'Report 4 mile base for runway two five left' - meaning?

Jeff Szlauko

Jeff Szlauko

Pre-takeoff checklist
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ChopperJeff
After radioing the tower and saying I was inbound for landing, the tower gave me the instruction:
''Report 4 mile base for runway two five left"

What exactly does this mean? I've Googled it, and it seems nobody can agree on the meaning of it. Some said it means your base is now 4 miles long, and others said it means your final will be 4 miles long.
I interpreted it as meaning that I should report to the tower when I'm about 4 miles from entering the base for the runway, so the final and base is the same distance they "normally" are.
 
It depends. Are you currently closer to a base leg that's a half-mile off the end of the runway and 4 miles out or are you closer to 4 miles out and half a mile off of the runway Centerline? Whichever one you get to first or whichever one is closest to you let them know. they basically just want to know you've got 3-5 minutes ish to land.
 
In my case I was about 8 miles out, and probably a couple miles off the runway centerline. So I take it in this case they wanted me to enter the base for the runway, with the base being where it normally is within the pattern, but report when I'm about 4 miles from entering the base?
 
Jeff Szlauko said:
In my case I was about 8 miles out, and probably a couple miles off the runway centerline. So I take it in this case they wanted me to enter the base for the runway, with the base being where it normally is within the pattern, but report when I'm about 4 miles from entering the base?
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That's what I would do.
 
Jeff Szlauko said:
In my case I was about 8 miles out, and probably a couple miles off the runway centerline. So I take it in this case they wanted me to enter the base for the runway, with the base being where it normally is within the pattern, but report when I'm about 4 miles from entering the base?
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Yep. I fly from the south side of Atlanta up to PDK a lot and I approach from the SE. The parallel runways are 3L and 3R. Most of the time they clear me for a base leg to 3L when coming from that direction. And like others said, you just report your position when you're 4 miles out. If you would have been at a more straight in position when you initially called, they probably would have cleared you for final and report 4 miles out.
 
What it means when I say it is that your base leg should be 4 miles out measured from your airplane to the approach end of the runway. Too many "there I was" stories to defend other controllers. Just saying what I expect and since I have radar I would never tell someone that is almost on final to begin with (like Jeff above) to report a 4 mile base. That doesn't even make sense.

If if doesn't make sense to you, ask the controller to clarify. Maybe they have you mixed up with someone else.
 
Didn't this just get discussed a few weeks ago?

Report a 4 mile BASE, means your base leg is gonna be 4 miles long because that's the direction you're approaching the airport from.
 
Proving my point Mark. Your definition differs from mine. To clarify, mine is base leg, four miles from the runway. Reason being is that a 4 mile base would make it easy for the controller to sequence you behind someone already in the pattern.
 
Timbeck2 said:
Proving my point Mark. Your definition differs from mine. To clarify, mine is base leg, four miles from the runway. Reason being is that a 4 mile base would make it easy for the controller to sequence you behind someone already in the pattern.
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Probably saying and meaning the same thing Tim. ;)
 
Timbeck2 said:
Maybe. Your final turn should be 4 miles away.
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huh? your final turn should be onto final, from a base leg that you have flown on for at least 4 miles (or at least reported, as asked, on the base leg 4 miles out. you still have to turn final.
 
Depends on the controller and that is the problem. What do they mean when they say "four mile base?" I know what I mean, but it doesn't matter anywhere else but my air patch.
 
Timbeck2 said:
How can one accurately measure where they are from the extended runway center line? That's why I don't think that's what the controller meant. But then again, I'm not that controller.
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I'm not a controller so take this with an absolute grain of salt, but given this instruction, I wouldn't think the controller would expect it to be based off of the center line. It's 4 miles from the airport based on GPS location.

BTW, one of these days I may fly into your patch of air, ya never know!
 
Prior to the top of the red arc is what I would expect. You gotta say it early otherwise you blow through final. The lower part of the arc could be considered the downwind.
 
Timbeck2 said:
Prior to the top of the red arc is what I would expect. You gotta say it early otherwise you blow through final. The lower part of the arc could be considered the downwind.
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So for you, you want them closer to runway center line and 4 miles out as opposed to 4 miles off the centerline when they make the call?
 
Timbeck2 said:
How can one accurately measure where they are from the extended runway center line? That's why I don't think that's what the controller meant. But then again, I'm not that controller.
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Think of a tower where controller needs to find you. He needs to know what direction you're coming from. This is why "base" is perpendicular to the runway. If he wanted you make a gigantic final, he'd call for "report final". Also, if you think that "report 4 mile base" places you almost on final, then what phraseology do you expect for placing your across the runway?
 
P.S. In some places like Santa Fe or Austin Exec, I report my location, like "3 miles, just passed the lake" or "3 miles, over the VOR" - if the frequency is not overloaded. If controller has a doubt where to look for me, he will know right away. Although, these days more and more airports have radars, so maybe there's no point in doing it anymore.
 
zaitcev said:
Think of a tower where controller needs to find you. He needs to know what direction you're coming from. This is why "base" is perpendicular to the runway. If he wanted you make a gigantic final, he'd call for "report final". Also, if you think that "report 4 mile base" places you almost on final, then what phraseology do you expect for placing your across the runway?
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Well see, my four mile base puts someone 4 miles from the runway. Another controller's four mile base puts them 8 miles (to fly) from the runway. This is why I say "ask the controller to clarify what they mean."
 
Timbeck2 said:
Well see, my four mile base puts someone 4 miles from the runway. Another controller's four mile base puts them 8 miles (to fly) from the runway. This is why I say "ask the controller to clarify what they mean."
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Are you some sort of an air traffic controller or something?

P.s. I don’t think people know
 
BrianNC said:
Seriously. I'm not sure why this is so complicated. :confused:
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Because if you look at my sketch and put your plane anywhere on the red arc pointing perpendicular to the runway you will be on a "4 mile base". (GPS says 4) However, Tim expects you closer to 4 miles east, another controller might expect you 4 miles south.
 
Timbeck2 said:
Well see, my four mile base puts someone 4 miles from the runway. Another controller's four mile base puts them 8 miles (to fly) from the runway. This is why I say "ask the controller to clarify what they mean."
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what? so a 4 mile base plus then a 4 mile final? this is totally new to me, never heard this before anywhere.
 
EdFred said:
Because if you look at my sketch and put your plane anywhere on the red arc pointing perpendicular to the runway you will be on a "4 mile base". ...
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no you won't.
 
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