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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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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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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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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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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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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132 views

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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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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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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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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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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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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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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How long does it take to die when we would in altitude that push us to hypoxia? [duplicate]

How long does it take to die when at an altitude sufficient to induce hypoxia ?
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How does cabin pressure vary with respect to ambient pressure during descent?

I came across this statement in a book - "During a descent, the cabin pressure in a pressurized aircraft usually climbs at as lesser rate than ambient pressure". Could someone explain this statement ...
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What is transition altitude?

Now I know the definition of transition altitude - it's the altitude where pilots change their barometric altimeter datum from regional pressure setting to 1013.2hPa. In USA the TA is 18,000ft. But I ...
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Is there a difference between altitude and flight level? [duplicate]

I came across a question in Quora asking the difference between altitude and flight level. One of the answers said that anything above the transition altitude is referred to as a flight level. So ...
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How does an aircraft descend without its nose pointing down?

I have seen many cockpit videos of airplanes landing, and nearly none of them have their nose down for losing altitude. How does this happen? and how does an airplane, such as A320, descend without ...
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Why is ISA Standard pressure 1013.2 not used for contour charts instead of QFF?

I am confused because QFF being actual mean sea level pressure is subject to change why would we use it for mapping terrain? Does this mean the height of a given terrain changes with the change in QFF?...
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Is there a database from which I can retrieve the Expected Crossing Altitudes of a Departure or Arrival Procedure?

I am stuyding FAA's Coded Instrument Flight Procedures (CIFP) file which uses ARINC 424 digital format to code its data. I noticed that only mandatory crossing altitudes and speeds are included in the ...
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Which altitudes are safest for VFR? [closed]

As a fairly new pilot who does a fair amount of x-country flying I find myself "feeling" safer going East at 5500 and West at 6500 happily burning extra fuel to get up there. Listening to the on route ...
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How is the total drag variation with velocity related to altitude?

Here in the question given I am confused how to relate the altitude with the given plot of total drag and velocity.
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280 views

Why does the spool speed increase with altitude for a turbofan engine (single spool & double spool)?

So, I want to see the effect of altitude on the compressor characteristic of a single spool & double spool turbofan engine at constant flight speed and TIT (turbine inlet temp). I am aware that ...
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Why is the B737 altitude display unneccessarily ambiguous?

I was playing FSX again lately and was flying the B737-400. So I hope it is simulated correctly and this question isn't dead on arrival :-) It always bugged me, that the altitude display on the MFD ...
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How do altimeters cope with varying lapse rate?

How do barometric altimeters measure altitude above atmosphere datum if the laps rate of the pressure is not uniform, not constant? Imagine these lines representing pressure lapse rate: ...
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How do flight procedure designers decide when to assign an altitude constraint to a waypoint?

I am studying procedure design manuals (TERPS, PBN 8260.58A manual, ICAO PANS-OPS 8168 manual etc.) and I haven't found any guidelines concerning altitude constraints that can be imposed on a waypoint....
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What is the limit between lower and higher airways in VFR?

On skyvector you see "World high", "world low" and the VFR map. VFR is always under the clouds, correct? But how high do you have to be to follow the high/upper and how high for the low/lower airways?...
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Why cruise at 7000' in an A319?

I was on a flight from Philadelphia (KPHL) to Boston (KBOS), after some delay and some change of route due to weather, the captain announced that we will be cruising at 7000' due to delays in the area....
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Is the transition altitude around Denali still 18 kft AMSL, and, if so, how is this handled?

In North America, the transition altitude - the altitude below which everyone reports their altitude in feet above mean sea level (AMSL) and sets their altimeter to whatever the weather dictates that ...
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How is paint embrittlement countered in high altitude aircraft?

There are cases of aircraft that are not designed for high altitudes that can still fly there and as a result the paint on these aircraft "falls off". Although most aircraft have paint that is chosen ...
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454 views

Why is True Altitude calculated using the difference from the QNH to 1013hPa?

