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Curvature of horizon?

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Curvature of horizon?

Old 11th Nov 2004, 17:53
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Curvature of horizon?

Apologies if this isn't quite the right forum to ask this question, but I suspect military aviators may be best placed to come up with an answer.

I've recently been re-reading 'Night Fighter' by C F Rawnsley and Robert Wright, which to my mind is a classic of aviation literature. In one of the chapters Rawnsley describes a high-altitude test flight in a Mosquito XV, and seems to imply that from 43,000ft he could see the curvature of the earth ("It was the first time that I had seen for myself that it really did curve, and that the earth was round").

The highest I've ever been was 47,000ft in a Hunter (on a gin-clear day over South Wales) and whatever flight levels 747s and the like habitually attain. However, on no occasion have I been aware of seeing curvature of the horizon, and a bit of mathematics suggests it's unlikely. Any FJ folks who've been there care to comment?

John
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Old 11th Nov 2004, 18:00
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You mean the earth isn't flat? Damn I knew that Copernicus bloke was on to something...........

Might explain why my studes are always failing the Nav phase though...........
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Old 11th Nov 2004, 18:28
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Been to the high fifties a couple of times (most certainly a 'guest appearance' rather than sustained), in the nanosecond that I looked away from the engine instruments, I did not notice the curvature of the earth. Been to 48 a lot, a more determined search did not reveal any sign of curvature. I think a lot of the 'curved earth' perception comes from photos - I take loads of photos and (because the lens is wide angle?) the earth appears curved - makes for a nice photo, but it's not what I saw with my Mk1 eyeball.

Ray
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Old 11th Nov 2004, 18:53
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once got up FL37.5 in the old Nimrod mighty war platform, (on an air test mind you so not much gas) which is a long way up for the old girl.

Not a chance of seeing the curve that low, but I,ve also been down at 200ft in one which is definately a bit low for comfort
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Old 11th Nov 2004, 19:43
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The curvature is just discernable when ‘above FL 550’ (Lightning days), the effect is clearer as the daytime sky darkens at altitude.
Modern jet pilots can deduce curvature due to the HUD horizon indicating the local geographic level, which is not aligned with the observed horizon, this is depressed due to the curvature of the earth.
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Old 11th Nov 2004, 19:46
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Not visible at FL 450 - the highest Ive been to.
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Old 11th Nov 2004, 19:53
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Hello Bluetail,
Have recently voyaged to FL410 in the Mighty Hunter, it may as well have been Mars for the venerable warbird....

ALWAYS assume NEVER check
ps. no curvature visible
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Old 11th Nov 2004, 20:19
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Done 410 in a Mark 1 Nimrod. Things got very quiet.

Reckon you can see the curvature at sea level on certain days too.
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Old 11th Nov 2004, 20:43
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I'm with safetypee
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Old 11th Nov 2004, 21:28
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A friend who regularly does 70k+ says you can see the curvature but it never goes dark just a deep blue.
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Old 12th Nov 2004, 05:14
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Yup - it can be seen at sea level sometimes. It seems to be more to do with the width of your field of view. I've only seen it when I had an unbroken view left to right that was all sea, calm and wider than my field of vision. On board ship & certain coastal places.
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Old 12th Nov 2004, 06:31
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this photo was taken at FL350 earlier this year, over Greenland at about 3am.



It just about shows the curvature of the earth.

Last edited by Yeller_Gait; 14th Nov 2004 at 18:07.
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Old 12th Nov 2004, 09:02
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Been to F420 before, but we were in a horrendous CB, very bumpy, and I was too scared to look outside!



kipper
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Old 12th Nov 2004, 10:23
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During a ride in Concorde (G-BOAC) on hot weather trials in the Far East (circa 1975) I attained FL650 several times. Rivet, the earth is round and the sky was very dark purple going on black. I even took some photos...
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Old 12th Nov 2004, 10:29
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I had a quick trip round the Bay (of Biscay) in Concorde a few years back and you could see curvature, the sky was dark and the windows were pleasantly warm.
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Old 12th Nov 2004, 11:00
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adrian mole, probably the David Clark visor effect then!
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Old 12th Nov 2004, 13:16
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I saw on a Concorde trip. I think it was about 55k ft to JFK.
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Old 12th Nov 2004, 14:18
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Went a fair bit above FL 500 in the Vulcan many years ago. But the view out of the windows was so limited, 'twas hard to tell whether or not the horizon was curved. Besides, we were turning hard at the time to pi$$ off the Phantoms which were failing dismally to get into missile launch parameters....
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Old 12th Nov 2004, 15:14
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Managed FL415 in the middle 70's returning from a direct NavEx to Bear Island (to eat the rations) at about 2000 in July, and the curvature was noticeable when looking north. Not much else though

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Old 12th Nov 2004, 21:11
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Best way to see the curvarure of the earth, is with your eye's pupil just slightly above sea level when you're bathing in the sea on a perfect, calm day.
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