By the way, does anybody know where the green E/D donut for the E/O drift down target sits when a route offset is in use? Is it on the normal route or on the dashed offset route?
Edit: Thread split from http://aerowinx.com/board/index.php?topic=4799.0
Quote
By the way, does anybody know where the green E/D donut for the E/O drift down target sits when a route offset is in use? Is it on the normal route or on the dashed offset route?
Hi Hardy,
I don't know if I have a definite answer for you on this, but I did learn something this morning that I didn't know and didn't think would work. I set up a 15-mile right offset prior to T/D to see if the T/D point would be displayed on the original course or the offset course. To our surprise, the dot was displayed on the offset course. You can make your own assumptions about this, but if it does it on the 767 for a normal descent, I'm thinking it would also display the E/O points on the offset route too.
(http://www.hoppie.nl/forum/var/img-20180704-00262-2-.jpg)
Hi Jon and all,
re offset route again: When an offset route is active, do you know what the x-track error display on the PROGRESS page refers to? To the normal route or to the offset route? E.g. when the aircraft is on the dashed offset route and the offset is 20 nm, will the PROGRESS page indicate 20 or 0 nm?
In the current PSX version, the display always refers to the normal route.
|-|ardy
Hi Hardy,
I fly tonight. I'll check it out if I can.
Jon
Thanks! By the way, to check this out, you don't even need to fly on the offset route. Here's a suggestion:
1. While on a normal leg, engage HDG SEL or HDG HOLD.
2. Enter and execute a RTE OFFSET of, say, 1 nm.
3. Check what x-track error is displayed on the PROGRESS page -- 0 nm or 1 nm?
4. Delete and execute the RTE OFFSET.
5. Re-engage LNAV.
This test may take just ten seconds ... :-)
|-|ardy
Quote from: Hardy Heinlin on Sat, 7 Jul 2018 08:01
Thanks! By the way, to check this out, you don't even need to fly on the offset route. Here's a suggestion:
1. While on a normal leg, engage HDG SEL or HDG HOLD.
2. Enter and execute a RTE OFFSET of, say, 1 nm.
3. Check what x-track error is displayed on the PROGRESS page -- 0 nm or 1 nm?
4. Delete and execute the RTE OFFSET.
5. Re-engage LNAV.
This test may take just ten seconds ... :-)
|-|ardy
Hey Jon, just make sure you don't end up testing the TCAS RA :-)
Here you go, Hardy. The test took a bit longer than ten seconds, but it is exactly what I ended up doing rather than getting a clearance to offset 15 right. Once executed, the x-track error is based on how far you are away from your offset route. No TCAS RAs on this one! https://youtu.be/W1qKwjSajsU
Cheers,
Jon
Fantastic. Many thanks! :-)
Cheers,
|-|ardy
Just an aside, LIFFT was the first waypoint on the SAMMR THREE ARRIVAL into El Paso and that's why we got the END OF OFFSET message in the scratchpad when I executed the offset -- The FMS will not let us offset on a STAR or SID.
I'm wondering what would happen if you were to enter an offset in 6R when you are already on a procedure (e.g. STAR etc.). Would the entry be (A) valid (and the ND would just hide the offset route, and LNAV will remain on the normal route), or (B) would the FMC deny the entry and say INVALID ENTRY? In PSX it's (A) ... and it will delete 6R after the next waypoint.
Profile points in general are now placed on offset routes when an offset is active, and the x-track error indication now refers to the offset -- in PSX update 10.36:
http://aerowinx.com/board/index.php?topic=4191.0
|-|ardy
QuoteI'm wondering what would happen if you were to enter an offset in 6R when you are already on a procedure (e.g. STAR etc.). Would the entry be (A) valid (and the ND would just hide the offset route, and LNAV will remain on the normal route), or (B) would the FMC deny the entry and say INVALID ENTRY? In PSX it's (A) ... and it will delete 6R after the next waypoint.
While on a SID or STAR, there is no offset feature displayed on the CDU, to wit, no place to insert an offset.
Jon
Aha!
