A Secondary Saga Southbound Sextant Adventure .. "Seeking Sally"

[Dil52]

To the Roaring 40’s:
In this flight we’re going to make at night flight fromMendoza (SAME) and arrive in San Carlos de Bariloche (SAZS), sometime nearsunrise.
We’ll make the flight plan to leave Mendoza at 3:00 AM localtime and arrive in San Carlos de Bariloche sometime near sunrise. The intermediateFix#1 Point will be located at S37° 00.00’ W70° 00.00’ just to make thesettings easy. Then SZAS located at S41° 10’ W71° 10’.
We can use the moon up until about 6:00AM local, when it’llbe setting in the west for our longitude reading and by the time we reach asfar south as 40° ACRUX, which is the Alpha star in the Southern Cross, will beavailable for our Latitude readings.
I’d say the fuel should be about 50% to allow an hour or soif we need it to locate SAZS.
SAME-Fix#1-SAZS Mendoza to San Carlos de Bariloche,Argentinea
TO Flight time: 13/08/2011 03:00AM local, 0700 UT (UTC -4)
SEXTANT (NAVAID) Fix#1 S37° 00’ and W70° 00’
Real World Weather: Yes
Winds 12,000’ W270 20kts;18,000 W270 39kts
Aircraft: DC3 RR41 (1940)
ASSUMMED POSSITION: SAME S-32° 50’ W-68° 50’ sextantsettings MAG VAR -4.3°
ASSUMMED POSSITION: Fix#1S-37° 00’ W-70° 00’ sextant settings MAG VAR -7.1°
ASSUMMED POSSITION: SAZS S-41° 10’ W-71° 10’ sextantsettings MAG VAR -9.8°
SAME-SAZS
Takingoff SAME 13/08/2011 06:00:00 UTC
TakeoffWeight: 23810 lbs
Fuel: 2400lbs
Payload: 5160lbs.
Crew 240 (Pilot200 Copilot 140)

 

[Dil52]

Well, we were close
Too busy taking readings and didn't notice the altitude.

And so the saga continues. We had turned to the east onto a 260°/80° LOP since the moon shot told us we were 10nm west of SAZS



View attachment 45860

View attachment 45861


http://fs-duenna.com/flights/ShowFlight.php?detail=flight&value=8WfA9rx25cNcDLoivbEXhkTZ0lg


We'll post the details later.

dil

 

[cputters]

I'm still getting flat STAR readings. I even tried taking off on runway heading and after 1/2 hour taking another one with SASA location entered and the new sun data from the sheet and it still came out flat. (horizontal)

It says in your comments not to fine tune the sextant while reading the first time, but should you every time after that as that fine tuning is what offsets your graph to give you a position indicator?

 

[teson1]

Have you clicked on one of the spots labeled Star-1, Star-2 or Star-3 above the sextant chart?
That loads the results from the current shot into the graph.

Is Azimuth = 0° (or 180°). In that case a horizontal line would be normal, as a star/sun directly N or S is assumed.

It may also be helpful if you could send a screenshot of the sextant during, and after a shot.
Ideally with shift-Z output showing real acft position (as in Dil's message below).

Alternatively, what have you entered as
Assumed position: LAT (deg, min), LON (deg, min)
Star: Azimuth (deg), Elevation (deg, min)
What is output?: Distance N.Miles

 

[Dil52]

Thanks Gunter,

It's obvious you understand to process.

pcutters,

I guess I should have been more clear when I said NOT to adjust the fine wheel when taking the shots at SAME. The reason we didn't need to move the fine adjustment is that we were merely confirming our coordinates at SAME. When we took the shot, the star naturally was already centered in the bubble.


If the ASSUMMED POSITION settings are not the same as your actual position, then you need to move the fine adjustment to center the star in the bubble. Whenever you must center the star the resulting shot line will be offset from the center of the graph and show the distance.

dil

 

[Dil52]

salt_air had suggested earlier that we compile a step by step list for taking sextant readings, which was a good idea.

