Data C : Airport Data File

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This data file contains information on the main airports around the world, gathered from various public sources. The data is useful in identifying the runway conditions (length and height) and estimating the geometrical distance between city pairs on a particular route (e.g. Los Angeles to Tokyo).

Tables C1 to C19 lists airports alphabetically according to location (Country shown in the first column). Airports formally part of the USSR are now listed under the appropriate country of the Commonwealth of Independent States. The second column shows the name of the city the airport serves. The airport name is shown in the third column. In some cases the city name is also used as the name of the airport but others use a different name (e.g. the name of a notable citizen, as in JFK). Some large cities have more than one airport (e.g. London; Heathrow, Gatwick Luton and Stansted). For analysis of aircraft performance, the height of the airport above sea level (elevation) and the available maximum runway length are significant factors. These are listed in columns 4 and 5. The last column gives the geographical location (longitude and latitude) of the airport. This can be used to determine route distance using the great circle method shown below.

Table C20 shows the busiest thirty airports in the world as reported (http://www.airports.org) in 1999. The dominance of US domestic air travel is shown by the relative ranking of London Heathrow (which is regarded as the leading international airport for passengers). Chicago O'Hare and Atlanta Hartsfield Airports occupy a dominant position in the tables due to them being used as US domestic hubs for major airlines. Of the busiest 30 airports only about a third are from outside the USA.

As mentioned above some of the world's major cities are served by more than one major airport (e.g. Denver) and this splits the total traffic between different airport sites diluting the significance of that city.

The dominance of some cargo companies in the market and their selection of specific hub airports influences the airport ranking in the cargo statistics. The expansion of trade in the Asia-Pacific countries accounts for the appearance of some airports higher in the cargo list than in the passenger sectors and the use of Anchorage as a staging post for some of this trade lifts this airport in the list.

The centralisation of passenger traffic on the main airports is illustrated by the fact that about half of the world's traffic is handled by the top 30 airports.

As we all learnt at school the earth is not a perfect sphere. It is squashed at its poles and bulges around the equator. To be precise the quoted mean equatorial radius is 6376km (3963 statute miles) and the polar radius is 6340 km (3950 statute miles).

To avoid the difficulties associated with navigating across the surface of the globe the ancient mariners adopted an approximation to these measurements. They invented a new measurement of distance which they called a ‘nautical mile’. They defined this as the distance travelled through one minute of arc on the surface of the earth (i.e. one degree of latitude represents a distance of 60 nautical miles). For the circum-navigation of the globe this works out at (60 x 360 =) 21600nm (40,003km). This is known as the great circle circumference (representing a mean diameter for the earth of 21600/p = 6875nm, giving a radius of 6366km). This compares with the accepted average value of 6883.2nm (or radius of 6374km). The approximation was accurate enough for the old mariners as they could manually steer the last few miles into port. Aircraft navigation requires somewhat better precision but for initial project design studies involving the estimation of aircraft range between two airports it is an acceptable approximation.

As an example of estimating the great circle distance between two airports we will consider a flight from Washington International (Baltimore) to Paris (Charles de Gaulle). From airport data in the tables of this data sheet, the positions (longitude/latitude) for the two airports are quoted as:-

Washington International (Baltimore) 3911N 7640W

Paris (Charles de Gaulle) 4901N 0233E

The positions of these two airports is shown diagrammatically on the next page and the method of estimating the great circle distance is illustrated.

1. Convert the latitude and longitude positions to degrees:-

3911N = 39 + (11/60) = 39.183 N

7630W = 76 + (30/60) = 76.500 W

4901N = 49 + (1/60) = 49.017 N

0233E = 2 + (33/60) = 2.550 E

2. Determine the angle at the earth centre from the North pole to each airport site (South is positive).

AOB = 90 + (-39.183) = 50.82 degrees

AOC = 90 + (-49.017) = 40.98 degrees

3. Looking down the polar axis determine the angle between the two points

(East is positive

(BOC)_polar = 2.55 (-76.50 ) = 79.22 degrees

4. From coordinate geometry, the true angle between two points on a sphere, referenced to the centre (BOC)True is given by:-

cos (BOC)_True = cos (AOB) cos (AOC) + cos (BOC)_polar sin (AOB) sin (AOC)

Calculating the component terms in the above expression:-

cos (AOB) = cos (50.82) = 0.6318

cos (AOC) = cos (40.98) = 0.7549

cos (BOC)p = cos (79.22) = 0.1871

sin (AOB) = sin (50.82) = 0.7751

sin (AOC) = sin (40.98) = 0.6558

(note, subscript p denotes polar)

Substituting these values in the above expression:-

cos (BOC)_True = 0.6318 x 0.7549 + 0.1871 x 0.7751 x 0.6558 = 0.5721

hence, (BOC)_True = cos-1 (0.5721) = 55.11 degrees

Using 60nm per degree gives:-

Great Circle distance = 55.11 x 60 = 3306nm (6123km)

The great circle distance is the minimum distance between the two airports. When flying the route it may be necessary to divert from the shortest path to comply with air traffic control regulations. It is advisable to add a contingency to the great circle distance to account for these possibilities (e.g. 540nm or 5% for long haul aircraft)

For accurate estimation of fuel used it is also necessary to take into account the effect of winds along the route. Obviously these are somewhat random but data is published giving the mean wind speeds and direction around the world on a seasonal basis. In aircraft project studies, still air range is often quoted as aircraft are not just deigned to fly on particular routes.