# 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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### 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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### Ceiling parameter Derivation

I read the absolute ceiling of an adequately powered airplane is determined by the formula, $\frac{W}{S} = \frac{1.4}{2} p M^2 CL$ Where, $W/S =$ Wing Loading $M =$ Mach Number $CL =$ Lift Coefficient ...
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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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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 ...