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WHY DIFFERENT MDA FOR CIRCLING APP ON RECIPROCAL R/Ws

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WHY DIFFERENT MDA FOR CIRCLING APP ON RECIPROCAL R/Ws

Old 14th Mar 2011, 00:18
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Originally Posted by BOAC
Presumably if you went round off Aterp's VOBZ NDB26 you would need to go left to pick up the NDB 250 track - or would you just fly the 'RNAV' track to the north of the correct track? My head hurts.
Disregarding the track dislocation at FN08, for a bit of head-spinning, take a close look at at where the magenta line goes in the region of the threshold. The NDB is just north of the opposite threshold (26).

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Old 14th Mar 2011, 07:16
  #42 (permalink)  
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BOAC, this is NOT a RNAV approach. It's a NDB approach constructed in accordance with PANS OPS 4 as shown in the left bottom corner. If it was overlay the title would be GPS or NDB approach. Once you've realized that, and rightfully pointed out deficiencies, you simply fly it raw data and use the FN point to commence your 3 degree descent towards the minimum instead of dive and drive. The title of the procedure states clearly what it is and how it must be flown.
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Old 14th Mar 2011, 07:32
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Originally Posted by 9.G
this is NOT a RNAV approach. It's a NDB approach constructed in accordance with PANS OPS 4 as shown in the left bottom corner. If it was overlay the title would be GPS or NDB approach. Once you've realized that, and rightfully pointed out deficiencies, you simply fly it raw data and use the FN point to commence your 3 degree descent towards the minimum instead of dive and drive. The title of the procedure states clearly what it is and how it must be flown.
That's not the way thousands of these approaches are flown. The FMS is used to fly the NDB approach; no "overlay" or "title" necessary. The primary purpose of FN26 and RW26 is to facilitate the FMS flying the approach. The final descent path is coded at 3° from FN26 to RW26. You are welcome to fly 3° raw data from FN26, but you may may well pop out above the PAPI at the MDA. If I didn't have a DME or FMS VNAV profile to follow, I'd be going down a bit/earlier than FN26 just to make sure I got to the MDA before it intercepted the GS ie Dive and Drive.
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Old 14th Mar 2011, 08:03
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Capn Bloggs:

That's not the way thousands of these approaches are flown. The FMS is used to fly the NDB approach; no "overlay" or "title" necessary. The primary purpose of FN26 and RW26 is to facilitate the FMS flying the approach. The final descent path is coded at 3° from FN26 to RW26. You are welcome to fly 3° raw data from FN26, but you may may well pop out above the PAPI at the MDA. If I didn't have a DME or FMS VNAV profile to follow, I'd be going down a bit/earlier than FN26 just to make sure I got to the MDA before it intercepted the GS ie Dive and Drive.
You are correct for those who have the necessary AFM and other authorizations. Lacking that an IAP like this one requires monitoring of raw data; i.e., the NDB.
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Old 14th Mar 2011, 08:10
  #45 (permalink)  
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Given what I see here there is indeed no other way to fly this particular plate. If all this 'Garmin'/GPS NAV stuff (as presented) is progress I want none of it. The whole thing appears to be a waste of effort and certainly possibly dangerous and needs to be put back in the 'interesting' box until everyone catches up.

GPS in itself offers enormous benefit in both situation awareness and ultimately in the flying of an approach, but we do not appear to be 'there' at VOBZ (nor YPKA!) as far as I can see. Capn B - I think if I was presented with that picture I would turn down the screen lighting. Take away the 'magenta line' and we have a useful SA tool. Leave it there.....................?

Regarding VOBZ, since the NDB26 is the ONLY IFR approach for CAT C, I am amazed the the procedure is not annotated NDB/DME!

Originally Posted by aterp
Lacking that an IAP like this one requires monitoring of raw data; i.e., the NDB.
- I cannot follow your logic there ie "requires monitoring of raw data;" - it seems to me that one needs to discard the fancy gizmos and USE raw data? Right now - March 2011, the only advantage I can see for the 'overlay' is for Flight Simmers. Are you saying this sort of flying is actually 'approved'?

