# Questions tagged [altitude]

A measurement of vertical distance. Usually measured at either Mean-Sea-Level (MSL) or Above-Ground-Level (AGL).

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### What is meant by altitude correction above Transition level?

I am a system engineer dealing with Thales ATC product. In my system there is a server called sensor data processor, one of its function is to receive QNH data to do altitude correction. I can't ...
1 vote
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### How does elevator control effectiveness change with altitude/ air density?

Suppose an unpowered, rigid, mechanical, lightweight aircraft (e.g. sport glider) is descending at a steady glide in a constant trim (hands off) configuration in a standard atmosphere. The pilot ...
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### How can skydivers start at 15,000 feet without the jumper suffering from hypoxia?

Many commercial skydiving facilities offer jumps at 15,000 ft. However, when I took my ground theory exams, it was reiterated many times that hypoxia starts at 10,000 feet. How does this work? Is it ...
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### What is a good sight picture for telling urban vs rural areas (wrt minimum AGL)?

I'm studying for PPL and am struggling to imagine a clear "sight picture" for urban vs rural areas with regards to minimum AGL. I found that urban areas are outlined over at the Federal ...
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### how to determine the optimum FL for A320 to make a flight plan?

I want to make an ifr flight plan for A320 based on fcom, but I don't understand how to make one
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### How is true altitude derived? [duplicate]

I read everywhere that the true altitude is computed as: True Altitude = Indicated Altitude + (ISA Deviation × 4/1000 × Indicated Altitude) But why is that the case? How is that derived? Where does ...
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### Is there anything important to know about flying at ~9000ft for the first time?

When I did my NPPL training, there was a module on flying at minimum altitude, but nothing around high altitude flying, in fact, I've never flown over 3,500ft. This weekend, I intend to fly up to ...
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### Am I correct about how airships control their altitude?

I have read about how airships work, especially about how they control their altitude. Because what I understand from readings about the Zeppelin airships is that they were able to perform long range ...
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### Is it possible to calculate Calibrated Airspeed from True Airspeed, Temp, and Pressure Altitude? [duplicate]

Looking at a digital E6B, there is a function for calculating CAS that I am trying to recreate and program myself. Inputs: Pressure Altitude Temp in Celcius True Airspeed Outputs: CAS Mach # ...
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### What are the component terms that make up this pressure altitude calculation?

I am a bit confused by pressure altitude, in my ground school we were taught and equation ((29.92 - altimeter setting)*1000)+ altitude) is equal to something. I believe that something to be pressure ...
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### What altitude does the "Apt Elev" on the Jeppesen charts represent?

What altitude does the "Apt Elev" on the Jeppesen charts represent? According to my research, the height we call "airport elevation" indicates the highest altitude on the landing ...
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### Why do all trend vectors in the G1000 on airplanes indicate the status 6 seconds later? Why 6? Why not 5 or 10?

Why do all trend vectors in the G1000 on airplanes indicate the status 6 seconds later? Why 6? Why not 5 or 10? The fact that the trend vector shows after 6 seconds allows us to turn 3 degrees per ...
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### Who was the first person to fly above 20,000 feet, and what aircraft was used?

Oh! I have slipped the surly bonds of Earth And danced the skies on laughter-silvered wings; Sunward I’ve climbed, and joined the tumbling mirth of sun-split clouds, — and done a hundred things You ...
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### How was altitude calculated before the invention of the altimeter?

I just read David McCollough's "The Wright Brothers," and was surprised to find several references to the exact altitude attained by various Wright airplanes. For example, on page 235: The ...
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### Although the missed approach point in the profile view is 1.1 DME-400 feet, the GS out reference altitude is given as 410 feet in 1.0 DME. HOW?

Although the missed approach point in the profile view is 1.1 DME-400 feet, the GS out reference altitude is given as 410 feet in 1.0 DME. HOW?! Based on GS out reference altitudes, we are expected ...
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### Why don't the Altitude-DME values in the approach profile match the Groundspeed-FPM values in the conversion table?

