Sextant and airplanes

[jcboliveira 1]

I'm trying to recreate a 1947 DC3 flight on FS2002. The flight is placed in Africa and for what I found the sextant was used. Does anybody knows how to use a sextant in an aircraft, specially during the day when you only have the sun. I found some material about ships but there the ground speed is known.ThanksJos

[Guest mberg]

The sextant used in those days was normally done by a navigator who in the absence of ADF or AM radio stations, ground light beacons, or radio beaming (A or N morse signals)--there were no TACAN or VORs to speak of-- unbagged his sextant, pulled out a stand and elevated himself into the dome behind the pilot. He had a number of books that contained calculations of the sun and star positions for a time of day and approximate position of the aircraft. The navigator would then try to keep the sextant level (dutch roll in the gooney was notorious)for about 4 minutes and track the sun in the sextant's bubble via a sighting lens on the sextant. After the time expired, he would then use the tables to establish a line on the map related to his Dead Reckoning position. A combination of the two would give an approximate fix (if he was real good, maybe within 10 miles). It was imperative that the navigator kept up an airplot during flight and applied any calculated wind to establish a DR position. The fix comapred to the airplot position would help establish a newly calculated wind. He would also use a driftmeter to determine drift and with the aid of an E-6B nav wind calculator, could determine wind. Good navs also could estimate wind by watching surface water, sea waves and even cloud patterns (rows). Night nav using the sextant was much more accurate since he could sight 3 stars and or moon/planets and get three lines forming a triangle, the center of which would be the assumed position.Markex-nav instructor (Mather AFB, 1965-68)

[Guest]

Mather AFB....humm...must be have been 323rd type of person. :) Hi Jose.A more recent aircraft that used the sextant was the C141. It had a port in the ceiling just aft of the Nav table for a specially designed sextant. The sextant was quite compact, and unlike sea bound sextants, it had a periscope assembly that passed through the special port into the slipstream. The port was about 2 inches in diameter. The Navigator would stand on a little stool (stowed on the flight deck) and take the shots for the LOP (lines of position). Then, using charts, some math and a plotting board a solution would be

[Guest DNelson]

I remember reading something in Ernie Gann's "Fate is the Hunter" about sky shooting techniques. If you're shooting something like a star it's relatively easy to put the crosshair on it, but daytime shots of large targets like the sun and moon required some kind of averaging mechanism in the sextant. Also, the sextant has a bubble level on it since the elevation readings depend on the sextant being level with the horizon.My father was a B-29 navigator and knew this stuff inside and out. He did most of his initial navigator training in Texas and I remember him talking about how fun it was to try to get good sextant readings while flying at low altitude in a twin Beech on those hot Texas afternoons. Almost impossible.Dan

[jcboliveira 1]

Thanks to all. I now have some ideas about trying to simulate sextant navigation. Of course I can't use the device but It's going to be fun to do what I can to simulate the situation and try to guess where I'm in a map.Jos

[Guest]

Hi Dan:"daytime shots of large targets like the sun and moon required some kind of averaging mechanism in the sextant"Actually you shoot the upper or lower rim of the body (sun or moon). There are compensations for the diameter of those objects (along with some fairly hefty filters for the sun and moon). "Also, the sextant has a bubble level on it since the elevation readings depend on the sextant being level with the horizon."The bubble level is to ensure that the sextant is perpendicular to the horizon

[Guest Joe]

Just a couple of years ago I was talking to my Uncle who was navigator on a B-58 Hustler back in late '50s or early '60s...somewhere around then. Our conversations always gravitate to aviation. :)Anyway, he said they routinely used a sextant to navigate. My chin was on the floor. I found it amazing that they were flying supersonic aircraft that could deliver nuclear weapons and were finding their way using technology that the early explorers used.Joe Sumrall[big]B[/bIG]USH [bIG]F[/bIG]LYING [bIG]U[/bIG]NLIMITED ...at home in the wild

[Guest]

Not all that surprising if you consider the scenario:- no GPS- no VORs, NDBs or TACAN (at first because they're likely turned off to prevent enemies from navigating accurately, afterwards because they're blown to smithereens in the nuclear explosions)- probably radiation causing atmospheric disturbances so radios and radio based navigation are useless basically they'd be limited to INS and stellar navigation (with INS being potentially unreliable.INS needs to be updated from time to time. Stellar navigation and GPS are the two most reliable ways to do that while underway (on the airfields they have specially marked spots the location of which is very accurately known and can be used as a reference), and in the 105-s and 1960s there was no GPS so the only way to update your INS was taking starshots.

[Guest mberg]

James Connally (Waco Tx--1963) Mather AFB--B-52 NBT Nav flight and academic instructor 3535 Nav Tng Wing, 1965-1968 (T-29D). F-111's 1968-1973 River Rat "Nam" 1972Preferred the old bubble and hand held sextant--much more of an art.

[Guest Joe]

Not all that surprising if you consider the scenario:None the less, in my very limited knowledge of everything that has to do with aviation, I was surprised when he told me of it. Okay? After all, I only got my ticket to carry passengers in January of '70 and Commercial in '90. That's hardly enough time in and exposure to aviation to have pondered the scenario that you, obviously, already had.Why is it, in this forum, that folks are waiting in the wings for the opportunity to take exception with what others post. Unless it is something blatantly wrong, why not just let a post stand? Huh?Kind of reminds me of the local FBO. There is always some super pilot that rolls thru that has been higher, flown faster, flown the most planes and generally knows more about flying than anyone else. LOL! Funny! And, he never misses the chance to expound on his vast knowledge...usually at someone else's expense. With a glance at my buddies I usually just give a roll of the eyes, turn on my heels and exit to the hangar to hang out with the mechanics. Yuck! I knew I should have stayed the heck out of this room.Joe Sumrall[big]B[/bIG]USH [bIG]F[/bIG]LYING [bIG]U[/bIG]NLIMITED ...at home in the wild

[Guest]

Taking no exception at all Joe. Just pointing out why they did it that way for people who don't have your background (as you could have done yourself but chose not to).

[Guest]

I've been trying to get a copy of a book, 'The Complete Air Navigator' by the Australian Donald Bennett (who became Air Vice Marshall Bennet-leader of the 'Pathfinders' in Bomber Command in WW2). Bennett published the book in 1936 and it was in print for 30 years and he was the first pilot to get a '1st class navigators' qualiification.The book details navigation by sextant.DaveT