VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

  #1  
Old 08-29-2013, 08:53 AM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
Posts: 4,966
Question Integrated Autopilot Failure Mode(s)

Hello all,

I?ve followed/searched the numerous threads concerning ?redundancy/backups/single point failure/etc.? and have not found the specific answer I?m looking for. It?s probably buried in there somewhere amongst the mountains of tangents this type of thread generates, so I?m going to try cut to the quick in this one.

Concerning integrated autopilot function in a single AHARS Skyview or G3x suite ?

In the unlikely event that the screen goes blank, will the autopilot continue to function?

The basis of my question concerns the tradeoff for capability offered by fully integrated system vs. the perceived safety aspect of a standalone autoflight system. For example, if the GRT screens die in the -8 at the same time I?m somehow in IMC, at least the TT will keep the wings level, maintain altitude, and can drive me somewhere else. Not sure I could do that with a fully integrated suite like I?m planning for my next airplane.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
1940 Taylorcraft BL-65
1984 L39C - SOLD
RV-8 - SDS CPI - SOLD
Reply With Quote
  #2  
Old 08-29-2013, 08:57 AM
Kahuna's Avatar
Kahuna Kahuna is offline
 
Join Date: Dec 2004
Location: Gold Hill, NC25
Posts: 2,422
Default

Quote:
Originally Posted by Toobuilder View Post

In the unlikely event that the screen goes blank, will the autopilot continue to function?
It depends on the reason the screen went blank, and which integrated AP you are using. They all have different failure modes and resistance to component failures.
__________________
Kahuna
6A, S8 ,
Gold Hill, NC25
Reply With Quote
  #3  
Old 08-29-2013, 09:21 AM
Mike D's Avatar
Mike D Mike D is offline
 
Join Date: Jul 2008
Location: Houston, TX
Posts: 456
Default

I have wondered this also.

To be specific, what if you have a GRT HXr single screen with remote radios and transponder and the GRT AP servos, and the screen goes blank or the EFIS dies completely?
1. Do you have AP still?
2. Do you have radios or transponder?

My plan is to always have a independent backup that will let me know the basics, but it sure would be nice to have the AP still functioning if it is bumpy and I am trying to sort things out.

And to compare, what about AFS, Garmin, or Dynon Skyview?
__________________
Michael Delpier
RV6A -O-320, fixed pitch, GRT Sport, 496
RV-10 - working on finish kit
Houston
Reply With Quote
  #4  
Old 08-29-2013, 09:41 AM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
Posts: 4,966
Default

Well,

I've run through the "glass with steam backup" and "redundancy" debates in my head and for me it comes down to something as simple as "not die" if the glass goes dark. I don't need to continue the approach to land if the primary display goes TU, I'm satisfied simply with a method to keep the wings level. To me, the best bang for the buck is to jump on already existing equipment as my "not die" plan - the autopilot.

So I guess the question is not quite as simple as I thought.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
1940 Taylorcraft BL-65
1984 L39C - SOLD
RV-8 - SDS CPI - SOLD
Reply With Quote
  #5  
Old 08-29-2013, 09:58 AM
Brantel's Avatar
Brantel Brantel is offline
 
Join Date: Mar 2006
Location: Newport, TN
Posts: 7,509
Default AS far as the G3X goes....

The G3X autopilot and servos need a functioning screen and a functioning AHRS to operate without a GMC305 in the mix. If you have multiple screens, you have screen redundancy and if you have multiple AHRS units, you have AHRS redundancy. (common mode failures excluded)

If you have a GMC305 in the mix, the G3X autopilot and servos can operate in certain modes without a working screen. They still require a working AHRS and in this case a working GMC305.