I have an example for true altitude calculation. The given Information is QNH: 983hPa, cruise in FL 85, ISA -10°C in this Alt. The math and calculations are not hard and i also get to the correct ...
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Why use turbofan engines for high altitude flight?

I noticed that a lot of high altitude aircraft have turbofans for engines. So I researched and figured out that turboprop engines are more efficient. But most high altitude aircraft like the Global ...
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1answer
395 views

How do changes in flight affect L/D max and the speed at which I must travel to maintain it?

I have an plane flying at L/D max and I want to maintain L/D max. Firstly, if this plane burns through a portion of fuel and becomes lighter, how would I have to change the speed to maintain it? My ...
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294 views

What is the highest a helicopter can fly?

What is the highest theoretical and current flight a helicopter can achieve?
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Why does V165 have two different MEAs over the same route section?

Why does V165 have two distinct MEAs which vary by a large factor (apart from the 180$^{\circ}$ rule of altitudes) considering they would be clearing the same obstacles and receiving signals from the ...
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Identify a change in Altitude based on direction and WCA applied?

Question below is from study material for the EASA PPL license MET course. It's an unlikely question but it's interesting to review. You are flying from west to east with WCA +6°. How is your true ...
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Why does the Hinch Mountain VOR (as an example) have void areas below certain altitudes published in the U.S. Chart Supplement?

I was digging around the SE region Chart Supplement, and I was reading KSRB (Sparta, TN), and this "VOR unusable" listing is contained in it: The sectional chart shows that it is nearly on top of a ...
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How is The Published Runway Touchdown Zone Elevation Decided?

The touchdown zone of a runway can be up to 3,000 feet long if the information I have is accurate. How is the published Touchdown Zone Elevation determined? Is it the center, an average of the ...
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How can I estimate pressure altitude?

How do I find pressure altitude? Find pressure altitude using rule of thumb for 1498 feet when the altimeter setting is 27.83" Hg. I did (29.92-27.83)*1000+1498=3588 Did I do this correctly?
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Calculation QNE and QNH, with flight level and QNH set lower (higher) than QNE

Hi Student pilot here. Lets say Mr pilot is flying at FL75 and QNH is set at 995 hpa, however there is a mountain in the way at 7000', will he below or above the mountain? If you could visually ...
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Is there a way to code Minimum Enroute Altitude using ARINC 424 file format?

I am studying ARINC 424 file format, and I have noticed that there is not any reserved space for coding Minimum Enroute Altitude (MEA), as far as Instrument Flight Procedures are concerned. I find ...
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How can I figure out critical altitude?

In Vmc situation (minimum speed where pilot can maintain altitude), How can pilot figure out the Vmc? And also, why critical altitude is important to know?
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What is the critical altitude?

What is the definition of critical altitude and why is important to know in Vmc graph? Also, is there any critical altitude in the Piper PA-44 Seminole?
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How are altitudes handled with airports near or above transition altitude?

Transition altitude refers to the altitude above which all altimeters are set to a standard pressure setting (typically 29.92 inHg) instead of to the local surface pressure, and altitudes are given in ...
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Wind vs high altitude cruise [duplicate]

Yesterday I flew back from Tokyo down south against great head wind around 150kt at 34000’, the original flight plan was to cruise at FL240 for a while then climb up, but the captain decided to get up ...
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How much the true altitude will be lower than indicated altitude by 10°C colder?

Aproximately how many perecent the true altitude will be lower than your indicated altitude , if the temperture is 10°C colder than standard ?
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How do pattern and overflight altitudes work for airports underneath Class C airspace?

Lowell City Airport (24C) has an elevation of 700 feet MSL. So normally, the pattern altitude is going to be 1,700 feet, and the altitude for overflying the pattern is going to be 2,200 feet. However,...
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Is there research suggesting that VFR cruise altitude rules improve safety?

In the United States, 14 CFR 91.159 prescribes cruising altitudes for level flight under VFR: (a) When operating below 18,000 feet MSL and (1) On a magnetic course of zero degrees ...