Steps for taking sextant readings

1. Under ASSUMED POSITION: set for Latitude and Longitude.This will be the coordinates of where you want to fly to or from for, example.
It can be the departure airport, the destination airport, or a fixed position anywhere along the route just as VOR an NDB would be when flying IFR flights.

2. Determine a time in the future that you want to take sextant reading shots:
(I usually take them on the hour or half hour unless I’m looking for a specific distance to the Arrival airport and want to know where to begin the descent.

3. Get Data Chart: Go to the USNO site and set the same coordinates and time when you’re going to take the sextant reading shots as in Steps 1 an 2. Then get the data.

4. Choose stars: as close to Zn (azimuth) of 90° or 270° to get an accurate longitude position. Choose a star as close to 0° or 180° to get an accurate latitude shot. Also choose stars with an Hc (elevation) of between +15 and +65 degrees. Readable stars will be in blue. The sun, moon, and planets will be in red.
During the day you'll only have the sun. The best longitude shots will be in the early morning and late afternoon. At High Noon you can get a pretty good latitude shot from the sun.

5. Under STAR: Set Hc (elevation) and Zn (azimuth) of one of the stars you’ve chosen using the course and fine adjustment wheels located at the right of the eyepiece.

6. Take a sextant shot: Click on the eyepiece, then adjust the bubble size by using the adjustment wheel on left side of the eyepiece. Start the shot 1 minute before the time you chose in step 2 and entered in step 3. That time can also be read at the top of the data chart.

7. Center the star in the bubble: by using the fine adjustment wheel. (you have exactly 60 seconds) When the lens and dancing bubble stop (disappears) see step 8. If you're reading stars choose and center the biggest one.

8. Under DISTANCE N. MILES: Read an remember the distance. The reading will tell you how far you are from the coordinates you set in step 1, ASSUMED POSITION.

9. Click on Star 1 on the chart. This will give you a line that is offset from the little green circle at the center of the graph. The littlegreen circle is your actual position of your aircraft at that time. (note that the distance reading will change Under DISTANCE N. MILES when you place a line on the chart). That's why it's important to read the distance first. Of course you can always get a good idea of the distance on the chart. Each square is 60nm latitude and longitude.

10. Repeat steps 5 through 9 again for a second or third star reading(s).

11. To advance to another fixed point or destination airport repeat all steps above.

Remember you must have a chart for each “time” you take a reading or series of shots together.Keep in mind that the earth is rotating at a rate of about 1000 miles per hourso the stars are constantly moving at that rate at the equator as well. Of course the North Star and the Southern Cross don’t move as fast since they’relocated above the axis of the earth.

 

[salt_air]

Still alive ...

Still here Dil.



Had my oldest Son up here for the weekend ... let everything go till tonight.

Got some reading to do (it looks like) and I'm going to do a quick and dirty flight then post what I did .... kinda like a quiz to see where I am.

If I do good then I'll keep rolling the same way ... if not I'll need to get back in the middle of the road before I go any further.




Thanks for making the list ... I've printed it and a couple more pieces to use as notes.

I'll post here when complete.




Cheers,

 

[cputters]

View attachment 45983
Sitting at SASA. Shot minutes before taking reading. (Set Assumed position a couple of degrees out)

View attachment 45984
Sitting at SASA. Shot after taking reading. All stars read horizontally 0 as the blue one.

I notice there is no Distance reading..is this because the reading is 0, or because I'm doing something wrong. (ie. Does a reading of 0 register?)

Do I let the reading run its course or do I have to manually stop it?


edit:

Here's step by step what I did for that reading.

1. Set assumed position a couple of degrees out from actual position.
2. Set sun's readings from chart
3. Bubble size = 3
4. take reading, letting the sextant run its course without interference.

 

[Dil52]

Sitting at SASA. Shot minutes before taking reading. (Set Assumed position a couple of degrees out)


Sitting at SASA. Shot after taking reading. All stars read horizontally 0 as the blue one.

I notice there is no Distance reading..is this because the reading is 0, or because I'm doing something wrong. (ie. Does a reading of 0 register?)

