Were Nav's gone from -141s when you were crewing them?
Celestial navigation and Machado's five questions
- Thread starter beasly
- Start date
Were Nav's gone from -141s when you were crewing them?
Orange Anchor
New Member
Virtual, yes, unfortunately. I fail to see the fascination with pushing buttons. I do see the fascination with dropping down to maybe 1500ft, navigating to points using only visual references and trying to arrive at a given time. Nice exercise.
When training as a FAC we often had to hunt for landmarks visually. The exercise was to go from a readily identifiable point to the desired point. One exercise was to find a house. No house. Go to another point and work back. No house. Finally, in the right light you could see the foundation of the home that had burned down a few years earlier. It was a fun way to fly.
LoadMasterC141
Well-Known Member
Not completely. They were on board for airdrop but not really anything else. I think they had to do one line mission per year for currency or something.
beasly
Well-Known Member
Hi JWscud.
Thank you. However the forum seems to enjoy the topic, so I will be posting online when I get back to you.
I did a 12 mile walk today to MCO and back and thought about this topic a couple of times during the trek.
Thought One was next to an open field where you can actually consider the horizon--i.e. your line of sight is not encumbered by buildings, trees etc. I think that will be a problem. Fortunately, the beach is 1.5 hours away and I am making it a point to get out there every payday.
Thought Two: From an earlier post about the accuracy of the stuff--being dead on or 3 miles or less. The poster mentioned that it was a 3 star reading. Couple that with a comment on Bowditch's book on Amazon about the need for accurate tables, sextant and time and I was surmising that the stuff could be reduced to drills--similar to the drill for diversions in VFR--what time is it? where am i? circle that on the chart. Where am I going? circle that on the chart. What is the rough heading? Turn that way. Terrain? Navs? Fuel? what comes next? what comes after that.
That is a drill.
I actually contemplated "step one" today and the answer is analguous to Heinlein's famous recipe: "First catch a rabbit!" i.e. "first locate the star ...."
That will occupy some time and is something I have wanted to do for a long time.
From there I surmised you would have to rinse-lather-repeat on the above and then go to your chrono-thingy, celestial tables, your sextant (or whatever is used in a.c.) and finally your nav charts.
Thought three was an actual aviation problem. Say I was flying A to B straight line and its a routine thing and I want to spice it up a bit. I have all these fancy nav tools and accurate time. What can I learn about the stars given these things? What I surmised is that the relative position of an astronomical body relative to my aircraft would change and would be predictable. So, say I am starting at time T0 at point A and will be at point B at time T1. at A at T0 the Constellation Beasly is at point C. What point D will Constellation Beasly be in relation to my A.C when I get to B at T1?.--I am guessing this is what you guys do. If I am correct, then we have a backup for situational awareness and something interesting to add to the mix. We can fly from A to B and actually see if Constellation Beasly is where it should be. If it is, then the derivative benefits--time, distance substitutes--are self evident.
Also, I lost a couple of pounds on the walk!
beasly
Well-Known Member
The Brits really emphasize that stuff.
I start my students on Pilotage before they can land--not a formal study mind you, but correlate "that large expanse of water out to the right with something on your chart" . It seems silly, but it is a fundamental a lot of people don't get. Starting with correlating "The Atlantic Ocean" with a spot on the map is an important thing. From there, they have fun and start looking for stuff--that group of lakes to "based on what you see here, what should be off aft of port?" and hearing--" a big city?" and then seeing them say "Wow! Look! A big city!" Then they start having fun and start actually piloting very early and gain a lot of confidence. Throw in navaids a couple lessons later and they are safe.
Then, drop down to 1500 ft AGL.
It completely changes.
The Brits will drop in 10 degrees of flaps to facilitate a nose down attitude in S&L flight. I have done it once during decreasing cloud layer with a PPL student of mine. I was monitoring ATC in case I needed to declare IFR. I was very familiar with the area, but at that altitude and visibility--VFR? I was lost--in real life, I would have put her down in a field.
There are two ways of getting an accurate fix at sea (the general technique for stellar observations is similar for bubble sextant observations from an aircraft, but I've never used a bubble sextant so I can't go into detail).
