Instrument rating questions

gay_pilot18

New Member
Hey guys I'm doing my instrument rating and have some really quick questions that I'd like you guys & gals to answer.


1.) What is a "waypoint"?

2.) What is the difference between a waypoint and a "fix".

3.) What is an "airway"?

4.) What is the difference between and airway and a radial? Can a radial be considered and airway?

5.) What is RNAV?

6.) There is no ground based navigation for airliners flying internationally i.e. no VORTAC or VOR/DME stations on the Pacific or Atlantic ocean or any major body of water. So how then do airliners navigate over large bodies of water for international travel? And how do they find there airways?
 

EatSleepFly

Well-Known Member
Well, here goes...

1.) A waypoint is an invisible point in space, used for navigation. They are defined by latitude/longitude or (in the case of RNAV) relative to a VOR. When you think of waypoint, think GPS, and RNAV navigation.

2.) Basically a fix and a waypoint are the same thing. Fix is a "generic" term for a specific point in space, waypoint is pretty much the same thing, but used when talking about GPS or RNAV.

3.) An airway is a defined radial in between VOR's (or NDB's in a few select places). Low altitude airways (below FL180) are called Victor airways, high altitude airways (above FL180) are called Jet routes. Example: V31, or J521.

4.) An airway is a radial, but a radial is not an airway. Look at a sectional sometime- airways are the blue lines coming off VOR's. Just like creating instrument approaches, theres quite a bit of work that goes into creating an airway- not just drawing it on the chart, slapping a V and some numbers on it, and using it.

5.) RNAV stands for Area Navigation. RNAV allows you to create an imaginary VOR anywhere you want using a real VOR, a radial, and a distance. Once you enter those items, and the unit is in RNAV mode, you can use the OBS to navigate directly to your imaginary VOR just like you would a real one. It gives you goundspeed/distance to it and everything.

6.) Someone else can explain this...I'm not too familiar with the workings of INS and transatlantic flights.

Hopefully I didn't forget anything...I had to type it quick before work...feel free to correct me if I screwed anything up.
 

mtsu_av8er

Well-Known Member
6.) There are several ways that an aircraft can navigate over the ocean, We'll take a flight from New York to London. Depending on a variety of factors ( to my knowledge...I'm not actually a pilot that has flown internationally, EatSleepFly....but I'm still gonna take a try...
- joking with you, man....smile!!!!), like weather and expected traffic, aircraft are assigned an oceanic route along what is called the North Atlantic Track System. This is a series of routes, based on a series of waypoints (which has already been explained) across the ocean. It simply becomes a matter of flying that route, along with some periodic position reports, and alot of speed adjustments to cross specified waypoints at exact times. How does the crew navigate to and from the waypoints?

Well, there are a variety of ways on any one of todays highly advanced commercial jetliners (no, I'm not selling one...could I??). The most common, I suppose, is the INS, or Inertial Navigation System. The INS is a completely self contained navigation system that is powered by a series of gyros and accelerometers. It has to be initialized by the crew before departure, with the LAT/LONG of the departing point. Once the aircraft begines to move, the INS detects the amount and direction of movement, rate of acceleration/deceleration, etc. It then has a database with all of the waypoints and fixes (and in some cases, company routes and flight plans, etc) that are needed, much like a Garmin GNS-430 (My favorite....
) or similar GA GPS.

INS systems aren't perfect, not by far. Remember, it's not telling what your position is....it's actually interpreting that from what your position WAS. Dead reckoning for sure!! Because of this, it tends to loose some of it's accuracy on a dependable schedule. It is, therefore, up to the crew to update the INS with a correct LAT/LONG coordinate when one is available. Many systems have the ability to recieve VOR and/or DME from stations within it's range, cross check with others, and then update the aircraft position based upon that info.

Not bad, huh!!!
 

mtsu_av8er

Well-Known Member
[ QUOTE ]
Once you enter those items, and the unit is in RNAV mode, you can use the OBS to navigate directly to your imaginary VOR just like you would a real one.

[/ QUOTE ]

Sorry if I come off as slightly irritated by this, but I ABSOLUTELY HATE the analogy of "imaginary VOR" It's not even similar (Not venting at you EatSleepFly...this one is to the world...).