Do I let the reading run its course or do I have to manually stop it? .

Let it run it's course which is 60 secs. while centering the star in the bubble.

letting the sextant run its course without interference.[/B]

4. as you take the reading, move the star into the center of the bubble with the fine adjustment knob, on the right side of the eyepiece.

Notice the values change under ELEVATION ANGLE as you move the star into the center of the bubble.

View attachment 45987

1. Center the bubble
2. Original ELEVATION value before takeing the shot
3. Notice the different value after centering the bubble. Since the original value was 12 DEG 40 MIN and New value is 13 DEG 40 MIN I already know the differnce is going to be about 60nm. Actually the reading should be about 55nm. Do you know why?

 

[cputters]

Well, it'll be less because of the lines being closer at the poles right?

Here's my readings being taken at 65, 0 and 90. (Still no diagonal lines..haha)

View attachment 45996

 

[Dil52]

OK Chris,

It appears to me that there might be something wrong with your sextant installation.

cfg files are not my forte, however I believe salt_air and teson 1 are better than I am at diagnosing those types of problems.


I haven't heard from Salt for a few days, but I'm sure he's still around here in these parts. I know they kidnapped Sally and he might be negotiating or paying a ransom or something to that affect. I hope he's OK. I'm about to fly back and go looking for him. I'm getting a little worried about the whole dilemma.


You can be sure Gunter's looking in and after us as well.


Keep the faith, we'll get you outfitted properly for a nice flight with the sextant, that I'm sure of.

I'm just glad those guys have our backs.

Well, it'll be less because of the lines being closer at the poles right? Absolutely correct!

 

[cputters]

That'd be right, after all this, my install is corrupt. HAHA

Ah well, all a part of the learning curve I suppose.

 

[dca910]

re horizontal lines

*****
The reason the lines are horizontal may be because your Azimuth is set to zero. To get a vertical line, you need to enter an az of 90 or 270 degrees.
*****

 

[Dil52]

*****
The reason the lines are horizontal may be because your Azimuth is set to zero. To get a vertical line, you need to enter an az of 90 or 270 degrees.
*****

dca910, Thanks for the input! first post, welcome!

Anyone who can help Chris get up and running is more than welcome to join in!

I'm assuming, when Chris said he took readings at 65, 0, and 90, he was talking about azimuth. That should have given him a diagonal (65), a horizontal (0), and a vertical (90) line. Unfortunately the screen shot is showing the AZIMUTH set at 0°.

dil

 

[Dil52]

To the Roaring40’s:

This is the documentation of the last flight.


In this flight we’re made at night flight from Mendoza (SAME) and to arrive in San Carlos de Bariloche (SAZS), sometime near sunrise.


We made the flight plan to leave Mendoza at 3:00 AM localtime and arrive in San Carlos de Bariloche sometime near sunrise.

The intermediate Fix#1 Point is located at S37° 00.00’ W70° 00.00’ just to make the settings easy even numbers. Then SZAS located at S41° 10’ W71° 10’.

We can use the moon up until about 6:00AM local, when it’ll be setting in the west for our longitude reading and by the time we reach as far south as 40°, ACRUX, which is the Alpha star in the Southern Cross, will be available for our Latitude readings.

The fuel is be about 50% to allow an hour or so in case we need it to locate SAZS.

SAME-Fix#1-SAZS Mendoza to San Carlos de Bariloche,Argentinea
TO Flight time: 13/08/2011 03:00AM local, 0700 UT (UTC -4)
SEXTANT (NAVAID) Fix#1 S37° 00’ and W70° 00’
Real World Weather: Yes
Winds 12,000’ W270 20kts WCA 8°; 18,000 W270 39kts WCA 16°
Aircraft: DC3 RR41 (1940)

ASSUMMED POSSITION: SAME S-32° 50’ W-68° 50’ sextantsettings MAG VAR -4.3°
ASSUMMED POSSITION:Fix#1 S-37° 00’ W-70° 00’ sextant settings MAG VAR -7.1°
ASSUMMED POSSITION: SAZS S-41° 10’ W-71° 10’ sextantsettings MAG VAR -9.8°