The traditional (and less taxing) method is two observations of the sun over a period of several hours. You generally (but don't have to) start with an assumed position, which is a rough idea of where you are. You take a morning position line when the azimuth of the sun is within +/-30° of true east, and at local noon you can observe the latitude. The requirement for an early sight within 30° of due east is to get the cut of the position lines as close to 90° as possible to minimise the ambiguity in the observed position.
You know what course and distance you think you have made between the two observations, and you can transfer your morning position line to where you think you are, and where that position line crosses with your observed latitude is your fix.
Star sights are taken at sea at morning and evening twilight, as they are the only times when both stars and horizon are clear enough to take good sextant observations. I understand that bubble sextants (which provide their own horizon) can be used at any time of the night.
You need a minimum of 3 position lines for a good fix, but normal practice is to observe 7 different stars (and planets if available) to guard against poor observations. The different position lines are then run forwards or backwards to a common time using the course and distance steamed as assumed above and your fix is at the best cut of position lines.
Both methods with practice are accurate to within 1-2 NM depending on how clear the horizon is.
The nuts and bolts of selection of stars and calculating your position lines are the difficult part of the evolution, and your textbooks will be far better than what I can offer here; the essence of the process is that knowing the UTC and your assumed position, you compare your observed altitude of the celestial body with the altitude you calculate using the time and data from the Nautical Almanac to determine the direction and location of your position line. The calculations can either be done using (in order of speed) sight reduction tables, a calculator or log tables.
It's not so much a drill as a methodical sequence of calculations. Going from your seven stars to a position on the chart takes about 30 minutes when you're well practiced.
The Rapid Sight Reduction Tables for Navigation are published by the British Admiralty and are what used to be used in air navigation. They contain a full explanation of their use in the front and might be worth adding to your list.
The traditional (and less taxing) method is two observations of the sun over a period of several hours. You generally (but don't have to) start with an assumed position, which is a rough idea of where you are. You take a morning position line when the azimuth of the sun is within +/-30° of true east, and at local noon you can observe the latitude. The requirement for an early sight within 30° of due east is to get the cut of the position lines as close to 90° as possible to minimise the ambiguity in the observed position.
You know what course and distance you think you have made between the two observations, and you can transfer your morning position line to where you think you are, and where that position line crosses with your observed latitude is your fix.
Star sights are taken at sea at morning and evening twilight, as they are the only times when both stars and horizon are clear enough to take good sextant observations. I understand that bubble sextants (which provide their own horizon) can be used at any time of the night.
You need a minimum of 3 position lines for a good fix, but normal practice is to observe 7 different stars (and planets if available) to guard against poor observations. The different position lines are then run forwards or backwards to a common time using the course and distance steamed as assumed above and your fix is at the best cut of position lines.
Both methods with practice are accurate to within 1-2 NM depending on how clear the horizon is.
The nuts and bolts of selection of stars and calculating your position lines are the difficult part of the evolution, and your textbooks will be far better than what I can offer here; the essence of the process is that knowing the UTC and your assumed position, you compare your observed altitude of the celestial body with the altitude you calculate using the time and data from the Nautical Almanac to determine the direction and location of your position line. The calculations can either be done using (in order of speed) sight reduction tables, a calculator or log tables.
It's not so much a drill as a methodical sequence of calculations. Going from your seven stars to a position on the chart takes about 30 minutes when you're well practiced.
The Rapid Sight Reduction Tables for Navigation are published by the British Admiralty and are what used to be used in air navigation. They contain a full explanation of their use in the front and might be worth adding to your list.
Orange Anchor
New Member
I've always enjoyed looking out the window but the FACing was one of the great periods in my life. Not just flying but life. I learned an a lot in a short period of time.
As for the chart read, you learned to look for stuff. Greener vegetation was often one of the cues to a stream or creek. Fly down-sun and look for the glint off the water.
And yes, dropping lower changes everything. One of the last sorties I flew in pilot tng was with a former -105 driver. We started out at 1500ft AGL and he kept saying, "you can see the whole world from here." We wound up at less than 500ft and rocking along over the west Texas scrub. All these years later and I still remember him saying, "I've got it" and doing a hard G pull up, roll off and head back down at a steep dive angle and then lighting the burners for the escape at low altitude. "That's the way we had to do it in Hanoi."