I really would appreciate someone who 'knows' explaining why the two circlings are different at VOBZ.

Last edited by BOAC; 14th Mar 2011 at 08:21.
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Old 14th Mar 2011, 08:36
  #46 (permalink)  
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C.B. primary and only approved navigational source is approach plate NOT the BOX. FMS is just advisory and in case of discrepancy Jeppesen prevails. That's how simple it is. You may elect to use it at your own peril and fly it out of the box.

If the title was, NDB or GPS approach then I wouldn't need to monitor the raw data but simply fly it of the box. Since it says NDB that's the primary navigational source. In case I lost both FMS I still can fly it following the needle unlike GPS.

Last edited by 9.G; 14th Mar 2011 at 08:47.
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Old 14th Mar 2011, 09:06
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You may elect to use it at your own peril and fly it out of the box.
Absolutely legal here if it is in the FMS database, as per my pic above. The PM monitors the approach in Rose/Appr display with the NDB needle. FMS Profile monitoring is not relevant as there is none.

In fact, the ADF display in my machine is so bad that the "only" way to do an NDB approach is with the box.
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Old 14th Mar 2011, 09:38
  #48 (permalink)  
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Originally Posted by Capn B
the "only" way to do an NDB approach is with the box
- I shudder to think how you do that based on the image you posted
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Old 14th Mar 2011, 10:38
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Yes, well, that's not an example of a well-programmed database approach!

Most are a bit better than that and do make life very easy/safe.
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Old 14th Mar 2011, 12:46
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C.B. one must pay very close attention to the details on the charts namely on your example GPA is shown in brakets (most probably ending at 50 ft over the THR.) thus it's the data based and the NDB approach RWY 08 can be flown out of the box with vertical guidance yet must be monitored by raw data. VOBZ, on the other hand doesn't have GPA in brakets, meaning it's a geometrical projection from the THR 3 degrees upwards. Now you tell me, will you fly this approach in LNAV/VNAV mode? Most probably you'll end up flying it in LNAV monitoring the needle and going V/S or FPA on the vertical mode. Not really overlay if you ask me.
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Old 14th Mar 2011, 14:07
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Some of this has to be laid at the door of the Indian aviation authority. Not only is there the imponderable about CTL minimums, both VOR IAPs should be VOR/DME because (forgeting LNAV for a moment) both require a DME fix for the FAF.

In my current Garmin database at least, both of these IAPs are called VOR/DME. Jeppesen apparently has that latitude with their database unlike the actual chart. Well, I guess the VOR 26 can be flown without DME as shown by the broken line in the profile. But, there is no such option on the VOR 08.

Maybe the guy who designed these IAPs also issues ATPs to Indian pilots.

As to wheter these three IAPs can be flown by an LNAV aircraft without use of raw data that is true for some operators, not true for others.

As to containment areas, they are very wide compared to the accuracy of LNAV. With U.S. TERPs the primary would be 1.25 miles each side of centerline at the NDB and 1.0 miles for the VOR. I believe the PANS-OPS values are a bit wider than that.
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Old 14th Mar 2011, 15:05
  #52 (permalink)  
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As I said there are quite few of them out there, ZMUB NDB 14 being one of'em. Have a look at that animal and tell me it's an overlay too?
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Old 14th Mar 2011, 15:57
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9.G:

As I said there are quite few of them out there, ZMUB NDB 14 being one of'em. Have a look at that animal and tell me it's an overlay too?
Indeed it is. It's in the database for monitoring for non-approved operators and for overlay for approved operators. Note the CNF [FN14].



