gopal
Topic Author
Posts: 168
Joined: Thu Jun 03, 1999 3:05 am

### Busy Airways And Tcas

Yesterday, I got a first hand experience of the busy skies over the US during my Airtran flight 676 from Orlando to Milwaukee. It was bright and sunny during most of the journey which enabled me to see our path being criss-crossed by contrails left by airliners at different levels. I was able to see a contrail every 7-10 minutes. The contrails were well defined, which means that they were left not too long before our arrival at that point. I was also very luck to witness at a Commuter jet ( may be a CRJ or an EMBRAER) whiz past us at a flight level above us (we were at 34000 ft).

The skies got progressively greyer as we approached Milwaukee. Milwaukee was shrouded by a thick cloud cover when we began our final descent into the airport. As soon as descended into the clouds, we suddenly started a steep ascent which continued for a 1-2 minutes. Soon we resumed our final approach course. The captain came on the air and explained that we got too close to a military tanker and had to back up to allow the safe distance between us and them. We landed safely in heavy cross winds.

On my way out I asked the Pilot about the incident who explained that the procedure was initiated by the them (I am assuming the Military tanker flight crew) because we got closer that 5 miles of them. My questions to the informed members are:

a) Could the crew of the Military tanker has remotely acitvated the TCAS the system on our plane which caused the temporary deviation from our approach path ?

b) Does the 5 miles separation only apply to Military planes only ?

Thanks,

tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

### RE: Busy Airways And Tcas

 Quoting gopal (Thread starter):a) Could the crew of the Military tanker has remotely acitvated the TCAS the system on our plane which caused the temporary deviation from our approach path ?

The current generation of TCAS is a cooperative system...both boxes talk to each other and figure out what the appropriate resolution is. So it's not really that one activates the other. But 5 miles is too far out for a TCAS resolution advisory, as far as I know.

Tom.

Mir
Posts: 19383
Joined: Mon Jan 05, 2004 3:55 am

### RE: Busy Airways And Tcas

 Quoting gopal (Thread starter):On my way out I asked the Pilot about the incident who explained that the procedure was initiated by the them (I am assuming the Military tanker flight crew) because we got closer that 5 miles of them.

I'm going to disagree with your assumption and say that the pilot was meaning that ATC requested the deviation.

 Quoting gopal (Thread starter):b) Does the 5 miles separation only apply to Military planes only ?

5 miles separation applies any time when under the control of an ARTCC, as their radars are less precise as a result of less dense coverage.

 Quoting tdscanuck (Reply 1):But 5 miles is too far out for a TCAS resolution advisory, as far as I know.

Way too far. Plus, a TCAS RA shouldn't last for 1-2 minutes.

-Mir
7 billion, one nation, imagination...it's a beautiful day

josekmlb
Posts: 195
Joined: Thu May 29, 2008 7:34 am

### RE: Busy Airways And Tcas

In the classes B-E airspace the separation for Approach is 3 miles laterally or 1000 ft vertically or visual separation for IFR to IFR aircraft.

IAHFLYR
Posts: 3957
Joined: Sat Jun 25, 2005 12:56 am

### RE: Busy Airways And Tcas

 Quoting josekmlb (Reply 3):In the classes B-E airspace the separation for Approach is 3 miles laterally or 1000 ft vertically or visual separation for IFR to IFR aircraft.

Not in all cases is it 3 NM. If you have aircraft which are 60 NM or further from an ASR-9 with MODE-S or 40 NM or more from an ASR-11 you must use 5 NM separation.

 Quoting Mir (Reply 2):as their radars are less precise as a result of less dense coverage.

