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.

Filter by
Sorted by
Tagged with
18 votes
5 answers
11k 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?
Super Hornet's user avatar
34 votes
3 answers
40k 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 ...
Hugh's user avatar
  • 1,967
48 votes
3 answers
197k 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 ...
Gabriel Brito's user avatar
33 votes
2 answers
6k 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 ...
Tony's user avatar
  • 459
26 votes
5 answers
94k 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?
Haris's user avatar
  • 1,017
4 votes
4 answers
2k views

What does the balance ball actually indicate?

Given answers and comments from a previous question, I realize that I need to clarify what the ball actually measure. I think it does not measure side slip but sideways acceleration, but I'm not quite ...
Manu H's user avatar
  • 16.5k
33 votes
6 answers
31k 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 ...
Hemang's user avatar
  • 1,129
29 votes
3 answers
18k 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 ...
shortstheory's user avatar
  • 3,976
19 votes
1 answer
96k 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,...
Lnafziger's user avatar
  • 58.8k
17 votes
3 answers
13k 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 ...
ithisa's user avatar
  • 1,702
8 votes
1 answer
18k 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 ...
Daniel R's user avatar
  • 744
37 votes
2 answers
65k 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 ...
asheeshr's user avatar
  • 1,614
20 votes
3 answers
13k 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 ...
Haris's user avatar
  • 1,017
20 votes
4 answers
5k 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 ...
user60684's user avatar
  • 847
17 votes
5 answers
22k 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 ...
h22's user avatar
  • 12.1k
15 votes
4 answers
18k 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 ...
NitinG's user avatar
  • 6,869
7 votes
3 answers
3k views

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

Are turn rate indicators calibrated to a certain speed? If they are, what speed are they calibrated to, and why aren't all the turn rate indicators calibrated for the same speed?
Adder's user avatar
  • 1,452
-3 votes
2 answers
639 views

In some "turn coordinators", does the gyro spin opposite to the direction it spins in a "turn rate indicator"?

In some "turn coordinators", does the gyro spin opposite to the direction it spins in a "turn rate indicator"? A "turn coordinator" has a symbolic airplane on the display ...
quiet flyer's user avatar
  • 22.2k
24 votes
7 answers
26k 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; ...
Claudi's user avatar
  • 1,575
13 votes
4 answers
17k 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 ...
shortstheory's user avatar
  • 3,976
11 votes
1 answer
3k 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 ...
FreeMan's user avatar
  • 16.2k
11 votes
4 answers
7k 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 ...
NathanG's user avatar
  • 6,135
11 votes
3 answers
3k 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 ...
Peter's user avatar
  • 4,097
10 votes
2 answers
11k 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?
flyingfisch's user avatar
  • 14.5k
6 votes
1 answer
16k views

What is the relation between roll angle and pitch angle?

I was wondering about roll angle and pitch angle values. Will I get same pitch angle at different roll angles and vice-versa? For example. At its initial position, the aircraft is standing on the ...
Pratik's user avatar
  • 63
5 votes
1 answer
2k 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 ...
Prashant Saraswat's user avatar
32 votes
4 answers
7k 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 ...
cjs's user avatar
  • 1,044
29 votes
2 answers
6k 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 ...
Bassinator's user avatar
  • 5,490
27 votes
6 answers
144k 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?
Danny Beckett's user avatar
20 votes
2 answers
21k 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 ...
Gabriel Brito's user avatar
20 votes
2 answers
4k 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 ...
kevin's user avatar
  • 39.7k
18 votes
1 answer
16k 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 ...
FreeMan's user avatar
  • 16.2k
16 votes
5 answers
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 ...
shortstheory's user avatar
  • 3,976
13 votes
2 answers
102k 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 ...
jskypilot's user avatar
  • 3,829
11 votes
3 answers
1k views

During "partial panel" flying, in what ways is a turn rate indicator more useful than a turn coordinator?

This question deals with flying by reference to old-fashioned "steam gauges", not a modern "glass cockpit". I recall hearing some pilots very experienced (ATP) pilots advocate for the older-style "...
quiet flyer's user avatar
  • 22.2k
9 votes
1 answer
3k 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 ...
eduardoguilherme's user avatar
9 votes
1 answer
4k 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 ...
Noah Krasser's user avatar
  • 9,002
8 votes
1 answer
769 views

How does Pitot Heat influence airspeed indication (assuming no ice or moisture)?

Should Pitot Heat ON (in dry weather conditions) decrease airspeed indication because warmer (so less dense) air flows through the tube?
sergyt's user avatar
  • 83
2 votes
2 answers
728 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 ...
securitydude5's user avatar
35 votes
4 answers
14k views

What is the meaning of the crosshatch marking on altimeters?

What does the crosshatched area on an altimeter tell you? It's only visible when below 10,000 ft indicated altitude. Can't be terrain awareness, a lot of terrain around here is over 10,000 feet. ...
Barrie Strachan's user avatar
31 votes
3 answers
4k 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 ...
Thunderstrike's user avatar
23 votes
13 answers
12k 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 ...
Pat's user avatar
  • 369
18 votes
2 answers
6k 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 ...
Steve's user avatar
  • 283
15 votes
2 answers
15k 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 ...
Eugene Osovetsky's user avatar
14 votes
4 answers
7k 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 ...
voretaq7's user avatar
  • 68.4k
12 votes
3 answers
16k views

How (and when) to use the BFO button on an ADF?

BFO (Beat Frequency Oscillator) is a function of the ADF, I know that it has something to do with different types of NDB, but I do not know which type. And how and when do I use it? I heard that ...
Andrea Ghilardi's user avatar
11 votes
2 answers
3k views

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 ...
mathrick's user avatar
  • 296
10 votes
3 answers
8k views

What is the difference between a pitot tube and a pitot-static tube?

What is the difference between a Pitot tube and a Pitot-static tube? If an aircraft fitted with Pitot tube and static holes on the fuselage, is it necessary to consider the static pressure ...
S.Prabhu's user avatar
  • 141
10 votes
2 answers
2k views

What steps have been taken to rule out instrument failure due to blocked static ports or pitot tubes?

In the case of Aeroperu Flight 603, a fatal crash was caused by duct tape that was accidentally left over some or all of the static ports on the underside of the fuselage after the aircraft was ...
Krishnaraj Rao's user avatar
9 votes
4 answers
35k 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 ...
Gabriel Brito's user avatar