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12-23-2016, 08:10 AM
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Join Date: May 2012
Location: AZ/MN
Posts: 376
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Quote:
Originally Posted by N804RV
But, I'm really curios to know if there are any others out there flying IFR behind behind a big single display, instead of the airliner style full redundancy.
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There are thousands of military fighters with nothing more than this and a tiny "peanut" stby attitude indicator.
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Jim
RV-4 '88-'09 Built & Sold
RV-8 Purchased
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12-23-2016, 08:27 AM
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Join Date: Jun 2010
Location: Stilwell, KS
Posts: 1,096
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Quote:
Originally Posted by N804RV
I'm planning for an IFR "capable" system. It seems like all the glass sales promotions are aimed at dual and triple redundancy. Yet, most IFR "capable" C-172s with vacuum systems do not have all this redundancy. And, they've trained how many thousands of instrument pilots?
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Old IFR panels may look like dinosaur-poo but they do have a lot of redundancy because the 6-pack is broken into 3 different systems. If the vacuum system (attitude, heading) goes, you use your pitot/static instruments, electric turn/bank and compass to stay upright. If the pitot/static goes, you use your vacuum gyros and electric turn/bank. If electric goes use the other two. In the EFIS scenario, all your instrument systems are electric and they are all in one box, so a reliable, independent backup to keep the blue side up is important.
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Katie Bosman
RV-3B sold, but flying!
Next project: ???
Builders gonna build...
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12-23-2016, 09:01 AM
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Join Date: Aug 2008
Location: Tucson, AZ
Posts: 190
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Modern redundancy
In a prior RV, we went with a similar approach (though I wasn't IFR trained at the time) & it worked nicely overall. One big 8.4in GRT Hx screen with dual AHRS, plus a Dynon D10a for back up provided dissimilar redundancy. You could select AHARS 1 or 2 for that single screen. Though if that one display failed, now you lost two sources at once.
Nowadays, I think a single big screen (even without dual AHRS), a different brand/software back-up (think G5, GRT mini, Dynon 10a), plus an iPad having a separate source of attitude info (Stratus 2/2S) gives you a tie-breaker and enough redundancy. Many fly with an iPad any ways for multiple reasons, so it's not an added equipment cost for them/me.
Even if some rare emergency destroys all electronics on board, this could provide basic attitude, altitude and ground speed to get down safely. Starting a flight fully charged, the battery life in the Stratus and iPad doesn't require keeping them connected to power except for the longest of XC days (more than 6-8 hours).
More commonly, if one brand/model of primary flight data acts up, it gives you sufficient independent options to compare and decide which to believe.
One downside -- I didn't like how I would lose the display of some desired information when displaying PFD, nav and engine information on the one screen. Specifically, if I remember correctly flap and trim indications come to mind. First world problem, I guess... I had to look over my shoulder to see flaps. Something to consider & assess with your specific model in mind for only one screen.
Just my thoughts with the modern tools readily available to us these days.
__________________
Ryan M
VAF donation next due June 2021
(Exempt but worth it!)
Prior partner in RV-9a & RV-10
Now flying RV-10 #40515
Last edited by vfr800 : 12-23-2016 at 09:08 AM.
Reason: Pile on
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12-23-2016, 09:28 AM
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Join Date: Feb 2016
Location: CA
Posts: 10
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mis-compare
The mis-compare function is the key.
I would assume it takes 2 AHRS talking to the same system to get the mis-compare function. Is this correct? A single AHRS would simply give the display (and autopilot I imagine) bad info until it died. Could be wrong as I'm new to these systems.
It seems to me 2 AHRS for a single screen and a independent stby would cover the tie-breaker problem. The question would be - is the backup AHRS being monitored when it isn't in use. I imagine so but not sure.
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12-23-2016, 09:36 AM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,686
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Quote:
Originally Posted by runt
The mis-compare function is the key.
I would assume it takes 2 AHRS talking to the same system to get the mis-compare function. Is this correct? A single AHRS would simply give the display (and autopilot I imagine) bad info until it died. Could be wrong as I'm new to these systems.
It seems to me 2 AHRS for a single screen and a independent stby would cover the tie-breaker problem. The question would be - is the backup AHRS being monitored when it isn't in use. I imagine so but not sure.
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Most of this was discussed in this thread I started some months ago...
http://www.vansairforce.com/communit...d.php?t=139717
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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12-23-2016, 09:47 AM
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Join Date: Feb 2016
Location: CA
Posts: 10
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Quote:
Originally Posted by Walt
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Yes, it was covered there. Looks like Garmin does monitor the background system. At least in the system mentioned.
Thanks for the link Walt.
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12-23-2016, 10:05 AM
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Join Date: Aug 2007
Location: Ontario, Canada
Posts: 2,291
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Quote:
Originally Posted by Dorfie
[ Where does the straight and level information comes from that will drive the AP? Does the AP have it's own independent AHARS?
Johan
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Short answer = YES for the TruTrak product.
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12-23-2016, 10:55 AM
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Join Date: Sep 2006
Location: Landing field "12VA"
Posts: 1,530
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Quote:
Originally Posted by Canadian_JOY
Short answer = YES for the TruTrak product.
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Trio Pro Pilot has it's own MEMS gyros and static, pitot ports, so I reckon it's a YES for them, too.
__________________
Bill Boyd
Hop-Along Aerodrome (12VA)
RV-6A - N30YD - Built '98 / sold '20
RV-10 - N130YD reserved - under construction
donating monthly to the VAF - thanks, Doug
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12-23-2016, 12:39 PM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,686
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Quote:
Originally Posted by Canadian_JOY
Short answer = YES for the TruTrak product.
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Quote:
Originally Posted by Bill Boyd
Trio Pro Pilot has it's own MEMS gyros and static, pitot ports, so I reckon it's a YES for them, too.
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Just my opinion but honestly I don't think there's any real comparison between an inexpensive 'gyro' found is some AP's and a true ADAHRS such as the Garmin GSU25/73.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
Last edited by Walt : 12-23-2016 at 12:43 PM.
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12-23-2016, 02:53 PM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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Quote:
Originally Posted by RV8JD
Yeah, but they have ejection seats! 
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This is not a joke. I have an old copy of an air force training manual; it says to do exactly that (eject), for loss of instruments or even if it's just your brain that's spinning.
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