B200/C90T Autopilot Vertical Guidance - RNAV LPV approach

[fppilot]

I am close to a decision to spring for the B200 now that the SPs are released and some valuable tweaks are available here from several skilled members. I do have a question from my C90T experience that I think will apply to the B200 as well because of the nearly identical avionics and which will get answered quicker here than in the C90T Forum as this forum is much more active at this point. The question is also specific to the RXP430.

 

With the King Air autopilot, is there the ability for the RXP430 and the King Air autopilot to track down the vertical path of an RNAV with LPV approach? I thought I had been able to do so with the A36 with the RXP430, but cannot seem to get the C90T to do so. I am selecting the appropriate RNAV approach and approach point in the RXP430, selecting the RXP430's CDI GPS setting, and setting the autopilot to NAV to track to the approach. Then when intersecting the RNAV approach laterally, I am selecting the APPR mode of the autopilot and leaving the GPS CDI selection at GPS. It couples to the lateral guidance, but does not couple to the vertical guidance. The two RNAV LPV approaches I have tried are RNAV RWY 17 at KBMG (Bloomington, IN) and RNAV RWY 22 at KSEN (Easton,MD). I have tried approaches like this with and without the AP's Altitude switch on. Any help would be appreciated.

[tttocs]

Well, since no one else has jumped in...

 

I haven't flown my C90 in a while, so I can't remember specifics, but I've not had any problems flying coupled LPV approaches with the King Air and RXP430. Works fine. One of the keys for vertical LPV guidance with the RXP units and various sim autopilots I've used is to not switch to approach mode until AFTER you see vertical guidance become active on whatever device you're using to display it (traditional CDI needles, HSI, EHSI...). If you engage approach mode too early, the autopilot won't capture vertically. You don't want to wait until virtual glideslope intercept, but you do want to wait until vertical guidance is available. Don't know what various GA autopilots do IRL, as I haven't flown since before there WERE LPV approaches :-), but that's the way it works in the sim.

 

Hope that helps,

 

Scott

[fppilot]

Thanks Scott. Do you find the B200 avionics behaviour to be highly consistent or identical with that of the C90T? I may try a few more approaches this evening. I seem to recall that the A36 did couple vertically but on two approaches a couple of days ago the C90 did not seem to. Also appeared the AP's Altitude function did not disengage upon selecting APR.

[Bert Pieke]

On my system, both the C90 and B200 will fly an LPV approach, guided by the RXP430 (or 530 for the B200).

 

I usually test at KTPA, RNAV01L via PIE.

 

If I remember correctly, the HSI required an update before it would display the LPV glideslope.

 

When you first power up the GNS, and hit OK the first time, the HSI should deflect the course indicator and glideslope needles. If the glideslope does not show at that point, you need the update.

[tttocs]

Sorry, can't help you there. Like you, I'm still considering the B200 but haven't bought yet. Still enjoy my C90 and thinking seriously about the B200, but haven't been in a King Air mood of late so haven't quite pulled the trigger. Also can't help but want to see what the other upcoming KA's are like and how well they do glass. I still prefer analog (or near analog), but if someone does glass really well...

 

Scott

[Bert Pieke]

The Carenado C90 and B200 have pretty much identical avionics.

 

One thing to note, is that for functional RXP B200 integration, you need

both the GNS530 and the Unlimited pack. Otherwise, you are going to have

one RXP 530 and one Carenado 530, side by side..

 

Re LPV aproaches, here is a C90 screenshot into 01L at KTPA.

[fppilot]

1) The Carenado C90 and B200 have pretty much identical avionics.

 

2) One thing to note, is that for functional RXP B200 integration, you need

both the GNS530 and the Unlimited pack. Otherwise, you are going to have

one RXP 530 and one Carenado 530, side by side..

 

??????? Bert. In my C90T I have an Avidyne and an RXP430.

 

BTW, I get needle deflection and vertical GS indications on the HSI at the point you mentioned.

[Bert Pieke]

??????? Bert. In my C90T I have an Avidyne and an RXP430.

