Questions tagged [flight-instruments]

Flight instruments provide the pilot with information about the flight situation of that aircraft, such as altitude, speed and direction; and are of particular use in conditions of poor visibility, such as in clouds, when such information is not available from visual reference outside the aircraft.

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Please describe ram pressure in simple terms

Please someone describe the following sentence in simple words: The Airspeed Indicator is calibrated for 'standard' sea level density, so it will only read TAS if the density of the air through which ...
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Can fuzzy dice help in IMC? [duplicate]

Just had this thought as I’ve read about multiple GA accidents that resulted from unintentional flight into IMC with planes not equipped for it (no attitude indicator), resulting in disorientation and ...
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4 votes
1 answer
418 views

Early turbojet RPM and thrust indicator

The flight operations handbook for the Douglas X-3 Stiletto (an experimental aircraft from the early 1950s) says that the instrument panel has instruments that indicate the thrust of the two ...
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Strange airspeed indicator in the Douglas X-3 Stiletto

The cockpit of the Douglas X-3 Stiletto has a rather weird looking airspeed indicator. (The leftmost instrument in the top row.) Two concentric circular scales, the outer one goes from 0 to 20, the ...
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How do aircraft on the deck of a moving aircraft carrier align their INS/IRS?

I know that the F/A-18C is equiped with a rotary switch for inertial alignment. The switch has two positions, one for ground and the other for carrier operations. Leaving aside the GPS/GNSS, I wonder ...
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Before certified GPS, how much did a full IFR panel cost?

Certified IFR GPS navigators are expensive, but the price of even used HSIs and DME seem to bring some perspective to that cost. How much did a full IFR upgrade cost back in the day before GPS?
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5 votes
1 answer
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Why not use the alternate static port at all times?

One of my club's small planes apparently has an intermittent problem with moisture in the static port line, so the recommendation is to always fly with the alternate static port open. That leads me to ...
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11 votes
2 answers
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Why is the ball no longer centred in a multi-engine airplane with inoperable engine?

I'm currently working on my PPL, and whilst trying to understand fully how the turn coordinator works, I got down a rabbit hole that makes me question my understanding, and that I can't dig myself out ...
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Does the Remote Indicating Compass (old type) both have precession motor and a torque motor?

I am teaching aviation students theory for the ATPL Exam. And one of the subjects, instrumentation, there is question on the exam that has stumped me. It claims that the torque motor that will drive ...
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6 votes
1 answer
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What does CPLD mean in aviation in general and on this altitude alerter?

I saw the shortcut CPLD on this altitude alerter from a Cessna 210, and could not work out what it could possibly mean: What does it mean on this altitude alerter, ...
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13 votes
2 answers
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What is the purpose of the leaf spring in an altimeter?

What is the use of the leaf spring present around the partially evacuated aneroid capsule of sensitive altimeter.
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4 votes
1 answer
224 views

How do you realign a directional gyro in an area of magnetic unreliability?

The primary means of determining heading in most small aircraft is the directional gyro, as this instrument is unaffected by the magnetic dip errors that cause a magnetic compass to give the wrong ...
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12 votes
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What specific hazard is the practice of identifying an ILS LOC by Morse code trying to prevent?

This question got me wondering about the practice of tuning a navigation frequency, selecting it on the audio panel, and then identifying it by listening to the three letter Morse code signal. I know ...
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4 votes
1 answer
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If the RMI heading rose is stuck, would the needle still display correct bearing?

If the RMI (Radio Magnetic Indicator) heading rose gets stuck, would the RMI needle still display correct QDM (magnetic bearing to station)?
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4 votes
2 answers
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How does HSI decide to give a left or right CDI indication?

Since there is no reverse sensing in HSI, it tells you to turn left or right, So Is the interpretation correct that it will tell you to turn to the direction to that direction, which requires less ...
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8 votes
2 answers
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What kinds of altimeter are used in modern airliners?

What's the mechanism of the altimeters in big jets?
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1 vote
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What would be VSI indications of an aircraft sideslipping to a blocked static vent while descending?

