MSN007
Topic Author
Posts: 70
Joined: Sat Sep 26, 2009 11:34 pm

How Close Is Too Close?

After looking at this picture following the link, I am wondering how close is to close?

http://www.airliners.net/photo/Turki...lines/Boeing-777-3F2-ER/2043884/L/

timz
Posts: 6216
Joined: Fri Sep 17, 1999 7:43 am

How Close Is Too Close?

6000 ft is definitely not too close.

Pe@rson
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How Close Is Too Close?

It's just an illusion.
"Everyone writing for the Telegraph knows that the way to grab eyeballs is with Ryanair and/or sex."

SEPilot
Posts: 5051
Joined: Sat Dec 30, 2006 10:21 pm

How Close Is Too Close?

Aircraft are normally separated at those altitudes (I believe it is over 31,000 ft) by at least 2000 feet unless reduced separation is in place in which case the minimum is 1000 feet. And that is for planes traveling in opposite directions; in the same direction the separations double. Since the listed separation is 6,000 feet and the planes are obviously traveling in the same direction reduced vertical separation is obviously being used.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler

Yflyer
Posts: 1289
Joined: Sat Feb 17, 2007 4:05 am

How Close Is Too Close?

Photos taken through a telephoto lense can be very deceptive. Here's another example of the same phenemonon with an explanation of why the planes aren't as close as they appear to be:

http://www.snopes.com/photos/airplane/closedhl.asp

Unfortunately the link in that article appears to be dead, but here's another good explanation of the "compression" phenomonon with telephoto lenses:

http://www.learnmyshot.com/Telephoto...+Compression+and+the+Angle+of+View

XFSUgimpLB41X
Posts: 3961
Joined: Fri Aug 25, 2000 1:18 am

How Close Is Too Close?

Those aircraft are a mile apart vertically.
Chicks dig winglets.

cargolex
Posts: 1202
Joined: Fri Apr 23, 2010 5:20 pm

How Close Is Too Close?

 Quoting SEPilot (Reply 3):unless reduced separation is in place in which case the minimum is 1000 feet.

What circumstances cause reduced separation to be applied? Too much traffic in the airway? Weather?

PapaChuck
Posts: 111
Joined: Mon Aug 16, 2010 2:51 pm

How Close Is Too Close?

The reduced separation mentioned above is RVSM, or Reduced Vertical Separation Minimum. Without RVSM, aircraft above FL290 are required to have 2000' vertical separation, with 1000' vertical below that. With properly equipped RVSM aircraft (and most big jets are these days), 1000' vertical separation is used up to FL410. Above that, it becomes 2000' again. 99% of the jets today, plus many high performance turboprops, are RVSM equipped. Aircraft cross paths 1000 feet apart all day, every day.

PC
In-trail spacing is a team effort.

SEPilot
Posts: 5051
Joined: Sat Dec 30, 2006 10:21 pm

How Close Is Too Close?

 Quoting PapaChuck (Reply 8):Without RVSM, aircraft above FL290 are required to have 2000' vertical separation

Thanks for the correction; I couldn't remember what altitude it started at.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler

roseflyer
Posts: 9605
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RE: How Close Is Too Close?

On top of that, the 777 crew probably could see the A330 for at least half an hour since at the higher altitude he was making a contrail. At first judging by relative size I thought the A330 was a 737.

It's always fun when in traffic like that to just watch the other airplanes. I remember being in a 757 as we overtook a E190 which was only 4,000ft lower. The E190 was in view for a good 15 minutes.
If you have never designed an airplane part before, let the real designers do the work!

KELPkid
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RE: How Close Is Too Close?

One of my most vivid memories as an airline passenger was watching a TWA 727 fly below us at 2,000   They were making contrails, and flew below us at a 90 degree angle (roughly) to our path over Utah. The whole encounter lasted about a second or two...wish I'd had a camera ready. Would have been film back in those days   No warning from the flight deck, either. Was on an HP 737.
Celebrating the birth of KELPkidJR on August 5, 2009 :-)

pilotpip
Posts: 2827
Joined: Fri Sep 19, 2003 3:26 pm

RE: How Close Is Too Close?

 Quoting KELPkid (Reply 10):One of my most vivid memories as an airline passenger was watching a TWA 727 fly below us at 2,000 They were making contrails, and flew below us at a 90 degree angle (roughly) to our path over Utah. The whole encounter lasted about a second or two...wish I'd had a camera ready. Would have been film back in those days No warning from the flight deck, either. Was on an HP 737.

