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

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3answers
1k views

Was the transatlantic crossing for Concorde too short to reach optimal cruising altitude?

When listening to Gander/Shannon ATC on shortwave, you could hear Concorde communicate its planned flight levels at longitudes from 20 West till 50 West. What I remember is that it would continue ...
5
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2answers
88 views

Is vertical separation based on geometric difference or altimeter difference?

In the comments below one of the answers to this question about the influence of temperature on vertical separation, the question was raised whether ATC ensure 1000ft vertical separation based on ...
30
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3answers
5k views

Why is 0 ft a valid target altitude for an autopilot?

Inspired by this story; The pilot of a Flybe plane that dropped 500 ft (152m) in 18 seconds had selected the wrong autopilot setting shortly after take-off, an inquiry has found... ...The ...
0
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3answers
120 views

What's the difference between flight level and pressure altitude?

When should we say flight level and when should we say pressure altitude? I know they both set QNE 1013.25, but there is a difference between them. Anyone know?
0
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2answers
113 views

Maintaining straight and level altitude [duplicate]

just a completely random question that I suddenly thought - doesn't straight and level flight prove that the earth's surface is not a globe? Once cruising altitude is reached, the plane remains at the ...
0
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1answer
134 views

Is this a viable way to construct a solar-powered balloon/parachute? [closed]

Is it possible to make a helium balloon with a clear side to create lift from the heat from the Sun entering a transparent side like a hybrid hot air/helium blimp? How would the direction of the ...
0
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1answer
208 views

Why can't I ever get my right ear to pop on descent in a plane?

Whenever I'm flying, there's a period of descent where my right ear just refuses to pop. This has been bothering me for at least ten years. There seems to be a long stage of descent where my ear is ...
-1
votes
2answers
233 views

Is there a rule of thumb for reading AGL vs MSL? [closed]

Recently, I read that as it pertains to directions: if you read it, it's true, if you hear it, it's magnetic. This is mostly correct, one edge case though is runways are written/drawn with magnetic ...
1
vote
1answer
286 views

Why would a plane drop 14.000 ft mid flight?

Just noticed American Airlines flight 221 dropped 14.000 ft mid flight today. Curious, what could have caused this? Here are the flight details.
0
votes
1answer
222 views

Why do planes fly so high? [duplicate]

It so occurs to me that commercial airliners cruise at altitudes of over 30,000 feet. But why do they fly so high if there are many dangers such as cabin de-pressurization when they can simply fly ...
0
votes
1answer
135 views

Calculating the maximum altitude of a drone [duplicate]

Is there an equation to find the maximum altitude that a drone or quadcopter can fly to ?
0
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1answer
301 views

Can a commercial aircraft theoretically reach 60,000ft? [duplicate]

As per this question: Altitudes above 60,000 feet are class E airspace. That means that, if you are lucky enough to have an aircraft that flies that high, once you get there you could ...
4
votes
1answer
335 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 ...
-1
votes
1answer
325 views

How much air does a GE90 ingest at sea level and at cruise level per meter?

I just wanted to know how much air PER METER a GE90 turbofan engine sucks in considering the same thrust output at different altitudes to better understand how the engine can travel further while ...
9
votes
4answers
2k views

What does it mean when ATC says “altitude indicates”?

I've noticed that ATC sometimes calls out traffic (a traffic advisory?) to aircraft using the "altitude indicates" phraseology, and sometimes a specific altitude is given without the phrase "altitude ...
0
votes
1answer
313 views

What are Altitude, Attitude and Heading Hold?

Can someone give a good and simple explanation about these three dynamics? Altitude Hold Attitude Hold Heading Hold
2
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2answers
75 views

How to interpret the published altitudes for each of US STAR procedures?

I have been studying the STAR procedures, as published by FAA, and I am trying to understand the way that the altitudes are defined for each fix/route. Take, for example, CAMRN4 of JFK. I see the MEA ...
2
votes
0answers
253 views

How do I calculate true altitude? [duplicate]

Currently doing my CPL and in class we were shown a formula on how to calculate the true altitude, which as I understand it is the distance between the ground and the plane while taking into account ...
6
votes
1answer
329 views

Why do we say “climb” and not “ascend”?

The term for moving to a lower altitude is "descending." Why, then, is the term for moving to a higher altitude "climbing" and not "ascending"? The latter goes better with the term "descending." Does ...
0
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0answers
44 views

Why do NY ARTCC Standard Operation Procedures have different altitude limits than the NY Class B airspace?

The NY Class B airspace is defined, officially, as seen in this document, which can be found in the VFR Class B Graphics in the FAA website. In this graphic (and in the corresponding shapefile, Class ...
1
vote
1answer
166 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 ...
2
votes
2answers
129 views

Does the reference for AGL include obstacles?

Let's say a plane flies 10m above some trees, that themselves are 10m above the underlying ground. Would that be 10m or 20m AGL? Or, in more abstract terms: What exactly is the reference point for ...
17
votes
3answers
2k views

What is the maximum altitude ATC would deal with?

What's the maximum altitude ATC would deal with? Any example of jets service ceiling certified for above 45.000? Commercial & Business jets?
3
votes
3answers
470 views

What is the relation between drag and weight?

Given an aircraft type and fixing its wing configuration (flaps, slats) and fixing its speed and altitude and assuming it flies horizontally, what is the relationship between the aerodynamic drag and ...
3
votes
1answer
473 views

How can you find AGL if the altimeter is set to MSL?

Without doing the math, how do you know your true altitude AGL when your altimeter is set to MSL
1
vote
0answers
267 views

Why do high altitude sky-divers say 'Exit' multiple times?

