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Questions tagged [altimeter]

The instrument which indicates the aircraft's altitude based on atmospheric pressure.

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What’s the setting range altimeters can handle?

What’s the setting range altimeters can handle? Is there a standard requiring a certain range for aircraft to be certified? Are there many occasions where a QNH is so high or low that airplanes have ...
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What is the cheapest way to track my balloon's altitude or GPS coordinates? [closed]

I want to build some extremely cheap high altitude stuff: balloon, paper plane :) anything. It's cold outside now, and I don't want to track down and collect my landed "spacecraft". So, I need a very ...
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Is true altitude vertical separation between airplanes dependent on temperature?

Does the "true" altitude vertical separation between airplanes (using the same altimeter setting) vary as the temperature changes? ( I fully realize that the "true" altitude of both airplanes is ...
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Barometric altimeter data during high vertical g-forces?

I’m contemplating that that under high vertical acceleration (such as the maximum limit of 2.5g for commercial airplanes), that hydrostatic atmospheric pressure wouldn’t be a complete model. Wikipedia ...
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When flying into an area with colder air, how will the altimeter read compared to true altitude? [duplicate]

When flying into an area with colder air, how will the altimeter read compared to true altitude? Air expands as the temperature increases and it compresses when the temperature decreases, shall I ...
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Can RVSM safely be further reduced?

Since the world population shows no signs of slowing down its rapid increase, it's pretty safe to say that means we can only expect more concurrent flights as time moves forward. Is it physically ...
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373 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 ...
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358 views

How altitude changes with changed QNH?

How the AGL altitude changes with changed QNH? I'd like only to confirm or correct my intuition.. Airplane is maintaining certain FL with some QNH, its instruments are showing some AMSL. Now the ...
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From which aircraft does this vintage altimeter come from?

I bought this vintage U.S. Navy Kollsman altimeter at a market in Bangkok, Thailand. Unfortunately, I don't have any info other than what you see in the photos. It's a Kollsman altimter and the ...
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187 views

What is the standard temperature used in this true altitude equation?

The control tower of a certain airport with true altitude of 2000ft informs the pilot that QNH is 900hPa and the temperature at the airport is -10 degrees Celsius. The airplane is at FL300 (vertically ...
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How to get the true altitude in non-standard temperature using a regular barometric altimeter? [duplicate]

I wondering how can we get the true altitude with non standard temperature on regular barometer altimeter, as we know that if we set Kollsman window to the current local setting the altimeter SHOULD ...
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Why is Landing Altitude displayed in amber on B777?

When I set the landing altitude manually, an amber LDG ALT and Landing Altitude EICAS message is displayed. There are no failures nor has the landing altitude been set incorrectly. Why do I still ...
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Are altimeters calibrated to ISA geopotential altitude or ISA geometric altitude?

Altimeters convert a pressure measurement to an indication of altitude. When set to standard pressure setting (1013.25 hPa / 29.92"Hg), they assume the atmosphere is according to the ICAO Standard ...
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What is the altitude of the nose vs tail in airplane flight?

Suppose you have an airplane flying level on a long flight. Now suppose you place one altimeter sensor in the tail, and one in the nose. Suppose you record and store these values independently (...
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How do radio altimeter systems compensate for objects on the ground?

My understanding of a radio altimeter is that it can provide more accurate altitude readings below the transition level. It occurred to me a number of days ago whilst sitting beneath the glide path ...
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Is it possible to get the QNH value in Austria using a web service?

I got a altimeter sensor which can be connected to a computer and can be adjusted by the QNH! I need the QNH for Austria, I figured out that the current QNH of the airports are streamed via radio. ...
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187 views

Who does have a responsibility to make altitude correction for cold temperature?

I work as air traffic controller in Asia and we refer to ICAO and FAA regulations both. As winter is coming, there is a debate on altitude correction(or altimeter correction?) for cold temperature. ...
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How are altimeter settings estimated?

So, I spotted another weird METAR from the same place that spawned the first one I asked about (it's a USAF base if you're wondering what kind of 'drome it is): K... 060846Z 00000KT 10SM OVC002 18/...
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How will the altimeter read in air colder than ISA?

When flying in air which is colder than ISA (International Standard Altitude), how will the altimeter read compared to true altitude? My manual says the altimeter will over read - why?
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How does changing the altimeter setting in the US and elsewhere compare?

I have been trying to track down an answer to this question and I stumbled upon this website. Apologies if this answer is already out there. I have seen the FAR regulation, 14 CFR 91.121 - Altimeter ...
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Why is a TFR issued when barometric pressure exceeds 31.00 InHg?

Why does a barometric pressure above 31.00 InHg trigger a TFR?
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How often is QFE set on an altimeter during flight?

In countries that use QFE rather than QNH (such as China), how often will a pilot set the QFE setting on their altimeter during flight? Is it only when they intend to land at an airfield, or does it ...
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What are “ground-based navigation systems which provide vertical guidance” and how do they compare to altimeters?

I am a total layman when it comes to aviation but for a school presentation I am trying to understand the reasons why Air Canada 624 crashed while trying to land on runway 05 at Halifax (CYHZ). I have ...
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What do the pointers on a Kollsman altimeter indicate?

