B747-400 Direct-to INTC CRS

[KOLMAN 0]

Hallo,I have a question about the initial value of the INTC CRS, when using the direct-to function. Shouldn

[michal 44]

G.K.No other takers so I will volunteer and do my best.In my opinion any resemblance of '318' to the 'true' course is purely coincidental here - we are working in the realm of magnetic courses, no doubts about it.I really don't know what your original flight plan was but this is what happens when you try to execute "direct to". After down-selecting and up-selecting your BSR immediately above the BSR shows up direct-to-course to this waypoint (in your case 302). To the bottom right you get the intercept course - this is NOT the direct-to course. Unless your hit the '6R' followed be EXEC you are not going to get this intercept course, you will get the direct-to. So no wonder that when you hit EXEC only you get to fly on the 302.Ok, so what is this 'intercept' course? The intercept course to your BSR is normally the original course leading to this waypoint in your unmodified flight plan. I can only assume that a minute before you down-selected BSR the course leading to this waypoint was either exactly 318 or very close to it.Had you hit '6R' followed by EXEC you would have seen a magenta line drawn on the display crossing the BSR exactly at 318 and most likely your aircraft would be to the right of this line - you would continue on the present course (302) until intercepting this line and the aircraft would then turn to 318.By the way the whole thing is a bit ambiguous since Honeywell's original 747's FMS documentation (Pilot's Guide) does state that the prompted value in 6R will be the direct-to course. But I verified independently in the Aerosim-747 desktop sim that it is not. If I am wrong I hope someone will correct me.Michael J.

[michal 44]

By the way, you should get a good hint what's going on here when you take a look at the page 12-35 of PMDG's FMC manual (FMC Flight Plan Modification). The course leading to BOS happens to be 072 (in the flight plan) and this is the exact intercept course you are getting when you down- and up-select it, though the direct-to BOS happens to be 090 at the moment.Michael J.

[KOLMAN 0]

Thanks

[michal 44]

G.K - it is confusing for me because on you previous picture it showed 302 above the BSR, but on your recent one it shows 318 (!!). Something keeps changing, clearly I am missing some key information to have a complete picture what's going on. Anyway, I gave you I think a solid explanation how it works including the reference in the manual, if you don't like the intercept course you are getting - you are the pilot in command and you can change it. Your are controlling the aircraft and not the other way around. ;)Michael J.

[KOLMAN 0]

The second screen shot shows a course of 318

[michal 44]

>as PIC I expect from my NAV equipment, that it provides>me with correct information

[cowpatz 243]

GK. What happens on other legs? Can you reproduce it elsewhere?CheersSteve

[KOLMAN 0]

Hallo SteveYes, it is easily to reproduce. Here a further flight, with an other mag. variation:Flight Plan:KIAD PRYME2.JERES J220 BUF.YOUTH2 CYYZWaypoints:KIAD-FUREE-THUMM-PRYME-JERES-MICAH-VALLO-OGESY-FORTT-BIGEO-WUNDR-SFK-ELZ-BUF-CYYZMy position between JERES and MICAH on J220 course 011

[michal 44]

>GK. What happens on other legs? Can you reproduce it>elsewhere?Steve,Let me first thank you again for your continued presence on this forum. You seem to be the only real 747 driver still left here and actively participating in technical issues.Going back to the problem at hand - PMDG's handling of the intercept course seems to be identical to the Aerosim's 747 simulator - therefore I suspect they can't both be "wrong" since they are two completely independent simulators developed by independent companies (Aerosim 747 trainer is not a consumer game-product - it is meant as a desktop training device for real pilots). Since you fly the real thing you may shed some light how it works in your case. By the way it is entirely possible that FMS has different versions of the software - some other FMS features (like for example treatment of winds aloft) do depend on FMS's software revision.Michael J.http://www.precisionmanuals.com/images/for...argo_hauler.gifhttp://sales.hifisim.com/pub-download/asv6-banner-beta.jpg