If I made a PA announcement every time traffic came into view you would be complaining that I was making too many PA announcements.

This is one of the perks of the job. Coolest one I've had was while in the 145 over Kansas going to DEN. Had a UA 747 overtake us 2000 feet above on the same airway late at night. Full moon and snow on the ground made it so bright I could see the logo on the tail. Was fun watching it creep up behind us on the TCAS.
DMI

SAAFNAV
Posts: 393
Joined: Wed Mar 17, 2010 5:41 pm

RE: How Close Is Too Close?

Even when you are 1 000' apart, but heading straight on... Quite interesting watching it!

Over Africa we, and I believe most other big carries fly a 2nm Right Offset, as there is no radar coverage.

Northwest727
Posts: 379
Joined: Sat Jul 30, 2005 10:38 am

RE: How Close Is Too Close?

 Quoting pilotpip (Reply 11):Quoting KELPkid (Reply 10): One of my most vivid memories as an airline passenger was watching a TWA 727 fly below us at 2,000 They were making contrails, and flew below us at a 90 degree angle (roughly) to our path over Utah. The whole encounter lasted about a second or two...wish I'd had a camera ready. Would have been film back in those days No warning from the flight deck, either. Was on an HP 737. If I made a PA announcement every time traffic came into view you would be complaining that I was making too many PA announcements. This is one of the perks of the job. Coolest one I've had was while in the 145 over Kansas going to DEN. Had a UA 747 overtake us 2000 feet above on the same airway late at night. Full moon and snow on the ground made it so bright I could see the logo on the tail. Was fun watching it creep up behind us on the TCAS.

I remember as a kid, nearly 16 years ago, while flying on a WN 737 enroute CLE-STL-PHX, the crew told us to look up. I remember seeing a UA twin (don't remember what twin) fly above about 2000ft, with contrails, at roughly a 45º angle from our course. Upon passing over us, the UA aircraft began a turn and then paralled us! (although it was a bit faster.) I didn't have a camera nor know how to use one, but it left a very vivid memory, and the crew even called it out for us!

Back to the topic, I think SEPilot is right. If I am not mistaken though, doesn't RVSM begin around FL280?

PapaChuck
Posts: 111
Joined: Mon Aug 16, 2010 2:51 pm

RE: How Close Is Too Close?

RVSM airspace begins at FL290, but that can be a bit misleading. A non-RVSM aircraft at FL290 cannot have an RVSM aircraft pass above it at FL300. Eastbound non-RVSM aircraft are typically capped at FL270 for this reason.

Also, it is fairly common for non-RVSM high-performance jets to cruise at FL430 and above. Once they reach FL430, RVSM doesn't matter any more. ATC just needs to be prudent and use 2000' vertical separation while climbing and descending these aircraft through RVSM airspace.

PC
In-trail spacing is a team effort.

Northwest727
Posts: 379
Joined: Sat Jul 30, 2005 10:38 am

RE: How Close Is Too Close?

Thanks, makes a lot of sense now. Unfortunately, I'm still a piston driver, so I have yet to make it up to the Flight Levels...someday, someday.

soon7x7
Posts: 2267
Joined: Thu May 04, 2006 10:51 am

RE: How Close Is Too Close?

They can't be that close as Air Berlin the only one laying out a contrail. Telephoto compression I suspect Telescope/ Hubbell?). Now the shot here below was close laterally and also consider I was in a 767 so three of us were in formation. Too bad the quality is so bad.
 767,767,777race

PapaChuck
Posts: 111
Joined: Mon Aug 16, 2010 2:51 pm

RE: How Close Is Too Close?

Amazing shot, but again the perspective is making it seem as if the aircraft are closer than they really are. Note the abundant blue sky backdrop and the great look at the bellies. This is indicating that the camera was angled up. Looks like a vertical stack with the United bird at the top. I'm willing to bet there was 2000' vertical and a couple miles lateral between each aircraft. Also note the United bird is a 777, throwing the proportions off a bit. Again, great shot, but the telephoto effect is playing games with us.

PC
In-trail spacing is a team effort.

817Dreamliiner
Posts: 3357
Joined: Sun Jul 27, 2008 4:12 pm

RE: How Close Is Too Close?