Personally I would like to do some point to point at 500ft but everyone gets their butt in a wad over a low flying airplane. Not worth the fun vs. the potential of dancing in front of a mahogany desk.
Now, the other end of the envelope is flying in wx and going to mins. That too is fun. Take off and whomph! immediately on instruments. Go someplace and see nothing enroute and ease down to 200ft (or lower on a CAT IIB) and FOOFH! there it is right in front of you.. a nice long runway.
beasly
Well-Known Member
Jwscud.
Thank you.
This part scares me:
Bubble Sextant for Beasly.
From the rest of your post, Celestial Nav is just GPS over a longer time frame.
With GPS, the "celestial bodies" are satelites and the time is C. Fixes are done multiple times per second and instead of a chart, we have a screen that displays all the work of centuries in milliseconds.
That is a good thing.
That said, backup is a good thing too.
I have sent an email to myself at work reminding me to bring this up as a possible project. My office mate is a mathemetician who does numerical programming and this might make our company some money.
It will certainly be a fascinating discussion.
CPS--Celestial Positioning System..
You heard it here first.
thx.
b.
Orange Anchor
New Member
The military is reportedly very concerned about GPS denial. Thus...
http://fer3.com/arc/imgx/kaplan2.ppt.
Autothrust Blue
”…trusting ze process…”
Well worth doing and a skill worth having...along with the ability to manage the automation, which is here to stay (I guess).
I flew aforementioned 182T today over the LA basin, IFR. It was very nice to have the airplane doing the flying while I talked, thought and watched for other airplanes. It arguably can make single pilot IFR a much safer experience when properly used. It sure saves on the workload a lot of the time.
That said, I am not really convinced it's any better[1] than when I fly the Twin Bonanza, with its VOR-DME RNAV set straight out of 1982, and no autopilot.
[1] LPV approaches obviously excluded...
Orange Anchor
New Member
The good and accomplished pilot can and does use all the tools available including the automation and the *windows*.
RICHARD5
Well-Known Member
This is very kind of you. I imagine you'll be getting bunches of PM's since working out a sight with the H.O. tables is not easy for beginners.
nocturnalaviator
AI Jedi
I guess I can see the curiosity about it, as I have done some research about celenav. For practicality, you would always have a compass when flying as it is a vfr requirement. There are those who can't hold an altitude or heading let alone using a sextant. I think practicing basic airmanship is woth more in life than celenav. Imho.
RICHARD5
Well-Known Member
I've only used cel nav when on the waters. Like most newbies, one of my first times by myself I deduced our position to be on land when we were 150 nm off shore. In the early 80s sailing from Morro Bay, CA south to San Diego with a planned stop at Catalina Is., I missed the island by about 50 nm. Much reading and practice cured that.
By the mid-80s I was pretty good. In 1986 on a 2 crew sailing a 65' sloop from CA to Hono, thence Apia, American Samoa, I was able to pin point our land fall at both destinations. I was within 10 nm rounding Koko Head and on the spot for our ETA. Coming into Samoa I was a wee bit more than 20 nm on our position and 12 hours early on our ETA. I like to think that was due to weather but who am I kidding.
Kauai to Dutch Harbor I missed our ETA so bad it was worthless. But we found the island without having to slog up or down the chain so I'll take what I can get.
After listening to the stories of duress the navigators of the air regaled me with I never had the nerve to try cel nav in a plane. One particular story about flying above the Artic Circle really drove home how awesome those guys are.
beasly
Well-Known Member
And then there are those who are trimmed for hands-off at 250 AGL after T.O. and planning for "what comes next"
beasly
Well-Known Member
This is what is fascinating about aviation.
I learned 3 things here:
- Green vegetation cue to stream or creek
- Fly down sun to see glint off of water (why can't you see it flying up-sun?)
- Just when you think 1500 feet is low, some body says, "you can see the whole world from here!):bandit:
absolutely fascinating stuff.
thx
beasly
Well-Known Member
It will be fun!
Like that Dr. Seuss book!
Payday is Friday--Bowditch's by next week.
Cheers.
granlistillo
Well-Known Member
Totally touchy feely here, but Dead reckoning/celnav in a modified Lockheed electra was challenging and romantic. Kinda feels like something out of a Ernest K Gann novel.