RNAV Procedure still an elusive mystery!
Having made several attempts to duplicate my one successful RNAV "glide path" approach, I am at a total loss. I have searched the internet and come up empty. I even urchased an airplane2sim Q400 FO course that promised to demonstrate the proper procedure but after 1 hour of useless conversation the video pilot made two bad attempts and gave up. In my one successful approach the GS actually activated and took control of the descent path allowing me to reset the altitude for miss approach without disturbing the descent. Every attempt since then either the approach mode in FMS is not available or it arms properly but when I activate it the "GS" symbol remains armed and visible but never engages. The aircraft simply captures and holds the final approach altitude. Even VNAV won't engage at that point so I have had to complete the approaches manually. The virtual glide path created by a properly setup RNAV approach is a mentioned feature in some of the literature but I can find nothing that steps me through the proper setup. I think my one success was a random accident. I must have accidentally set it up properly but have been unable to duplicate it again since though I am using the exact same flight and weather. By the way, I am selecting the approach directly out of Q400 FMS and attaching it as my flightplan arrival without any alterations. It appears to be recognized properly but just will not function. I am using F35 but that shouldn't make any difference. Again I can find no detailed literature about the procedure other than the mention that it is available on the Q400.
Craig
Comments
Correct me if I'm wrong, but isn't the Q400 equipped for LNAV/VNAV approaches only? As far as I am aware, the "GS" is not functional as long as you are in FMS mode.
It was indeed a pleasant surprise for me to discover the "virtual" glide path that Q400 would create for an RNAV. It will not do so with any other non-precision approach as far as I am aware. The trick, as I have eventually realized is to input the Q400 version of the arrival RNAV into the FMS and leave it alone other than closing the disconnect. I have been deleting the duplicate waypoints that the FMS puts in when I attach an arrival. When I left them alone I was able to fly the RNAV as if it were an ILS, automatically down the glide path. My procedure (that I have now been able to duplicate successfully):
Craig
I think you've got it Craig, except for arming APR on the FGCP (or whatever it's called in the Q400 - I forget) - I don't see what purpose that would serve, as LNAV APR will appear if you've armed the approach in the FMS. Apart from that, I think you've got to the bottom of it. I'm going to post a video on it, but these things take ages to record and edit, so you'll have to bear with me.
John.
Hello Craig and John,
Being an oldtimer I am not a big fan of the VNAV and I prefer the ILS or VOR App but as this is becoming the way for the future I have to adapt to the new technology.
Regarding the BARO RNAV, I do not know how to make videos so I enclosed 12 screens from a small flight from LFRD to EGJJ.
Here is the link for the screens:
https://www.dropbox.com/sh/vlstlv16kr7dihj/AACoBhbufUHt1dLgHmYT9GcAa?dl=0
1- Enter your RNAV APP.
2/3- Clear the NO LINK but make sure not to alter the APP WP.
4- Enter the EXACT QNH otherwise you'll get a false virtual GS with an error of 28ft/mb.
5- VNAV Page - VNAV to WP6: JJ26F which is the TOD on the virtual GS. It could be another WP like the IAF. I did not find it made a difference.
6- Enter an ALT about 500 ft below the TOD. Press VNAV but do not Press ALT SEL.
7- Select APP on the FMS. It could be done earlier.
8- When you have initiated your descent, Select MISS APP on the FMS and then you can enter your Miss App ALT and ALT SEL in case of GA.
9- Descending on the virtual GS.
10- Approaching Minimum. On the GS.
Of course you should not carry on with the A/P below the minimum. The following screens are just for the exercice.
11- Below Min, still on the GS.
12- 35ft, still on the virtual barometric GS but slightly low on the path as the BARO RNAV is not as precise as an ILS.
May be I am wrong somewhere so please correct me.
Regards,
JP
@jp:
Interesting to note on 2 points. One, that you entered an altitude of 500 below the T.O.D so you could arm VNAV and that makes sense. I have been entering the MDA which really unnecessary since I am going to enter the Miss altitude as soon as I am established anyway. Good point! The second, is that you press the FMS Miss Alt which I have never done. Of course, so far I have not tried to execute a miss approach out of RNAV. I was afraid to press that option out of concern it would immediately interrupt my virtual glide path. I did watch a video of a Miss out of RNAV by Q400 instructor and I don't remember seeing him touch the FMS after he had "activated" the APR. Is there some added automation available to the Q400 by activating the FMS "miss" option?
Craig
"Is there some added automation available to the Q400 by activating the FMS "miss" option?"