SAME-SAZS
Taking off SAME13/08/2011 06:00:00 UTC
Takeoff Weight:23810 lbs
Fuel: 2400 lbs
Payload: 5160 lbs.
Crew 240 (Pilot 200 Copilot 140)


Star Shots 7:30AM UT LOP S-32° 50’ W-68° 50’
MOON 117 57.0 S12 33.4 +40 53.8 282.5 Lon reading Star1 Blue
ALPHERAT 71 38.4 N29 09.4 +27 57.2 357.2 Latreading Star2 Green
Note: The highlighted numbers are the Hc +40 53.8 (elevation) and Zn 282.5 (azimuth).
We merely copied and pasted the lines from the USNO Navigation data charts.
http://aa.usno.navy.mil/data/docs/celnavtable.php
If anyone decides to fly this flight at any other (date and time) the star shots and Moon shots will be different.
Shot 1View attachment 46017
We’re getting heavy turbulence at 3:45AM local time. We’regetting 200’/min fluctuations in level flight It’s becoming obvious that we’reapproaching the roaring 40’s.
(Please note my unconventional way of calculations. To save agebretic processes as dividing both sides by the same number to cancel, we just converte hours to minutes and did the math.

Formulas: Speed or (Rate) = Distance/Time or Time=Distance/Speed orDistance=Speed*time
d=r*t or r=d/t or t=d/r
r=d80*60/t30=160kts


Star Shots 8:00AM UT LOP S-37° 00’ W-70° 00’
ALPHERAT 79 09.6 N29 09.4 +23 17.3 351.3Lat reading Star 1 Blue
MOON 125 13.0 S12 28.1 +35 05.0 281.5Lonreading Star 2 Green
Shot 2View attachment 46016
Reading was 80nm: Note that once you place the line of the graph the distance reading under DISTANCE N. MILES changes value and is not the true reading distance.
Speed (rate) = Distance/Time

First we must first figure out how far we’ve traveled since the first reading. From our flight plan we know the total distance to fix1 was 257nm so (257 to fix1) – (80 from 1st reading) = (177 miles to fix#1 after 1st reading)
From (177nm from fix1) – (80nm to fix1 forshot 2)= (97nm traveled at cruise speed in the second half hour)
Speed was r=d/t or d97*60/30t=194kts.
At rate of 194kts. we should reach 80/194*60=24.7min or 4:25AM



Star Shots 8:25AM UT
ALPHERAT 85 10.6 N29 09.4 +22 19.7 345.7 Latreading Star 1 Blue
MIAPLACI 309 07.0 S69 46.0 +25 01.1 160.9Latreading Star 2 Green
MOON 131 01.9 S12 23.8 +30 27.8 277.5 Lon reading Star 3 Red
Shot 3 View attachment 46015
It looks like our average speed calculation worked prettywell.
I notice by the now, by the Moon shot we were just west of Fix #1


Star Shots 9:00AM UT
ACRUX 269 38.8 S63 10.1 +15 22.4 171.5 Latreading Star 1 Blue
HAMAL 64 29.6 N23 31.1 +25 01.2 6.8Lat reading Star 2 Green
MOON 139 45.2 S12 17.4 +24 07.2 274.7Lonreading Star 3 Red
Shot 4View attachment 46014
Speed was r=d/t or 255-155=100nm and 100*60/35=171kts.Obviously we had a strong headwind during this period of time.
At rate of 171kts we should reach SAZS 155/171*60=77min orat 5:54AM


Star Shots 9:30AM UT
ACRUX 277 10.1 S63 10.1 +16 22.7 168.1 Lat reading Star 1 Blue
MENKAR 58 15.1 N 4 08.2 +43 11.1 17.8 Lat reading Star 2 Green
MOON 147 01.3 S12 12.0 +18 35.9 269.9 Lonreading Star 3 Red
Shot 5View attachment 46020
Speed was r=td or 155-65=90 and 90*60/30=180 knots
At rate of 180kts we should reach SAZS 65/180*60=21min or at5:51AM

Hind sight is 20 20:

At this point we made a mistake by keeping our heading anWCA the same. Notice that the red line is the moon shot. The moon was exactly270° azimuth and our longitudinal position right at ASSUMED POSITION at SAZSLOP.
At this time we should have turned to heading 180 degrees true or 170.3degrees magnetic and, allowing for about a 15° WCA, we should have turned to aheading of 185° magnetic.


