Normally a STAR will end far enough away from the IAF to allow ATC to assign vectors as necessary (for spacing, etc.) before clearing to the approach. It is never to be assumed (unless loss of communications) that an aircraft proceed directly from the final STAR fix to the IAF without ATC authorizing. That NO LINK stops this from inadvertently happening. But when "cleared for the approach" ATC usually suggests a heading and restates a target altitude to maintain until intercepting the final course. But the heading is just a suggestion and at the discretion of the pilot. At this point in the sim it would seem logical to either delete the NO LINK or perform a Direct To. Once on an acceptable intercept, select VNAV (but no ALT SEL) and a lower altitude on the FD Panel. Then the approach can be activated either from the FMS or by selecting APR on the panel. In the Q400 simulation, it seems to be more reliable if I am first established and level at my IAF crossing altitude BEFORE I setup the RNAV. My steps that now have been working every time:
(After established and level on an intercept heading): Set a lower altitude (I set the MDA, but anything lower by 200 ft will do)
Switch to NAV (even though you are on a heading) then Arm VNAV (but not ALT SEL)
Assuming that the APP has already been "armed" in FMS (if not, then "arm' it), select ACT APPR in FMS/ or, SELECT APR on the EFIS FD Panel.
Usually LNAV APR will occur and "GS" will appear in white. Now the RNAV is armed and a virtual glide slope will appear before the FAF and the aircraft will intercept and follow it right to the threshold if you let it.
I have flown these approaches in RW but definitely not in the Q400! But this algorithm has been working for me in this sim. Hope this adds some clarity.
The reason the necessity of DirTo is that after vectoring by ATC there is no need to re-intercept a course which is what clearing the link would do. Once cleared, the objective would be to just go to the IAP (or maintain a heading to intercept the RNAV path.) The RNAV will work in the sim without having to re-intercept the course since the logic seems to view the RNAV as beginning at the FAF not the IAF. Just completed one using that exact example.
And on another note: it was mentioned that the RNAV logic on the Q400 was not accurately tracking the glide path as indicated on the chart. The only time I experienced that (having now completed 12 successful RNAV approaches) is when I discovered that the descent path was using the VNAV rather than creating a virtual glide slope. That can be checked on the NAV page of the FMS. If it is actually established on the RNAV then it will display that info. If not then the VNAV is the operational mode and it does not provide altitude protection automatically as the generated glide path would (since it is generated in consideration of any intermediate altitude restrictions beyond the published FAF.)
@hifly said:
The reason the necessity of DirTo is that after vectoring by ATC there is no need to re-intercept a course which is what clearing the link would do. Once cleared, the objective would be to just go to the IAP (or maintain a heading to intercept the RNAV path.) The RNAV will work in the sim without having to re-intercept the course since the logic seems to view the RNAV as beginning at the FAF not the IAF. Just completed one using that exact example.
Ah, okay, got it. The thing is: I never get vectored (with ProATC) and always fly using LNAV so for me simply deleting the NO LINK works like a charm. If you got vectored away from the planned path I can understand DTO is a wiser decision.
Comments
Normally a STAR will end far enough away from the IAF to allow ATC to assign vectors as necessary (for spacing, etc.) before clearing to the approach. It is never to be assumed (unless loss of communications) that an aircraft proceed directly from the final STAR fix to the IAF without ATC authorizing. That NO LINK stops this from inadvertently happening. But when "cleared for the approach" ATC usually suggests a heading and restates a target altitude to maintain until intercepting the final course. But the heading is just a suggestion and at the discretion of the pilot. At this point in the sim it would seem logical to either delete the NO LINK or perform a Direct To. Once on an acceptable intercept, select VNAV (but no ALT SEL) and a lower altitude on the FD Panel. Then the approach can be activated either from the FMS or by selecting APR on the panel. In the Q400 simulation, it seems to be more reliable if I am first established and level at my IAF crossing altitude BEFORE I setup the RNAV. My steps that now have been working every time:
Usually LNAV APR will occur and "GS" will appear in white. Now the RNAV is armed and a virtual glide slope will appear before the FAF and the aircraft will intercept and follow it right to the threshold if you let it.
I have flown these approaches in RW but definitely not in the Q400! But this algorithm has been working for me in this sim. Hope this adds some clarity.
Craig
I know. I suppose real world pilots also have their own way of doing things...
The reason the necessity of DirTo is that after vectoring by ATC there is no need to re-intercept a course which is what clearing the link would do. Once cleared, the objective would be to just go to the IAP (or maintain a heading to intercept the RNAV path.) The RNAV will work in the sim without having to re-intercept the course since the logic seems to view the RNAV as beginning at the FAF not the IAF. Just completed one using that exact example.
And on another note: it was mentioned that the RNAV logic on the Q400 was not accurately tracking the glide path as indicated on the chart. The only time I experienced that (having now completed 12 successful RNAV approaches) is when I discovered that the descent path was using the VNAV rather than creating a virtual glide slope. That can be checked on the NAV page of the FMS. If it is actually established on the RNAV then it will display that info. If not then the VNAV is the operational mode and it does not provide altitude protection automatically as the generated glide path would (since it is generated in consideration of any intermediate altitude restrictions beyond the published FAF.)
Craig
Ah, okay, got it. The thing is: I never get vectored (with ProATC) and always fly using LNAV so for me simply deleting the NO LINK works like a charm. If you got vectored away from the planned path I can understand DTO is a wiser decision.