With the 3rd party autopilots like the TT GX Pilot, if you lose the G3X system, you are left with the native modes supported by the AP. They do have built in independent gyro's. Be aware however that these gyro's are not capable of full 360? of pitch and roll and can saturate/tumble if the limits of pitch, roll, or rate are exceeded. They may or may not be able to recover in flight if they do saturate/get tumbled.
__________________
Brantel (Brian Chesteen),
Check out my RV-10 builder's BLOG
RV-10, #41942, N?????, Project Sold
---------------------------------------------------------------------
RV-7/TU, #72823, N159SB
Lyc. O-360 carbed, HARTZELL BA CS Prop, Dual P-MAGs, Dual Garmin G3X Touch
Track N159SB (KK4LIF)
Like EAA Chapter 1494 on Facebook
Reply With Quote
  #6  
Old 08-29-2013, 10:37 AM
jjconstant's Avatar
jjconstant jjconstant is offline
 
Join Date: Dec 2006
Location: Oakland CA
Posts: 771
Default

This was one of my big concerns when designing my panel 10 years ago, when the Garmin 430 was the most popular radio for my desired level of capability. I was not comfortable with the notion that if I spent all my money on one integrated radio rather than 2 separate, cheaper but non-integrated radios, if the screen went out, I was out of luck.

Integration is great but you have identified one of the downsides...single point failure.

I think it's a philosophical decision, made easier with copious amounts of $$$$
__________________
All Best

Jeremy Constant
RV7A "Stella Luna" ECI IO-360 WW200RV Pmags 360hrs
VAF 2019 paid plus some for those who can't
Reply With Quote
  #7  
Old 08-29-2013, 10:44 AM
N941WR's Avatar
N941WR N941WR is offline
 
Join Date: Jan 2005
Location: SC
Posts: 12,883
Default

One major advantage of the integrated EFIS and AP is that the AP knows what the plane is doing, its limiting speeds, etc.

Thus, if you get into a death spiral, or worse, and your speeds are still in the green, many of the integrated systems will let you engage the AP function and fly safely away. Independent systems simply can't do that.

If you go with an integrated system, regardless of who the manufacture is, I strongly recommend a Dynon D1 Pocket Panel. I had the honor of being a beta tester on this unit and I can't say enough about it and its capabilities. Between that and a handheld GPS, you should be able to keep your plane upright long enough to find a safe place to land.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Reply With Quote
  #8  
Old 08-29-2013, 10:46 AM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
Posts: 4,966
Default

Thanks Brian for the insght on the Garmin system.

So what are the circumstances that can take down both the pilot interface (display) AND the autopilot function of a Skyview; and conversely, is there a different set of circumstances that can leave one or the other functional?
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
1940 Taylorcraft BL-65
1984 L39C - SOLD
RV-8 - SDS CPI - SOLD

Last edited by Toobuilder : 08-29-2013 at 10:51 AM.
Reply With Quote
  #9  
Old 09-01-2013, 10:18 AM
walkman's Avatar
walkman walkman is offline
 
Join Date: Oct 2011
Location: Atlanta
Posts: 897
Default

My thought is that if the screen is dark, lets say a failure mode that only appears to affect the display not the functionality of the EFIS/auto-pilot, then its still "all dead to me".

If the screen is dark how can you know what your auto pilot is doing or is getting ready to do? What happens if the thing comes back alive again?

If my EFIS goes dark, I think the second or third thing on my list is to power down the A/P servos.
__________________
RV-8 IO-360 (Bought)
RV-6 O-360 C/S (Sold)
Walkman aka Flame Out
Reply With Quote
  #10  
Old 09-01-2013, 07:58 PM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,308
Default

The issue only matters if you are IFR.

If VFR and the screen goes U/S and you have nothing else, fly the plane. You do not need any bit of information contained on a G3X or sky view to effect a safe outcome.

In fact you do not need anything. Turn your Master Switch off one day and try it.

If you are IFR, having just one panel with one source of power to the bus and having two screens but on the same breaker, is just plain and simple silly.

I had a A/P failure due to a shear screw breaking in turbulence. In fact twice now, and one time it was about 45 minutes of bumpy IMC, the other was 2.5 hours of constant bumpy IMC. Had the primary screen failed and that took out my A/P it still would have been the same result. I kept on flying by hand on the EFIS.

I am not saying do not know your systems, even VFR it pays to know as much as you can, but so long as you do not sweat it.
__________________
______________________________

David Brown

DYNON Authorised Dealer and Installer


The two best investments you can make, by any financial test, an EMS and APS!
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 08:16 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.