That's a really cool shot!

I remember just a couple weeks ago when I was flying on AA 211 to JFK I spotted what appeared to be a UA/CO star alliance 777 flying in our direction. Although it didn't appear to be 2000ft above us, because it looked kinda close, but maybe it was.
Please let me know... If you know this is the end of the world, Let me know... If you know the truth...

soon7x7
Posts: 2267
Joined: Thu May 04, 2006 10:51 am

RE: How Close Is Too Close?

Negative...While both were a bit higher than my aircraft, the two pictured were same level...no tricks here...

 Quoting PapaChuck (Reply 17):I'm willing to bet there was 2000' vertical and a couple miles lateral between each aircraft.

Way off...
I was so amazed when I saw this I knocked the girl seated next to me out of her seat when I instinctively jumped up to the overhead baggage bin for my camera bag. (All apologies after the shot is taken)...Even the flight attendant was surprised to see the three of us in this cozy three way race back to the states..

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

RE: How Close Is Too Close?

 Quoting soon7x7 (Reply 19):Quoting PapaChuck (Reply 17): I'm willing to bet there was 2000' vertical and a couple miles lateral between each aircraft. Way off...

They may be at the same flight level, but there's a lot of lateral separation there...the angular size of the 777 against the 767 shows that pretty clearly.

Tom.

unattendedbag
Posts: 2169
Joined: Wed Oct 08, 2003 10:35 pm

RE: How Close Is Too Close?

 Quoting MSN007 (Thread starter):After looking at this picture following the link, I am wondering how close is to close?

Just looking at the picture isn't enough. If it was, this would be a close call too!

View Large View Medium

Slower traffic, keep right

timz
Posts: 6216
Joined: Fri Sep 17, 1999 7:43 am

RE: How Close Is Too Close?

 Quoting soon7x7 (Reply 19):While both were a bit higher than my aircraft, the two pictured were same level.
If they were, UA was... maybe 10 nm beyond Delta? And Delta was 5 nm from you?

PapaChuck
Posts: 111
Joined: Mon Aug 16, 2010 2:51 pm

RE: How Close Is Too Close?

I'm sorry, but there is absolutely no way that those two aircraft are at the same flight level. To get those two aircraft in the same photo at the same flight level, you would also had to have been at the same flight level. If that were the case, unless both aircraft were in a bank to the right, you should be seeing none of their bellies. If you were looking up to catch the Delta bird above you, another aircraft at the same altitude five miles further away would be completely out of sight below the frame. You have to consider the distances involved. It is deceiving from the pic, but trust me, the 777 is higher than the 767.

PC
In-trail spacing is a team effort.

timz
Posts: 6216
Joined: Fri Sep 17, 1999 7:43 am

RE: How Close Is Too Close?

We can do a pretty good job of proving that, if we can assume that the Delta 763 is wings-level.

If it is, comparing the wingspan of its image on the screen with its length we see it's 25 degrees above a horizontal line from the camera. So if it's 2000 ft higher than the camera it's 4700-4800 feet away, and (comparing the 767 and 777 lengths) the 777 is 11000+ feet away. If the 777 were also 2000 feet above camera level, it would be 9+ degrees above a horizontal line from the camera, or 15+ degrees below the 767.

Which is impossible, since the 767's length subtends 2+ degrees at the camera (it's 176 feet long and 4700+ ft away).

Likewise if the 767 is 4000 or 6000 or 8000 feet above the camera.

speedbird128
Posts: 1562
Joined: Tue Oct 28, 2003 2:30 am

RE: How Close Is Too Close?

 Quoting soon7x7 (Reply 19):Negative...While both were a bit higher than my aircraft, the two pictured were same level...no tricks here...

Why no contrails for the 777? The 777 is lower than the Air Berlin, and you were lower than the 777.

 Quoting SAAFNAV (Reply 12):Over Africa we, and I believe most other big carries fly a 2nm Right Offset, as there is no radar coverage.

I'd fly offset regardless of radar coverage. SLO any day thank you very much. Request should be approved by ATC.
A306, A313, A319, A320, A321, A332, A343, A345, A346 A388, AC90, B06, B722, B732, B733, B735, B738, B744, B762, B772, B7

soon7x7
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RE: How Close Is Too Close?