Star Shots 9:51AM UT
ACRUX 282 25.9 S63 10.1 +17 16.4 165.8 Lat reading Star 1 Blue
MENKAR 63 31.0 N 4 08.2 +44 09.6 10.7 Lat reading Star 2 Green
MOON 152 06.5 S12 08.3 +14 43.8 266.6 Lonreading Star 3 Red
Shot 6View attachment 46019
Before we could get a screen shot to the readings we crashedinto the mountains somewhere west of SAZS. This shot we took later at theapproximate location of where we crashed at 5500’

I don't shy away from my errors. I'm getting so good at them, they're just 2nd nature to post now.

We were in the process of taking these shots and were taking documenting the flight and didn’t realize our altitude dropped to 5500’. By still failing to correcting our heading and even while descending we ended up about 25 or 20 nm west of SAZS when we took the Moon shot for Longitude. Notice That the longitude (redstart3) line is offset. It should have been cutting directly through the littlegreen circle at SAZS.

The sextant was giving us good information, we just failed to analize it properly. Obviously the wind direction changed from the original forcast at SAME.



View attachment 46018

The moon in the western sky approximately a Zn of 270°.
Notice that the Moon phase is a waxing crescent which is out of sync in FS9.
In FSX it's only about 2 1/2 days off so far. It'll get worse as the years pass since the phases are varible.
The rise and set times, azimuth and elevation of the Moon, in the Celestial Navigation Data Charts, are still correct.
Actually the Moon phase would be a Full MOON when this flight was made.

I hope everyone can follow this step by step documented flight.
Except please stay above the surrounding terrain until you spot the airport at SAZS.

dil

 

[teson1]

Chris, are you using FSX by any chance ?
The sextant gauge does not work with that version of FS.

 

[cputters]

Yes....yes I am... dang it.

Ah well, them's the breaks. Can't say we didn't give it a go.

There seems to be a lot of modding available for FS9 and extemely little for FSX, why is that?

 

[Dil52]

SAZS-SCCI

http://fs-duenna.com/flights/ShowFlight.php?detail=flight&value=RVBJHIisbEWmG25wG4qU1dW0M

Why I believe that's a picture of Carmen my copilot in Punta Arenas !!!
Bottom row 2n d from left.

Maybe not, perhaps a look alike.

To the Furious Fifties:
This is another night flight from San Carlos de Bariloche, Argentina (SAZS) to Punta Arenas, Chile (SCCI).

S C De Bariloche, Argentina at 11:30 Local and 3:30 UT and Arrivein Punta Arenas, Chile in at about 3:30AM Local 7:30 UT. Our intermediate Fix#1Point for this flight plan will be located at S47° 00.00’ W71° 00.00’ just tomake the settings easy. Then SCCI located at S53° 00’ W70° 50’.


SEXTANT (NAVAID) Fix#1 S47° 00’ and W71° 00’

Real World Weather: Yes

Winds 12,000’ W270 20kts WCA 8°; 18,000 W270 39kts WCA 17°

Aircraft: DC3 RR41 (1940)

ASSUMMED POSSITION: SAZS S41° 10’ W71° 10’ sextant settingsMAG VAR -10°
ASSUMMED POSSITION: Fix#1 S47° 00’ W71 00’ sextant settingsMAG VAR -12.7°
ASSUMMED POSSITION: SCCI S53° 00’ W70° 50’ sextant settingsMAG VAR -15.3°

SAZS-SCCI

Taking off SAZS 08/16/201123:30:00 Local
Takeoff Weight:23810 lbs
Fuel: 2400 lbs
Payload: 5160 lbs.
Crew 240 (Pilot 200 Copilot 140)

Arrived OK

A soft landing for a change.


dil

 

[salt_air]

Who said he wasn't comin'?