The RNAV unit doesn't create an imaginary VOR. All it does is lets you navigate directly to a fixed-distance/radial position. It's not an imaginary VOR you're going to....it's just a fixed-distance/Radial position. An example would be as follows.

Let's say that you're flying from airport A to airport B. Your destination airport is in the middle of nowhere, about 27 miles from the closest VOR station, along it's 176 radial. When you file and IFR flight plan, remember that you must file to a point from which you may commence and instrument approach procedure.

If there are no NDBs around the airport, then really, using only VOR equipment, the best that you could hope for would be an airway that ran somewhere near the airport, and that the approach would have a feeder route comming from that VOR. That could be your onl....but wait....ah-hah!! I guess we could just file direct to the Hillbilly VOR, then to a point on it's 176-degree radial, at 27 miles. Of course, this is assuming you have DME.This would be written in the flight plan as HLB HLB 176027. This tells the FDIO computer (this is the system used by ATC to accept and control our flight plans, routes, etc) exactly what we want to do!! There's no ambiguity. The most awesome thing about it is that it's sooo useful, even without touching the RNAV yet. It really helps you when you need another legal, but safe and creative way to get ibnto an airport. Want to fly, on a day with 3 miles vis and overcast at 2,000, to an airport with no IAP or control tower?? If the MVA (minimum vectoring altitude) of the controlling agency will allow, why not file to a fixed distance/radial point right near the airport, and then see if you can get in VFR! It's legal, although safety is operationally dependent. What's safe for Salina, Kansas may not be safe for Jackson Hole, Wyoming....

So, how does the RNAV come into play? Well, if we fly direct Hillbilly, and then our radial to the position, that's going to suck, especially if we're only 10 miles from where we want to go, it's IFR ( or low VFR), and Hillbilly is 35 miles out of our way. Buuutttt...wait!! We have lots of money and hey, it's 1974!!! Since we have RNAV in our aircraft, all we have to do is tell it that we want to go straight to the Hillbilly 176 Radial, at it's 27 mile point...and there you go!! It does all of the triangulation for you, and tells you where to go. No need for out-of-the-way flying. One caveat...you must be able to recieve the VOR signal. No signal, no RNAV.

RNAV is one of those things that even flight instructors that think they know it all don't have a clue about. They just don't have a clue.
And too many people use that imaginary-VOR thing (if you've ever flown with an RNAV, you'll never say that again). And fortunately, for all of us, it's 2003!!! RNAV was a cool thing, but it's going the way of LORAN and the NDB...and good riddens to it!! Anything you can do with RNAV, you can do with GPS...just alot more reliable, alot more accurate, and you don't need to be receiving the signal to make it operate.

Whewww....sorry for the long version, but that was actually pretty short. Just wanted to make sure that you got the entire thing, and really understood it. Any more questions, feel free to ask!!!!!

Take care, and Fly Safe!!
 

EatSleepFly

Well-Known Member
[ QUOTE ]
RNAV is one of those things that even flight instructors that think they know it all don't have a clue about. They just don't have a clue. And too many people use that imaginary-VOR thing (if you've ever flown with an RNAV, you'll never say that again).

[/ QUOTE ]

I use RNAV all the time. I still say imaginary VOR- makes more sense to me than, "phantom station," which is what the book calls it. THAT is a silly souding term, if you ask me. Phantom station, imaginary VOR, same thing. And it realllly is brainless to use. Once you can use a VOR and DME, RNAV takes all of about 5 more minutes to learn. I teach it to primary students (we have it in one of our 172's) all the time, and they don't have a problem with it.

[ QUOTE ]
The RNAV unit doesn't create an imaginary VOR. All it does is lets you navigate directly to a fixed-distance/radial position. It's not an imaginary VOR you're going to....it's just a fixed-distance/Radial position.

[/ QUOTE ]

But you navigate to that point just like you would a VOR. Its not in reality a VOR, it just acts like one. Hence, "imaginary VOR."

 

PurduePilot

New Member
[ QUOTE ]
6.) There is no ground based navigation for airliners flying internationally i.e. no VORTAC or VOR/DME stations on the Pacific or Atlantic ocean or any major body of water. So how then do airliners navigate over large bodies of water for international travel? And how do they find there airways?

