47

In a word, the tropopause. Gas turbine engine efficiency improves with colder & denser air. As an airplane climbs through the troposphere, the density & temperature both drop, and the loss of density is more than offset by the lower temperature. Above the tropopause, however, the density continues to drop while the temperature holds (approximately) ...


39

Flight levels use QNE or pressure altitude, while altitude references QNH or local pressure adjusted to sea level pressure. Altitudes are used at low levels and flight levels at higher levels. The transition between altitudes and flight levels differs by country and is generally just above the highest obstacle in that country. In the US the transition ...


32

There are multiple factors that affect an aircraft based on its cruise altitude. The cruise altitude directly affects the aircraft pressurization and aerodynamics. In order to keep the cabin altitude around 6000 to 8000 feet, the fuselage would have to withstand a higher pressure differential. This would require more material, and make the plane heavier. ...


25

I know there is already an accepted answer, but some key facts are missing. Mainly, the optimum cruise altitude is where thrust and lift requirements for both take-off and cruise balance well. An additional benefit is the cooler air which increases the efficiency of heat engines. With increasing flight altitude, the airliner needs: Bigger engines to ...


19

For flights above FL410, 2000 feet of separation is used. Which makes all flight levels odd numbered, →410, ←430, →450, ←470, →490, ←510, ... So for each direction as indicated above by arrows, it'll be 4000 feet. The 2000 feet separation is because the higher up you go the less accurate an altimeter becomes, so it's for safe separation. Even/odd is just ...


16

This can be calculated by knowing a few formulas, or temperature relationships related to altitude. Note that all these calculations are an estimate based on standard ISA temperature and altitude relationships. See this page for other examples of this type of question. Note the following from the question: FL170 represents a pressure altitude of 17,000 ft ...


13

Every country's Civil Aviation Authority issues an Aeronautical Information Publication (AIP) as part of their Aeronautical Information Services (AIS) which contains the information you are looking for. Most likely the information about Flight Level rules will be contained in the GEN (General) or ENR (En-Route) section. For Europe, most information from the ...


12

FLC mode maintains airspeed during a climb or descent, while VS mode maintains a specific vertical speed. Often air traffic controllers will request that you "maintain 250 knots in the descent" or something to that effect, which is much easier to achieve when using Flight Level Change. As another answer points out, by maintaining airspeed, climbs are made ...


12

FL180 and FL300 stand for Flight Level 180 and Fight Level 300. Flight levels are spaced 100ft apart on an altimeter that is set to the standard sea level pressure (QNE) of 1013.25 hectopascals or 29.92 inches of Mercury. So indeed, FL300 means 30,000 ft. Altitude 18000 means that the altimeter indicates 18,000 feet and that the altimeter is set to the ...


11

(Source) The basics Height: absolute height above ground, measured using a radar altimeter (like the helicopter on the right) QFE: the barometric setting an airport broadcasts that makes an altimeter on ground read zero. This gives height only around the airport if the area is relatively flat. Also known as Above Field Elevation QNH: the barometric setting ...


10

The flight plan contains the requested cruise flight level, as well as step climbs or level changes along the route in the route field. Example 1: (Image Source: skybrary.aero) Example 2: SAM UN621 BASIK/N0412F330 UZ150 BADUR/N0426F340 UN472 ARE/N0424F350 UN864 PIMOS Fxxx being the requested flight level.


10

Just MHO: Vertical speed should never be used when climbing because you could stall if insufficient power is added for the requested climb rate. Using FLC when climbing guarantees you maintain the best airspeed (best rate or best angle, depending on the situation) On the other hand, when descending I always use VS mode because it gets you down to the ...


9

They are different modes that control aircraft pitch in different ways, and as a pilot you select what you want based on your current requirements. Note that the modes even behave differently depending on the aircraft / autopilot, so referring to the actual aircraft/autopilot documentation is essential. Many autopilots don't even have a Flight Level Change ...


8

Asia Hong Kong: 9,000 feet Africa South Africa: fixed and to be at least 1000 ft above the highest ground within 25nm radius of an airfield (AIC 20.2) Europe Belgium: 4,500 feet (AIP Part 2,, ENR 1.7.2) Netherlands: 3,000 feet (IFR) / 3,500 feet (VFR) (AIP Part 2, ENR 1.7.1.1) Oceania Australia: 10,000 feet MSL (AIP ENR 1.7 (2.1.1)) New Zealand: 13,...