From the Peanut Gallery Advocate ....



I'm enjoying the play by play of each flight and I've gotten a grip on how to make shots with the sextant ... thank you!


Slowly grasping what shots I want to take (logic behind choices) ... pretty good mix of reasoning made understandable ... well done!


Still drawing a blank when planning a new or different flight (one that has no examples) as to how best to utilize the sextant.




[from the short story "Notes So Far" by salt_air]

Take a shot at Departure airport using the lat/lon coordinates of that airport .... then (at least) one at the half way mark along the course and another 30 minutes to a hour before reaching destination .. this time using the lat/lon coordinates for the destination airport.

Splitting the distance between the two points lessons the margin for error.

This will give me a "check" on distance along the course line to destination ... along with my time and ground speed math ... a balance and check ... like when your traveling by car and check your odometer against the mile markers along the road.

This is what you do in daylight flying.

The option of triangulating a fix comes into play only when there are more celestial bodies visible in the sky.

Under no circumstance do you ever spit into the wind.






Later on (return trip) I would want to use the sextant to help me "carry" an idea of where I was across the no signal zone between the ranges of two NDB's along the flight path.

That would be a check or performed in addition to regular wind drift checks ... by meter or e6-b calculations.

A fix would not only help me figure how far down the course line I had flown (since the last fix), but it would give me an indication of whether or not I had drifted off course.






Question ... When simply flying along a course line and taking LOPS at regular intervals, can you (by looking at the blue, green, red) lines on the chart know if you have drifted right or left of course line?



Still pounding on all of this off line in different aircraft on different (than posted) flights hoping that will force the light on quicker.

 

[teson1]

Chris, are you using FSX by any chance ?
The sextant gauge does not work with that version of FS.

Hi Chris,
I'm in error. The sextant gauge DOES WORK with FSX.
I mixed the sextant gauge up with the Radio Range gauge. Sorry!

I installed bbsxa.zip in FSX, and it works. Not 100%, but satisfactorily. (Someday I'll have to make the switch to FSX...)

The gauge is slightly less functional in FSX than in FS9 as so far as there is no "Distance N.MILES" shown after the shot.
However, the distance between assumed position and LOP can easily be calculated from the difference between Assumed "Star Elevation" and measured "Sextant Elev Angle" (1 MIN = 1 nm).

The LOP plotted in the chart are positioned correctly.
See example at Salta SASA. The only difference between the shots is Azimuth=90°, 45°, 0°.

1. (Bottom image) During third sun shot. Sun and bubble are visible.
2. (Middle image) After 3rd shot. The three LOP intersect perfectly.
3. (Top image) Cursor moved with green arrows onto the fix, to measure Lat/Lon (cursor lat/lon is indicated at right and bottom of the chart). Excelent agreement between measured and real position of SASA for this three sun fix .

The chart is always centered on the current assumed position.
The cursor can be moved with the green arrows at the side of the chart.

Note however that if assumed position is changed the old LOP lines on the chart don't move accordingly, i.e. they are then positioned wrongly and don't give usable information any more.

Also note that in your shots posted a few days ago 0° is shown as lat/lon at the side of the chart. That's definitely wrong...

My panel.cfg entry for default FSX DC-3:

File: bbsxa.zip (place BB_sextant4.cab into gauges folder)

Window07=Sextant
...
// Simulated Aircraft Bubble Sextant - D Bitzer M Beaumont - flightsim - dc3_bbsxa.zip
[Window07]
Background_color=0,0,0
size_mm=650,277
visible=0
window_pos= 0.000, 0.050
ident=18
gauge00=BB_sextant4!sextant, 261,3,386,270
gauge01=BB_sextant4!CH, 1,3,270,270