Usually pressing the TOGA button on the power levers will initiate the missed approach.
All the TOGO button does is set the flight director bar to 10 degree climb. You still have to manage power and pitch to that bar. So my question is whether pressing the "Miss Apr" in the FMS/Nav page has any effect on the miss procedure. Some other automatic effect?
Craig
Hello Craig,
From a RW Q400 operator they say that we should enter an altitude of at least 200 ft below the current altitude so I assume that 500 ft should be OK and an easy figure to calculate.
I did not find any way to have the App activated automatically, you have to ARM APPR on the FMS. However there is no need to ACT APPR, this is done automatically.
Regarding the activation of the MISD APPR, you have to activate it yourself on the FMS. If you fail do it, sometimes you have a NO LINK after the Rwy and it could create problems during the App like disengaging the VNAV and you'll get PITCH instead.
Please note that it happens sometimes, even that everything looks perfect that you suddenly get PITCH instead of VNAV. In that case, no worries, just hit V/S and adjust your V/S to stay on the virtual GS. Then, this is just your minimas which are different as you are not VNAV anymore but LNAV.
Personnally it is the way that I prefer as it is smoother than the VNAV and more like a VOR or NDB App.
To activate the Miss does not say that you initiate the Miss. It just creates the lateral path. If you have to execute a Miss, then you press the TOGA.
It is part of the procedure to have the Miss prepared and ready to be executed, either by conventional means or FMS.
There are quite a number of reasons to execute a Miss: Minima reached without seeing the Rwy, Rwy incursion, the aircraft in front of you did not clear the Rwy, you are not stabilised, windshear, wind gusts, etc.
It is the same when TOFF, you have to be prepared to come back quickly in case of emergency.
JP
Make sure to also deselect the navaid updating for the IRSin the FMS before conducting these types of approaches. You want GPS as the sole navigational source.
I would love a video of all this...!
Or a definitive list of things to do. I am having a hard time collecting all the proper steps from this topic. 
I prefer RNAV approaches because there simply are more of them over where I fly.
This one confuses me. Where exactly on the FMS can you select APP...?
Hm, well, I think I got it already...
It's pretty simple, really. Instead of using VNAV for the final approach only I used it for the entire descent.
I flew from Bergen to Oslo. During cruise I set VNAV on the FAF of the RNAV approach I selected. (Why should you set TOD for earlier waypoints when VNAV keeps all contraints anyway?) I asked ATC for a Direct to the intersection of the RNAV approach (hence skipping all the odd turns you have to make when flying into Gardemoen
).
Close to the TOD I set a lower altitude (ProATC assigned me FL150 so I set that) and I armed VNAV. After a while VNAV PATH was active. I didn't set ALT SEL so from there on it doesn't really seem to matter what ALT you set: VNAV will fly the path regardless, so it seems.
Decent went perfectly fine. Close to the intersection I armed the approach on the FMS and after passing the intersection, so flying towards the 'virtual approach path', I activated the approach. The PFD now showed LNAV HDG INT: not sure what I had to do there but I simply let the plane fly on... Near the 'virtual approach path' the PFD switched to LNAV APPR. VNAV simply kept on going down the 'virtual GS'.
At minimums I disabled the AP and had a perfect landing. All in all pretty easy to do and less cumbersome than an ILS landing. No course to set, no radio to set and no source to switch.
I do wonder though what happens if you don NOT arm and activate the approach on the FMS: won't LNAV and VNAV simple keep on flight the exact same path down to the runway anyway...? Does it make any difference?
EDIT
Oh, btw: I also pressed MISS APP on the FMS to set the GA alt but that didn't work out well...! Suddenly the modes changed to regular LNAV (I think) and PITCH MODE: not what I wanted! Luckily I managed to get back to LNAV APP and VNAV PATH again by clicking a few buttons... I won't touch that MISS APP anymore, that's for sure.
Hello JvanE,
Regarding the TOD when you are in cruise, the FMS would give you the TOD but ATC could say differently due to traffic. It is good practice to request descent a bit earlier than shown on the FMS and personnally I prefer to follow the path with the V/S than VNAV which would be more comfortable for the PAX. Some operators do that as well especially when you know that there is a big difference between 1013 and the QNH.
Personnally (old school) I rather prefer the ILS which relies on ground equipment checked permanently than the VNAV where it is YOU building the G/S and as I mentionned earlier a small mistake entering the QNH could be fatal.
If I have no choice and if I have to use VNAV, I prefer the V/S that I can control and adjust depending of my Ground Speed and check every Nm with the chart, exactly like a VORDME.
