If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
LPV vs LNAV/VNAV?
Andrew Sarangan wrote:
That mental calculation could be easily performed by the GPS and displayed as a glideslope. But I have not seen any GPS do that. Certification is irrelevant. Certification is most certainly relevant to your query, as that is most likely what kept that feature out of the TSO C129a certified IFR GPS's. A handheld Garmin 196 (I think that is the model a pilot-friend had with him a couple of years ago) that we took up on a practice IFR flight did just that. It displayed a glideslope for a non-precision approach. If the cheaper handhelds can do it, then why don't their IFR-certified TSO C129a big brothers do it? Because it wasn't part of the certification and therefore, regardless of their ability to provide this feature, are restricted from doing so due to the certification. -- Peter |
#12
|
|||
|
|||
LPV vs LNAV/VNAV?
Andrew Sarangan wrote:
displayed as a glideslope Just took a "flight" using the GNS400W simulator (the GNS430 with WAAS) becasue I wanted to see if the new WAAS upgrade for the 430/530 would do this. I flew both a VOR approach and an RNAV/GPS approach that only had LNAV minimums. For the VOR approach the GPS did not provide a glideslope, but for the RNAV/GPS approach into Weedsport, NY (B16 - RNAV/GPS 28): http://www.myairplane.com/databases/...s/09225R28.PDF the GPS went into LNAV+V mode and a glideslope indicators on the HSI went live, as you can see he http://img119.imageshack.us/img119/6...7010417ev0.jpg -- Peter |
#13
|
|||
|
|||
LPV vs LNAV/VNAV?
Mike Adams wrote:
Sam Spade wrote: paul kgyy wrote: Both of these options require a WAAS receiver, I presume? Yes, and if WAAS is not available to the standards required by the specs then the 146 box will not accept the WAAS solution, which means (using Garmin as an example) LPV, L/VNAV, and LNAV+V will not be available; only LNAV will be available. I don't think so. A TSO C129a GPS driving a FMS with baro VNAV should be able to fly RNAV(GPS) approaches using LNAV/VNAV minimums. No WAAS involved. Mike That has been true for a long time. The context of the recent discussions in this forum have been about TSO C-146 (RTCA DO-229C). |
#14
|
|||
|
|||
LPV vs LNAV/VNAV?
Andrew Sarangan wrote:
Sam Spade wrote: paul kgyy wrote: Both of these options require a WAAS receiver, I presume? Yes, and if WAAS is not available to the standards required by the specs then the 146 box will not accept the WAAS solution, which means (using Garmin as an example) LPV, L/VNAV, and LNAV+V will not be available; only LNAV will be available. Something I never understood is why LNAV approaches don't automatically show a glideslope so that the airplane arrives at the MDA at the VDP. With the 146 spec you will often have an advisory glideslope to MDA. That is the LNAV+V mode and will be provided if Jeppesen has coded that capability into the approach's database string. As Garmin says in the W handbood, not all LNAV-only IAPs have been so coded. |
#15
|
|||
|
|||
LPV vs LNAV/VNAV?
Andrew Sarangan wrote:
Peter R. wrote: Andrew Sarangan wrote: Something I never understood is why LNAV approaches don't automatically show a glideslope so that the airplane arrives at the MDA at the VDP. Perhaps because it wasn't part of the certification at the time? Perhaps my comment was not clearly stated. When you fly an LNAV approach (or any nonprecision approach for that matter) instead of the traditional dive and drive you can mentally calculate the vertical speed required (VSR) to arrive at the VDP at a constant glide angle . That mental calculation could be easily performed by the GPS and displayed as a glideslope. But I have not seen any GPS do that. Certification is irrelevant. We are not talking about a lower minimum or anything new that we not already allowed to do. LNAV+V |
#16
|
|||
|
|||
LPV vs LNAV/VNAV?
Peter R. wrote:
Andrew Sarangan wrote: That mental calculation could be easily performed by the GPS and displayed as a glideslope. But I have not seen any GPS do that. Certification is irrelevant. Certification is most certainly relevant to your query, as that is most likely what kept that feature out of the TSO C129a certified IFR GPS's. True, and that capability is permitted by the 146 spec. It does require WAAS. This is from the Garmin 500W handbook: LNAV/VNAV and LNAV Approaches with Advisory Vertical Guidance GPS approaches with vertical guidance may be either LNAV/VNAV or LNAV approaches with advisory vertical guidance. LNAV-only approaches with advisory vertical guidance only have LNAV minima listed on the bottom of the approach plate. The glidepath is typically denoted by a light dashed line on the vertical profile (Jeppesen only) with an associated glidepath angle (usually in the 3.00° range). These approaches are indicated with “LNAV+V”. For approaches with LNAV/VNAV minimums, those will be controlling. For LNAV approaches with advisory vertical guidance, the LNAV minimums will be controlling. Approaches confirmed as “LNAV/VNAV” approaches in the Jeppesen NavData are indicated with an “L/VNAV” annunciation. At the time of this publication, not all of the LNAV/VNAV approaches have been identified as such in the Jeppesen NavData, therefore some LNAV/VNAV approaches may still be identified with “LNAV+V” annunciation. |
#17
|
|||
|
|||
LPV vs LNAV/VNAV?
Sam Spade wrote:
Andrew Sarangan wrote: Sam Spade wrote: paul kgyy wrote: Both of these options require a WAAS receiver, I presume? Yes, and if WAAS is not available to the standards required by the specs then the 146 box will not accept the WAAS solution, which means (using Garmin as an example) LPV, L/VNAV, and LNAV+V will not be available; only LNAV will be available. Something I never understood is why LNAV approaches don't automatically show a glideslope so that the airplane arrives at the MDA at the VDP. With the 146 spec you will often have an advisory glideslope to MDA. That is the LNAV+V mode and will be provided if Jeppesen has coded that capability into the approach's database string. As Garmin says in the W handbood, not all LNAV-only IAPs have been so coded. I misstated that somewhat. If I read it correctly (assuming WAAS is available and passes muster) you will always get LNAV+V on an LNAV-only IAP, thus you will have vertical guidance to MDA. If, on the other hand, it is an LNAV/VNAV approach you will get L/VNAV if Jeppesen has that approach so coded, otherwise you will get LNAV+V. You'll have vertical guidance in both cases, but I presume you can only use the DA concept and VNAV minimums if you get the L/VNAV annuciation. |
#18
|
|||
|
|||
LPV vs LNAV/VNAV?
"Sam Spade" wrote in message ... Sam Spade wrote: If I read it correctly (assuming WAAS is available and passes muster) you will always get LNAV+V on an LNAV-only IAP, thus you will have vertical guidance to MDA. Can an RNAV approach have stepdown fixes on the final approach segment? |
#19
|
|||
|
|||
LPV vs LNAV/VNAV?
Peter R. wrote: Andrew Sarangan wrote: That mental calculation could be easily performed by the GPS and displayed as a glideslope. But I have not seen any GPS do that. Certification is irrelevant. Certification is most certainly relevant to your query, as that is most likely what kept that feature out of the TSO C129a certified IFR GPS's. A handheld Garmin 196 (I think that is the model a pilot-friend had with him a couple of years ago) that we took up on a practice IFR flight did just that. It displayed a glideslope for a non-precision approach. If the cheaper handhelds can do it, then why don't their IFR-certified TSO C129a big brothers do it? Because it wasn't part of the certification and therefore, regardless of their ability to provide this feature, are restricted from doing so due to the certification. I am sure you are correct, but it doesn't seem to make a whole lot of sense too keep a useful feature out of certification unless there is something dangerous about it. I don't see anything unsafe about providing a glideslope to a nonprecision approach. |
#20
|
|||
|
|||
LPV vs LNAV/VNAV?
Andrew Sarangan wrote:
Peter R. wrote: Andrew Sarangan wrote: That mental calculation could be easily performed by the GPS and displayed as a glideslope. But I have not seen any GPS do that. Certification is irrelevant. Certification is most certainly relevant to your query, as that is most likely what kept that feature out of the TSO C129a certified IFR GPS's. A handheld Garmin 196 (I think that is the model a pilot-friend had with him a couple of years ago) that we took up on a practice IFR flight did just that. It displayed a glideslope for a non-precision approach. If the cheaper handhelds can do it, then why don't their IFR-certified TSO C129a big brothers do it? Because it wasn't part of the certification and therefore, regardless of their ability to provide this feature, are restricted from doing so due to the certification. I am sure you are correct, but it doesn't seem to make a whole lot of sense too keep a useful feature out of certification unless there is something dangerous about it. I don't see anything unsafe about providing a glideslope to a nonprecision approach. The G/S has to be either Baro VNAV or WAAS "electronic" to be certified for the approach phase of flight, primary or advisory. The VNAV path provided by a receiver that doesn't have WAAS TSC146 certification would be very unreliable. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
LNAV, VNAV and LPV | Andrew Sarangan | Instrument Flight Rules | 5 | January 14th 07 01:57 PM |
LNAV preferable over LNAV/VNAV | [email protected] | Instrument Flight Rules | 4 | October 16th 05 06:34 PM |
GPS approaches with VNAV vertical guidance | Doug | Instrument Flight Rules | 18 | November 2nd 04 10:36 PM |
CNS-80 VNAV | John R. Copeland | Instrument Flight Rules | 17 | October 28th 04 04:24 AM |
Which GPS Support LNAV/VNAV? | C Kingsbury | Instrument Flight Rules | 1 | October 23rd 04 12:28 AM |