Edit: Is 6R blank then? Or is another key displayed, e.g. "APPROACH>" or "LEGS>" or something like that. I know on the ground it shows "TAKEOFF>".
|-|ardy
I think it's blank, but I'm off for a while, so I can't check it right away. I go to the United sim towards the end of the month. I'll try to check it there.
Jon
Hi Hardy,
Maybe you want to split this string off to a separate post on offsets, but I was talking to a friend over at a very large transportation company (whose name shall not be said), and he was telling me about departing out of CGO (Zhengzhou) and how it was SOP for ATC to tell them to offset to the right on a SID. He asked me if I knew how that was done and I could only guess it was done in HDG SEL.
Well, I learned something new here. Apparently, if you are on a SID or STAR where the OFFSET feature will not appear at 6R, the way you offset is to go direct to whatever your TO waypoint is, execute, and go back to the RTE 1 page. There you will see the offset. He said it works in both the sim (they actually teach this) and he did it a few days ago in the 744 with the legacy box. I would have never guessed. Here's a pic of his route briefing. Check the fifth box down on the right side under Remarks.
(http://www.hoppie.nl/forum/var/offset-on-sid(1).jpg)
What if the direct-to fix still belongs to a procedure? I doubt that the RTE page will enable an offset then.
It's clear that the offset will be enabled if the direct-to fix lies beyond the procedure. I guess when ATC gives you a direct, that direct will usually skip the entire procedure. No wonder that this will enable the offset on the real aircraft and on the big sim -- and in PSX too.
The text says: "If given an offset on the SID". This can be interpreted in two ways:
1. ATC wants to see an offset "on the SID", and wants you to stay within the SID (with offset).
2. While the aircraft is "on the SID", ATC wants you to skip the SID by a direct-to out of it (with offset).
|-|ardy
It's a typical "double reference" that makes a language vague. Another example:
"I was told my hat is blue on the ground." -- That might mean:
1. My hat is blue and my hat lies on the ground.
2. While I was walking on the ground I was told my hat is blue.
.. and a third-
My hat is Blue ON THE GROUND (and some other color when airborne)...
:)
C
He said that if you are going to any waypoint on a SID or STAR and you bring that waypoint down to the s/p, up to 1L and execute, it will display the offset at 6R on the RTE page. Then you can offset -- even along your route to the original direct-to waypoint. The route briefing is a bit vague but he is 100% sure that it works in both the sim and the airplane. They do it on virtually every departure out of CGO and it is a stated offset (e.g., 2 miles right, 3 miles right). Of course, you can't offset before takeoff because the offset feature is never available on the ground, even using this technique above.
So we have three SID waypoints: AA, BB, CC.
I downselect AA and upselect it to 1L.
Offset is enabled, and I enter and execute an offset.
ND shows dashed offset line from aircraft to (abeam) AA.
Will the dashed line continue along BB, CC, and through the cruise segment till the first STAR?
|-|
QuoteWill the dashed line continue along BB, CC, and through the cruise segment till the first STAR?
It will continue to offset the entire SID for sure. Whether it continues to offset the route
after the SID I'm not sure. I'll have to ask him.
His reply:
QuoteWhen you're on a star or a sid and select the fix in front of you and place it upon itself and execute you are essentially getting rid of the coding in the box that makes it a Sid or a star. It will offset all the way to the end of your flight plan until you cancel offset.
And what if the SID contains conditional waypoints, procedure turns, open hooks, holds, vectors, arcs? There is simply no reasonable offset headroom for such tiny curves. Will it at least, as usal, discontinue at course changes greater than 135°?
When they apply offsets on the real ship on certain SIDs, is it always applied to normal, non-conditional SID waypoints? Have they ever tried it on conditional SID waypoints?
It's on the departure out of CGO, so I'll have to check and see if there are conditional waypoints. I am almost certain that no one has ever flown a whole oceanic trip on an offset route because when you coast out you're going to want to be in a non-offset position at the coast-out fix, even if you did want to offset for the oceanic part. And coming into PANC on an offset star is not normally done.
