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09-03-2013, 01:17 PM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,147
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I don't see it as any different than having a "single-source" failure point such as a single pitot tube. You can have as many displays of the data as you want (within reason to accommodate display failure modes) but you are still subject to a grasshopper being in the wrong place at the wrong time during your takeoff roll.
Myself, I have a fully glass panel, dual 10" Skyviews with battery backup, plus an MGL EXtreme Mini-EFIS as a Plan B EFIS - but they are all still tied into one single pitot tube. For attitude, I've got the Dynon and the MGL ADAHRS boxes, with dual alternators and battery backup on the Dynon.
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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09-03-2013, 02:02 PM
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Join Date: Jan 2005
Location: England
Posts: 1,087
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I think you have to consider your own personal view of risk taking, and what you are prepared to pay to mitigate those risks. Pitot static instruments are very reliable, as are good quality electric gyros. All uncertified electronics has an unknown reliability and unpredictable failure modes - but most are much more reliable than vacuum gyro instruments in your average spamcan (vac pump is the limiting factor). Most people building a $100K airplane can afford an ASI, altimeter and electric AI - do you feel you need that insurance?
I think you should assess the risks you might be taking (in the context of single engine IFR) with your choice of primary instruments, think carefully about your appetite to accept those risks, and therefore how you want to mitigate them (or not).
Pete
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09-03-2013, 02:31 PM
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Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,351
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I was and still am a firm believer of steam gauges for back up. My reason for that is ,
- It is simple and reliable
- Requires no electrical component/backup in case of electrical melt down
- No learning curve to stay proficient for IFR use whereas you will need to stay proficient in learning/retaining usage of both system.
__________________
Mehrdad
N825SM RV7A - IO360M1B - SOLD
N825MS RV14A - IO390 - Flying
Dues paid
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09-03-2013, 02:43 PM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Quote:
Originally Posted by Bavafa
I was and still am a firm believer of steam gauges for back up.
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Me too.

__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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09-03-2013, 03:38 PM
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Join Date: Mar 2010
Location: KSGJ / TJBQ
Posts: 2,039
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Quote:
Originally Posted by airguy
Myself, I have a fully glass panel, dual 10" Skyviews with battery backup, plus an MGL EXtreme Mini-EFIS as a Plan B EFIS - but they are all still tied into one single pitot tube.
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Which is no different than if you had steam gauges instead of glass. The question is regarding glass versus steam instruments, not about 100% redundant IFR capable aircraft. These are extremely few, even in the certificated single engine GA world.

Last edited by GalinHdz : 09-03-2013 at 03:44 PM.
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09-03-2013, 03:59 PM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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Quote:
Originally Posted by Bavafa
I was and still am a firm believer of steam gauges for back up. My reason for that is ,
- It is simple and reliable
- Requires no electrical component/backup in case of electrical melt down
- No learning curve to stay proficient for IFR use whereas you will need to stay proficient in learning/retaining usage of both system.
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What is your non-electrical, reliable source of attitude information?
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09-03-2013, 04:44 PM
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Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,351
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Quote:
Originally Posted by BobTurner
What is your non-electrical, reliable source of attitude information?
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Bob,
You got me there
I have a TT ADI, which of course is electric but short of putting a vacuum pump, this was the best I could come up with, but with a battery backup of course.
DSC_6147 by bavafa1, on Flickr
__________________
Mehrdad
N825SM RV7A - IO360M1B - SOLD
N825MS RV14A - IO390 - Flying
Dues paid
Last edited by Bavafa : 09-03-2013 at 04:52 PM.
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09-03-2013, 07:36 PM
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Join Date: Jun 2005
Location: Woodinville, WA
Posts: 1,499
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We think it's safe. We make this stuff for a living, see the failure rates, and know the issues. Yet, this is our airplane, fully IMC equipped. No dissimilar systems, no steam gauges. We would not say that you should fly in IMC with NO backups, but in my opinion, pretty much any backup is reasonable given the failure rates of a modern EFIS system.
I realize it's not for everyone, but if you are willing to fly IMC with a single engine, a single pilot, a single pitot, single com, etc, yet worried about crazy redundancy in your panel, you may not be focusing on the real and likely failure points.
The advantage of a fully integrated system like this as well is the reduction in workload when everything is working normally. No cross-checking stuff yourself, no setting two barometers, huge screens full of information, no "partial panel" when a screen does go out. You need to balance the use of a system in IFR for the 99.99% of the time it's working well with your capability if it ever does go out. Most accidents are not equipment failures, they are human failures, and anything that reduces that is a huge mark in the win column.
Oh, and we have 3 screens because we can and we use them for testing, not for redundancy. 2 screens are as good as 3 in my book.
--Ian Jordan
Dynon Avionics
Last edited by dynonsupport : 09-03-2013 at 07:41 PM.
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09-03-2013, 11:24 PM
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Join Date: Nov 2006
Location: Calgary, Canada
Posts: 408
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VFR flying
Gotta post for us VFR pilots, with no plans to take our VFR suited RV's into IMC.
I have dual screen G3X's. One AHRS. One pitot (unheated). One magnetometer. One transponder. Two comms (convenience). No steam gauges.
What if I lose my AHRS/pitot/both screens?!?!? Well, then I fly to a convenient airport and land. Period. No drama. I may land a bit faster without AS, but I can pick a long (i.e. anything >2500 ft) runway to do so. The airframe tells me my speed with enough granularity to land (and I ain't no test pilot). To find the airport I pull out my 296, or look at my iPad with foreflight. Both will also give me ground speed and GPS altitude as well.
I've thought about this a lot. I can't understand the need for steam AS and ALT backups for VFR flight, equipped as I am otherwise. Open to other opinions though. Convince me...
__________________
JV
Calgary, Alberta, Canada
RV7 QB - Airframe largely complete, sans canopy and glass... unfortunately sold
RV6 - O-360-A1A, Hartzell CS, dual G3X VFR... purchased
Dues paid 2015
"Being defeated is only a temporary condition; giving up is what makes it permanent."
-- Marilyn vos Savant
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09-04-2013, 12:19 AM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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I don't think anyone suggested that backup flight instruments were needed for VFR operations.
For those with a TT ADI: this may look like a conventional AI but it is hardly a 'steam gauge'. Inside there are no spinning gyros. It uses the same accelerometers as the efis's do.
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