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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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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33 votes
1 answer
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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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8 votes
2 answers
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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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1 vote
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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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1 vote
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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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6 votes
1 answer
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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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What is the minimum altitude needed to return to the takeoff airport in a 737 after dual engine failure?

Last week, I had my first lesson in a 737 sim. The instructor, when talking about risks with flying the 737, said the only time it would be "game over", would be if you had a double engine ...
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How to calculate density of ISA+10ºC at 11705m? [closed]

I know how to calculate the density under normal ISA conditions at a given altitude, but I'm unsure about how to go about calculating it at ISA+10ºC, or at any ISA+XºC conditions.
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How is a design cruise altitude picked? [duplicate]

Different planes have different design cruise altitudes, given by the manufacturer. You can find these in their Airport Planning Manuals or in Jane's All the World's Aircraft. I know that the first ...
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1 vote
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Do aircraft travel faster at higher altitudes?

I'm aware of the difference between TAS and IAS, and how IAS gets lower in reference to TAS as you climb and the air gets thinner. What I'm trying to figure out is whether or not an aircraft's IAS ...
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8 votes
6 answers
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If absolutely nothing changes except temperature, does indicated altitude increase, decrease, or stay the same?

I have gotten conflicting answers from CFI's on this one. In bold are the only things that changed or would potentially change. Initially: Aircraft is parked at a very dry (to factor out humidity) ...
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2 votes
1 answer
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Can a hybrid electric turboprop reduce fuel consumption 30% on regional flights?

UTC has a hybrid electric research project called Project 804, in which it claims that augmenting takeoff turbine power with electric power allows a smaller turbine for cruise, thus saving 30% of fuel ...
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What happens when I set my altimeter at the starting of my flight?

When I set my altimeter to 29.92 mm Hg, I have my pressure altitude. However, what am I doing, when I set my altimeter before each flight. My instructor tells me to hear for AWOS, and set the ...
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5 votes
1 answer
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What was the most efficient cruising altitude of the Lancaster bomber?

An earlier question concerning lower high altitude cruising fuel efficiency of the B-29 bombers with 4 x Wright R-3350 air-cooled radial Cyclone engines made me wonder about the Lancaster bomber, ...
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2 votes
1 answer
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Is the true altitude always lower than the indicated altitude as long as a correct local altimeter (QNH) is set on the altimeter?

Given the fact that the altimeter setting is corrected for the temperature of the airport, on the condition that a correct local altimeter setting (QNH) has been made to the altimeter, is the true ...
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What is the altitude record for the F/A-18 Hornet?

Does anyone know how high (above MSL) the F/A-18 ever went? Its service ceiling is 50,000 ft, but when going up steeply, is it able to surpass 100,000 ft altitude?
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Is there a regulation that defines when to use QFE or QNH for landing?

Is there an EASA regulation that says to use QFE or QNH when landing?
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What is baro corrected altitude?

I have data from an aircraft which I am trying to understand. One column contains the baro corrected altitude (in ft, e.g. 256) and another the pressure altitude(also in ft, e.g. -44). The two example ...
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Why doesn't temperature affect Pressure Altitude?

In this picture: it states the tops and bottoms of the 3 columns of air have the same pressure. This explains the error in altitude indications given in a non-standard temperature. Pressure only ...
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4 votes
1 answer
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How to obtain true altitude from indicated altitude, temperature and QNH?

maybe it's a little impolite to ask but I got stuck with knowing bunch of formulas and not understanding how to use it: Can you help me on understanding how the correct answer 7300ft came out of the ...
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0 votes
2 answers
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What airspeed is required at sea level to create the same aerodynamic pressure as cruise altitude?

I would like to know what speed would be required, at sea level, to exert the same aerodynamic pressure as experienced at cruise altitude. For example, if an airliner were traveling at 500kn at 35,000'...
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18 votes
4 answers
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Is air to air refuelling possible at "cruising altitude"?

When an aircraft uses air to air refuelling are there constraints on the maximum altitude this can take place at? For instance I'm guessing that a Boeing Globemaster when on a long journey would ...
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Why is Transition Altitude fixed but Transition Level is not?

In Jeppesen approach plates we see that the Transition Altitude of the aerodrome is fixed but the Transition Level is not fixed and is given by ATC. What is the reason for this?
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4 votes
2 answers
326 views

Can Transition Altitude (TA) and Transition Level (TL) be equal?

In Europe, is it possible that Transition Altitude and Transition Level are equal, that is, TA=8000 ft and TL=FL080? In that scenario, at 8000 feet, what pressure (QNH or QNE) should be set in the ...
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How can I work out Sea Level Pressure from QNH?

