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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19
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5answers
8k views

Why is there a difference between GPS Speed and Indicator speed?

I just played with flight simulator and noticed that the GPS shows different speed from the speed indicator in the cockpit. Also, GPS speed is higher than the Indicator. Any Idea why?
34
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3answers
29k views

Why don't pilots always use autoland?

In aeroplanes that are equipped for autoland and landing at an airport with a working and adequate instrument landing system for the conditions, why would a pilot choose not to use autoland? If I had ...
42
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3answers
122k views

What are N1 and N2?

When I'm reading something about jet engines, it's common to see references to N1 and N2. I've never fully understood what N1 and N2 are on engine instruments and how they relate to thrust and the ...
21
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5answers
66k views

What does the term “trimming” most commonly mean in aviation?

Why does an airplane need trim, and what does it do during the flight? Does an autopilot adjust the trim automatically?
13
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3answers
9k views

How are attitude indicators kept accurate?

The attitude indicator is very important for any sort of instrument flying, so it must be accurate at all times regardless of the plane's movements. I presume that the indicator would be connnected ...
29
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2answers
49k views

How does an alpha (AoA) vane work?

The alpha vane (also called AoA vane) is an external probe used to measure the angle of attack. I have been trying to understand how exactly it works, but I can't find any clear explanation or ...
21
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3answers
10k views

Who decides what measurement units are used for altitude, and why is there no standard?

I know that some countries (Russia and China for instance) use meters to measure altitude while the rest of the world uses feet. Why isn't this standardized around the world? I guess all modern ...
15
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4answers
16k views

How do aircraft altimeters calculate altitudes accurately while airborne?

While an aircraft is airborne, the local barometric pressure can change, causing an altimeter to no longer display the correct altitude. How are altimeters re-calibrated to display the correct ...
15
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1answer
70k views

What is the difference between OAT, RAT, TAT, and SAT?

When I first started flying jet aircraft, I found different instruments that measure temperature in different ways and it was quite confusing. What is the difference between Outside Air Temperature,...
28
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3answers
13k views

How does a Mach Meter determine the speed of sound at a given altitude?

By my understanding, the Mach Number at a given altitude is calculated by dividing IAS by the speed of sound at that altitude. So how is this speed of sound calculated to display the Mach Number on ...
20
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4answers
3k views

Why is a clock necessary for IFR?

According to FAR 91.205 (d)(6), one instrument required for IFR is: A clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation. Why is it necessary to ...
13
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4answers
11k views

What is the advantage of combining the rudder and brake pedals in aircraft?

I've read about several aircraft having their rudder and brake pedals very close together. To me this seems confusing and prone to error. It looks easy to mistake the rudder / brake pedals and ...
30
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1answer
4k views

Can we replace an attitude indicator with a ball half full of liquid?

Attitude indicators (artificial horizons) use a gyro to display pitch and bank. I was wondering if it would work to use a ball half full of liquid to replace the artificial horizon (using the water ...
11
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3answers
4k views

How much lag does an Attitude Indicator experience?

How much lag does an Attitude Indicator exhibit when it is working as designed? Other than well-known problems like tumbling beyond certain limits in pitch and roll, and precession errors from the ...
9
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2answers
4k views

Where does the term 'steam cockpit' come from?

Why are traditional style cockpits with gauges called 'steam cockpits'? Do the instruments actually run on steam?
30
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5answers
21k views

How can pilots fly inside a cloud?

I heard that sometime an aircraft fly inside a cloud, and I'm wondering how that works - how clearly can the pilot see while inside the cloud? What if a cloud is "too large"? (Is there a maximum size ...
29
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2answers
5k views

Can instruments be fixed via a swift punch?

I remember reading a book about private piloting techniques, (I can't remember the title; it has been so long; perhaps I can check my library history or something to see later), and I saw something ...
22
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5answers
99k views

What's the difference between True vs Magnetic headings?