You guys crack me up...if had my 600mm lens in my lap your arguments may hold water however the largest focul length lens I had available was a 200mm. The below 767 shot was recorded with that lens but revealed blurry results through the acrylic window. I then recorded the former (above) shot with my 28-70mm. So your arguments of ten miles, 2000ft and all that are quite moot. Sadly my camera was not set up correctly at the time and my ship was being overtaken by the accompanying pair quite rapidly so I just took the shots. If I enlarge them they just fall apart. So what you see is what I saw. Two heavy transports , nearly level in flight about 1/2 to 3/4 mile lateral separation from each other. I'm quite familiar with distance and perspective...clearly some here are not... It was over the mid Atlantic...that is the way I shot it...argue away. The thread asked..."how close is too close"?...I think my image demonstrates just how close some like to get.

 Quoting PapaChuck (Reply 23):I'm sorry, but there is absolutely no way that those two aircraft are at the same flight level

All things considered, give or take a few hundred feet, at cruise in this tight formation they are close enough to be considered same flight level unless your PeterPan with a tape measure and you want to mince words...or measurements...then be my guest.

 Quoting timz (Reply 22):If they were, UA was... maybe 10 nm beyond Delta? And Delta was 5 nm from you?

When your on the ground and you observe a transport plane at altitude, you first see contrails then you try to identify the white dot or delta shaped object,...the aircraft. That is typically 6.5-7.5 miles up. You actually think these two are 5 and 10 miles respectively from my aircraft?...Remember, the lens was a 28-70mm...not a 2400mm telescope. Aircraft size as they appear to the naked eyes diminishes rapidly with surprising minimal amounts of distance.

 Quoting unattendedbag (Reply 21):Just looking at the picture isn't enough. If it was, this would be a close call too!

My point exactly...
 70-200mm

PapaChuck
Posts: 111
Joined: Mon Aug 16, 2010 2:51 pm

RE: How Close Is Too Close?

I crunched a few numbers myself. Grab a ruler and a calculator and follow along. Just make sure nobody's watching, because onlookers will point and laugh as you hold a ruler up to the monitor, just as my dear sweet wife did.

Warning: These are ballpark figures. I am aware that there is some room for error, but these numbers do prove a point. I won't give you my measurements since different monitor sizes and resolution settings will give you different numbers if you measure for yourself (as if anyone is actually going to try this).

While not the true definition of the term, I'm using distance from wingtip to wingtip to define lateral separation. I'm also assuming that the wings of both aircraft are level and interpolating the extended wingtip line as a line drawn fore and aft of the wingtip parallel to the contrails. With me so far?

First, measure the distance between the wingtips of the 767, then continue that line down and measure the distance from the right wingtip of the 767 to the extended left wingtip line aft of the 777. Divide that distance by the wingspan distance. I get a ratio of about 2.4. Multiply that by the wingspan of the 767, which is 156 feet. I get a distance if about 380 feet.

Now let's do the same thing in the opposite direction with the 777. I get a ratio of about 5.5. Multiply that by the 200 foot wingspan of the 777, and I get 1,100 feet.

So the 777 is 380 feet to the right of the 767, and the 767 is 1,100 feet to the left of the 777. Huh?

First of all, neither figure is anywhere close to 5 nautical miles, or 30,400 feet. Secondly, if both aircraft were at the same flight level, both figures should be roughly equal. We're obviously missing something here.

So now let's assume that the aircraft are vertically stacked, as I mentioned in a previous post. The 777, the 767, and the photographer are all in roughly a straight line, each aircraft separated by 2000 feet vertically, more or less equally spaced out. The 777 is then basically twice as far away from the photographer than the 767. We cut the 1,100 foot distance is half to compensate.

We now have 380 vs. 550. Closer, but still not quite lining up. Divide the 1,100 feet by three to assume the 777 is 4000 higher than the 767 and three times as far from the photographer than the 767.

Now it's 380 vs. 367. That pretty much matches up, but that would put the 777 2000 feet higher than I originally thought. Granted, these figures are basically guesswork. If either aircraft were rolled a few degrees from wing level it could mess everything up. My guesswork suggests a 2000/4000 foot stack, but it could just as easily be 2000/2000 allowing for some wiggle room. However, the basic math holds up. There is no possible way that those two aircraft are at the same altitude, laterally separated. There has to be a vertical component.

I'm done now. I need a nap.