7

Altitude The vertical distance of an object measured from mean sea level. Flight Level To understand a flight level, we should understand how altitude is measured in an altimeter, which is essentially a calibrated barometer - it measures air pressure, which decreases with increasing altitude. To display correct altitude, a pilot re-calibrates1 the altimeter ...


7

In addition to ymb1's excellent answer, here are a few thoughts from the controller perspective. Various rules and regulations for cruising level allocations exist. For flightplanning purposes, the semicircular rules are very notable. As pointed out by ymb1, the exact rules vary from place to place. In some regions, flights flying on a westbound track shall ...


6

According to the EUROCONTROL Performance Database, the usual climb rates and speeds for an A320, for ATM purposes, are those depicted on the image below: Source: https://contentzone.eurocontrol.int/aircraftperformance/details.aspx?ICAO=A320&ICAOFilter=a320 Note that rate of climb (ROC) is given in feet per minute, not degrees. If measuring degrees, you ...


6

By definition, the transition level is the lowest usable flight level above the transition altitude. So if there is a transition altitude, there is a transition level. In the USA, the transition altitude is 18 000ft. If the QNH (altimeter setting) is higher than 1013.25 mbar then the transition level is FL180. This provides at least 1000 ft separation from ...


6

Agreeing with @Antzi, high engine speed when combined with some sort of small scale physical damage or corrosion is a typical failure mode for propeller engines. Combining that logic with the fact that propeller engines run more efficiently at lower elevations (higher air density) I would recommend against climbing. In fact, lowering your elevation and speed ...


5

If ATC offered me a heading change or an altitude change and I was happy with the altitude I was at, I'd take the heading change in a heartbeat. Compare: Altitude change: Dial the alt preselect up. Select speed or VS mode (usually speed). Set climb thrust. Monitor the capture. As the AP captures and pitches over, start bringing the thrust back to keep ...


4

The ATC Flightplan (FPL) does not directly contain the optimum cruise levels for a flight. These levels are calculated and printed in the Operational Flightplan (OFP). The FPL does contain the requested cruising levels for the flight along its planned route. The requested flight levels (RFL) in the FPL will often be quite close to the optimum cruising ...


4

No. The transition attitude in a defined area is fixed. For example, in the USA it is 18.000ft and in many European countries it is 5.000ft. It's impossible to have different transition altitudes at one airport, because that would make it impossible to use vertical separation between aircraft close to the transition layer.


4

There are a few kinds of traffic advisories but generally pilots don't (and can't) have a preference at least not one they can generally act on. Keeping routes as short as possible and staying on time is what any pilot wants but you cant always get what you want! Those that come from TCAS require a quick climb or dive and preference is irrelevant you do ...


4

Good question! First practical detail to note would be that I doubt there is any airplane with such stability (without electronic aids etc) that you could left flying hands-off for long enough period to perceive effects of Earth curvature without other disturbances affecting flight path and attitude much more. But lets take this as a theoretical problem: ...


3

puts the aircraft higher in the sky What you are talking about, above your standard altimeter adjustment is altimeter/temperature Error Correction. The article describes when to apply corrections generally speaking and what should be applied. In short pressure altimeters are calibrated for standard lapse rate so if the air temperature changes at a constant ...


3

I will attempt an answer, although the question is a bit unclear. Climb rate is not measured in degrees or any other angle measurement unit. It's altitude per time unit (feet per minute usually). What you are mentioning is the climb gradient. See relevant question for details Now regarding your questions: Do climb rates for a given flight mission stay ...


3

ICAO PAN-OPS (v1) 2.1.2.2: "Where two or more closely spaced aerodromes are located so that coordinated procedures are required, a common transition altitude shall be established. This common transition altitude shall be the highest that would be required if the aerodromes were considered separately." – mins 2 days ago This comment should be the answer for ...


3

The answer is yes they're separated, but not necessarily with the East/West Odd/Even rule. Exceptions to the rule are: The airway is one-way: For example North Atlantic Tracks and some over land airways are by design one-way. Flights above FL410: 2000 feet of separation is used. Which makes all flight levels odd numbered, →410, ←430, →450, etc. If the ...


3

The adoption of semi circular rules is not meant to prevent collisions on its own. Rather, it is one of several safety nets contributing to a safe and orderly flow of air traffic. In uncontrolled airspace, normal rules of the air apply, for example, two aircraft meeting head on must both alter their heading to the right in order to both pass with the other ...


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