These are tough question and ones that they will probably never be able to test in real life. And in the sim there's no time to test a whole trip like this. I know it's impossible to program the unknown into PSX, but my friend is certain that it offsets the SID and continues after the SID. At what point beyond that where it stops the offset feature is a mystery. Maybe you can come to some middle-ground position like it would allow it to offset the SID and the enroute part, buy go back to the END OF OFFSET as it approaches the first fix in the STAR?
I just gave it a try in one of the 747 Freeplay FMSTs (FMC Systems Trainer) I have access to ... (which surely has it's own limitations and might not be a complete replica of the 747-400 FMC). Here it works as I expected. On a EGLL departure via a Dover SID, I get the the offset prompt on 6R only once past DVR VOR. In the FMST, selecting direct to a waypoint/navaid (which is part of the SID) did not bring up the offset prompt.
Speaking of the CGO departures, there are conditional waypoints, but it surely depends on the database supplier (we know that different NDB manufacturers having different coding styles).
Anyway, looking into the database there are some conditional waypoints but mostly early in the procedures (like CA - Course to Altitude) and some FD (Fix to Distance; I think that one is fixed in space) ones. The ones which are applicable for a direct are mostly TF fixes.
Markus
Thanks for checking this, Markus. I talked to my buddy again and he said it is also SOP to get offsets out of PVG. When Hardy's conditional waypoint question came up, he said that some of these SIDs are very long -- like 100 miles long -- and they don't ask you to offset prior to departure; so the conditional waypoints are not an issue -- They are always past them before they are asked to offset anyway.
Another friend of mine at the FAA is a nav specialist and he issues oceanic ops specs for US carriers. I remember a conversation with him years ago about the Chinese controllers having UPS offset on SIDs out of PVG and he was not happy about it because he believed the only way to do it would be in HDG SEL (which is how they did it at the time). So maybe the solution by Boeing/Honeywell was to "trick" the system into allowing an offset using the technique that is now being used by the same carrier on virtually every departure from that airport.
I'll see if the United 767 sim will allow this when I go to Denver for CQ later in the month. I guess this is one of those "not in any book" techniques, just like the deletion of the VECTORS condition in 1L on a vector SID when you press HDG SEL.
Cheers,
Jon
Here's a theory that might simplify the background. The theory is probably wrong, but anyway:
The offset feature may be enabled whenever the active waypoint is no conditional waypoint (and no hold, no arc, or similar un-offset-able waypoint); the texts in the manuals which say the offset is disabled on SIDs, STARs, approaches, may be simplified texts; perhaps they just refer to the fact that such conditional waypoints are usually in SIDs, STARs, approaches. So you may get the offset feature not only by activating a direct-to but also by autosequencing to a non-conditional waypoint, even if it's a SID leg. Perhaps pilots don't notice it because they don't look at the RTE page when flying a normal SID. -- End of theory.
Regards,
|-|ardy
I'm pretty sure the offset doesn't appear until the end of the SID, regardless of the waypoint type. On a video I did earlier, I was heading to the first fix on a STAR and that waypoint was not conditional. I was getting a message END OF OFFSET. So if your theory is correct, wouldn't it still allow an offset at this waypoint?
Yes, my theory is probably wrong (or incomplete).
Quote from: Hardy Heinlin on Sat, 14 Jul 2018 23:00
Yes, my theory is probably wrong (or incomplete).
Don't worry HH, if it's worth it's better being incomplete anyway... Godel is your friend :-)
Theory No. 2:
The direct-to obviously destroys the SID, so to make the rest consistent, the remaining SID legs become enroute legs (if there are no conditional waypoints). As a side effect, these legs will allow an offset. This destruction trick only works on the SID (and perhaps on the missed approach). Why? The SID guides us away from an airport, whereas the arrival guides us to an airport. Nobody wants to end up abeam the airport, but there's no problem to end up abeam a cruise leg (in most cases). So if you make a direct to an arrival fix, the remaining arrival legs will not be changed to enroute legs. -- End of theory No. 2.
|-|ardy
I'll have to check this one out when I get back to the airplane. I'm not so sure it's so much a question of whether anyone "wants" to end up abeam the airport as it is some trick that Honeywell added afterwards when they found out that China was making crews offset on SIDs and they looked for a way to get the box to do it instead of using HDG SEL. But I think your theory No. 2 is probably more correct.