PC
In-trail spacing is a team effort.

soon7x7
Posts: 2267
Joined: Thu May 04, 2006 10:51 am

RE: How Close Is Too Close?

I applaud your enthusiasm...BUT...Having been a pilot for nearly 30 years (really good at realizing apparent distances) and a surviving full time aviation photographer for 26 years, (sort of kind a has a grasp on lens compression and all that) an architectural illustrator for most of my career, Great eye for perspective) I think that when I observed a pair of Boeings overtaking my host Boeing, my observations, while not by the numbers spot on of course, are fairly accurate. Word?...(I can't believe i said that)...I know what I saw and documented it as no one would have believed me and even with photo evidence..."the planes never really hit the towers."...what more can I say. Pilots do this...not the first time I've seen this 'cept this time I was up there with them...Lucky me!...g

mandala499
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Joined: Wed Aug 29, 2001 8:47 pm

RE: How Close Is Too Close?

 Quoting soon7x7 (Reply 26):So what you see is what I saw. Two heavy transports , nearly level in flight about 1/2 to 3/4 mile lateral separation from each other.

Lateral... on different levels... the question is... how different? So we get onto:

 Quoting PapaChuck (Reply 27):The 777, the 767, and the photographer are all in roughly a straight line, each aircraft separated by 2000 feet vertically, more or less equally spaced out.

RVSM require vertical separation of 1000ft... so two aircraft going in the same direction isn't always 2000ft vertically separated from each other. In the case of the "NATS cross the pond rallies" (biggrin) the separation is 1000ft from aircraft going along the same track, and tracks going the opposite direction are some distance away...

So, now, if it's 1000ft vertical separation, what are the lateral distances now?

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !

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

RE: How Close Is Too Close?

 Quoting soon7x7 (Reply 26):Two heavy transports , nearly level in flight about 1/2 to 3/4 mile lateral separation from each other.

I think we're overthinking this...how close were they to you? From that, you can get a pretty good estimate of how far apart they each are just by their lateral extent in the frame.

From the photo you posted, it looks like a 767-300 and a 777-200 (based on proportions). Those aircraft are 180 and 206 feet, respectively, nose-to-tail based on the ACAP documents (nose-to-tail eliminates distortion from potential bank angle).

In your photo, the 767 is 512 pixels nose-to-tail and the 777 is 246. That works out to 0.352 ft/pixel for the 767 and 0.837 ft/pixel for the 777. Since we're talking small angles here, basic similar triangles set up the geometry...however far you were from the 767 when you snapped the shot, the 777 is .837/.352 = 2.38 times farther away. Put another way, if the distance from you to the 767 is 1, the distance from the 767 to the 777 is 1.38 (2.38 - 1).

So if the 767 and 777 are 0.5-0.75 miles apart, you would have had to be 0.36-0.54 miles from the 767 (0.5...0.75/1.38) ...possible, but it means you were considerably closer to the 767 than the 767 was to the 777.

Tom.

PapaChuck
Posts: 111
Joined: Mon Aug 16, 2010 2:51 pm

RE: How Close Is Too Close?

Are we over-thinking this? Absolutely. It's what we do around here.

One of the first lessons we learn in ATC 101 is that vertical is the easiest way to separate two aircraft. Once you establish 1000 feet vertical, you can get as close as you want laterally. As mandala499 said, there could just as easily have been 1000 feet between those two aircraft. I was just throwing 2000 feet out there as a general rule for aircraft cruising in the same direction. Bottom line is, it doesn't matter how close they were as long as they were at different flight levels.

And soon7x7, I by no means doubt the validity of the pic you posted. All I was trying to say is that there is an altitude difference. I apologize if I offended you with my little rant. I'm a little embarrassed to have posted that in the first place.

PC
In-trail spacing is a team effort.

timz
Posts: 6216
Joined: Fri Sep 17, 1999 7:43 am

RE: How Close Is Too Close?

 Quoting soon7x7 (Reply 28):I know what I saw and documented it as no one would have believed me and even with photo evidence..."

The photo evidence is good, and it shows the 777 was at a higher altitude than the 767. (That's assuming the 767 was wings-level; if we can't assume that, then we can't conclude anything either way.)

[Edited 2012-01-10 13:29:00]

[Edited 2012-01-10 13:32:58]

[Edited 2012-01-10 13:42:53]

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