What is the difference between a true and a magnetic heading? Why are/were magnetic headings used in aviation?
15
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4answers
2k views

Why don't both black boxes hold the same data?

As I understand, there are two black boxes on-board an aircraft. One black box, the Cockpit Voice Recorder holds the cockpit conversations and the other, the Flight Data Recorder holds essential ...
13
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5answers
12k views

Can the pitch be very different from the angle of attack?

How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to ...
11
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1answer
2k views

How does a pitot plate work?

I understand the basic concept of the pitot tube in that it measures the air pressure coming into the tube in order to compare it to a static pressure measured elsewhere on the aircraft. The B-2 ...
17
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1answer
8k views

What is the difference between “sensitive” and “non-sensitive” altimeters?

In this answer reference was made to "sensitive" and "non-sensitive" altimeters. What is the definition of each, what are the differences, and why would one be used in preference to the other? And ...
7
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1answer
10k views

How is the wind direction and wind speed measured in flight?

Most large aircraft have a wind direction and wind speed indicator. How is this measured? The vector difference between TAS and ground speed? How accurate is this? In the below picture (taken from ...
20
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2answers
14k views

How does the weather radar work?

I was reading this question about turbulence and how pilots foresee it, and in one of the answers, @Rhino Driver states: Weather Radar Just like using your eyes, except the radar can see further ...
19
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2answers
3k views

If I fly a balanced turn long enough, will the AI show I'm level?

Attitude Indicators are essentially gyroscopes. Mechanical gyroscopes have a "rigidity in space" property, which allows them to preserve their orientation when the support rotates. However, like ...
11
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3answers
2k views

Is the altimeter setting corrected for temperature?

In an ATIS or AWOS/ASOS recording, is the reported altimeter setting corrected for temperature? I think it must be, because on a hot day, the altimeter should still show correct field elevation. If ...
8
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1answer
2k views

What is the correct crew procedure for an unreliable airspeed alert?

When the crew receives "airspeed disagree" message on the primary flight displays, they may face some hazardous situation. Is there any procedure, using a table containing pitch, power, altitude and ...
5
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1answer
612 views

Why would a Mode-C transponder report a different altitude than an altimeter/GPS?

This is related to a small single-engined plane. On a recent flight, the controller kept telling me that I was 300 ft higher than it appeared on my altimeter and GPS (which were in sync). This was ...
2
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2answers
286 views

Measuring speed and altitude from personal phone midflight [duplicate]

Given that there is no need now for one to swith off their cellphone midflight, inflight wifi is now a norm and common, Is it possible for me to measure the velocity and altitude of an aircraft using ...
9
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1answer
1k views

Where are the locations of the elevators or horizontal stabilizers in a Concorde?

I don't find the horizontal stabilizers or the elevators of a Concorde at the tail section like other aircrafts. Are they fitted beside the ailerons in the wings?
26
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2answers
2k views

Why does the speed tape on the Lockheed U-2 go the opposite way?

I found this clip online that shows the speed tape on the Lockheed U-2 going what I perceive is the opposite direction to the 'normal' convention. On most aircraft, the higher values are above and so ...
19
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2answers
2k views

What is the purpose of the string taped to the front of the canopy on gliders?

What is the purpose of the piece of string taped to a glider canopy? Is it effectively a turn coordinator, but then what advantages would it have over a gauge such as the ones fitted in powered ...
24
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13answers
10k views

How did planes measure their speed relative to the ground before GPS?

How did planes measure their ground speed before GPS? If they used some sort of anemometer to measure speed, that would only measure the speed of the plane relative to the air through which it is ...
14
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2answers
11k views

How precise are altimeters?

How precise and how accurate are typical altimeters these days? That is, if two planes are flying (side-by-side, very near each other), and both altimeters show the same Flight Level, what is the ...
12
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4answers
4k views

When/How may I replace the Turn Coordinator with an Artificial Horizon?

