Wind correction for GC steering
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nooooo its back
Nothing had changed in this area
Please fly 30kt crosswind to show if there is a problem
Here I just see what could be a rounding issue
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The one thing that is clear from the above is that I shall not call it the tadpole or GCSC anymore. Herm the Sperm it will be for now on.
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Tadpole placement represents GC steering error by position relative to FPM. There’s nothing wind corrected about it. When GCSC is on FPM that’s zero GC steering error by construction. Since GCSC-FPM relative position is how the steering error is expressed then putting the thing on the thing works the same, drift c/o or not. The GCSC tail however might not be perfectly vertical at thing-on-thing alignment. At no steering error you might have a relative bearing to steerpoint other than 12 o’clock in a crosswind.
I have read however that the steerpoint diamond isn’t rendered on the HUD with the same care as the GCSC and can be wrong at long distances. Falcon isn’t a spherical navigation environment and I seriously doubt the code is copy-pasted from the real jet as we’d have a lot more noticeable discrepancies. For fun real world Kunsan-Pusan is calculated constant azimuth and GC:
291.64° initial
290.29° final
290.97° constant directionThat’s a 124NM path and up to about ~1° difference from sitting in the middle which would be noticeable on the HUD as a diamond misalignment. That shouldn’t happen in a flat Falcon Earth of course as GC and constant az solutions are one and the same.
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Seems to be working now. Perhaps it was just a small amount of roll, or a heading misalignment, or something. Pendulum effect perhaps.
Although according to FoxThreeTwoShip above, the current DRIFT C/O mechanism is incorrect.
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Great circle route (shortest route) vs constant bearing route (loxodrome or Rhumb line).
On the two pictures below, the shortest route is the red route. The constant bearing is the blue route:
To get something more visual go there: http://www.sciences.univ-nantes.fr/sites/genevieve_tulloue/Meca/RefTerre/Orthodromie1.php
… Clic Orthodromie (9729Km) and then Loxodromie (11354Km).
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Pretty sure no one is confused between great circles and rhumb lines, but that is quite visual enough.
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Pretty sure no one is confused between great circles and rhumb lines, but that is quite visual enough.
… I’ve just seen the opportunity to give some info for ppl who are not familiar with this. Not everybody here are professionals.
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I can’t really tell but is everyone on the same page? Without the -34 I know when you put the FPM on the tadpole it does not always align with the steerpoint diamond in azimuth.
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with DRIFT C/O in NORM, shouldnt the FPM, tadpole and STPT diamond all be aligned in azimuth?
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with DRIFT C/O in NORM, shouldnt the FPM, tadpole and STPT diamond all be aligned in azimuth?
I don’t believe so but I haven’t played with it enough STS to say for sure. When I get a chance I will mess with it. DCO should only affect where the FPM is. If you are not corrected for winds then you are just homing to the point. The tadpole and steerpoint have to do with the route flown.
The way I see it there are 4 ways to fly:
- DCO - OFF and FPM on tadpole
- DCO - ON and FPM on tadpole
- DCO - OFF and FPM on steerpoint diamond
- DCO - ON and FPM on steerpoint diamond
With (1) being the best.
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And here I naively thought 1 and 3 were identical :S
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Slightly OT but related - what does the tail on Herm the Sperm represent? Looked in the -1 but could find nothing.
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you would need to look in the -34 to get an answer, not the -1.
The tail is roll stabilised to the wings, and points to the heading towards the STPT diamond.
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GCSC tail shows “relative bearing” which would be the difference of aircraft heading and azimuth to destination. It’s not a given that the manual expresses everything absolutely 100% accurately to the smallest detail. It can favor concise and functional approximation for “good enough for the stick jockey” over "well technically it’s this vector minus this vector sourced from this data stream "etc. However if the text is taken literally then it’s relative bearing. Example as follows: destination is 090, true flight path heading is 090, GC steering says fly heading 085 due to wind from north, airplane heading is 085, GC steering error is zero. In this case the relative bearing of destination is 005 degrees right. Airplane heading is 085, true bearing to destination is 090, that’s a relative bearing of 5 degrees right. Taken by exact wording the GCSC tail should show a 5 degree angle to the right despite the FPM being on the GCSC (no steering error).
Diamond I don’t think is placed using the most exact math like GC cue is.
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GCSC tail shows “relative bearing” which would be the difference of aircraft heading and azimuth to destination. It’s not a given that the manual expresses everything absolutely 100% accurately to the smallest detail. It can favor concise and functional approximation for “good enough for the stick jockey” over "well technically it’s this vector minus this vector sourced from this data stream "etc. However if the text is taken literally then it’s relative bearing. Example as follows: destination is 090, true flight path heading is 090, GC steering says fly heading 085 due to wind from north, airplane heading is 085, GC steering error is zero. In this case the relative bearing of destination is 005 degrees right. Airplane heading is 085, true bearing to destination is 090, that’s a relative bearing of 5 degrees right. Taken by exact wording the GCSC tail should show a 5 degree angle to the right despite the FPM being on the GCSC (no steering error).
Diamond I don’t think is placed using the most exact math like GC cue is.
The GCSC knows nothing about the wind. The only thing affected is the displacement of the FPM for wind which is determined by the DCO switch.
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Slightly OT but related - what does the tail on Herm the Sperm represent? Looked in the -1 but could find nothing.
Think of it like the HSI - if you are steering directly at the steerpoint, it points straight up. If not, it’s telling you which way to turn and by how much.