Navigation; and how they get from here to there.
Parvaz
Have you ever wondered how your pilots know where they are going when
it is dark or when the airplane is in the clouds and you know they
can't see anything out of their windows? How do they navigate across
the vast oceans when you know one wave looks just like another from
38,000' up in the sky?
When commercial aviation was in its infancy navigation aids (nav
aids) were placed in centers of population (towns, cities). If the
distances were too far between then additional nav aids were placed
along the route to help the pilots along their way. Those navigation
aids started out as signal fires and evolved over the decades into
different kinds of electronic stations.
The next step was to connect the dots. Just as roads on the ground
were built to connect the centers of populations so we built "roads"
in the air. On the ground these roads are called the interstate
freeway system. In the air they are called "Victor airways" and later
"Jet airways" were added. Just as there is an I-90 that runs from the
East Coast across the country to the West Coast, so there is a J 90
that stretches across the country in the air roughly following I-90.
You can't see them with your eyes but when you look up in the sky it
is crisscrossed with many highways. Sometimes, when conditions are
favorable, you can see the contrails of the jets way up in the
atmosphere crossing each other. On occasion those contrails are
outlining the highways in the sky for you to see.
Both ground based nav aids and their navigation instrument
counterparts in the airplanes have gone through phenomenal changes
over the years. What started out as pilots looking for signal fires
evolved into airborne radio operators (navigators) in the airplanes
interpreting different sounds coming over their headsets. Those
distinct tones told them which side of the highway in the sky the
airplane was on.
Eventually instruments were developed that pointed in the direction
of the stations located on the ground. That was the age of the ADFs
(Automatic Direction Finders), NDBs (Non-Directional Beacons). To
navigate your pilots would follow a pointing needle located in an
instrument mounted in front of them. Navigating became an exercise in
calculating relative bearings off magnetic headings to determine
magnetic headings to and from these stations under constantly varying
wind conditions.
The next major improvement was the capability to emit a radio signal
that marked a magnetic bearing from the station to the aircraft.
These became known as VOR stations (VHF Omni-directional Radio
range). They are still in use today.
VLF, LORAN and Omega systems were initially developed to help pilots
navigate across oceans where terra firma based navigation stations are
not possible. What these stations had in common was that they were
all dedicated land based facilities strategically located around the
globe that emitted a powerful long range unique radio signal. This
signal bounced off the upper atmosphere and the earth/oceans below
eventually being received by the airplane in flight allowing the crews
to locate their position (with varying accuracy).
The next stage in the journey was to break away from the ground based
navigation facilities. That move was made possible by the development
of inertial navigation systems (INS and later IRS still in use
today). INS systems are entirely self contained instruments installed
in aircraft that had the capability to measure the acceleration forces
exerted on the airplane with great accuracy. That information is used
to keep track of movement. Once the system was up and running, in a
known location, it can kept track of where the airplane was moved.
Using that information and comparing it to where it was when it
started the journey the INS/IRS system is able to determine a current
position.
In the early stages of this technology inertial systems were spinning
mechanical gyros. Over time, brilliant minds were able to do the same
thing with laser gyros and vibrating crystals. With each step in the
mechanical evolution the instruments got more accurate, dependable,
and inexpensive. I stand in awe of the minds of those who are able to
visualize and then create such things. Those people are truly
brilliant!
The latest step in the evolution of aircraft navigation came with the
deployment of the GPS satellites. By triangulating off those
satellites it is possible to fix your position, in three dimensions,
just about any place on the planet at just about any time with
incredible accuracy. Some in the industry are actually using this
technology to safely navigate to remote locations where the airplane
is flying below the tops of nearby mountainous terrain following the
lowest topography into remote airports.
We are fairly unique at our airline in that we operate up in the high
arctic as well as tropical regions. In our operations specifications
we actually still have authorization to use "flare pots" to mark the
runway borders in the arctic if conditions warrant it. That practice
harkens back to a time where the pilots looked for signal fires on the
ground to guide them on their way. And, I believe, we have the only
authorized route system where we can fly visually between several of
our remote airports under visual conditions entirely-just look out the
windows and go. I don't think any other major airline in the country
has FAA authority to fly (being dispatched) under visual flight rules
between two cities. It is breathtaking to be trucking along in a jet
close enough to the ground to watch the ice bergs, fishing boats,
whales and bears go by as we make our way from one town to another.
There are several areas in our route structure where the only
available ground based navigation facilities are the old ADF
stations. Occasionally I still get to use the same navigation aids
the World War II pilots used when they finished their flying careers
commanding commercial airplanes. I think about them crossing the same
remote fix decades before me flying Constellations, DC6s and other
luxury airliners of a bygone era when piston radial engines and
massive propellers ruled the skies.
Most of the time in flight your pilots are monitoring the on board
navigational computers that have been programmed to command the
autopilot system(s) to fly a specific route. The route can either be
a jet airway following ground based stations across the country or it
can be a route going direct from the aircraft's present position to
wherever the destination is located.
There is another tool your pilot uses to navigate and that is the old
reliable "radar vector". The "radar vector" is an assigned heading
the pilots are told to fly by the air traffic controller who is
watching the flight progress on their radar display. The controllers
can tell the pilots what course to fly to get them where they want to
go.
Finally, if the weather is good, you are close to your destination
and nearing the end of your flight, your pilots are familiar with the
area and you are out of the high altitude airway system they may be
flying visually to the destination. In that case they are looking out
of the windows and driving the jet where they want to go. There is
nothing high tech about that.
All of these are tools at your pilot's disposal to get you safely
from one airport to the other. In flight we have the ability to use
ground based navigation facilities to fly a highway in the sky. We
have the capability to use the satellites to take you to your
destination. The airplane itself has navigation computers on board
that can determine its position and the necessary course to fly to get
to the destination. And we have a national air traffic control
system, staffed by professionals for whom I have the utmost respect,
standing ready to assist your pilots. Your pilots have a whole
arsenal of tools to keep them fully informed of their current
position, progress, and exact location of their destination.
Blue skies & tailwinds.....................