It happens also few times to me that the VNAV disconnected and went to PITCH MODE so it is why I rather prefer to use V/S all the time.
Arming the MISS APP gives you the LATERAL path that you'll have to follow and it should be done. Same with conventional, the Miss is always prepared.
Something that we have to keep in mind: most of the time in a Sim you fly on your own but the Q400 is designed for two pilots.
Regards,
JP
But when should this be done? As I said I clicked on (the LSK next to) MISS APP after activating the approach and immediately my AP modes changed. As if clicking on that LSK activates a missed approach instead of letting you arm (or set?) it.
As soon as you see MISS APPR, usually after passing the IAF, and before to start the descent on the G/S you click on the LSK.
If you enter it when you have started your descent on the G/S it is then that it could disconnect the VNAV and go into PITCH.
Even if everything is set correctly (QNH and speed) I found out that the VNAV path is not exactly as it should be and most of the time we are below the G/S about 100 to 150 ft which is too much and it is why I rather prefer to use V/S and correct the ROD when checking the distances giving you the altitude where you should be.
Again I insist that I am not an expert on VNAV as never used it in RW.
Ah, okay, thanks. I think I clicked on it too late then!
I am also no expert but up to now all my RNAV approaches worked perfectly fine, including the altitude, even if I let the plane fly on AP until (or even passed) minimums (which I usually don't do btw).
Chaps this is a video I’ve done on my channel - I hope it’s of some use:
I see you ARM the APPR but you don't activate it...? I myself am having problems as soon as I activate the approach: shouldn't I do that at all then? Will the approach activate itself...?
Okay, something is wrong somewhere. In your video you say that when you ARM APPR on the FMS the mode changes to LNAV APPR. It doesn't on my PC! When I press ARM APPR nothing happens but... as soon as the plane intercepts the final path towards the runway it automatically switches to LNAV APPR!
Things were going wrong on my PC because pressing ARM APPR didn't seem to do anything so I pressed ACT APPR but then I switched to LNAV HDG SEL and then the plane simply didn't intercept the final approach path...!
Turns out I only have to ARM and the plane does the rest.
Are you sure that on your PC the mode changes to LNAV APPR as soon as you select ARM APPR...?
Yes - I’m pretty sure that LNAV APPR will appear once you route direct to the IF or intercept the final approach track after arming the approach in the FMS. You are to arm the approach in the FMS only once you’re cleared to intercept the final approach track, or you’re cleared to the IF.
Other than that, I don’t quite understand what question you’re asking.
At 15:22 you are saying that when you ARM approach the mode will change to LNAV APPR. That doesn’t happen on my pc. On my pc nothing happens when I ARM APPR: only when I get to the final approach track it automatically changes to ARM APPR. So my question is how come you get LNAV APPR as soon as you select ARM and while you even aren’t on the final track! I’m not expecting an answer from you directly, because you probably don’t know, but from Majestic.
You don’t select ACT APPR yourself, do you?
By the sound of it, from your other post, you’re possibly not getting LNAV APPR because you’re editing the flightplan by removing the NO LINK or routing direct from the end of the STAR to the IAF - if so, I said in the video that doing this will result in undesired behaviour. only navigate to the IAF when you’re cleared to do so using the DTO feature in the FMS, then arm the approach, and the mode will then switch to LNAV APPR. And no, ACT APPR is not required.
Aaaah, okay, understood. That might be it indeed!
However... I wonder if removing that NO LINK doesn't make things easier...? Then you don't have to use the DTO feature, you will simply keep on flying the LNAV path all the way to the final track and (if you have armed the approach) VNAV APPR will be enable automatically anyway at the time you reach that track! Less steps, less hassle.
Yes, you won't see LNAV APPR until you reached the final track but as long as things work, that's no problem, I guess.
Another advantage is that you can set TOD using a waypoint beyond that initial NO LINK, like even the IF or FAF, if you want to, something you can't do with the NO LINK (because you can't set TOD for a waypoint beyond a NO LINK).
There are a lot of different ways to get things done, according to YouTube...
Some never even arm approach, other activate approach, get on LNAV HDG SEL and then CNCL HDG in order to get to LNAV APPR... None of the video's I've seen so far keep the NO LINK: they all seem to remove it. Seems that removing the NO LINK and arming the approach (and letting it switch to LNAV APPR automatically at intercept) seems the most simple way to get things done.