Jon
Quote from: emerydc8 on Sun, 15 Jul 2018 22:36
I'm not so sure it's so much a question of whether anyone "wants" to end up abeam the airport ...
I was just mentioning that because I think the trick only works on SIDs and not on arrivals.
|-|ardy
I'll check that. I think it works on arrivals too, but we'll see.
Jon
Just got an email from my friend who confirms that they get offsets on the STAR going into PVG all the time too.
And where does it end?
I'll ask, but I doubt he will remember. What happens is you will eventually get vectored off the STAR for the approach and at that point you are just going to extend from the CF or FF and the STAR is flushed out.
> The direct-to obviously destroys the SID
Has anybody (ever) checked what's happening on the route page when choosing a direct-to on a SID? Does it keep the SID identifier or does it say DIRECT on 1L?
The question "what happens when you choose direct-to?" with two possibilities is probably the same, just in different words:
1) does it pull the direct-to-fix freshly out of the waypoint/VOR/NDB/... database inside the box?
2) does it just up-select the existing fix from the LEGS page?
(Keeping the route page should also answer when the offset prompt appears.)
There is one difference with offsets on STARs - it's well documented in CBTs that route offsets will end at the last route waypoint and the airplane will keep its present heading and say END OF OFFSET. I learn this from this random 767 CBT from youtube:
https://youtu.be/-5zYseI6ddk?t=588
Markus
I didn't know it was possible to set the start and end fixes for the offset...
https://youtu.be/OOfOneUP-dE?t=5201
Also got this from a 737 driver: "You can offset up to the approach or approach transition on the 737."
And this @ PPrune regarding 777: https://www.pprune.org/tech-log/527957-lateral-offset-fmc-777-a.html
Quote from: Markus Vitzethum on Mon, 16 Jul 2018 12:04
1) does it pull the direct-to-fix freshly out of the waypoint/VOR/NDB/... database inside the box?
2) does it just up-select the existing fix from the LEGS page?
It must be (2) as the direct-to also works for pilot created fixes like PBDs or Lat/Lons. Why should the FMC pull it from the nav database if the pilot refers to an existing route fix?
|-|ardy
jcomm, the 737 and 777 FMCs are different to the 744 FMC.
Quote from: emerydc8 on Mon, 16 Jul 2018 10:22
I'll ask, but I doubt he will remember. What happens is you will eventually get vectored off the STAR for the approach and at that point you are just going to extend from the CF or FF and the STAR is flushed out.
I just implemented the same trick to STAR legs. Most STARs contain normal legs anyway.
It works very well. The offset ends at the approach transition.
(The VIA identifiers of the STAR legs remain intact.)
The trick has a desired side effect: Once a direct-to has "destroyed" the STAR procedure, the procedure becomes a pilot created route segment, and therefore it will not be autodeleted when another STAR is selected. As we know, the selection of another procedure normally deletes the previously selected procedure.
|-|ardy
Wow, that was fast. Thanks, Hardy! I'll still see what I can find in the United 767 sim next week. I have to make a stop at our HQ for about four hours next Monday and we have the 744 sims and FTD there. Maybe I can get one of the brain surgeons to check it.
Hi Hardy,
> Why should the FMC pull it from the nav database if the pilot refers to an existing route fix?
you're right ... this make no sense.
