IFR separation and vectoring

L

LV-ARG

Well-Known Member
What is the minimum separation the controller should have between IFR/IFR VFR/IFR traffic. Is there any difference if the weather conditions are VMC or IMC?

If weather is VMC and you are approaching the airport in a little C172, do they have to vector you out on a long downwind to put you out a set distance from the airport because you are IFR? If traffic werent a factor, could you expect to get the visual approach and fly something like a 1nm final or the controllers are not allowed to give you such a short final because you are IFR?

I was just thinking about this because I remember being vectored like 7nm out into the sea at night before I was instructed to start my base leg. There were no other traffic at the time, so now I wonder... If I had canceled my IFR flight would the controller had turned me earlier? If so, then is it a smart practice to cancel IFR to give controllers a break once you are arriving to the airport in perfectly good VMC?

Airport was KDAB
 
LV-ARG said:
What is the minimum separation the controller should have between IFR/IFR VFR/IFR traffic. Is there any difference if the weather conditions are VMC or IMC?
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[captain obvious]
I would just assume (WAG) that IFR/VFR separation will be much greater when the weather is IMC.[/captain obvious]

-mini
 
If you are flying an instrument approach (other than a visual approach), you will be vectored to follow traffic (seemingly forever in a 172) no matter if you cancel IFR or not. ATC will provide IFR separation between you and the aircraft in front of you, and vector you to join the final approach course at least 3 miles from the final approach fix (unless you request otherwise). At DAB, this would put you at least 5NM offshore even without any other traffic.

Now if you'd like a visual approach, all bets are off and ATC may be able to keep distances a little closer if you've cancelled IFR (Daytona approach will use about 1.5 miles for VFR's instead of 3 NM behind the preceeding a/c). Much of the time, however, it won't matter if you've cancelled IFR or not, they will have to put you in the same line for the runway either way.
 
Speaking of the offshore coming into Daytona, I'd say its a safe bet they were using the 25's for operations. One of the big quirks about the flight schools on the field, is that they don't allow their aircraft (for the most part) to fly the approaches to 25L/R, but rather use the approaches to 16/34 and a circle to land, in order to prevent flight over water. So, it could have been a case of ATC trying to fit you in with what was likely quite a bit of traffic that would circling around for the 25's.

On the other hand, if you want a visual approach, help them out by telling them you've got the field in sight.
 
Basic rule in the terminal envoronment IFR/IFR 3 miles lateral or 1,000 feet of altitude. IFR/VFR is half 1.5 miles and 500 feet (unless the higher aircraft is a heavy). VMC/IMC makes no difference. As far as in a landing situation with a C172, depending on what you're following, seperation can decrease to 2.5 miles or increase to 6 miles for wake turbulence depending on what you're following (I think it may be 8 for the A380, don't see them, don't know) Start talking about diverging courses etc and I could fill a book... but since that book has been written I'll refrain.

Some facilities have directives stating you can't allow an aircraft to commense a visual approach until they are a set distance past the airport. VFR and IFR to the same runway doesn't really change anything. The first aircraft still has to clear the active. Thinking about it, I probably do issue base turns to Skyhawks and the like further out than I'd like if I were the pilot (8 or so miles) mostly out of habit since we don't get many single engine props where I'm at. The ones we do get usually are straight ins or take the crosswind runway.

Another thing to consider is as someone else said, call the field in sight. If you don't call it on the downwind, it may be VMC, but for all you know the last 5 airliners they worked couldn't see the field in the sun or haze until right at the approach gate. When I get one of those, the next guy is going to go out a bit further to ensure that I can give a legal intercept to the ILS should it be necessary. Strange things happen. It can be clear and a million and just a puff of smoke can obscure things.
 
Genot gave a lot of excellent information there.

my only thoughts:
Genot works Class B airspace somewhere, cuz the IFR/VFR separation he noted are within Class B. I work a Class B so I recognized the standard.

outside of Class B or C there are NO IFR/VFR separation. we obviously don't want them too close. but, if they end up 1/2 mile and 200 feet were still good in the legal sense. not so good on the moral sense.

i THINK it's 10 miles behind the super A380/A388. i don't see them in Vegas either...just trying to remember the genot (no pun intended) i read months ago.

we don't get CAT I aircraft to our main runways either, but if we did we would still have to take them far enough out to intercept the localizer legally. 10SM and CLR and i'm turning a 172 base as soon as i feel comfortable that the aircraft will be able to descend normally and make the runway.
 
Everytime I drive to work I have a cassette tape that plays over and over

"Five Miles, or a Thousand Feet"
 
LV-ARG said:
If so, then is it a smart practice to cancel IFR to give controllers a break once you are arriving to the airport in perfectly good VMC?

Airport was KDAB
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Canceling IFR is the best thing we hear all day. Separation minima may still exist between VFR/IFR aircraft depending on the class of airspace you're in, but it would still be less than full IFR/IFR separation.

Though there may be situations where canceling won't help much (because of volume or airspace configuration), it certainly wouldn't hurt.

If it doesn't negatively affect your flight and the conditions are good, canceling, at best, will get you to your destination faster. At the least, you won't be any worse off (save some really specific situations that I haven't thought of).

Either way, it always makes out job easier. Of course that's not your first priority :)
 
FM_Weasel said:
Canceling IFR is the best thing we hear all day. Separation minima may still exist between VFR/IFR aircraft depending on the class of airspace you're in, but it would still be less than full IFR/IFR separation.

Though there may be situations where canceling won't help much (because of volume or airspace configuration), it certainly wouldn't hurt.

If it doesn't negatively affect your flight and the conditions are good, canceling, at best, will get you to your destination faster. At the least, you won't be any worse off (save some really specific situations that I haven't thought of).

Either way, it always makes out job easier. Of course that's not your first priority :)
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good to get some insight on this. Ill try to make your lives easier from now on (whenever feasible)
 
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