PPRuNe Forums > Flight Deck Forums > Tech Log > Chasing the sun PDA View Full Version : Chasing the sun R2000/18302nd Dec 2007, 22:37Sorry guys I could figure this out in College but cant remember how!! If you flew at the equator in the direction of the setting sun at what speed would you have to fly in-order for it to never set? I know the sun passes through 360 degrees of longitude in 24 h, so it moves at 15 degrees an hour and I know one degree of latitude = one NM but I cant seem to put it together. As you can guess Im studying for CX NZScion2nd Dec 2007, 22:45If my maths is correct, 15 degrees per hour = 15 * 60 = 900 knots. R2000/18302nd Dec 2007, 22:54that's what I thought but I know 1 degree of latitude = 1NM but what about 1 degree of longitude, at the equator does it = 1NM too. or do I have this all messed up. Shiny side down2nd Dec 2007, 23:09R2000. a mile a minute...! Hint, 1 nm mile per degree is a very small circumference i'll leave the rest to you. YRP2nd Dec 2007, 23:42Well the earth is pretty close to spherical, so 1 degree on any great circle ought to be the same. As pointed out above, it is 1 nm per minute of lattitude not degree. So I think the 900 kt figure is right. kiwi chick3rd Dec 2007, 00:03So, then? 1 nm per minute, and there's 60 minutes per degree? So if it moves 15 degrees per hour, 60 nm x 15 per hour = 900 nautical miles per hour? I don't think I could quite keep up in my cherokee. But just about. enicalyth3rd Dec 2007, 01:07The sun appears to trace an ecliptic. When its declination declines to the Statute of Limitations set by ICAO, whether it is visible or not, it must switch off its logo because it is above 10,000ft. Some countries file a difference and so sometimes, despite hemispherical, quadrantal and RVSM rules, the sun never sets or rises or performs an autoland. This is often due to the time of the month and is therefore never mentioned in polite society. But the equator must be 21600 nautical miles from start to finish because of a geographical causation known as Jepps. Unfortunately the sun has also filed an ICAO exemption, mutually agreed by the earth and does not always and everywhere take 24hrs to come back to the same place. This is known variously as "bidding", "seen my roster" and "seniority". The sun in the solar system has seniority number one. Its name in the Star Almanac is "Nigel" and is found in that part of the Sky remotest from Ryanosaur, Virgo, the Star Alliance and also the Constellation TriStar 411A. But roughly speaking if an aircraft flies to the west along the equator covering 21600 nautical miles in very approximately 24 hours the local hour angle of the sun appears to be stationary. In which case you can write on the back of it whether you have been naughty or nice, put a stamp on it and send it to the North Pole. Whether the sun rises or sets also has to do with ATC clearance. At 90 odd million statute miles above I have an idea that the sun does not set, ever, basta cosi. When this happens cabin temperature rises above 24 deg C. The fun really starts when instead of flying west you fly east. Interesting things happen when you cross the International Date Line. 24hrs is blotted out of your life and your International Date has cleaned out your credit cards. So the answer is 900knots or thereabouts with x1 set on MSFS Options. Now, am a reet or a meringue? Of course everyone knows that man never went to the moon, the world is flat and duty time cannot exceed 12 hrs. Therefore unless someone sets x2 on the MSFS Options no one will ever know for sure. Anyone who says anything different is either a liar or a professional pilot. Merry Xmas to One and All from the "E" and KO Sally. I'm still on the green side of the turf. kiwi chick3rd Dec 2007, 01:13Could you please send me a bottle of what you just drank? knox3rd Dec 2007, 01:20This one too 900*COS lattitude Think it gives the speed of the sun in kts at any lattitude. Knox NZScion3rd Dec 2007, 09:26Merry Xmas to One and All from the "E" and KO Sally. I'm still on the green side of the turf. Could you please send me a bottle of what you just drank? I think it was smoking a bit too much of that green stuff on the side of the turf... :) Der_dk.3rd Dec 2007, 16:35Hi all Feel free to correct me if i´m wrong, but I would say that altitude plays a part. So the 900 kts is only correct if you were to fly really low (0 ft) Shiny side down - maybe that was what you were suggesting... Regards White Knight3rd Dec 2007, 16:46and of course if you fly anywhere north of the arctic circle around June 21st, the sun ain't gonna set anyway - even if you fly east. Not Helpful I Know:}:} IRRenewal3rd Dec 2007, 17:29Feel free to correct me if i´m wrong, but I would say that altitude plays a part. Correct. If you fly 1 nm high (to pick a random number), this increases the circumference by 6.28 nm. So, not 900kts but 900.261 kts. Or roughly 0.25 kt per nm of altitude. (edited cause I'd forgotten how much PI is :}) Shiny side down3rd Dec 2007, 18:32Of course, if you have the kit to do the speed, I'm sure the thrill will be enhanced by doing it at a lower level, say, just enough to cause a nuisance. but thats getting silly. stator vane3rd Dec 2007, 18:41that was not drink inspired-- it was genetic. Tmbstory4th Dec 2007, 07:42R2000/1840 The apparent rise and fall of the Sun, is our planet rotating to the East at 15 degrees each hour. Tmb