This is something that has always puzzled me. https://sndup.net/6vn8/a Unfortunately, I can't find a video in which I heard them say it, but right before they left the plane, I heard Exit exit ...
25
votes
2answers
3k views

How exactly can an airship lose lift?

On this wiki page (under 'Comparison with heavier-than-air aircraft'), the altitude record of the L-55 Airship states: The ultimate altitude record for a rigid airship was set in 1917 by the L-55 ...
9
votes
2answers
693 views

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 ...
6
votes
2answers
247 views

What is the reference point for AGL? [duplicate]

I am about to start my PPL soon (still flying in FSX) and I do not understand one thing. As per FAR 91.159 if my altitude is above 3000' AGL I must maintain certain altitude depending on my course, ...
18
votes
6answers
6k views

Would a slower speed and lower altitude reduce fatal incidents?

If it became plausible to fly commercial aircraft much lower in the future (due to developments in technology and airway regulations permitting it), say at a standard height of 5,000ft, but with a ...
1
vote
1answer
258 views

Why do some airplanes fly at a very low speed (like this one) at a speed of 433 km/h (234 knots) at a whopping high altitude of 26,500 ft?

Okay. So I'am just having a doubt on this flight (BA359) flying from Lyon, France en-route to London Heathrow. It is flying at a way low speed of 433 km/h (234 knots) in which i think is a bit weird. ...
16
votes
1answer
1k views

On Air France 447, what would have been the lowest altitude to initiate recovery after the stall developed?

What could the lowest altitude of Air France 447 have been to recover the (stalled) flight, where the co-pilot informed the captain that he was pulling up the whole time? The co-pilot didn't inform ...
1
vote
1answer
276 views

What VFR cruising altitude should be flown to the west below 4500 feet?

This is similar question to this question, but different scenario. Let me describe the situation: I am at KDYL in class G airspace. Accroding to ATIS the clouds are at 4700 scattered. I am going to ...
9
votes
3answers
575 views

How do I know my AGL altitude while in flight?

I am about to start my PPL, still flying in my FSX. I have a question, let's say I am flying from airport A to airport B. Both airports are in G airspace and I would like to stay in G airspace and ...
12
votes
1answer
741 views

Why are there non-standard altitude callouts?

I just saw a YouTube video with an A340 landing. There were the regular altitude callouts (1000, 500, etc.) until the callout "110". I was quite puzzled by this. What are the conditions that the ...
0
votes
1answer
196 views

What Height Atc radar reads from pilot selection [duplicate]

Just want to know whether ATC radar always reads aircraft height with respect to standard altitude setting or will read the change in height if we select QNH instead of standard 1013 hPa (QNE)?
0
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4answers
766 views

How to calculate altitude in a flight simulation?

I guess altitude from sea level in the real aircraft is read from barometer, while for the altitude from ground a radar is used. For the purposes of very simple simulation, and assuming aircraft is on ...
6
votes
1answer
156 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. ...
2
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1answer
317 views

How is cloud height measured?

In general, cloud height is measured from ground or AMSL (above mean sea level)? If they measure from AMSL, how are low level clouds' height measured in higher terrain?
7
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2answers
656 views

How slow could the U-2 fly at 50,000 ft?

How slow could the Lockheed U-2 fly at 50,000 ft? It was surely subsonic as its max speed is 500 mph.
15
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2answers
1k views

Which source to use when reporting the current altitude to ATC?

While flying from KSNA to KVCB VFR at night, Norcal Approach asked for my current altitude. I was somewhere between 12.0 and 12.5 depending on which reading I was going to use. ATC had me confirm. ...
2
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1answer
137 views

Why is there a provision of pressure setting in GPS?

Some of the GPS have a provision of setting barometric pressure (QNH/QFE). How does it work?
4
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1answer
646 views

What is the highest operational ceiling for an air breathing jet engine?

Air breathing jet engine can only operate at relatively low altitude where atmosphere is dense enough. But some jet aircrafts can operate at an altitude higher than 20 km (e.g. the SR-71). For really ...
2
votes
2answers
181 views

Why isn't the Transition Altitude depicted on SID charts?

Why isn't the Transition Altitude depicted on SID charts? I would assume it would be a relevant information to be presented on this type of chart.
0
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1answer
132 views

In the ARINC specification, why is baro altitude (label 204) measured in Knots?

I am currently designing a system that reads the baro altitude (on label 204) from an LRU. Ultimately in my software I would like to display the baro altitude reading in real-time using a graphical ...
6
votes
1answer
674 views

Why do some countries separate a transition level and a transition altitude?

The US airway system uses a single transition level (or altitude), but some other countries like China separate a transtion altitude and a transition level with the transition layer in between. ...
13
votes
3answers
2k views

What is the geoid undulation used for in aviation?

In addition of the altitude found on aerodrome information, the French AIP also mentions the value of the geoid undulation:: AIP for Lyon - Saint Exupéry (LFLL) Geoid undulation is also found in ...
3
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1answer
479 views

Why are the transition altitudes/levels different around the World?

I got tasked by my instructor pilot to find out why each country has a different transition altitudes / levels. For example in the US it's FL180 and in Saudi Arabia it's FL150. Can someone help me ...
6
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2answers
150 views

Can different departure procedures have different transition altitudes at the same aerodrome?

Is it possible for operations and ATC to have different departures procedures with different transition altitudes at a single aerodrome? For example: SID RWY11 with a transition altitude of 2,000 ...
1
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2answers
257 views

Are airliners' cruising altitudes we know indicated or true altitudes?

Are airliners' crusing altitudes, which commonly range from 25000 to 45000 feet depending on various conditions, indicated altitudes or true altitudes? If they are indicated altitudes, what are the ...