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ddgates 
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Joined: 12 Aug 2011 Location: Deer Valley Status: Offline Points: 1100 |
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 Topic: Configuration QuestionPosted: 03 Apr 2017 at 6:54pm |
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Way back when - shop installed dual MLBs, AXP340, and TAS605A. The shop had done no other Avi installs before. They couldn't get the TXP to report altitude from just the 540. (There is also an Aspen PFD wired). So they left a blind encoder in place and put it on RS-232 port one. Since that time, I've had the Aspen rewired to bypass the ACU 1 which drives the AP.
Shouldn't the AXP340 get either GPS ALT from the IFD540? Doesn't it use that. Can it use alt reporting out of the Aspen (on the ARINC 429)? Bottom line, shouldn't I be able to turn off the Shadin alt port on the IFD540 and remove the blind encoder? Thanks for any help with this. |
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David Gates
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safari
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Joined: 28 Apr 2014 Location: Sedona Status: Offline Points: 55 |
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Posted: 03 Apr 2017 at 9:58pm |
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mine uses the aspen I do not have a blind encoder
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Dave
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ddgates
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Posted: 03 Apr 2017 at 10:09pm |
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Is that on the ARINC 429 feed?
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David Gates
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195pilot
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Joined: 11 May 2016 Location: KDPA -IL Status: Offline Points: 17 |
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Posted: 03 Apr 2017 at 10:46pm |
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Perhaps somebody who really knows will chime in, but it's my understanding that all transponders report pressure altitude. Mixing in GPS altitudes would gum up the works for traffic alerts, methinks.
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mfb
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Posted: 03 Apr 2017 at 11:21pm |
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The Aspen reports pressure altitude and feeds it to the transponder on the 429 bus. Not GPS altitude. That's how our 182 is set up. The old blind encoder came out when the Aspen went in.
Mike |
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n7ifr
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Posted: 04 Apr 2017 at 12:07am |
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David,
I will send you pics tomorrow of my dual 540 maintenance pages... Incidentally, flew with IFD100 synched with #1-540 WiFi. . Frequencies synched . Designated Wpt block works great. But, . Traffic Thumbnail never populated . No synched ADSB Wx, Traffic or TFR's Anybody else have issues? Tom W.
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AzAv8r
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Posted: 04 Apr 2017 at 12:59am |
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GPS altitude cannot be used for the transponder, which can only use pressure altitude. The Aspen can provide pressure altitude, but I do not think the IFD can forward the pressure altitude to the transponder. You'd need to connect the Aspen PFD directly to the transponder.
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oskrypuch
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Posted: 04 Apr 2017 at 8:54am |
Although the 340 allows for two inputs, it does not have a fall back mode, for example if the serial fails, to move to the parallel Gray code input. BUT, with the remote 322 transponder, the high resolution PA on the 429 bus from the ASPEN to the 540 will be used if present, else it will accept a Gray code input as a fallback. I have a good quality nano installed, and left it in as a backup. If the ASPEN goes TU, I don't lose my Mode S. * Orest Edited by oskrypuch - 04 Apr 2017 at 8:56am |
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AzAv8r
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Posted: 04 Apr 2017 at 11:10am |
Does the 322 have the same connectivity as the 340, such that this approach would also work with the 340? If so, then either the original poster has an ACU, and the shop didn't\ know to use the alternate (star-topology) 429 wiring for the Aspen. |
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chflyer
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Posted: 04 Apr 2017 at 11:50am |
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What if there is no Aspen, and only an IFD540 / AXP340 pair with serial encoder input to the xpdr? Anyone know of a way to get altitude leg sequencing without an FADC such as the Aspen or Sandia or ...?