I've seen a few panel shots where the traditional turn coordinator has been replaced with a second artificial horizon, as shown below. The benefits seem obvious - if my artificial horizon failed I'd ...
10
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2answers
49k views

What are the differences between an OBS, a CDI, a Heading indicator, and an HSI?

What are the differences between an OBS, a CDI, a Heading indicator, and an HSI? As far as I can tell they all use VORs. Why would 4 different version of the same instrument be invented? Is the HSI ...
6
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2answers
569 views

How does an altimeter deal with the non-linear pressure gradient?

Altimeters work via an aneroid barometer to sense the atmospheric pressure. If I climb from 2000ft to 4000ft, the altimeter senses that the pressure has reduced by, let's say, 70hpa, and is calibrated ...
5
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1answer
2k views

What are the pros and cons of vacuum and pressure gyros?

Inspired by this question, I would like to know what the pro's and con's of the mostly used vacuum-gyro and the less used high-pressure-gyro is. Side-question: Are there any other ways to make the ...
25
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3answers
6k views

How does an A330 detect stall without airspeed?

On Air France 447 the crew had experienced complete failure of the pitot static system, which meant they lost their readings on their airspeed indicators, but according to the Mayday / Air Crash ...
25
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6answers
6k views

Why would a C150 tachometer bounce so much that the needle fell off?

On a long flight in a C150E, the tachometer started bouncing a little bit and the severity of the bouncing gradually increased until it was extreme: The tachometer was spinning in loops and making a ...
7
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5answers
4k views

How is a confusion possible between Western and Russian Attitude Indicators?

Yesterday I watched a documentary on Crossair Flight 498 accident. One of the factors that might have contributed to the accident was the confusion of the pilot on interpreting the attitude indicator; ...
7
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4answers
24k views

What is the difference between Turn Coordinator and Artificial Horizon?

I was reading this question about Turn Coordinator and Artificial Horizon, and now I want to understand the differences between those two components. What is the main difference between Turn ...
5
votes
2answers
880 views

How does altimeter reading vary when departing from ISA conditions?

I am a soon-to-be student-pilot and am struggling with a basic concept that is altitude. After watching multitude of online videos, I feel that most of the people do not have good teaching skills. ...
4
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2answers
1k views

What type of altimeter is this?

What type Altimeter is an SA-91? It has three pointers 100, 1000, 10000. Don't know if it is Kollsman. I can't find any info as far as repairing unit.
28
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4answers
5k views

Is it normal for gliders not to have attitude indicators?

This answer shows a picture of and describes a "modern" glider instrument panel, with two variometers, airspeed indicator, altimeter, compass, temperature gauge and radio controls. Notably (at least ...
13
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5answers
4k views

What will the pilot do if all the airspeed indicators fail?

Are there any alternate instruments to indicate the airspeed in case of pitot tube failures?
12
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1answer
400 views

How should this Bendix course deviation indicator from the '50s be read?

This is a Swissair photo from a DC-7C panel. Source I have seen photos on airliners.net of these in DC-6s, VC-118 and Constellations. It appears that other companies besides Bendix made these ...
8
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2answers
9k views

How does a horizontal situation indicator (HSI) work?

I am trying to understand the Horizontal Situation Indicator. To my understanding there is a slaving transmitter, usually in a wing (the left wing in the Piper Archer and Seminole), which sends ...
6
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2answers
1k views

Are turn and slip indicators calibrated to a certain speed? If so, what speed?

Are turn and slip indicators calibrated to a certain speed? If they are, What speed are they calibrated to, and why aren't all the turn and slip indicators calibrated for the same speed?
6
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2answers
2k views

How to navigate an aircraft without GPS? [duplicate]

In case of loss of GPS: how can an aircraft not only be navigated but navigated so precisely that it can pinpoint its destination airport ? (case in point: Finland and Norway are telling airline ...