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Old 14th Mar 2011, 17:20
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Well, flying a scheduled service to ZMUB the only thing I can say it's not in the data base. What is the data base is the way point FN14 where the descent will be commenced. It's a substitute of FAF in absence of such. Overlay to me is when I can just press the approach button and the a/c flies both LNAV/VNAV following the published NPA profile, NOT the case here. The approach is flown using raw data aided by the FN14 to identify the descent point.
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Old 14th Mar 2011, 20:12
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9.G

Well, flying a scheduled service to ZMUB the only thing I can say it's not in the data base. What is the data base is the way point FN14 where the descent will be commenced. It's a substitute of FAF in absence of such. Overlay to me is when I can just press the approach button and the a/c flies both LNAV/VNAV following the published NPA profile, NOT the case here. The approach is flown using raw data aided by the FN14 to identify the descent point.
All that says is the equipment you fly into ZMUB doesn't have the procedure in its database. The coding on the chart shows both FN14 and the final segment VNAV path angle. It's up to the airframe vendor and/or the airline what Jeppesen-provided data is included in a particular aircraft or aircraft fleet's nav database.

The database I am looking at has the complete procedure with base legs for A/B and C/D, and a VA leg to 7,600 for the missed approach, followed by a turn back to the NDB.

Anyone who would descend below MDA and past the early MAP is asking for trouble unless good VFR is assured. But, you know that since you fly there.
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Old 14th Mar 2011, 21:03
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aterpster, I dunno your data base and I don't exclude discrepancies. One thing though I read on Jeppesen approach chart is the description of approved data based DPA. It states that data based DPA is depicted in brakets unlike this one. I believe, that's the reason why we don't have it in the data base.
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Old 14th Mar 2011, 21:41
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I certainly hope that it wasnt manually added....

even CNF's have 5 place settings....
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Old 15th Mar 2011, 00:11
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FlightPathOBN:

I certainly hope that it wasnt manually added....

even CNF's have 5 place settings....
More specifically, it is a sensor fix. They are four letters.
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Old 15th Mar 2011, 03:58
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Originally Posted by 9.G
C.B. one must pay very close attention to the details on the charts namely on your example GPA is shown in brakets (most probably ending at 50 ft over the THR.) thus it's the data based and the NDB approach RWY 08 can be flown out of the box with vertical guidance yet must be monitored by raw data. VOBZ, on the other hand doesn't have GPA in brakets, meaning it's a geometrical projection from the THR 3 degrees upwards. Now you tell me, will you fly this approach in LNAV/VNAV mode? Most probably you'll end up flying it in LNAV monitoring the needle and going V/S or FPA on the vertical mode. Not really overlay if you ask me.
No GPA in brackets for my NDB at YPKA, approach flown the whole way in LNAV and VNAV. In the database and approved for use. Raw data monitored. We've never had overlay approaches. We went straight to dedicated GPS NPAs (now called RNAV/GNSS) when no suitable navaid approaches exist.

Originally Posted by OBN
even CNF's have 5 place settings....
Yes, some of our new charts indeed now have 5-letter waypoints eg FS26Y on the YPKA VOR-Y Rwy 26.
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Old 15th Mar 2011, 08:19
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C.B, please have a closer look at Jeppesen plate 16-1 YPKA on lateral & vertical profile VPA is depicted in brakets (3,00) starting from FN08Y till EP08 whereas neither VOBZ bor ZMUB do have it depicted this way. I dunno how to copy paste it here perhaps someone else will be helpful. However here's something to think about:
The GPS Approach Overlay Program is an authorization for pilots to use GPS
avionics under IFR for flying designated nonprecision instrument approach procedures, except LOC, LDA, and simplified directional facility (SDF) procedures. These procedures are now identified by the name of the procedure and “or GPS” (e.g., VOR/DME or GPS RWY 15). Other previous types of overlays have either been converted to this format or replaced with
stand-alone procedures. Only approaches contained in the current onboard navigation database are authorized. The navigation database may contain information about nonoverlay approach procedures that is intended to be used to enhance position orientation, generally by providing a map, while flying these approaches using conventional NAVAIDs. This approach information should not be confused with a GPS overlay approach (see the receiver operating manual, AFM, or AFM Supplement for details on how to identify these approaches in the navigation database).
NOTE: Overlay approaches are predicated upon the design criteria of the ground-based NAVAID used as the basis of the approach. As such, they do not adhere to the design criteria described in paragraph 5-4-5k, Area Navigation (RNAV) Instrument Approach Charts, for stand-alone GPS approaches.

Last edited by 9.G; 15th Mar 2011 at 09:37.
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