It looks to me from the AXP340 IM (sec. 6.5.4) that it can forward the serial altitude received from the encoder on to the IFD540, also in RS232 format, out on pin 6. The IFD540 IM seems to indicate that it can receive this as RS232 uncorrected PA per section 6.8.1.1(5). But a baro-corrected altitude source would need to come in on an Air Data system or from a transponder on ARINC per 6.8.1.2(3), which the AXP340 doesn't provide. A baro-corrected altitude is necessary for altitude leg sequencing (section 2.4.2 ... "IFD5XX should be interfaced to an Airdata source for automatic
altitude leg sequencing (optional). If no baro-altitude data is
supplied, altitude leg types must be manually sequenced"). I don't have an air-data computer (FADC) of any sort, and am not inclined to fork out the $5'000 or more to get one installed just for altitude leg sequencing. I thought that Steve said at one point the a software release would allow use of GPS altitude for leg sequencing, but I can't find it any more in the forum. Personally, I don't see why GPS can't be used for this if it is accurate enough for an LPV approach. :-( ;-)
Edited by chflyer - 04 Apr 2017 at 11:51am |
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Vince
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ddgates
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Posted: 04 Apr 2017 at 1:11pm |
OP: When the install was first done, the Aspen IM did not permit a parallel connection between pins 26 and 27 when there was an ACU in place. Unfortunately the ACU(ACU1) blocked PAlt and BaroAlt as a pass through on the 429 data stream, only passing through Course and Heading. Since that time, Aspen has changed the verbiage of its IM permitting a parallel connection, which I had done by the shop. That gives me back PAlt, BaroAlt, and True Airspeed. Since the 540 is now getting those labels off the 429 feed, I would think I could turn off the blind encoder, since PAlt is now available for pass through to the txp. I would also think that the 540 could use BaroAlt for VNAV guidance on approaches (?). Not sure what it is using now.
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David Gates
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mgrimes
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Joined: 22 Sep 2015 Location: Lakeland FL Status: Offline Points: 26 |
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Posted: 04 Apr 2017 at 2:46pm |
I've had the opportunity to use the IFD100 on 6 different flights now. I have pretty much the same results except I was able to see ADS-B METAR information on the IFD100. (No TFR or Traffic). I have SkyTrax for ADS-B In. But I wasn't able to see TFR information on my 540 either. The status page says 'Not Received'. Couple of additional items I found: I can't update my UTC offset time on the IFD100 so my Local Time and Local ETA at Destination is not correct. On the IFD100 I can only see the map in North Up mode. Can't see a way to change it to Track up. I like that the new designated Waypoint does not sync between the IFD100 and IFD540. For what it's worth - no stability problems on my IPAD Mini. Thanks, Mike |
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rfriend
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Posted: 04 Apr 2017 at 3:12pm |
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Touching the Track Box top center alternates north up and track up for me on ifd 100. Still can not see intersection labels though not unless included in a flight plan.
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AzAv8r
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Posted: 04 Apr 2017 at 9:39pm |
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So I went and reviewed the AXP340 Install manual, and it does not identify any 429 interfaces. My installer told me it had a 429 output for traffic (because it is the same as the Trig TT31, I believe), but he hooked it up and no traffic was present.
Per the AXP 340 Install manual, the serial input accepts a handful of pressure altitude formats. Per the IFD Install manual. a serial out wired to a transponder can be configured to ADS-B(Avi) (which is position only) for the 340 and the TT31 , to Aviation (which is position and air data) for the Garmin 327, and AXP322 (undefined content) for the 322. So you could try Aviation and AXP322, but test carefully! But presumably your shop tried those configuration options? |
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Kentucky Captain
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Posted: 05 Apr 2017 at 12:36am |
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I have an install with an IFD540 and Aspen. During test flights the old blind encoder failed and ATC was not getting altitude readout. We had to replace it. I'm pretty sure that all that goes on behind the panel is magic so did I spend money that I didn't need to or what?
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Woo Hoo!!!
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oskrypuch
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Posted: 05 Apr 2017 at 9:20pm |
It would not have been free, as getting to the wiring harnesses can take a bit of time, but you could have used the PA data block on serial RS232 sent by the ASPEN to drive your transponder as well. That has a 10ft resolution, vice the 100ft resolution on blind encoders outputting Gray code. * Orest Edited by oskrypuch - 05 Apr 2017 at 9:20pm |
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AzAv8r wrote: