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Distance Between Aircraft In Flight  
User currently offlineFemme From , joined Dec 1969, posts, RR:
Posted (7 years 2 months 3 weeks 6 days 5 hours ago) and read 18473 times:

Hi Folks

My question is when airborne on any commercial Airliner, at cruising altitude, what is the minimum safe distance between you and other traffic. Is there a legal ( perhaps the wrong word) required distance in miles? I have 5 miles in my head but that can't be right as I have watched other Aircraft pass by much closer, or seem to. It's just something that I think about when up there and am curious to know.

Also, are there varying distances allowed depending on the amount of traffic ? I was thinking of decent into particularly busy air space perhaps around Major hubs.

Apologies if this topic/question has been previously covered,

Thanks
Claire

9 replies: All unread, jump to last
 
User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 1, posted (7 years 2 months 3 weeks 6 days 4 hours ago) and read 18469 times:

Hi Claire....hope I am able to provide some answers to your questions from the U.S. criteria!

Separation standards are set and must be adhered to or the controllers get time in the chapel so to speak....the FAA is not too lenient with errors within the system, so most of the standards are maintained very close, and in some facilities there is software that will detect less than standard separation for you, so that tap on your shoulder could be the start of listening to tapes, watching replays of your position, and much more fun. All of the enroute facilities have the software and some terminal facilities are getting it soon to test and then be put in place all over the joint.

You are correct, there are different separation requirements for aircraft in the enroute environment (center airspace) than there is in the terminal environment (approach controls). Then there is the wake turbulence issues with the different aircraft weight classes for the terminal controllers.

The density of traffic does not change the separation standard however it might and often does generate a greater distance for aircraft arriving over a specific fix to an airport or route which could be due to weather, amount of traffic in a particular sector, an airport capacity issue, or any number of reasons. That restriction would be a traffic management initiative put in place where the traffic management folks (they are not controlling a particular sector) may say to an adjacent facility, provide 10 miles in trail for the next hour for all arrivals over XXX....but that is not changing the separation standard set in the controller handbook, 7110.65.

So having said aaaaaaaaaaalll that......centers use 5 NM at the same altitude in almost every case, there are some places that are able to reduce that down to 3 NM with certain RADAR conditions being met but for the sake of confusion on my part let's stay with the 5 NM at the same altitude. With reduced vertical separation from FL410 and below it is 1,000' vertical separation if less than 5 NM. It is very difficult to guess what 5 NM looks like sitting in an airplane at FL370 and determing if the plane you see off the right side is even at your altitude or could be at FL380 or FL360....that 1,000' is sure deceptive.

The approach controls (including departure control) use 3 NM at the same altitude, 1,000' vertical if less than 3 NM. There are situations when landing that some airports are able to use 2.5 NM on final when the aircraft are within 10 NM of the landing runway threshold and certain conditions have been met, that is called reduced separation on final. Then you have the requirements for aircraft making approaches to parallel runway either dual or triple and those requirements which essentially allow aircraft to be side by side by side on final, again if certain requirements have been met.....a few airports that are able to conduct triple simultaneous approaches would be DFW, IAH, DEN, CVG and others.

Visual separation is another tool for the controllers to use, basically used in terminal facilities with provisions for enroute facilities to use it as well, but visual is used primarily in the terminals with a number of ways to utilize visual separation to reduce the standard separation that would be required.

You should be able to go to faa.gov and search for the 7110.65, go to chapter 5 which addresses RADAR separation standards........remember you asked for it!  Smile

Sure hope this helps answer your question.  Smile



Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 2, posted (7 years 2 months 3 weeks 6 days 2 hours ago) and read 18435 times:

Take it from the air traffic controller (IAHFLYR)...very nice. So all of this stuff I learned in my ATC class has a very good use  wink 

User currently offlineATCT From United States of America, joined Mar 2001, 2265 posts, RR: 38
Reply 3, posted (7 years 2 months 3 weeks 6 days 2 hours ago) and read 18431 times:

I was gonna reply with all the rules but looks like the ole' man beat me to it. He types fast for his age. :P


-A TC T


(All in jest man, take care)



"The way to get started is to quit talking and begin doing." - Walt Disney
User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 4, posted (7 years 2 months 3 weeks 6 days 1 hour ago) and read 18422 times:

Quoting N231YE (Reply 2):
very nice.

 Cool

Quoting ATCT (Reply 3):
-A TC T

Cute , very cute for a pup!  Smile

Quoting ATCT (Reply 3):
He types fast for his age.

It's all about copy n paste my friend.



Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineFemme From , joined Dec 1969, posts, RR:
Reply 5, posted (7 years 2 months 3 weeks 5 days 23 hours ago) and read 18373 times:

Quoting IAHFLYR (Reply 1):
Sure hope this helps answer your question

Thanks very much IAHFLYR ! It does. Much appreciated

Claire

 Smile


User currently offlineTimz From United States of America, joined Sep 1999, 6785 posts, RR: 7
Reply 6, posted (7 years 2 months 3 weeks 5 days 19 hours ago) and read 18328 times:

Quoting IAHFLYR (Reply 1):
3 NM at the same altitude, 1,000' vertical if less than 3 NM.

You're just talking about IFR traffic? VFR aircraft are allowed within 500 vertical feet of an IFR?


User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 7, posted (7 years 2 months 3 weeks 5 days 18 hours ago) and read 18316 times:

Quoting Timz (Reply 6):
You're just talking about IFR traffic? VFR aircraft are allowed within 500 vertical feet of an IFR?

Yes I am addressing strictly IFR separation standards as her question was directed to aircraft at cruising altitudes.

You are correct in most cases for the IFR/VFR separation within Class B airspace. When a heavy or B752 is involved then you need 1,000' below a VFR, if not lateral separation, lateral separation is 1 1/2 NM for IFR/VFR same altitude if either is a large. Small aircraft then you only need the have "green between" or targets don't touch if you don't have the 500' vertical separation.......confused yet, I am!  Smile

There is much more I am sure I've missed but it is Miller Time as we say here in Texas!!!!  bigthumbsup 



Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineMohunk From United States of America, joined May 2007, 56 posts, RR: 0
Reply 8, posted (7 years 2 months 2 weeks 2 days 4 hours ago) and read 18012 times:

I was a passenger Kuai (LIH) to SFO on UA last year (night flight) and very early on saw a plane that seemed not too far off our right wing that stayed there for hours. Came out of??OGG?HNL... Fell asleep shortly before SFO so don't know where he went. How close are they allowed in uncontrolled space like that? Did IAHFLYR answer it in his last post--yes, I'm confused?!?

User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 9, posted (7 years 2 months 2 weeks 2 days 2 hours ago) and read 17997 times:

Quoting Mohunk (Reply 8):
How close are they allowed in uncontrolled space like that?

Most likely you were in controlled airspace just not RADAR controlled airspace. I am not all that familiar with oceanic rules (nor care to be  Smile ) but, the separation is much greater at the same altitude, so what you probably saw was another aircraft with 2,000' vertical separation between you which at altitude and night looks almost like the same altitude, if it was 1,000' vertical then even more so.



Any views shared are strictly my own and do not a represent those of any former employer.
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