Why don't the Altitude-DME values in the approach profile match the Groundspeed-FPM values in the conversion table? When the calculation is made with the values given in the conversion table, the ...
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### Why are the altitudes on an RNP IAC shown on the point while for a conventional approach are parallel to the route? Is there an actual difference?

The RNP approach for LGIR runway 27 has the altitudes on some of the points underscored. I had the impression (and I'm afraid I'm wrong) that these are "crossing restrictions" and the ...
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### Does this symbol in the pictures below represent height above ground level or altitude above sea level?

Does this symbol in the pictures below represent height above ground level or altitude above sea level? There are huge differences between them and the Grid MORA values, so I think there may be ...
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### ADSB DF17 Altitude decoding

I develop ADSB DF17 messages decoding device. I see that barometric height decoding differs between documents, describing the encoding standard: https://mode-s.org/decode/content/ads-b/3-airborne-...
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### Payload capacity of a quadcopter/helicopter with increasing altitude

I am trying to create a simplified model of a heavy-lift drone payload at different altitude during hover mode. I tried to derive it simply by considering that the thrust, $T$ is equal to the weight ...
1 vote
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### Why does true airspeed decrease with altitude?

I was having a discussion with a friend who's going for a record speed over distance attempt. We were discussing which altitude will have the fastest TAS, and I suggested it would be the highest ...
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### What difference does altitude make on fuel efficiency? [duplicate]

Most commercial flights are between 29,000 and 42,000 feet in altitude apparently. But I realise I don't know why. My guesses are: If you fly too high the air pressure gets very low and you have to ...
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### Does baro altitude from ADSB represent height above ground level or height above mean sea level?

I am retrieving ADSB data from Opensky-network.org. I would like to know what the baro altitude represents, is it the height above ground level or above mean sea level ?
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### Confused about this Pressure Altitude vs True Altitude Question

The standard question on a knowledge test: "Under which condition will pressure altitude be equal to true altitude?" The answer is: "when atmospheric conditions exist, i.e., 29.92" ...
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### How to convert barometric altitude to gps altitude? [duplicate]

In my work I have some challenge with an aircraft altitude values: I was provided with some data from aircraft flight in my country. The data contains variety sensors data (like lat, long, altitude, ...
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### How to compute the airspeed change based on the Altitude change

The plot shows that: when I fly with fixed MACH, the true air speed decreases when the altitude increase; when I fly with fixed CAS, the true airspeed increases when altitude increase. So how could I ...
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### Why did this flight, that usually flies around 40,000ft only fly at around 29,000ft for the route?

Looking at the flight BY6272 BRS-PMI, it was considerably delayed and flew (according to the flight radar app) at 29,000 feet rather than its usual 40,000 for this same route. It is a Boeing 787 ...
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### Is it safe for a huge all black helicopter to be flying BELOW 500 feet over my house, for an hour now, spraying pesticides all over the area

How dangerous is it for a huge all black helicopter to be flying below 500 feet over my house, for a half hour now, spraying pesticides all over the area and my farm animals. It is shaking the whole ...
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### Is the ISA still up to date?

The Standard Atmosphere dates back to 1962 when Earth was colder. The 1976 update didn't make changes within 50 km altitude (the tropo- and stratosphere). It assumes 15°C at sea level, decreases until ...
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### Does a plane's service ceiling vary with season/temperature?

Aircraft use barometric altitude, e.g. FL300 is the barometric altitude of 30,000 ft MSL. In winter however, FL300 is actually lower than the absolute altitude of 30,000 ft because of a cold and ...
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### What was the reason for my flight’s low cruise altitude?

I’m a fairly new aviation enthusiast and am just curious to know the answer to this question. I flew Boston to Newark yesterday 14/6/22 (UA2396) and we cruised at or under 16000 feet for the whole ...
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### Why does ADS-B altitude from multiple landed planes vary so much from one plane to another?

