The Sextant Lesson 103 for a Master’s degree in FS Sextant Navigation.
Thanks to Gunter's link we now know that this flight from Palmer Station to McMurdo Station is similar to Lincoln Ellsworth’s trans-Antarcticflight in 1938 from Dundee Island to Little America. Our course is slightly different since Palmer Station is more Southwest than Dundee Island.
The Challenge:
The planning and preparation for this flight has required considerable preflight navigation.
As most know, the wind direction in FS isgiven as a Magnetic not True direction.
We won't use "control Z" so the magnetic wind direction is of no use when flying and using pure Celestial Navigation. Everything must be converted just as we must convert True wind direction when figuring the WCA with the E6-B computer.
We’ll navigate strictly with the sextant.
The magnetic variation changes are quite erratic and the longitudinal lines are merely about7.8nm in the S80s.
We’ll determine the (true) wind direction and speed using thecalculator incorporated into the Sextant chart
We'll take star shots each hour to determine, by DR calculations, ourfuture EP from our present apparent position (AP). That sounds real difficultuntil you break it down.
First we calculate our IAS/TAS/GS in static conditions.
In this casein the C47 we’ll fly at 12,000' at an average speed of IAS=145/TAS=172/GS=172knots.
As example, If we find we’ve traveled a distance of 162nm in the past hour we know thatwe’ve been flying into a 10 knot headwind. It could be that it’s actually a 20 or 30 knot cross wind and that’s where the sextant wind calculator will be useful for determining the WCA. Each reading should help us update our ETE.
That’s simpley using DR from our AP to determine EP in one hour.
Preflight Navigation and Planning:
Flight Plan: NZ0B Palmer Station to NZIR McMurdo Station
NZ0B Lat/Lon: S64°45.29' W064°01.88'
Fix01 Lat/Lon: S67°18.03' W065°59.81'
Fix02 Lat/Lon: S69°59.85' W068°40.09'
Fix03 Lat/Lon: S72°38.58' W072°07.62'
Fix04 Lat/Lon: S75°09.93' W077°03.57'
Fix05 Lat/Lon: S77°35.30' W083°35.15'
Fix06 Lat/Lon: S79°50.40' W092°41.72'
Fix07 Lat/Lon: S81°29.03' W107°16.04'
Fix08 Lat/Lon: S82°34.78' W126°30.83'
Fix09 Lat/Lon: S82°45.06' W149°02.89'
Fix10 Lat/Lon: S81°37.25' W168°34.12'
Fix11 Lat/Lon: S79°59.65 E176°33.07'
NZIR Lat/Lon: S77°52.60' W166°33.82'
To eliminate any confusion we've compiled our true and magnetic heading changes between LOP readings, which are spaced at one hour intervals. (172nm in this case)
In FS, the winds direction is given in degrees magnetic.
Since we don’t want to cheat and use Ctrl Z we need to compute our WCA from our True heading.
When using the sextant W hot key the wind direction is in true degrees.
We can use our E6-B to compute the WCA. Then by using the formula,TC+/-WCA=TH(-E+W) VAR=MH(-E+W) Dev(0 in FS)=CH we'll get our actual Course Heading.
Rather than executing all the computations each time we take a reading we’ll do as Ellsworth and Noonan when planning flights and simply make a chart showing all these differences at a glance.
The flight:
Aircraft: 1940 USAAF C-47 EW 5 tanks for a total of 1604 Gal,9624lb. Cap.
Departure Time: Leaving Palmer Station 0900AM Local 1200 UT 28/08/2011
Weather forecast: Weather looks mostly clear with 42 knot winds217M/232T at cruise altitude of 12000’.
In static conditions (No wind, average temperature and pressure altitude) and flying at an IAS of140 knots at 12000 feet our TAS/GS shouldequal to 172 knots. On the flight plan we’ll space our reading LOPs at 172nm apart as mentioned above.
You can referenct this great tutorial:
In his sextant chart example NA08 (located in the dc3_bbsxa documentation) Dave Bitzer explains that, in order to use the W (wind)indicator on the sextant graph, we must know the coordinates of where we were 1 hour prior then:
1 Take a reading of two to three stars at present time ofcoordinates of 1 hour prior location.
2 Move the green dot from the center of the graph to where thestar shots cross
3 Observe the true wind direction and speed using the W “wind”hotkey.
It’s important to note that we if we change course more than 20 degrees in the past hour the wind calculator will not work properly and give us an erroneous calculation.
View attachment 47024
Since the RW at Palmer Station is pure Ice we step back to do our run-ups on the hard pack before easing onto the runway for TO. The Brakes are useless in the RW.
View attachment 47023
Since the fight plan In FS is rather strange looking Earth Google shows the actual flgiht plan more clearly.
The quick way to circumnavigate around the world.
dil
Thanks to Gunter's link we now know that this flight from Palmer Station to McMurdo Station is similar to Lincoln Ellsworth’s trans-Antarcticflight in 1938 from Dundee Island to Little America. Our course is slightly different since Palmer Station is more Southwest than Dundee Island.
The Challenge:
The planning and preparation for this flight has required considerable preflight navigation.
As most know, the wind direction in FS isgiven as a Magnetic not True direction.
We won't use "control Z" so the magnetic wind direction is of no use when flying and using pure Celestial Navigation. Everything must be converted just as we must convert True wind direction when figuring the WCA with the E6-B computer.
We’ll navigate strictly with the sextant.
The magnetic variation changes are quite erratic and the longitudinal lines are merely about7.8nm in the S80s.