In this thread: What type of altimeter is this? there are 3 images of altimeters that have a pointer that moves around the outside diameter of the scale markings and they have another pointer that ...
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What is wrong about this interpretation of QFE and QNH?

I'm a little confused about the QFE and QNH definitions, and its application on aviation. I learnt that: $QFE$ = pressure measured by an altimeter which is adjusted to ground level (it gives a height ...
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Is it OK practice to use one altimeter on QFE and one on QNH (local flight, dual altimeters)?

PPL student, wondering on how this practice is viewed. The aircraft I'm learning to fly in has a small Dynon EFIS which displays horizon, airspeed, heading & altitude. It also has a regular ...
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When calculating takeoff performance why include airport elevation in pressure altitude?

When calculating the pressure altitude for aircraft performance I learned to calculate it the following way: Pressure Altitude = (29.92" - altimeter setting) * 1000' + elevation So at an airport at ...
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What is the maximum altitude of barometric altimeters?

An altimeter works by sensing static air pressure. As altitude goes up, the pressure decreases. If I take a barometric altimeter up to space (e.g. up to satellite orbit), at what altitude does its ...
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Where does the altimeter measure from?

During the landing flare, the cockpit can sometimes be twenty/thirty feet or more above the rear landing gear, especially with larger aircraft. http://valkaviation.com/news/wp-content/uploads/...
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How can I calculate QNH from QFE?

Can someone please explain in simple terms how to work out your QNH from QFE? For example, you take off at 0' but leave the circuit, what do you set the altimeter to? How do you know the QNH?
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Why isn't transition altitude standardized in Europe?

In the US, the transition altitude is standardized at 18,000ft, however in Europe it is different for every airport. Why is it not standardized like it is in the US? I could see situations where ...
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What is the meaning of “altimeter three-zero-one-one”?

I've been listening to a lot of liveatc.net recently (mostly at CYVR). What does it mean when the ATC give an "altimeter" reading (usually around the 3000 area). Altimeter three-zero-one-one. I'm ...
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How can an altimetry system error during cruise (500 ft at 35000 ft high) cause an insufficient fuel situation?

So my boss gave me a question today as my daily quiz: Let's say an A321 is cruising on a 6-hour flight. It reaches FL350 30 minutes after take-off. After another 8 minutes there's a discrepancy ...
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When is QFE used?

When is QFE, instead of QNH, used for the altimeter setting? QFE: If you set the subscale of your altimeter to read ... millibars, the instrument would indicate its height above aerodrome elevation ...
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Can a change in altimeter setting make you change the airspace?

If you are at 17999 MSL VFR, you twist in 29.92 into the altimeter, and it raises your altitude to above 18000, did you bust the class A? Then theoretically, could you be in class A airspace with a ...
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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.
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How can true altitude be calculated from pressure altitude, temperature and altimeter setting?

The manual that came with my Jeppensen E6B has the following sample... If an aircraft is flying at 12,500 feet with an outside air temperature of -20C and the altimeter is set on 30.42 inches of ...
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What does one do when the weather report has a bogus altimeter setting?

I saw a METAR for a nearby airport that had A2248 ... SLPNO in it with no maintenance indicator. Is the SLPNO a sign that the altimeter setting in the METAR is untrustworthy as well? How else does ...
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Altimeter disagreement. What's the crew procedure to deal with that?

The crew is facing a situation, in which, the altimeters indicate different altitude (the port and starboard ones - cpt´s and FO´s). Is there any procedure to perform an IFR landing? If we consider a ...
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369 views

Why is the Inertial Reference System not used to determine true altitude?

Given three very accurate laser gyros and accelerometers I believe the Inertial Reference System (IRS) should be as accurate in determining true altitude as it is in determining lat/long, providing ...
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1answer
558 views

Do pressure altimeters take into account differences in temperature? [duplicate]

I work as ATC in Korea and recently, I have some question about winter altimeter setting. In my facility, we use winter altimeter adjustment because the aircraft's pressure altitude is lower than ...
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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. ...
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How accurate is the barometric altimeter in Tu-154?

If the Smolensk disaster was to be traced down to a single decision (other than attempting landing in the first place), it would probably be the choice of radio altimeter to control altitude over a ...
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How is non-standard OAT accounted for?

This pdf from Airbus has a chart from ICAO showing the amount of correction to be applied to altimeter readings for temperatures below 0°C. Do aircraft with flight data computers automatically ...
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1answer
1k views

Does radar altimeter work over the ocean?

I'm wondering if radio waves are reflected by the sea. If so then the usual radar altimeter would work. If not, then is there any other fallback besides barometric altimeter? According to the wiki ...
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Why might an altimeter read incorrectly by 4000ft after sitting on the ground for some time?

My friend landed at Timaru Airport and when he put the aircraft into the hangar the altimeter reading was approximately 100ft [airport elevation is 89ft]. When he got back to go flying two weeks later ...
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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 ...
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If left stationary at a specific height, would altimeter change the displayed value over time?

I have been reading a lot about how altimeters work, and from what I understood, most common altimeters are based of atmospheric pressure to calculate the altitude. The question that I still have ...
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396 views

To which reference point on the aircraft is the altimeter reading relative to?

To which point of the aircraft is the altimeter reading referred to? Is it referred to the probe position or is it offset to read as if it was at the bottom of the fuselage or the landing gear? If it ...
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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 ...