When viewing ADS-B data from sites like FlightAware and Flightradar24 (and also from a personal antenna), the landed altitudes vary greatly from one aircraft to another. What accounts for this ...
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### Is it appropriate to determine approximate flight altitudes based on ADS-B landed altitude compared to runway elevation?

For small aircraft flying below 2,500 ft. AGL, is it appropriate to compare the landed ADS-B altitude (pressure calibrated AMSL) to the elevation of the runway in order to compute a reference offset ...
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### Minimum Safe Altitude vs Emergency Safe Altitude

Is there a difference between Minimum Safe Altitude and Emergency Safe Altitude? Or are they same things used by different authorities (MSA by EASA and ESA by FAA)?
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### What is the operating altitude of jetliners?

I am performing a science project, and this involves knowing the average operating altitude at which commercial passenger airplanes (jetliners) fly. I am trying to find minimum operating altitudes and ...
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### Do pitot tubes account for reduced pressure at altitude?

Do pitot tubes account for reduced pressure at altitude? Does indicated airspeed reduce with altitude? If so, how much? Is it different for small planes vs big commercial airliners?
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### What is the AeroVironment Helios' Kármán line?

If it's true that the NASA/AeroVironment Helios maintained level flight 96,000 ft above sea level at a maximum airspeed of 23.5 kts (43.5 km/h) I assume it must have a very high Kármán altitude, the ...
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### Is the U2's 74,000 ft the highest a turbofan plane ever has gone?

What is the altitude record for a turbofan? The (usually) turbofan-powered U2 has gone to 74,000 ft (22.6 km) MSL, but did any turbofan plane surpass that, in a zoom climb for instance and with ...
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### At what altitude can the sonic boom no longer be heard at sea level?

As others have stated here, you can hear the sonic boom of planes flying by at a fairly high altitude, ~80 000 ft. At what altitude would the sonic boom no longer be noticable at sea level? To add to ...
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### Would an airliner climb higher late in the flight because of the consumed fuel (lighter airplane) to save more fuel?

Some people said airplanes would fly higher in the late period of each flight, because the fuel is consumed, and the airplane is lighter. Higher altitude and less dense air is enough to support the ...
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### Air density decreases as temperature increases - but air also gets cooler as it expands; does this create a feedback loop? [closed]

First, I apologize for the sloppy title. I had a tough time phrasing this as a concise question. For a column of air at a given pressure, density decreases (the air expands) as temperature increases. ...
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### Do private jets ever fly at FL510? If so, at what occasion?

Most private jets have a service ceiling of 51,000 ft. A service ceiling is the altitude at which a plane can climb no more than 500 ft/min, right? However, on flightradar24 I don't remember having ...
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### Is a balloon's record altitude measured from the top of canopy, the bottom of the basket, or some other point?

I wonder where exactly on the balloon is its altitude measured. By the time a space balloon reaches its maximum altitude it is extremely large, the higher the larger. The record altitude for a balloon ...
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### Is there a place where altitude while flying is negative?

while testing and working with avionics systems I have never seen an altitude near 0 or negative. Is there a place when flying above the Altitude tape shows -ve value ? Maybe while flying between ...
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### Are ERA5 Pressure Level and ADS-B Geometric Height comparable?

I have two wind data sets that I want to compare: a) Aircraft derived data (ADS-B and Mode-S). b) ERA5 Reanalysis data. To compare both I need altitudes to be comparable. On data set a) I have the ...
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### How can I compute indicated altitude?

I would like to compute what an altimeter would display given a true altitude and atmospheric conditions. Specifically: Given: True altitude, in feet Outside air temperature, in degrees C Local ...
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### Correcting uncorrected pressure altitude on recorded data

I have some recorded commercial flight data that contains altitude readings defined as "uncorrected pressure altitude." So I have a sequence of lat/lon/alt/timestamps as the aircraft travels ...
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### How to most likely get a flight that will go above 40,000 ft?

I wonder if there are passenger flights that would reach cruise altitudes higher than 40,000 ft (i.e. reach 41,000 ft for instance) more likely than others. It also depends on the plane of course, but ...
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