.com, archived from the original on October 29, 2014
- ^ Safety expert proposes low-cost loss of control fixes , FlightGlobal, 2011-03-04
- ^ Federal Aviation Administration (FAA). "AMT Handbook - Chapter 10. Aircraft Instrument Systems".
- ^ murphy, alan. "4-4". www.faatest.com. Retrieved 22 March 2018.
- ^ murphy, alan. "4-5". www.faatest.com. Retrieved 22 March 2018.
- ^ "Flight-Director/Atitude Indicator". www.hq.nasa.gov. Retrieved 2016-12-01.
- ^ "Apollo Flight Journal - Apollo Operations Handbook. Volume 1". history.nasa.gov. Archived from the original on 2015-12-24. Retrieved 2016-12-01.
- ^ "Apollo Guidance, Navigation, and Control (GNC) Hardware Overview" (PDF). NASA Technical Reports Server. NASA. Retrieved 12 October 2018.
- ^ "NTSB Safety Recommendation". 2010-11-08.
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