YPPH VOR/DME - ILS Approach problem
Printed From: Avidyne
Category: Avidyne General
Forum Name: IFD 5 Series & IFD 4 Series Touch Screen GPS/NAV/COM
Forum Description: Topics on Avidyne's IFD 5 Series and IFD 4 Series Touch Screen GPS/NAV/COM
URL: http://forums.avidyne.com/forum_posts.asp?TID=2488
Printed Date: 14 Mar 2025 at 1:16am
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com
Topic: YPPH VOR/DME - ILS Approach problem
Posted By: Mike_vonb
Subject: YPPH VOR/DME - ILS Approach problem
Date Posted: 20 Mar 2023 at 2:40am
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I have a problem with performing the YPPH Rwy 21 ILS-Y approach with my IFD550 and DFC-90 equipped SR22. The DME arc is only 9nm and from the lead radial the DFC turns for an approx 30deg intercept of the ILS. The problem is the intercept point is after the FAF! I also have a secondary issue of not being able to set the inbound track on the localiser prior to reaching the localiser - if I set it on the arc the track changes and I have had the autopilot fly through the localiser on the arc. This approach is on the training app and the app autopilot tracks from the LR to intercept AFTER the FAF as happens in flight. Can someone provide some clues re correct autopilot mode, how to set the final approach course and how to intercept the localiser in a more appropriate manner? Cannot understand from the manuals or training book how to get this approach to work properly and it’s unpleasant enough trying to do this in visual conditions…in IMC this would be a disaster!
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Replies:
Posted By: AviSteve
Date Posted: 21 Mar 2023 at 10:30am
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The procedure is designed with the assumption that it will
take a while for the aircraft to make a right turn to join the final approach
course. If the aircraft could turn on a
dime, you would get the first picture below, which was the scenario you
described such that the lead radial intercepts after the FAF. The FMS doesn’t predict the right turn after the
end of the arc (D004I), so it just draws the heading leg from D004I to the
intercept point. Since the heading leg
doesn’t actually intercept the next leg when started from D004I, the line is
drawn out for 50nm. However, once the
aircraft actually crosses D004I and the heading leg becomes active, then the
FMS draws the line from the aircraft position.
As the aircraft continues eastward during the turn, the heading leg will eventually intercept the final approach course and the leg will be drawn as
you expect, as shown in the second picture below.
------------- Steve Lindsley Avidyne Engineering |
Posted By: Mike_vonb
Date Posted: 23 Mar 2023 at 4:29am
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Thanks for this clarification. Using the training app I approximately get your result but only if the speed on the arc is kept a little high - I have a SR22 G2 with 50% flap speed at 119 kts and at a (simulated) 110 kts on the descent from 2500ft at the LR to 2000ft on the localiser this gets me to approximately VIKIS (FAF) as the point of intercept to the localiser. I also note that in the training app the aircraft passes through the localiser before turning. I understand this may not be the way the actual aircraft may work but getting some clarification on this would be great.
Just to push a little further into this... QUESTION 1) What is the appropriate AP mode(s) on the DFC-90 when on this approach? Is there are requirement to change modes during or after the arc for this approach? The experience with my instrument instructor on the few approaches in the SR22 hasn't yielded predictable results thus far! QUESTION 2) Is there a means of continuing the arc beyond the LR with automated turn anticipation onto the localiser, or change to a 45 deg intercept instead of the default 30 deg to establish on the localiser & GS well before the FAF? Rolling onto the localiser immediately before the FAF makes confirming a stabilised approach a bit challenging for an inexperienced instrument pilot like myself! QUESTION 3) How do I set the localiser/RWY course whilst still on the arc and not have it change when turning onto the localiser? For ref I have the Entegra PFD/MFD. I have also read through the DFC-90 and IFD550 pilot guides but to ne honest not super clear where this isnt working for us and its a bit of a challenge to have to book an ILS training slot just to experiment a bit. Unfortunately YPPH is the only airport within 1000nm that has an ILS approach available for training and it is slightly unusual in having the 9nm arc instead of a more usual 12/15nm. Thanks in advance. |
Posted By: vuk3@me.com
Date Posted: 23 Mar 2023 at 8:29am
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Hi Mike, I thought I may shed a little light on this approach for you. I can see your point with the way the approach is depicted on the IFD trainer. I’m no instructor, just letting you know how I would fly it. When you’re actually flying the approach the lead radial is designed as the place you commence your rate one turn onto the localiser. If all goes well you’ll complete your turn and be close if not established on the ILS. So you can use the gpss mode on your AP to fly the arc. Make sure you have the ILS localiser tuned and identified. At the LR pop the AP into heading mode set your HSI onto the ILS course and intercept the localiser with the HDG bug. while you’re doing this Arm approach mode on the AP. Make sure your IFDis in VLOC mode and the AP should couple the GS and ILS then you’re set. Check that you’re at the published altitude at VIKIS (FAF). You’ll find in real life you’ll have plenty of time when you’re at Apch speeds. Do this in in visual conditions a couple of times and you’ll quickly get the hang of it, If you have a second VOR instrument, tune and set that to the inbound track for the ILS. That way you can watch the intercept and have a backup ready to go if you need it. If you get tired of shooting the ILS at Perth I think YPEA have a very similar 11 DME arc into the ILS with an IAF at SAMLA. I’m pretty sure you’d be ok to do that there outside tower hours seeing it’s a RAAF base… See ERSA. Hope this helps. I’m not in a cirrus, so it may be a little different for you, but I think the principle would be the same. Look me up if you ever over in YMMB Vic. Cheers Andy ------------- VH-UAR YMMB |