[/ QUOTE ]

Here's the website of the current Atlantic Track System (which changes daily according to the winds -- the Pacific Track System is fixed but works the same way): Atlantic Track System

First you have to understand that tracks S-Y go eastward across the Atlantic while tracks A-G go westward.

Let's assume you're taking off from JFK and you've been assigned track T:

In order to get on to Track T they have given you this routing:
TRACK T/ JFK.GREKI3.MARTN..EBONY.N109B.DOTTY.TRAKT

All this means is that you're departing JFK on the GREKI3 departure to the MARTN intersection. After crossing the MARTN intersection you'd continue to the EBONY intersection (which, I'm assuming is in Maine somewhere). After crossing EBONY you'd continue to the DOTTY intersection where you'd probably have to hold because spacing on the tracks is done with time. There is no radar coverage over the Atlantic. This is why reporting your position over the Atlantic is crucial.

Now this part comes into play:
T DOTTY 52/50 53/40 54/30 53/20 MALOT BURAK
EAST LVLS 320 330 340 350 360 370 380 390 400
WEST LVLS NIL
EUR RTS WEST NIL
NAR N109B N113B-

Your entrance to track T is DOTTY as I explained earlier. Your first reporting point is the lat/long position of 52/50, second is 53/40, 54/30, and so on. Your exit point off the tracks is MALOT (probably over England or Spain). If you plot these on a map, they should form a bending line across the Atlantic.

EAST LVLS refers to the altitudes that are legal across that track. I forget the seperation standards across the Atlantic, but I do know that it's huge.

Communications are done via HF (as opposed to VHF that is used on land) through a third party known as AIRINC. The reason this has been contracted out is because HF is very difficult to operate and communications are very poor so it takes a specially trained person to operate. It was tried with normal air traffic controllers, but this failed miserably because they spent most of their time trying to work the radios instead of seperating aircraft.

Since the quality of communications is so poor, the pilots don't have to listen to the radio constantly. An operator at AIRINC will ring the cockpit using a special code and frequency. This will work much like someone calling you on your phone. In fact, the device used looks much like a telephone.

I hope this has answered your questions.
 

mtsu_av8er

Well-Known Member
Hey, eatSleepFly...you're actually pretty good in a heated debate...where up noth do you fly? We need to hook up some time and shoot the proverbial breeze.......
 

PurduePilot

New Member
[ QUOTE ]
Good Deal, Purdue....where did you find that?

[/ QUOTE ]

To find the current tracks, I did a Google search. The rest is my own knowledge.
 

DE727UPS

Well-Known Member
gaypilot...

First of all, I'll second the statement that you should look it up in the AIM/FAR. Are you happy with the way this thread turned out? One guy bothered to breifly answer your questions. There is much more that you need to know but it's all in the book. Plus, you come here and you're liable to get some bad or conflicting information. I'd say look it up in the book FIRST and then if you still have questions...fire away.
 

EatSleepFly

Well-Known Member
[ QUOTE ]
Hey, eatSleepFly...you're actually pretty good in a heated debate...where up noth do you fly? We need to hook up some time and shoot the proverbial breeze.......

[/ QUOTE ]

haha...thanks (I think
). I'm pretty mellow in person, (really!)! Its just hard to convey mellow with words...it usually comes out sounding wrong. Anyways, I'm flying in northeast Ohio right now (near Akron). If you're ever going to be in the neighborhood, shoot me a PM- I'll buy ya lunch!
 

EatSleepFly

Well-Known Member
[ QUOTE ]
One guy bothered to breifly answer your questions.

[/ QUOTE ]

Sorry, they were brief because I was on my way to work...and I like a challenge every once in a while. But I agree...good to look things up when you have questions- that way you know exactly where to find the info. when you need it again!
 

DE727UPS

Well-Known Member
No need to apologise...at least you said what you did. I have a hard time getting excited about answering questions that a guy could look up. On the other hand, if he came back and asked "Why is an airway 4nm wide". Now that sorta doesn't make sense unless you knew they used to be 5sm wide and when the FAA went nautical, they just switched it to 4nm. That isn't really written down anywhere in the AIM.
 
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