How the flight altitude is planning or selected before any flight begins?

6 Answers

  • 1 decade ago
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    Flight altitude is chosen as a function of many factors. Let's consider some of the factors that affect commercial jet airliners, for example:

    First, in order to get the best fuel economy, you'll want to fly at a specific altitude that will produce the lowest fuel burn per mile for the weight of the airplane (after adding passengers, cargo, and fuel). This usually turns out to be an altitude that is close to the maximum altitude for the aircraft.

    Second, you need to worry about regulatory restrictions. Under instrument flight rules (all commercial flights are IFR), there are minimum altitudes that you must stay above, and maximum altitudes that you must stay below. The minimums are there to protect you from hitting the ground, and the maximums are there because you have to be able to get to a lower altitude within a certain number of minutes if the cabin becomes depressurized. In addition, you have to follow general rules for altitudes (even thousands for westbound traffic, odd thousands for eastbound traffic), and you have to make sure you are above any restricted airspace (if you're not going around it).

    Third, you have to think about winds. It's usually quite windy at altitude, and if you fly at one altitude, you might find yourself struggling against a very stiff headwind (perhaps 120 mph or more), whereas if you fly at a slightly different altitude, you might have a tailwind helping you along. So you have to check the winds aloft and select (if possible) an altitude that has you flying with the wind, instead of against it.

    Fourth, you have to look at weather. This is especially true for small planes flying visually (VFR), as they have to respect strict requirements for visibility and thus cannot fly through clouds. VFR flights will choose altitudes that are more likely to provide the necessary visbility. IFR flights may choose altitudes that are less likely to take the flight into heavy weather (storms or unstable areas) or areas with icing.

    Fifth, you have to look at the overall flight and figure out how long it will take to reach your chosen altitude. For any flight, there's a specific climb and descent profile and cruising altitude that will produce the most economical fuel burn. Usually a computer is necessary to figure this all out and recommend an altitude. On very long flights, you may have to plan step climbs, which are periodic increases in altitude that you carry out as fuel burns and the aircraft becomes lighter, in order to get maximum fuel economy. Short flights tend to have lower cruising altitude than long flights, because you have to balance the fuel required to get to a high altitude with the economy that the high altitude will provide—and the shorter the flight, the lower the cruising altitude that works best.

    Sixth, you may want to consider speed. The altitude that provides the best speed to your destination may not be the one that provides the best fuel economy. If speed is important, you'll have to find a compromise that suits you, taking into account the other factors.

    The considerations for small private planes are somewhat different from those for large commercial airliners, but the factors that must be taken into consideration are similar. Considerations may also vary depending on whether you are flying visually (VFR) or by instruments (IFR), and whether the airplane is pressurized or not (unpressurized airplanes can only go so high before everyone on board must start wearing an oxygen mask).

    There are other considerations, but these are the basics.

  • The principal consideration here is safe terrain clearance. within the airways and off the airways this is shown on the AERAD radio Navigation. the final selection of altitude/flight level will be influenced by the weather conditions.

    Where as flights on airways will be height controlled by ATC those outside controlled airspace must be conducted in compliance with the quadrantal rule.

  • Anonymous
    1 decade ago

    Altitude is chosen based on many factors.

    For low altitude flights (typically in small aircraft):

    Terrain (mountains in the way)

    Obstructions (radio towers, tall buildings)

    Weather (how high the clouds are)

    Winds (tailwind=faster groundspeed=shorter time enroute)

    Efficiency (the higher you are the less fuel you burn, but the more fuel you must burn to get to that altitude)

    High altitude flights in jets and large propeller airplanes:

    Winds (same as above)

    Efficiency (same as above)

    Aircraft altitudes also depend on direction flown. Airplanes flying to the east fly odd altitudes (3,000, 11,000, 31,000) while airplanes flying to the west fly even altitudes (4,000, 12,000, 32,000). Traffic flying VFR add 500 feet to these altitudes. This helps separate traffic and avoid head-on approaches of aircraft at the same altitude.

    Source(s): Flight Instructor
  • Anonymous
    1 decade ago

    In flight planning you look at every object and bit of airspace you're flying over and select an altitude that will avoid any hassles and that conforms with any noise abatement procedures for a local area.

    You'll want to avoid flying into airspaces that require you to call a tower just because that tends to be annoying and towered airspaces are crowded enough and of course you want to avoid C-FITing into a tower or a mountain so fly a good height above them. (C-FIT=controlled flight into terrain)

    The heights of all the tall objects (mountains, cell phone towers, etc) should appear on your sectional map.

    And of course you want to take the day's cloud ceiling into account, you definitely don't want to fly into a cloud unless you're an instrument flight rated heavy craft.

    Oh, and you'll want to avoid any and all parachuting or gliding zones....You do NOT want to plow into a formation of thrill seekers holding hands as they fall to the earth...very bad...Parachuting and gliding zones are marked on your sectional map, with a parachute and a glider mark respectively.

    Source(s): student pilot.
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  • Anonymous
    1 decade ago

    For GA airplanes, I start with the altitude for optimum efficiency (around 7500 ft density altitude), weather, icing, then adjust for terrain, favorable winds, turbulence.

    For airline flights, we look for optimum winds, avoiding severe weather and turbulence.

  • 1 decade ago

    Terrain clearance, VFR cruising altitude (even/odd thousands plus 500 feet, depending on heading), weather.

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