The aircraft has two static vents, each on left and right side of fuselage. Left static port is blocked and aircraft is sideslipping to left at an INCREASING rate while descending. Would VSI overread ...
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1 answer
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What would be the ASI readings incase of pitot leakage?

If there is a leak in the pitot tube in the a/c, what would be the readings for a pressurized and unpressurised aircraft? I've read that if there is leakage in pitot tube within the structure of a/c, ...
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5 answers
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How do airplanes measure cross-wind?

Are aircraft equipped with any instruments that measure actual crosswind velocity during a flight? What is that instrument called and is it used by autopilots to apply wind correction?
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3 votes
1 answer
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Can you fly with INS/ IRS at higher lattitudes?

IRS can't be aligned at higher lattitudes ( above 70 deg) , but if once aligned near equator, can we fly till higher lattitudes with IRS in that flight?
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3 votes
1 answer
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How are degree of freedom and gimbals related in a gyro?

Why does it mean to say a gyro has an even degree of freedom? Why does this degree correspond to the number of gimbals ?
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4 votes
1 answer
356 views

What is gimbal error in DGI compass gyroscopes?

I'm unable to find an explanation of gimbal error in a Directional Gyroscope Indicator (DGI) anywhere. Can someone please explain what this is?
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3 votes
1 answer
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What are the three different altitudes shown in the Perlan II?

The Perlan II glider has two altitude indicators and an altimeter on the navi screen, each showing different altitudes: How is each of the altimeters different? One indicator certainly shows MSL and ...
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4 votes
0 answers
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Anybody recognise the model of ADI on the XB-70?

Is this a model that was used on other aircrafts of the era, too? Looking for technical information about it and knowing the manufacturer and model number would make that easier. The Interim Flight ...
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9 votes
1 answer
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Were the original gyroscopic artificial horizons "upside-down"?

Looking at an article in Flight magazine from March 1945 titled "Sperry Attitude Gyro" that you can find online, the picture of the instrument is interesting: It seems that the orientation ...
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What kind of analysis is done in front wheel plane? [duplicate]

I’m not sure how to describe this as a question… So here is an image: What is the device? (marked in red) What could the ground crew be analyzing near the wheel (marked in green) They’ve been at it ...
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1 vote
1 answer
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If a plane was put into a vacuum chamber, what would its altimeter read? [duplicate]

Just curious. What if you put a (general aviation or airliner) plane into a hard vacuum chamber? Would its altimeter simply read the highest possible altitude it could? That's rather impossible for ...
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23 votes
3 answers
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Why do digital flight instruments seem to fluctuate/flicker during landing or takeoff?

I happened to watched videos where landing was aborted due to some or other reasons. However, something interesting stuck me eyes: the digital flight instruments fluctuate/flicker (such as the ...
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1 answer
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Why the speedometer in Mig21 have 2 needles? [closed]

How pilots are able to read of the speed ? It's hard enough for one needle.
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1 answer
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If the altitude of the aircraft is given by the pitot tube, in icing condition with heat on, how is real altitude /speed interpretation done? [duplicate]

If the altitude of the aircraft is given by the pitot tube, in icing condition with pitot heat on how is real altitude /speed interpretation done? Because the air density and temperature is not ...
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5 votes
1 answer
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Why is the turn coordinator gyro tilted?

I’ve read many places (such as the FAA’s Instrument Flying Handbook) that a turn coordinator can sense both roll rate and turn rate due to the gyro being tilted 30 degrees. However, why does tilting ...
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1 answer
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Why do planes not employ a non-technological banking indicator? [duplicate]

I apologise if this is a very daft question with an obvious answer. I've been enjoying Air Crash Investigation episodes and there have been a few where the pilots, through differing training or faulty ...
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Is the turn coordinator showing yaw or roll a mix of the two?

I'm not talking about the ball, but instead the plane symbol shown on the instrument: Is it showing a roll or is it yaw that it shows? Or is it a mix of the two? IE, if I do my darndest to fly ...
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2 votes
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What are those green LED arrays on top of the instrument panel called?

