Welcome to this episode of Dwayne’s Aviation,
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Airports like Hartsfield-Jackson Atlanta International Airport handle nearly 100
million passengers a year. That's almost 20 times the number of people living in Atlanta itself and
the same number of people living in a sizable country, say Ethiopia or Vietnam. Moving those
people to their ultimate destinations requires 34 different airlines, which collectively make up the
airport's 2,500 daily arrivals and departures. That's a lot of planes, a lot of passengers, and
a lot of airport personnel to make sure everything runs smoothly, so how do they make this possible?
There are about 5,000 airplanes in the sky every hour in the U.S alone,
this translates to approximately 50,000 aircraft operating in the sky each day.
When an aircraft makes its way through the skies, air traffic controllers in the respective area and
division monitors its flight. At the moment an aircraft enters a different zone, the traffic
controller officer passes this information off to the new division to take control.
Their job is not just to coordinate the movements of thousands of aircraft, keep
them at ¬safe distances from each other, direct them during takeoff and landing from airports,
direct them around bad weather and ensure that traffic flows smoothly with minimal delays,
their job also extends to helping planes fly at the correct altitude. For example, an Altimeter
onboard an aircraft is basically just a pressure gauge, and this technology is pretty much the same
as the one's airplanes back in the 50s, '60s, and '70s had. So, the first thing you need to
understand, is that when it comes to altimeters, the reason pressure is used to measure altitude
is because the atmosphere has a nice feature of having a linear decrease of pressure as you climb.
So basically, when a plane takes off, every 30ft it climbs, the pressure is going to drop with
approximately one Hector pascal. If it climbs 60ft up, the pressure drops two Hector pascals.
Relying on pressure reading alone to calculate altitude can be dangerous since the atmosphere is
not completely uniform all over the globe because we have areas of high mountains and deep valleys,
these areas have different pressure reading that can trick the altimeter to think the aircraft is
higher above the ground than it truly is because altimeters are essentially a pressure gauge,
it also means that it does not really know where we are to start with, the only thing
it knows is that the pressure is decreasing or increasing, and it uses this reading to
calculate altitude. So, pilots use something called the QNH at the airport of departure,
since the atmospheric pressure changes over time and from place to place, you might have high
pressure at your airport of departure, and low pressure on the airport of destination, so pilots
have to listen to the air traffic control for the local QNH value. Every time an aircraft gets
cleared to an altitude, they will be getting the local QNH value from the air traffic controller,
let’s say the QNH is 1000 hector pascal, what pilots do is to give that value to the altimeter,
then the system will use the local atmospheric pressure as a reference to calculate the correct
altitude of the aircraft above sea level. QNH basically gives us the pressure setting to know
how high we are above the sea level with reference to the airport we are at. Now,
why is this interesting to know is because the QNH values are different between different airports,
so pilots must ask the ATC for the correct pressure setting at the airport they are in.
If for example you are at JFK airport with a QNH of 1015 and then you wait for few hours
and the pressure drops by 5 hector pascals, the altimeters will assume that the airplane climbed
150ft higher, while the airplane is actually on the ground, because the QNH dropped by 5 hector
pascals. This is why pilots continuously update the pressure setting when either departing from
an airport or descending into an airport. As you might have understood by now,
that since the pressure value differs between different airports and we have a
lot of aircraft taking off from these different airports flying to their various destinations
For example, let's say you take off from JFK then you are flying towards California, you're
going to meet other aircraft that are flying from other airports where the pressure was different,
pilots won’t know their vertical separation with these other aircraft, because they took
off from a different airport with a completely different QNH value and altitude reading,
this can easily lead to a midair collision, So the way that has been solved is that by making
use of a standard pressure value at transition altitude, which is QNH 1013.25 Hector pascal,
so all airplanes flying above the transition altitude will set the same pressure because,
in the air, airplanes fly so high that how high and how high they are above the ground
doesn’t matter, only the vertical separation with other aircraft matters, So whenever you hear an
aircraft that is been cleared to a flight level, it means they now using the standard QNH value.
At a busy airport like Atlanta's Hartsfield, 2,500 flights take off and land every day.
That means that each day, perhaps as many as 250,000 people move through the airport and need
certain services. Airports provide those services in their concourses and terminals,
the heart of any airport. There you'll find the space for airlines to handle ticket sales,
passenger check-in, baggage handling, and claims.
When you think of the size of an airport and the enormous volume of people it serves,
you can imagine that providing these logistics services can be a daunting challenge.