EDIT
Just flew into ENTO runway 18, using the following STAR:
https://ais.avinor.no/no/AIP/View/41/aip/ad/ento/EN_AD_2_ENTO_4-11_en.pdf
and the following RNAV approach:
https://ais.avinor.no/no/AIP/View/41/aip/ad/ento/EN_AD_2_ENTO_5-3_en.pdf
I removed all NO LINKS and asked for a DTO to BAMIX. I set TOD using ASLAK (not the one I should have picked officially but well...). LNAV and VNAV flew me all the way down perfectly. While approaching AKIPU I armed the approach (ARM APPR on the FMS) and nothing else. The PDF kept on showing LNAV. But as soon as I hit ASLAK the mode changed to LNAV APPR! Seems that mode doesn't get activated when you intercept the final track, which I did at AKIPU already, but when you hit a certain waypoint: probably the IF.
I will test this method with another approach this weekend because this one is a bit different (because AKIPU was in line already with the final track).
Well done Rondon 9898.
Your analysis regarding the VNAV is very interesting and it is true than in Europe we do not use it so much but as it is only the baro VNAV that we can use presently, I do not like too much as I explained before.
LPV looks a bit different and acting more like an ILS with 200 Ft minima but, so far anyway, it does not appear to be working with our beloved Q400.
Regarding the NDB, you are right that even that I used these procedures extensively for many years on some airports, it is quite dangerous mainly during sunrise and sunset with sometimes a 30° error.
Right again to point out that the Q400 is for two pilots and nearly impossible to do it right with only one person. It is why I built a small home cockpit that can be used by two persons. The use of a "virtual" co-pilot like you do is very good.
From an operator's book (that I believe you should know quite well), the altitude to set has to be at least 200 Ft below so there is no need to set the DA and I found out that 500 Ft below is enough and easy to remember as we would have to set the Miss App altitude soon after starting our final descent.
I know that it would have been a much longer video but it would have been quite interesting to show how to set the VNAV on the FMS when you start your initial descent to understand the whole process.
There is a case where we have to be very careful, it is the Approach / Approach procedure between two airports which are very near like example that I did: LFRD to EGJJ where you'll be cleared to 2000 Ft and you would not have an initial descent so you have to set your VNAV on the FMS otherwise it won't work.
There is something else that I forgot to mention before, with FSX the runway elevation is not taken into account, it is the airfield altitude and we can have some errors like with LFRN: Airfield 124 Ft / Rwy 28: 120 Ft which is fine but Rwy 10: 77 Ft which could be a problem with the Baro VNAV.
Very good work that you have done for us, thank you,
JP
JP: pleasure - glad it was of some use. I’m pretty sure I showed the VNAV descent in another video on my channel when I did a flight from Birmingham to Jersey.
JvanE: If that works for you, great - I only mention it because the Universal FMS manual specifically states that you should not delete NO LINKS or duplicate waypoints in any FMS-based approach.
The system manual of the Majestic Q400 says this:
"The usual procedure is to erase the NO LINK in front of the STAR after ensuring that it properly links into the flight plan, but leave the NO LINK ahead of the first approach point (IAP), until the ATC clearance for performing the approach is received."
So in the end you do have to delete the NO LINK but just not before you get clearance. It doesn't say anywhere you should never ever delete the NO LINK. And when you DO get clearance you shouldn't do a DTO but simply remove the NO LINK. This way you can go from cruise to landing on LNAV without being forced to do a DTO.
Do you have a link to that Universal FMS manual? I am curious what it says exactly.
Furthermore the system manual says:
"When the approach is armed, the approach can be activated either:
This also shows you actually HAVE to delete the NO LINK!
In addition (which answers a previous question of myself), when you select ACT APPR manually, the procedure is this:
"When FMS establishes that the aircraft is on the acceptable intercept course to the final approach segment, the INTERCEPT prompt will appear on the NAV page. Pressing the INTERCEPT LSK will enable the FMS to automatically switch to the approach mode, when the aircraft nears the approach path."
Double post, sorry.
You've just quoted a passage from the Majestic manual that is exactly what I said - I didn't mention NO LINKS in the STAR, I said that the NO LINK ahead of the IF, and any associated with the FMS approach, should be left, and the Universal manual says the same. I don't have the link, but it's easily googled. You most certainly do NOT have to delete the NO LINK in relation to the approach, and shouldn't.
> You most certainly do NOT have to delete the NO LINK in relation to the approach, and shouldn't.
The quote says you have to leave that NO LINK until you get clearance, in other words: after getting clearance you may, or even should
Using the DTO function is not the same as clearing the NO LINK, but anyway. Glad you've worked it out.