Below is the link showing a fire fighting aircraft From 0:23 to 0:45 an LED array can be seen. The peculiar thing about that is as aircraft approaches the site, all ...
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4 votes
1 answer
240 views

If an airplane has a Vertical Speed Indicator is there a requirement that it be periodically checked for accuracy?

I believe I understand that there is no specific US FAA requirement for aircraft to carry a Vertical Speed Indicator (VSI). I believe I understand the basic operation of a VSI. It measures the rate ...
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6 votes
3 answers
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What aircraft equipment produced the three recordings of unidentified aerial phenomenon released by the US Pentagon in 2020? What does black signify?

I don't follow these things closely and my question is carefully scoped to ask ONLY about the type of aircraft equipment used and what the various gray levels in the images indicates. In CNN "The ...
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14 votes
1 answer
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What is that instrument with two knobs and what looks like range rings?

I just flew a Piper Warrior today and I got confused with the instrument shown below, it's the one above the CDI and to the right of the altimeter.
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5 answers
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What causes the ball to not be centered in a slip/skid?

I've reviewed quite a few questions on this forum including Forces in a slipping turn is-this-vector-diagram-of-the-forces-at-play-in-turning-flight-correct what-does-the-balance-ball-actually-...
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19 votes
5 answers
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Low visibility spins and spirals: difficult-to-understand explanation of false perception

I'm not a pilot. In the following excellent explanatory video I understand everything except for a single point. The presenter says that in cloud, if the instruments tell the pilot to level the wings ...
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3 votes
0 answers
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Is this vintage altimeter from the Cuatro Vientos?

My father who was a pilot, passed away some years ago and I have a vintage altimeter that he told me someone gave him. They assured him that it belonged to the Cuatro Vientos airplane, but I'm not ...
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1 vote
1 answer
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Is rate of turn information (both Turn Coordinator and Turn Indicator) accurate only in balanced turns?

I was studying the difference between the TC and TI, and I thought I heard or read somewhere before that the turn rate information on the TC or TI are only accurate when the ball is in the middle. Let'...
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19 votes
1 answer
7k views

Why do airplane indicators start at 12 (o'clock), unlike cars that start at 7?

A car's speed and RPM indicators usually start at 7, lower left, but airplanes' altitude and airspeed indicators start at noon. What's the origin of this convention?
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Where do flight sims get their data on aircraft flight characteristics?

Flight sims offer very realistic simulations of how a particular aircraft feels, claimed by pilot interviews on youtube. But how do sims get their data? First, does all this data even exist, i mean ...
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6 votes
2 answers
339 views

Have attitude indicators ever had triple failure in a commercial aircraft?

I'm wondering about couple of well known crashes (mainly AF447 and AirAsia 8501) and thinking: is there any case where triple redundant attitude sensor failure has ever occurred? In those accidents it ...
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2 votes
2 answers
370 views

Do the rules used in modern soaring competitions forbid gyroscopic flight instruments, or forbid the use of AHRS-driven attitude displays, etc?

In the past, the rules for soaring competitions in the US and many other countries have not permitted gliders (sailplanes) to have working gyroscopic instruments installed, to prevent pilots from ...
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3 votes
1 answer
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What is this instrument?

I am looking to sell this instrument, but it has no part numbers or any other identifying marks other than it says "Kollsman" on the back. Anyone know what it is and what it might be worth?
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What is the required accuracy of an airspeed indicator?

What FAA document specifies the accuracy to which an airspeed indicator must be calibrated to?
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3 answers
230 views

What kind of airspeed does a (3D) GPS measure?

Assuming a GPS receiver is advanced enough to compute 3D position/velocity with reasonable accuracy, it can indicate not only the aircraft's ground speed (which ignores altitude changes), but ...
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3 votes
2 answers
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What are the ANT and ADF modes on an NDB receiver?

I am seeing this in a simulator, so I don't have a manual for it… On the Bendix King KR87 NDB receiver, the leftmost button labelled “ADF” switches an indicator above it from “ANT” to “ADF” When ...
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How does the heading selector on the ADF work?

How does the ADF indicator work in terms of pointing the needle in the direction of the NDB signal? I understand that the ADF needle points towards the direction of the NDB signal for a given ...
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