Terminal RADAR systems update at 4.7ish sweeps a minute while the enroute Long Range RADAR updates at 12 seconds a minute. There are a few approach control facilities with ADS-B and an automation system which takes input from the ADS-B radio stations as well as RADAR sensors. The system is called FUSION and it provides a 1 second track update. There will be more faclities coming online this year.
Any views shared are strictly my own and do not a represent those of any former employer.

gopal
Topic Author
Posts: 168
Joined: Thu Jun 03, 1999 3:05 am

### RE: Busy Airways And Tcas

 Quoting IAHFLYR (Reply 4):In the classes B-E airspace the separation for Approach is 3 miles laterally or 1000 ft vertically or visual separation for IFR to IFR aircraft.

What is B-E Airspace ? Thanks.

DiamondFlyer
Posts: 2642
Joined: Wed Oct 29, 2008 11:50 pm

### RE: Busy Airways And Tcas

 Quoting gopal (Reply 5):What is B-E Airspace

He meant Class B, C, D and E.

-DiamondFlyer

dxing
Posts: 5859
Joined: Wed Nov 12, 2008 5:14 pm

### RE: Busy Airways And Tcas

 Quoting gopal (Thread starter):As soon as descended into the clouds, we suddenly started a steep ascent which continued for a 1-2 minutes. Soon we resumed our final approach course. The captain came on the air and explained that we got too close to a military tanker and had to back up to allow the safe distance between us and them. We landed safely in heavy cross winds.

Did you climb back out of the clouds? I'm wondering if there was a restricted area that went hot due to tanker activity and that caused the deviation? That happens a lot off the west coast and to a lesser degree off the east coast. I hope the cpt. used his mirrors for safety when he "backed up"!
Warm winds blowing, heating blue skies, a road that goes forever, I'm going to Texas!

BigSaabowski
Posts: 130
Joined: Fri Jul 04, 2008 1:33 pm

### RE: Busy Airways And Tcas

 Quoting dxing (Reply 7): Did you climb back out of the clouds? I'm wondering if there was a restricted area that went hot due to tanker activity and that caused the deviation? That happens a lot off the west coast and to a lesser degree off the east coast. I hope the cpt. used his mirrors for safety when he "backed up"!

If this was on descent to Milwaukee, a Combat Air Patrol was set up over Chicago on Thursday evening with a tanker and several fighters, due to the President's visit.

[Edited 2011-04-16 17:36:05]

gopal
Topic Author
Posts: 168
Joined: Thu Jun 03, 1999 3:05 am

### RE: Busy Airways And Tcas

 Quoting BigSaabowski (Reply 8):If this was on descent to Milwaukee, a Combat Air Patrol was set up over Chicago on Thursday evening with a tanker and several fighters, due to the President's visit.

It was indeed Milwaukee airport we were trying to land in. Thanks for the clarification. Now that I recall, we were on some kind of a holding pattern even before we descended into the clouds for our final approach. It could have been due the extra level of security due the president's visit. Also after coming out of the jetway to the terminal we heard an announcement related to Homeland security elevating the threat level to a particular color ( I do not remember which). All related to the President's visit, I think.

Thanks to all for their answers.

 Quoting josekmlb (Reply 3):In the classes B-E airspace the separation for Approach is 3 miles laterally or 1000 ft vertically or visual separation for IFR to IFR aircraft.

So if the 5m/3m horizontal separation is violated by a commerical airplane, does the ATC warn the pilot and does pilot have to take action or does the corrective action happen automatically?

IAHFLYR
Posts: 3957
Joined: Sat Jun 25, 2005 12:56 am

### RE: Busy Airways And Tcas

 Quoting gopal (Reply 9):So if the 5m/3m horizontal separation is violated by a commerical airplane, does the ATC warn the pilot and does pilot have to take action or does the corrective action happen automatically?

If you're asking about ATC required separation, hopefully ATC has taken action to provide the correct separation standard.

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

Mir
Posts: 19383
Joined: Mon Jan 05, 2004 3:55 am

### RE: Busy Airways And Tcas

 Quoting gopal (Reply 9):Also after coming out of the jetway to the terminal we heard an announcement related to Homeland security elevating the threat level to a particular color ( I do not remember which). All related to the President's visit, I think.

