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How Far Away Can One See From A Aircraft?  
User currently offlineB747forever From Sweden, joined May 2007, 17067 posts, RR: 10
Posted (4 years 3 months 3 weeks 15 hours ago) and read 15668 times:

I am sorry if this is not the right forum for this thread.


Let's say that a aircraft flies at FL380 on a clear day how far away can one see from the aircraft. Also if one is on the ground how far away (distance) from where the aircraft is can you see it?


Work Hard, Fly Right
16 replies: All unread, jump to last
 
User currently offlineViscount724 From Switzerland, joined Oct 2006, 25458 posts, RR: 22
Reply 1, posted (4 years 3 months 3 weeks 13 hours ago) and read 15624 times:

Here's a calculator which should answer your questions. Just plug in the altitude to obtain the approximate distance to the horizon.
http://www.ringbell.co.uk/info/hdist.htm


User currently offlineB747forever From Sweden, joined May 2007, 17067 posts, RR: 10
Reply 2, posted (4 years 3 months 3 weeks 13 hours ago) and read 15609 times:

Quoting Viscount724 (Reply 1):



So when a airplane cruise at FL380 one can see about 239miles away and the airplane can be seen by people on the ground 239miles away.



Work Hard, Fly Right
User currently offlineBellerophon From United Kingdom, joined May 2002, 583 posts, RR: 59
Reply 3, posted (4 years 3 months 3 weeks 12 hours ago) and read 15589 times:

Viscount742

An interesting and useful little calculator - thanks for posting the reference - I've been playing around with it.

Cruising at max altitude, on my latest aircraft type, the horizon is 28 minutes flying time away.

Cruising at a much higher max altitude on a previous aircraft type, the horizon was only 14 minutes flying time away! 

Best Regards

Bellerophon


User currently offlinetimz From United States of America, joined Sep 1999, 6839 posts, RR: 7
Reply 4, posted (4 years 3 months 3 weeks 11 hours ago) and read 15528 times:

If you're looking at Mt Shasta from FL 380 over the Central Valley it should be visible from at least 300 miles. Roughly, distance to the horizon from Mt Shasta, plus distance to the horizon from FL 380.

User currently offlinej0rdan From Canada, joined Feb 2010, 127 posts, RR: 0
Reply 5, posted (4 years 3 months 3 weeks 10 hours ago) and read 15512 times:

Another formula you can use is:

Distance seen in miles = 1.23 (X) square root of altitude in feet

Jordan


User currently offlinetimz From United States of America, joined Sep 1999, 6839 posts, RR: 7
Reply 6, posted (4 years 3 months 2 weeks 6 days 13 hours ago) and read 15180 times:

That's distance to the horizon, with some allowance for refraction.

User currently offlineTS-IOR From Tunisia, joined Oct 2001, 3488 posts, RR: 6
Reply 7, posted (4 years 3 months 2 weeks 6 days 13 hours ago) and read 15169 times:

When you are FL380 the horizon is 239NM away, but people on ground won't see you when you are 239NM from their vertical. The maximum i have ever seen from ground is contrails from approx. 80NM.

User currently offlineArniepie From Belgium, joined Aug 2005, 1265 posts, RR: 1
Reply 8, posted (4 years 3 months 2 weeks 6 days 13 hours ago) and read 15150 times:

AFAIK, the answers are incomplete, for instance you can see farther on the poles vs the equator due to the shape of the earth, also air temperature changes the light behaviour properties.
I remember reading somewhere that on a cold ,clear winterday some mountains on iceland can be seen almost from 400 miles away on cruising altitude. (IIRC)

[Edited 2010-06-13 15:02:55]


[edit post]
User currently offlinexero9 From Canada, joined Feb 2007, 153 posts, RR: 0
Reply 9, posted (4 years 3 months 2 weeks 6 days 10 hours ago) and read 15068 times:

Quoting Arniepie (Reply 8):

Soooo in other words, you can't know for sure how far, but either way we can agree it's pretty far!


User currently offlineSlowFly From South Africa, joined Jun 2009, 15 posts, RR: 0
Reply 10, posted (4 years 3 months 2 weeks 5 days 15 hours ago) and read 14815 times:

Some useless knowledge: a quick rule of thumb for radio line-of-right calculations is to pretend the earth's radius is 1.33 bigger than actual. Due to diffraction.

User currently offlinecobra27 From Slovenia, joined May 2001, 1016 posts, RR: 0
Reply 11, posted (4 years 3 months 2 weeks 5 days 14 hours ago) and read 14769 times:

Quoting TS-IOR (Reply 7):
When you are FL380 the horizon is 239NM away, but people on ground won't see you when you are 239NM from their vertical. The maximum i have ever seen from ground is contrails from approx. 80NM.

True. No way you can see 240 miles


User currently offlinetimz From United States of America, joined Sep 1999, 6839 posts, RR: 7
Reply 12, posted (4 years 3 months 2 weeks 5 days 13 hours ago) and read 14734 times:

I've seen contrails 170+ miles away (747s making the turn over the Avenal VOR, seen from the hill above Berkeley, California). If I were standing on a higher mountain, with clear air and low sun backlighting the contrail against a fairly dark sky, 240 miles would be no problem with 10x binoculars.

http://www.jstor.org/pss/208390


[Edited 2010-06-14 14:54:36]

[Edited 2010-06-14 14:57:05]

[Edited 2010-06-14 14:59:20]

User currently offlineAncientPelican From United States of America, joined Apr 2009, 34 posts, RR: 0
Reply 13, posted (4 years 3 months 1 week 4 days 17 hours ago) and read 14178 times:

I recall a TWA transcon heading westbound one evening where the pilot came on and said the people on the left side of the plane could see the lights of St Louis while those on the right could see Chicago.

User currently offlineunattendedbag From United States of America, joined Oct 2003, 2328 posts, RR: 1
Reply 14, posted (4 years 3 months 1 week 4 days 17 hours ago) and read 14176 times:

Quoting B747forever (Thread starter):
Let's say that a aircraft flies at FL380 on a clear day how far away can one see from the aircraft.

On a clear day, you can sometimes see the moon, and that's more than 238,000 miles. If it's dark outside, then you can usually see the stars.

[Edited 2010-06-22 10:31:32]


Slower traffic, keep right
User currently offlinerolypolyman From United States of America, joined Mar 2009, 159 posts, RR: 0
Reply 15, posted (4 years 3 months 1 week 1 day 23 hours ago) and read 13912 times:

I recall one night on AA in November 1996 we were at FL390 on a leg from the AEX to FZT VOR into DFW. I've been all over Texas and know the layout of cities like a map, and that's just what I was seeing with it being a particularly clear autumn night with city lights painting out the location of everything. Just before starting our descent I recognized our position as being just north of Nacogdoches. From that location I was able to easily distinguish the city lights of Waco, Temple, Austin, College Station, and Houston all at once. On the distant horizon I could distinctly see a nebulous but bright pancake smear of San Antonio, which was about 220 nm from where we were.

That was an amazing sight as I was seeing territory in one single glance that took many hours to traverse by car. It was almost like being in space. One of my best memories while flying, and definitely the furthest distance I can ever recall seeing from the air.

[Edited 2010-06-25 04:56:20]

User currently offlinenomadd22 From United States of America, joined Feb 2008, 1871 posts, RR: 0
Reply 16, posted (4 years 3 months 1 week 1 day 17 hours ago) and read 13851 times:

Diffraction will only add about 40 miles to the distance of the horizon.
If you're flying around Tibet, all things considered, you should be able to see Everest peeking over the horizon at close to 500 miles.



Andy Goetsch
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