We’ll determine the (true) wind direction and speed using thecalculator incorporated into the Sextant chart
We'll take star shots each hour to determine, by DR calculations, ourfuture EP from our present apparent position (AP). That sounds real difficultuntil you break it down.
First we calculate our IAS/TAS/GS in static conditions.
In this casein the C47 we’ll fly at 12,000' at an average speed of IAS=145/TAS=172/GS=172knots.
As example, If we find we’ve traveled a distance of 162nm in the past hour we know thatwe’ve been flying into a 10 knot headwind. It could be that it’s actually a 20 or 30 knot cross wind and that’s where the sextant wind calculator will be useful for determining the WCA. Each reading should help us update our ETE.
That’s simpley using DR from our AP to determine EP in one hour.
Preflight Navigation and Planning:
Flight Plan: NZ0B Palmer Station to NZIR McMurdo Station
NZ0B Lat/Lon: S64°45.29' W064°01.88'
Fix01 Lat/Lon: S67°18.03' W065°59.81'
Fix02 Lat/Lon: S69°59.85' W068°40.09'
Fix03 Lat/Lon: S72°38.58' W072°07.62'
Fix04 Lat/Lon: S75°09.93' W077°03.57'
Fix05 Lat/Lon: S77°35.30' W083°35.15'
Fix06 Lat/Lon: S79°50.40' W092°41.72'
Fix07 Lat/Lon: S81°29.03' W107°16.04'
Fix08 Lat/Lon: S82°34.78' W126°30.83'
Fix09 Lat/Lon: S82°45.06' W149°02.89'
Fix10 Lat/Lon: S81°37.25' W168°34.12'
Fix11 Lat/Lon: S79°59.65 E176°33.07'
NZIR Lat/Lon: S77°52.60' W166°33.82'
To eliminate any confusion we've compiled our true and magnetic heading changes between LOP readings, which are spaced at one hour intervals. (172nm in this case)
In FS, the winds direction is given in degrees magnetic.
Since we don’t want to cheat and use Ctrl Z we need to compute our WCA from our True heading.
When using the sextant W hot key the wind direction is in true degrees.
We can use our E6-B to compute the WCA. Then by using the formula,TC+/-WCA=TH(-E+W) VAR=MH(-E+W) Dev(0 in FS)=CH we'll get our actual Course Heading.
Rather than executing all the computations each time we take a reading we’ll do as Ellsworth and Noonan when planning flights and simply make a chart showing all these differences at a glance.
| Magnetic Variation Chart | |||||
| leg | |||||
| heading | Mag | True | WCA | ||
| change | Heading | heading | |||
| RW19 | 16.7 | 0 | 191 | 207.7 | |
| NZ0B | 16.7 | 177 | 193.7 | ||
| Fix 01 | 19.2 | -2.5 | 175 | 194.2 | |
| Fix 02 | 23.1 | -3.9 | 174 | 197.1 | |
| Fix 03 | 27.2 | -4.1 | 174 | 201.2 | |
| Fix 04 | 32.3 | -5.1 | 169 | 201.3 | |
| Fix 05 | 40.2 | -7.9 | 164 | 204.2 | |
| Fix 06 | 49.6 | -9.4 | 166 | 215.6 | |
| Fix 07 | 62.4 | -12.8 | 154 | 216.4 | |
| Fix 08 | 84.2 | -21.8 | 149 | 233.2 | |
| Fix 09 | 106 | -21.8 | 158 | 264 | |
| Fix 10 | 125.3 | -19.3 | 160 | 285.3 | |
| Fix 11 | 137.2 | -11.9 | 167 | 304.2 | |
| NZ0B | 145.8 | -8.6 | 167 | 312.8 | |
| RW7 | 145.8 | 0 | 69 | 214.8 | |
| RW25 | 145.8 | 0 | 247 | 392.8 | |
| RW15 | 145.8 | 0 | 149 | 294.8 | |
| RW33 | 145.8 | 0 | 329 | 114.8 |
The flight:
Aircraft: 1940 USAAF C-47 EW 5 tanks for a total of 1604 Gal,9624lb. Cap.
Departure Time: Leaving Palmer Station 0900AM Local 1200 UT 28/08/2011
Weather forecast: Weather looks mostly clear with 42 knot winds217M/232T at cruise altitude of 12000’.
In static conditions (No wind, average temperature and pressure altitude) and flying at an IAS of140 knots at 12000 feet our TAS/GS shouldequal to 172 knots. On the flight plan we’ll space our reading LOPs at 172nm apart as mentioned above.
You can referenct this great tutorial:
In his sextant chart example NA08 (located in the dc3_bbsxa documentation) Dave Bitzer explains that, in order to use the W (wind)indicator on the sextant graph, we must know the coordinates of where we were 1 hour prior then:
1 Take a reading of two to three stars at present time ofcoordinates of 1 hour prior location.
2 Move the green dot from the center of the graph to where thestar shots cross
3 Observe the true wind direction and speed using the W “wind”hotkey.
It’s important to note that we if we change course more than 20 degrees in the past hour the wind calculator will not work properly and give us an erroneous calculation.
View attachment 47024
Since the RW at Palmer Station is pure Ice we step back to do our run-ups on the hard pack before easing onto the runway for TO. The Brakes are useless in the RW.
View attachment 47023
Since the fight plan In FS is rather strange looking Earth Google shows the actual flgiht plan more clearly.
The quick way to circumnavigate around the world.
dil