Consider baggage handling as an example, the first step, which occurs as part of
the check-in process, is generating a bar code that includes information about your flight,
including layovers and final destination. An airline attendant attaches this code to your bag
and then places it on a check-in conveyor, which carries it away. A machine on the other side of
the desk, armed with an array of scanners capable of "seeing" the bar code regardless of its angle,
reads the encoded data and then routes the bag accordingly. Based on these instructions,
your bag follows a continuous chain of conveyors, which both move it along rapidly and change its
orientation as necessary. Additional scanners along the way check and double-check the bar code
to make sure your bag continues to follow the right path. Eventually, your bag reaches human
handlers, who load it onto a trolley and drive it to the plane, where it is loaded into the hold.
At the same time, an airline must keep track of the people flying on their planes.
During the check-in process, an agent must scan an e-ticket or manually input passenger data,
noting any upgrades, to first class, for example, or special needs. For international flights,
agents must also enter a passenger's passport information. All of this data, plus a code for
the final destination, appears on a boarding pass, which is printed out and given to the passenger.
At the gate, during boarding, the passenger hands the pass to another airline agent,
who scans the barcode and confirms that the person on the flight manifest.
When all passengers have boarded the aircraft, the agent prints a copy of
the manifest so a member of the flight crew can check that all passengers successfully boarded.
Once all passengers have been accounted for, the airline issues a final manifest,
which can be used to notify relatives in the unlikely event of an air disaster.
In terms of security, before the nine eleven attacks, private companies provided airport
screening services. These companies worked under the guidance of the F.A.A, and although
their representatives scanned passengers using metal detectives and X-rayed bags,
limited federal security requirements existed for cargo and baggage screening. Some incidents
have been the result of travelers carrying either weapons or items that could be used as weapons on
board aircraft so that they can hijack the plane. After 9/11, the U.S. government established the
Transportation Security Administration to improve and strengthen aviation security. By November
2001, the TSA rolled out a number of new security measures: armed air marshals, reinforced cockpit
doors, and no-fly lists identifying people who could pose a threat and designating them
for enhanced screening or, as appropriate, prohibiting them from boarding an aircraft.
Today, the TSA screens 100 percent of checked baggage for explosives using combinations of
software, conveyance systems, and screening technologies to conduct full in-line screening
without interrupting or delaying the movement of luggage from the ticket counter to the aircraft.
Airports have also increased their on-site police forces since 9/11.
At Los Angeles International Airport, for example, the police crew has grown from 100 sworn officers
before the terrorist attacks to 430 today. This makes the airport force almost as large as others
performing their duties out on the city streets. Airports complement their police forces with
separate crews to handle fire and emergency medical services. An airport may have several fire
stations on the ground because the FAA requires that emergency crews be able to reach the midpoint
of a runway within 3 to 5 minutes. The crews are usually employees of the city or municipality
and are stationed at the airport. At their disposal are specially designed and equipped
fire and rescue vehicles capable of extinguishing jet-fuel fires with thousands of gallons of foam.
These 44-ton, six-wheel vehicles can accelerate from 0 to 50 miles per hour
in less than 35 seconds and come equipped with a variety of turrets,
nozzles, and booms to attack a fire efficiently and protect escaping passengers.
Finally, airports are huge businesses. How big? Well, Denver's airport cost about $5
billion to build, and operating costs are $160 million per year.
But its economic impact on the state is huge. According to the Colorado Department
of Transportation, Denver International Airport generates $22.3 billion for the state
every year. Commercial airports are publicly owned and generally financed through municipal bonds.
Airports typically own all of their facilities and make money by leasing them to airlines,
air-freight companies, and retail shops and services, as well as by charging for services
like fuel and parking and through fees and taxes on airline tickets.
The revenues pay off the municipal debt and cover the operating costs.
Airports often require other sources of funding as well, such as airport bonds and government
grants. But most airports are self-sustaining businesses once they become operational.
About 90 percent of employees at airports work for private companies, such as airlines, contractors,
and concessions. Most of the remaining 10 percent work directly for the airport as administrators,
terminal- and grounds maintenance personnel, and safety crews. Air traffic controllers
are employees of the federal government. Airports have their own departments of finance, personnel,
administration, and public relations, much like any city or municipality.
Whether or not you find heaven or hell in the complex world of a commercial airport
largely depends on your personality and the circumstances of your travel.
Airports will continue to be all-important nodes in the
international transportation system - at least until someone perfects teleportation.