 

BTW, I get needle deflection and vertical GS indications on the HSI at the point you mentioned.

 

Right, the C90 has a 430, the B200 two 530s..

 

If you get the needles showing, the HSI should be OK.

 

Just fly the approach as indicated in an earlier post... and all should be well.

 

You've got to make sure that the approach is either LPV or LNAV+V, or there

will be no vertical guidance (!)

[fppilot]

Bert.

Well. I am a case here of "shake and wake"! You gave me a key cue when you advised that the RNAV 01L at KTPA had LPV and it worked. I did some local approaches this evening at KESN (Easton, MD) to RNAV 22, which as currently published shows LPV. I went up first in the A36, then in the C90T. Could not get the LPV indication. So then I watched a Sporty's youtube video on WAAS approaches again and noted that the 430 will indicate LPV only if it is available and active. From there I switched locatons to KTPA and flew an approach to RNAV 10L, which you had referenced. Got the LPV and flew the approach accordingly. GPS and autopilot brought me down, though the descent started slightly after the slope on the published approach. I did so first in the A36, then flew the same approach in the C90T. OK. Switched to another airport I frequent, KBMG, (Bloomington, IN), where RNAV 17 shows LPV. Flew the approach in the C90T. The other day into KBMG I did not get vertical autopilot guidance. This time it worked. But this time I was more patient with the autopilot's Altitude function. The published approach shows descent beginning from 3000 at ITYEF, which is 10.5 out. The other day when the autopilot did not start me down immediately after ITYEF I believe I got nervous and deactivated the AP Alt function myself. In retrospect, that forced me to control the descent. Tonight I was patient, even though the PAPI was bright white from side to side, and after some anxiety the Alt function extinguished and the GPS started the descent. The LPV descent from 3000 did not start until the FAF at OGUSY. The approach indicates 2500 at OGUSY.

 

Anyway. Now I'm good! In regard to KESN, I am using the current published approach plate. My Garmin database is May 11, 2011. So shake me and wake me.... Some current RNAV APV approaches were not in place as of May 2011. So now I have learned to pay attention to, and trust the CDI message on the GPS!

[Bert Pieke]

Bingo, the database is mid-2011, and the real world keeps changing... Maybe, one of these days, Garmin will publish a trainer update with a newer database.. but until then, this is what we've got!

[fppilot]

AHH! A quick Google and here in the results is a link to a page containing an Excel file with a list of dates for US APV approaches, accompanied by the initial publication date (rightmost column). The spreadsheet is configured with filters, so you can use the dropboxes to control sorting:

 

http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/approaches/index.cfm

 

Interesting that the RNAV 22 approach to Easton is listed in this LPV spreadsheet and has an initial publication date of 05-JUN-08, which is three years before the Garmin update I am using with my RXP GPS's. You would think any of these before 11 MAY 2011 would be included in the current Garmin trainer database. The KTPA RNAV 01L was published 31-JUL-08. The KBMG RNAV 17 on 07-MAY-09.

 

I've added this spreadsheet to my archives for reference.

[fppilot]

Bert an tttocs,

I posted my learning experience in a new topic here on Avsim today. http://forum.avsim.n...tical-guidance/. Thank you both for your great help.

 

Frank

[tttocs]

Frank,

 

Every once in a while I run into similar anomalies with the June 2011 data. It's generally solid, but there do seem to be a few omissions or errors that have caught me out a few times.

 

Glad if I could help in some small way. Heaven knows others, like Bert, have assisted me immensely.

 

Scott

[Bert Pieke]

Happy to be of assistance

[fppilot]

I flew the RNAV approach into KESN again last night and stayed patient until it hurt. Finally almost all the way to the last fix ZULIV, the RXP430 ennunciated a change from TERM to VNAV and started on the descent. The GP indicator on the HSI did not become active until then as well. Most of the approach fixes in the June 2011 Garmin database for the RNAV 22 are different than on my approach plate, which is dated 13DEC11.