Besides, it does not make any difference anyway because the FMC works internally such that any given fix is only stored once in the database and any procedure or airway making use of it uses just a pointer to the waypoint, navaid, airport or runway database. (Just like any proper database would do. It's more efficient, too)
Markus
SID/STAR offset features are now implemented in PSX 10.39:
http://aerowinx.com/board/index.php?topic=4191.0
Regards,
|-|ardy
Just a follow-up on this, Hardy. I just tried the offset trick in the United 767 sim between KSFO and KLAX on the WESLA 3 Departure EBAYE transition to AVE, FIM and the SADDE 8 Arrival to LAX. I was able to get the offset to show at 6R in the RTE page by first going direct to PORTE on the SID. After that, going to the PLN page, as you can see in the picture below, it offset the SID and entire route but it stops abeam the first fix on the STAR into LAX (in this case FIM). Keep in mind that the picture below is the PLN page so you are looking at a north-oriented ND even though we were going south.
Also, out of curiosity, on climbing out on the SID, I put in /9000B at SUSEY and ran the MCP up to 10,000. The aircraft leveled off to obey the 9000' altitude restriction even though it was offset.
Also, the T/C doughnut appeared on the offset route, just as the T/D appeared on the offset T/D route on my previous video.
Jon
(http://www.hoppie.nl/forum/var/Offset_SID_RTE_but_not_START.jpg)
Thanks! So all is correctly modified in the latest PSX updates.
Cheers,
|-|ardy
Thank you!
I'll have to modify the descent path prediction calculation for offset routes. It currently uses the DTG to the true active waypoint as shown on the ND's upper right corner, and this DTG will never reach zero when flying an offset route. When passing the active waypoint on a 2 nm offset at the correct altitude constraint, the FMC thinks the DTG is 2 nm, concluding the aircraft is below the path (too early to hit the constraint). So the DTG should refer to the abeam point of the true active waypoint (while the ND indicates the DTG to the true active waypoint).
Does anybody know whether the DTG on the LEGS page for the active waypoint indicates zero when passing the active waypoint on an offset route? E.g. when the offset is 2 nm and the active waypoint will be sequenced in a second, will the first LEGS page line indicate 0 nm or 2 nm? The ND will indicate 2 nm.
|-|ardy
Hi Hardy,
I think the LEGs page is displaying the distance to the offset waypoint so it should say 0 (or very close to it) when it crosses over and switches to the next waypoint, just like the ABEAM PTS feature displays when you are perpendicular to the waypoint; otherwise, on a routine crossing, all the ETAs on the LEGs and PROG pages would be slightly off if you offset right by say 2 miles. I can check it out in the airplane, but unfortunately it will be a few weeks (still recovering from Continuing Qualification). I'd bet Peter knows the answer to this one.
Jon
Just a follow-up on this from the real plane. On a trip I just did from KATL to KCVG, we were on the PADGT2 Departure SMTTH transition, direct DOLLI then the JAKIE4 Arrival to CVG. DOLLI is the first fix on the JAKIE4 to CVG. While on the SID, heading to SMTTH the offset was not available on the RTE page until I down-selected SMTTH and installed it in 1L. This allowed the offset to appear on the RTE page (see pic). I offset 15 miles right of course to see where the offset stopped. As I expected, it stopped at the first fix on the arrival (DOLLI). So, the "trick" previously discussed to get an offset on the SID will offset the current SID and enroute portion (the leg from SMTTH to DOLLI, connecting the SID to the STAR), but it will not offset the STAR.
(http://www.hoppie.nl/forum/var/img_0500(1).png)
(http://www.hoppie.nl/forum/var/img_0499(1).png)
(http://www.hoppie.nl/forum/var/img-20180818-00359(1).jpg)
(http://www.hoppie.nl/forum/var/img-20180818-00360(1).jpg)
Very nice. Thank you for the confirmation.
|-|ardy
P.S.: Another question here: http://aerowinx.com/board/index.php?topic=4847.msg51694#msg51694
I just talked to a friend of mine in HKG who flies the G650. We talked about the Chinese ATC apparent obsession with offsetting on SIDs and STARs. He did some digging and found out the reason -- They are using ancient radar screens and if the flights are close enough together they can't see the identifier strip info for each flight. I would have never thought that. He's going to see if the offset feature discussed above will work on his modern FMS since it's also a Honeywell. We'll see.
Oof... not being able to move the data block around is a major pain. I've been playing ATC games for 30 years now and without that feature, you are indeed lost very quickly.