The threat level has been the color of an orange for a while, and will probably continue to be the color of an orange for the remainder of eternity (or at least until someone decides to ditch the system). So I wouldn't read too much into that.

This is correct, but it will not happen at 3 or 5 miles - the two aircraft need to be closer than that.

-Mir
7 billion, one nation, imagination...it's a beautiful day

IAHFLYR
Posts: 3957
Joined: Sat Jun 25, 2005 12:56 am

### RE: Busy Airways And Tcas

 Quoting Mir (Reply 11):This is correct, but it will not happen at 3 or 5 miles

It might if they're closure rate is fast enough, but I don't wish to be involved in that test!
Any views shared are strictly my own and do not a represent those of any former employer.

B747FE
Posts: 217
Joined: Mon Jun 21, 2004 11:09 pm

### RE: Busy Airways And Tcas

 Quoting Mir (Reply 2):I'm going to disagree with your assumption and say that the pilot was meaning that ATC requested the deviation.

 Quoting Mir (Reply 2): Way too far. Plus, a TCAS RA shouldn't last for 1-2 minutes.

Not so fast.
TCAS protection is based on tau area, not range.
And it's threshold is basically defined by time. If the rate of closure is fast enough, you could very well have a RA at 5 NM.

Regards,
B747FE.
"Flying is more than a sport and more than a job; flying is pure passion and desire, which fill a lifetime"

gopal
Topic Author
Posts: 168
Joined: Thu Jun 03, 1999 3:05 am

### RE: Busy Airways And Tcas

A top headline from about 2 hours ago states that the First lady's plane had to abort landing because it came too close to a military cargo C-17. Her plane was ordered to perform a series of "S" maneuvers which did not help. Therefore it was asked to abort it landing and circle the airport. It was allowed to land after a while. FAA is investigating if this due an error on the part of an ATC.

http://www.msnbc.msn.com/id/42669951/ns/politics-white_house/

After all ATC incidents that we have been reading in the news, I am beginning to wonder.

Mir
Posts: 19383
Joined: Mon Jan 05, 2004 3:55 am

### RE: Busy Airways And Tcas

 Quoting B747FE (Reply 13):If the rate of closure is fast enough, you could very well have a RA at 5 NM.

True, but I shudder to think at what the closure rate would have to be for that to happen.

 Quoting gopal (Reply 14):A top headline from about 2 hours ago states that the First lady's plane had to abort landing because it came too close to a military cargo C-17. Her plane was ordered to perform a series of "S" maneuvers which did not help. Therefore it was asked to abort it landing and circle the airport. It was allowed to land after a while. FAA is investigating if this due an error on the part of an ATC.

The FAA will find that it was a simple case of "well, I thought that separation would work out, but it turns out it didn't, so I have to send the second airplane around to keep things safe". Happens all the time, and if anyone other than Michelle Obama had been on board, this wouldn't have even made the news.

 Quoting gopal (Reply 14):After all ATC incidents that we have been reading in the news, I am beginning to wonder.

Wonder not. This one is a non-event.

-Mir
7 billion, one nation, imagination...it's a beautiful day

IAHFLYR
Posts: 3957
Joined: Sat Jun 25, 2005 12:56 am

### RE: Busy Airways And Tcas

 Quoting Mir (Reply 15):Wonder not. This one is a non-event.

For sure. But begs the question, why push the edge of the separation envelope particularly with the recent activities with naps and movies?

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

josekmlb
Posts: 195
Joined: Thu May 29, 2008 7:34 am

### RE: Busy Airways And Tcas

 Quoting gopal (Reply 9):So if the 5m/3m horizontal separation is violated by a commerical airplane, does the ATC warn the pilot and does pilot have to take action

ATC will give vectors for traffic if need be or tell the pilot in trail to maintain a visual separation or even follow when on appch to the rwy with a visual separation.

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