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  #11  
Old 12-23-2016, 08:10 AM
springer springer is offline
 
Join Date: May 2012
Location: AZ/MN
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Quote:
Originally Posted by N804RV View Post
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.
There are thousands of military fighters with nothing more than this and a tiny "peanut" stby attitude indicator.
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  #12  
Old 12-23-2016, 08:27 AM
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KatieB KatieB is offline
 
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Location: Stilwell, KS
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Originally Posted by N804RV View Post
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?

.
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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  #13  
Old 12-23-2016, 09:01 AM
vfr800 vfr800 is offline
 
Join Date: Aug 2008
Location: Tucson, AZ
Posts: 190
Default 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.
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Last edited by vfr800 : 12-23-2016 at 09:08 AM. Reason: Pile on
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  #14  
Old 12-23-2016, 09:28 AM
runt runt is offline
 
Join Date: Feb 2016
Location: CA
Posts: 10
Default 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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  #15  
Old 12-23-2016, 09:36 AM
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Walt Walt is offline
 
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Quote:
Originally Posted by runt View Post
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.
Most of this was discussed in this thread I started some months ago...

http://www.vansairforce.com/communit...d.php?t=139717
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EXP Aircraft Services LLC
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  #16  
Old 12-23-2016, 09:47 AM
runt runt is offline
 
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Quote:
Originally Posted by Walt View Post
Most of this was discussed in this thread I started some months ago...

http://www.vansairforce.com/communit...d.php?t=139717
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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  #17  
Old 12-23-2016, 10:05 AM
Canadian_JOY Canadian_JOY is offline
 
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Location: Ontario, Canada
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Quote:
Originally Posted by Dorfie View Post
[ Where does the straight and level information comes from that will drive the AP? Does the AP have it's own independent AHARS?
Johan
Short answer = YES for the TruTrak product.
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  #18  
Old 12-23-2016, 10:55 AM
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Bill Boyd Bill Boyd is offline
 
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Location: Landing field "12VA"
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Quote:
Originally Posted by Canadian_JOY View Post
Short answer = YES for the TruTrak product.
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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  #19  
Old 12-23-2016, 12:39 PM
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Walt Walt is offline
 
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Quote:
Originally Posted by Canadian_JOY View Post
Short answer = YES for the TruTrak product.
Quote:
Originally Posted by Bill Boyd View Post
Trio Pro Pilot has it's own MEMS gyros and static, pitot ports, so I reckon it's a YES for them, too.
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.
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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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  #20  
Old 12-23-2016, 02:53 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
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Quote:
Originally Posted by RV8JD View Post
Yeah, but they have ejection seats!
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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