Kudos to Chinese ATC for putting up.
/-/
I was doing a flight today from EGLL to CYYZ. I created the flight plan using Simbrief, all seemed to go well however on the departure I went to use RTE offset but 6R did not say 'offset' it was just blank. I read in a previous post from Hardy that offset was enabled in sid/stars. Am I doing something wrong, I am using 10.68.
Thanks John
The offset is only available when no conditional waypoints are included in your SID.
Conditional waypoints are waypoints whose location may drift depending on current aircraft position, altitude, performance, wind etc. -- When the active waypoint is a conditional waypoint, the top right corner of the ND will display dashes "-----" instead of a waypoint identifier.
|-|ardy
I haven't tried the conditional waypoint on a SID so I can't confirm this in the real plane; But another thing I noticed this morning coming into SFO is that if you are not on a STAR yet, but you are given direct to the first waypoint on a STAR, you still can't offset the course until one of the waypoints on the STAR has cycled through.
In other words, on the DYAMD 5 Arrival we were cleared direct to INYOE and I tried to offset, but the option wasn't available on the RTE page. Once INYOE sequenced through (we passed over it), and DYAMD was the TO waypoint, I was able to get the offset feature if I brought DYAMD down to the scratchpad and brought it up to 1L and executed.
(http://www.hoppie.nl/forum/var/star(1).jpg)
QuoteThe offset is only available when no conditional waypoints are included in your SID.
Just checked this a few hours ago out of SFO RW01R on the SSTIK 4 Departure. There is a conditional waypoint at 520A right off the end of the runway. That is the first waypoint in 1L. There is no way to downselect it, so no way to get the RTE OFFSET to appear. I suspect that once passing the conditional waypoint you could get it to offset, but I didn't have time to try it.
Jon
I have flown out of CGO three times this week, and all times asked to offset while on the SID.
Proceeding direct to the active waypoint (Legs page, LSK1L, LSK1L, EXEC) did not give an offset cue on the Route page.
Only by line selecting all remaining points on the SID (there were three remaining) were we able to see an offset cue.
We did this by: (Legs Page, LSK1L, LSK1L, LSK2L, LSK2L, LSK3L, LSK3L, EXEC).
At this point, the SID did not appear an the left side of the Route page at all. Only Direct for all remaining points.
Eventually we did this prior to departure, to avoid having to fiddle with it while airborne.
Funny, the aircraft behind us told Zhengzhou Departure they "Could not offset departure route due to aircraft limitations." To which, the controller replied, "Then offset the course manually."
Replacing a VIA identifier (airway, procedure etc.) with a DIRECT on the RTE page by pushing the related left LSK on the LEGS page twice, -- is this a general feature in all FMC versions? (I mean the other LSKs beyond #1.)
Re offset on SID: I think this is FMC version specific; older versions probably deny it for all procedure legs (be it a conditional waypoint or not), and newer ones may only deny it for conditional waypoints.
Hardy,
I had not known of the ability to modify the Via column of the Route page through manipulation of the Legs page, except for the top (Active) waypoint, until this week. You know, proceed direct to a waypoint by dropping it on top of LSK1L, then execute, and the Via on the Route page becomes Direct. In the plane, this works for all subsequent waypoints on the legs page. When the waypoints are selected into the SP and dropped back on themselves, the associated Via on the route page is replaced by a Direct. It is as if you manually loaded the waypoints by sequentially loading them on the Route page, but with the advantage of retaining the speeds and altitudes associated with points from the SID.
I have not read of this technique in the system manual or Honeywell manual.
Thus, with no associated SID routing in the via column associated with the points, the box allows a route offset. Pretty slick!
Thank you. I will implement this effect in the next update PSX 10.80.
|-|ardy
I have also realized that there is a big danger with this SID and STAR offsetting. Off the route, you may be outside of the protected airspace of the MEA/MOCA. Doing this procedure out of Hong Kong would certainly not be advised. There is a reason Honeywell made it difficult to deviate from the procedures in the low altitude environment.