I am a little confused, is the QNH the current pressure at Sea Level? Therefore putting it into the altimeter will give your current altitude on the ground in pressure altitude relative to current sea ...
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4 votes
1 answer
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Is it likely that an aircraft could have been near 10° 08' north at local midnight August 26/27, 2003?

Edit: The astronomical data turned out to be different. I'm keeping the constraints below as they where, but those are not relevant to finding the closest person to Mars. This is part of an effort to ...
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2 votes
2 answers
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How does altitude affect the TAS and thrust of an electric fan powered aircraft?

I'm confused about the relation between IAS, TAS, thrust, and shaft power, for an electric application. Yes, higher air is thinner, and thrust goes down due to higher airspeed. What I've researched ...
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15 votes
3 answers
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How high can a ramjet go?

Yesterday, there was an off-topic question on Space.SE, asking if a ramjet-missile could place itself in orbit. Impossible for a ramjet, obviously, as it requires a high speed flow of air and is too ...
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What is the definition of "geometric height" referred in the ISA Model?

The International Standart Atmosphere document always mentions the "geometric height" (along with the geopotential hieght) in their calculations. I predict that it means orthometric height, ...
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6 votes
2 answers
601 views

How high could Concorde potentially reach by going fast and pulling up?

If Concorde was travelling at mach 2 and FL 600 then pulled up, it would enter a trajectory that went above its normal flight altitude before diving back down. I assume that it couldn't pull up to ...
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3 votes
2 answers
703 views

How is Altitude/QNH defined state when passing transition altitude?

Let's say an airplane is climbing towards transition altitude (TA = 5000 ft), and it has it's altimeter set to QNH = 1030 hPa. ...
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7 votes
2 answers
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Can climbing above RVSM airspace cause temporary loss of separation with an aircraft in RVSM airspace?

Consider Aircraft A cruising at FL400 and Aircraft B cruising at FL410. Both in close proximity, heading in the same direction. Ignore altitude for direction of flight issue. When aircraft B requests ...
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0 votes
1 answer
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Is QNE pressure altitude? [closed]

In trying to understand pressure altitude better, am I wrong or right when I say this? I am at an airfield. The pressure altitude at that airfield is 200 ft a.m.s.l. If I set subscale 1013 mb on my ...
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2 answers
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How does fuel economy quantitatively depend on altitude for a jet?

We already have a few questions and answers about the qualitative effects of altitude on fuel economy: How do I determine the best altitude to fly for fuel economy? Why does fuel consumption decrease ...
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Could a plane take-off at 20,000 feet above sea level if the temperature is above freezing?

I’ve read that “humans have survived for two years at 5,950 m (19,520 ft, 475 millibars of atmospheric pressure), which is the highest recorded permanently tolerable altitude” and that “Daulat Beg ...
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Why can APU supply both bleed air and electrical power up to 10.000 feet but bleed air alone up to 17000?

I am reading my company's FCOM and I saw there the following information. APU Bleed + Electrical Load: Max Alt 10000 ft. APU Bleed: Max Alt 17000 ft. APU Electrical Load: Max Alt 41000 ft. If APU ...
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14 votes
3 answers
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How high can an airplane be spotted with eyesight?

How high can an airplane be spotted with eyesight? Suppose a plane has a wingspan of 15 m then at what distance it will appear as a faint dot? What is the correct way to calculate this?
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1 answer
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What was the record for the highest man-made flight before Gagarin's spaceflight?

My recent conversation with uhoh reminded me of something which stays kind of unmentioned in history of air and space flight, namely the altitude record prior to Gagarin's Vostok 1 mission. I wonder ...
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2 votes
1 answer
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What is the altitude required to bypass Russia's airspace restrictions for airlines? [duplicate]

Given that Russia charges a lot for flights over Siberia from Europe to Asia, would flying above the Kármán line (100km) effectively bypass this restriction (from legal perspective) ? If not, what ...
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0 votes
2 answers
401 views

Is there a standard international Minimum Obstacle Clearance Altitude (MOCA)?

In Turkey, the Minimum Obstacle Clearance (MOC) in primary areas is 300m; what about other countries and region?
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2 votes
2 answers
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What does the altimeter indicate if it's at a certain elevation

The purpose of the altimeter is to show the pilot the altitude and the pressure above a fixed level. It uses barometric pressure and is 29.92Hg in ISA conditions. What I dont understand is, how can ...
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