Wind correction for GC steering
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Ok … we neeeeed … someone …
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I thought this was what the DRIFT C/O switch was for…if it is OFF (HUD “caged”, in my lingo) you’d fly the arcing path to/over the steerpoint, and if it is in NORM that the system will show you the wind corrected steering to fly?
…which is a reason I prefer to land with it in OFF. For VFR approaches, anyways.
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mmm … sorry but, IMO, everything is fine in 4.33.2
NORM
DRIFT C/O
Looks alright to me! (?)
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Clearly merits investigation. Ill have to see about replicating my results from yesterday.
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Holy sh*t… 6 pages on steering. The steerpoint diamond is based off LOS. Herm the Sperm or the GCSC or the tadpole is all based off, surprise surprise, great circle steering.
The shortest route is by placing the FPM over the tadpole. This is wind corrected as long as you’re not in DCO. If you are in DCO then you will just home to the station with a constantly updated heading.
At long distances the tadpole and FPM will not match the steerpoint diamond in azimuth because because you’re not flying a straight line to the steerpoint but an arcing path with the curvature of the Earth. As the distance decreases then the difference (or error as the -34 calls it) will become less and less. This is because your heading is actually changing when you fly a Great Circle route. Think of it this way, when you’re looking at the steerpoint diamond you are looking at some point in space by looking through the Earth (at far distances). That’s all it is. Additionally, if you could just put the FPM on the steerpoint diamond there would be no reason for Herm the Sperm.
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Er… got a page number for that?
A constant line of sight doesnt have a constant heading anyway. That cannot be the source of this error.
The tip about drift cutout is very useful - I dont think BMS reflects that presently.
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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.