Page 1 of 2
How do commercial airliners navigate?

Posted:
Tue Jul 08, 2003 7:07 pm
by Big_Al
Question:
I enjoy flying the default 737. Lets say I was a real American airline flying this plane from airport to airport.
How would I navigate it to its destination? Would I switch on the autopilot after submitting my IFR flight plan and just do as the ATC said?
Or do the real pilots use the nav radios to point the airplane to the next nav beacon?
I'm interesting because I always want to do exactly what they do in real life... or at least try.
Any help would be appreciated. Plus if you can point me to a website which explains how to do the correct navigation that would be excellent!
Re: How do commercial airliners navigate?

Posted:
Tue Jul 08, 2003 10:18 pm
by Scottler
Most commercial airliners use the Flight Management Computer. The pilot inputs the waypoints, and presses "Execute", and the plane does the rest. Unfortunately, I have yet to find a downloadable plane that has this amazing feature. (Though I did have a payware add on for 98 that had it...)
Maybe someone else knows of an aircraft or utility that will do that for us...
Re: How do commercial airliners navigate?

Posted:
Tue Jul 08, 2003 10:47 pm
by fisharno
Maybe.
But, the pilots still have to follow, and sometimes deviate from their filed flight plan. The pilots are still responsible for executing any instructions from ATC, and they still have to monitor the navigational and communication equipment, and make any adjustment necessary.
If the flight has to be diverted or put in holding, someone has to be there to manually take over until frequencies can be changed, and plates can be read and comms between the pilot and ATC can be exchanged.
I guarantee you. Those guys have 100% of their attention on that aircraft. And no matter what engineering masterpiece is working the controls, they still "fly the plane".

Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 12:42 am
by Heber98
To answer in a more general way, from what I understand entering the waypoints into the FMC is much like creating a flightplan with the default FS planner and flying the GPS route. Usually this route will be based on high altitude airways although sometimes it can be a direct route. I think the autopilot is slaved to the FMC, the pilot isn't actually flying the VOR radials that define the airways. Most pilots say they fly manual until they get to cruise then hit the buttons and go back to manual for descent and touchdown. At busy airports there are departure procedures to send all departing flights in a uniform fashion and arrival procedures to merge flights into a line and then they receive ATC vectors for the runway. (DP and STARs)
It's difficult if not impossible to make STARs work in a default IFR flightplan in FS. The ATC will always start vectors at least 50 nm out, so you would not get to really fly the arrival precedure. Plus they would get on to you if you descended and then tried to re-contact them when you were close, they would say to climb back to your filed cruise altitude and if you didn't they would cancel your plan. I think the FS2004 will be better at this.
Did I miss anything?
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 1:33 am
by Big_Al
thanks for the replies. So what setting for the flight plan should I use? VOR or High Altitude?
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 1:51 am
by Heber98
It really doesn't matter. GPS direct routes are coming into the picture these days, but I think currently airlines pretty much stick to the High Altitude airways which will create a flightplan utilizing a mix of VORs and Intersections as waypoints, the FMC will incorporate GPS fixes as waypoints. Sometimes you have to add or delete a VOR waypoint to suit your departure or arrival, depends on what you like. On the FS cockpit panels there is a NAV/GPS switch and when it is on GPS then the autopilot will follow the flightplan (you have to enable NAV or VOR hold).
I like to actually see what VOR radials define the airways and track the radials while checking my progress with the GPS, but I'm most certain this is not done by airline pilots.
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 1:56 am
by Big_Al
thanks again for the reply...
so now how do i input the VORs into the aircraft?
I create a flight plan using high altitude airways, now what do I have to do to get the airplane to go there without using the GPS to guide it? I'm guessing I use the nav radios, but how do I get each number for each intersection?
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 2:35 am
by Heber98
It sounds like you are asking basic VOR navigation. I guess you don't want to fly like the real airlines! only kidding. This is what I do:
-File the plan and look at the heading to each waypoint
-If I'm flying to a VOR, I track the radial that is the reciprical of the heading in the planner. (ie, hdg170, track radial 350 to the VOR)
-If I'm flying to an intersection, I track the radial AWAY from the VOR I just left (ie the radial and planner heading will match)
- If there are more than one intersection in a row it can get tricky, but usually they can just be ignored and used as a method of determining progress.
The VOR frequencies are under the map view (world menu). Intersections do not have frequencies, they are an imaginary point in space where two radials from two different VORs intersect. I find them difficult to locate on the airliners because you have to use both NAV radios, and the NAV2 on airliners is just a pointer. It doesn't really tell you if you are on a radial.
Did I confuse you? You can learn here:
http://www.navfltsm.addr.com/vor-nav.htm
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 7:26 am
by Scottler
I guarantee you. Those guys have 100% of their attention on that aircraft. And no matter what engineering masterpiece is working the controls, they still "fly the plane".

Having been in the pit on many commercial airliners during flight ranging from the DC-9 to the 777, I assure you that I in no way meant to imply that the flight crew is useless. In fact, quite the opposite.
However, there's an old joke among pilots about the future of the commercial pilot. It goes something like this:
In the future, the only things in the pit will be a pilot and a dog. The pilot is there to make sure nothing goes wrong, and the dog is there to bite him if he touches anything.
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 10:57 am
by fisharno
Absolutely. I know what you meant.
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 11:40 am
by Scottler
Flying the plane isn't exactly the same as piloting the plane...
VERY well said...
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 2:12 pm
by hikariken
yes now most aircraft got a nav computer but as say my father who is pilot on A340 Fly with nav computer is not fly
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 2:45 pm
by Scottler
Hikariken-
I'm getting ready to begin my real world flight school (next week), and I can choose between the Cessna 152, 172, and 172SP...can you ask your father which he thinks would be best to learn on? Thanks!
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 2:59 pm
by Oz
[quote]Most commercial airliners use the Flight Management Computer.
Re: How do commercial airliners navigate?

Posted:
Wed Jul 09, 2003 3:00 pm
by hikariken
hyperion
My dad think that the 152 is better for begginer. the 172 is too big