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partial panel and backups?

airguy

airguy

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Another thread in this section got me thinking about IFR panels, partial panels, and backups. I'm very close to building my panel and the timing is good, so I thought I would generate the Q/A session and get some opinions.

I'm planning a dual 10" Skyview screen with single ADAHRS, and either a 430W or GTN650, dual nav/comm. The requirement during training for doing partial panel has me a bit concerned, I'm not sure what pieces/parts of the system are going to be "failed" and I would need backups for. With dual screens I obviously have full backup of all items on either screen, and the single ADAHRS can input data to either screen if one goes down, but I'm guessing in this scenario the DE would get an evil little grin on his face as he failed my single ADAHRS? I was not planning on any round guages for backups - but the more I think about that the more I think a second ADAHRS would be a good idea. Electrically speaking, the screens are good because each will have it's own backup battery so that's not an issue in the event of full ship electrical failure, which is remote occurrence in itself since I'll have main and standby alternators.

Thoughts?
 
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This is pretty simple Greg - with a single AHRS and no backups, you are ZERO fault tolerant to a single failure. Even the old Cessnas with vacuum gyros were single-fault-tolerant with thier electric T&B's. If you go with a Dual AHRS, you still have "like" redudnancy - what happens if there is a software issue that affects both units? Dis-similar redundancy is your friend.

This is more than a training issue, of course (and I'd consult the latest Practical test Standards for the IFR ticket to see exactly what they expect to see/fail for partial panel work) - I know that I won't fly IFR without a reasonable instrumentation backup.

Paul
 
Back-up

It will be interesting to hear other replies as I am in the planning process for a IFR panel.
So far I am considering an EFIS and 430W but for back-up I think a Gemini would make sense. It gives a digital attitude, air speed and altitude.
And as Paul mentions it would be a separate software.
The Gemini eliminates the need for ASI, altitude and attitude from separate round guages.
 
My personal opinion is a backup should be from a different vendor. It matters not if you have dual AHRS. Dual AHRS protects against hardware failure, not bugs in software.

A electrical backup should be from a different vendor running different code.

Why not just stick something like a Trutrak Gemini PFD in there and be done with it?
 
Jamie said:
My personal opinion is a backup should be from a different vendor. It matters not if you have dual AHRS. Dual AHRS protects against hardware failure, not bugs in software.
Click to expand...

I agree with Jamie but the question becomes, if those EIFS start disagreeing with one another, which one are you going to trust?

With the steam gauges, there is no software bug and there is no second guessing, if they are still working. One other argument against all Electric equipment, it will not help you if you have an electric meltdown AND learning and staying proficient with two different vendors will be harder.

As for the partial panel, my DR required me to use something other than my EIFS, which is dual screen/dual AHAR. He agreed instead of turning them off, just to turned both screen to engine page and use other means of navigation. My back up steam gauges was used for this purpose.
 
I went with a 10" skyview, totaly separate Dynon D6 for backup, and a panel mounted Aera to boot. If I have a total electrical failure, each of those devices have battery backup. I don't think I would want to rely on the Aera instrument display on a down to your socks approach, but it is another source of info.
If the Skyview fails, I still have lateral navigation on the GNS430W.

If Pitot and static ice over, I still have mutliple gps data.
 
I'll admit that I haven't really given it much thought until this morning. I had been thinking of dual Dynon with a possibility of dual ADAHRS until someone (of relatively decent credibility) brought up the issue of a possible software issue taking out the redundant components, which is a valid point.

Right now today, I'm looking at tossing the second Dynon screen in favor of another vendor - MGL or Gemini are currently in my consideration, though I'm early in the process and still looking for answers. I would really LIKE to have dual Dynon screens so I can keep EFIS on the left and engine monitor on the right with a small backup EFIS (like MGL Extreme) in the center radio stack on top, but I'm open to options at this point.

My intention is a hard-IFR capable machine (yeah I know, lots of you don't consider that possible in an RV, I'm talking as much as realistically possible without dual turbines and autothrottles) that will occasionally be flown VFR with normal light-to-occasional-moderate IFR use. I'm not ever going to launch into zero-zero conditions, and I'm not likely to ever plan a flight into 1/2-200 conditions. I want the capability of dealing with "oh carp" equipment failure in real-world conditions.

Bavafa said:
I agree with Jamie but the question becomes, if those EIFS start disagreeing with one another, which one are you going to trust?
Click to expand...

Simple. The primary, since it's the one you use most often - until you have the first reason to distrust it - which is why you have the secondary. If the primary is confirmed faulty then power it down, ignore it, and go with the secondary.
 
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Dual Electronic + steam

My current thinking is for IFR with full redundancy and I am looking at the following configuration:

  • Dual AFS5500 with dual ADHARS
  • AFS AP
  • Garmin 650N
AND

should a logical (read programing) failure occur,
  • Trutrak ADI,
  • Altimeter and
  • Airspeed

http://www.mykitlog.com/users/displ...ator&project=1932&category=0&log=141587&row=2

I am also going with 2 alternators, 1 battery and a VPX or like for the electronic management. For reducdancy of the electronic management, I will have 2 emergency bus, (primary and secondary) that will allow me to bring back on line all instruments, in 2 phases, should the VPX go down.

Most likely overkill, however, will allow me to sleep well at night. :)
 
Jamie said:
My personal opinion is a backup should be from a different vendor.


You can "what if" to great length on how equip a panel. Your bank account will probably be your guide. I designed my panel with Jamie's logic of differ vendors and independent systems. Dynon EFIS, TT auto pilot w/alt hold, Garmin WAAS nav/ com system, wet compass. The TT autopilot has a limited attitude indicator and a slip indicator.

This panel provides what I call minimal basic redundancy. If EFIS fails, the auto pilot can be engaged to keep wings level and maintain altitude. The Garmin WAAS avionics provides a page with altitude and is connected to the autopilot for course guidance.

In doing training, flight reviews, and crewing with guys at work, I find their knowledge of the avionics is often limited to the operations they use daily. Importantly, be proficient at operating what you have. A panel of opulence may not save a pilots day, it may only serve to confuse the moment.
Click to expand...
 
I like redundancy

I probably have more redundancy than I need but even for Day VFR I really like what I have:
Dual GRT EFIS with single AHRS
Dual GPS feeds to the GRT's - one IFR certified GPS (GNS480) & another from my 696
Full size TSO'd steam gauges: AS, Alt, VSI
Trutrack ADI with backup battery
Autopilot can take input from either the EFIS or the GNS480
Standalone Engine Monitor (but it sends data to the EFIS also)
Independent idiot lights for Oil Pressure and Voltage
Garmin 696

I find that I use all these instruments on a regular basis. I tend to use the steam AS & Alt as my primaries during T/O and Landing. I prefer the steam VSI to the one on the EFIS during most phases of flight.

I also really like having both GPS's they each have their strong points. Plus, while I'm using the 480 as the primary to the EFIS, I can plug in alternate courses on the 696 prior to loading them into the 480. I also use the 696 for weather, approach plates and other info.
 
If one is truly flying "hard IFR" frequently, then I believe your chances of getting hit by lightning go up considerably.

What I am planning on using for flying IFR is a G3X panel, Trutrak Autopilot upgraded to Gemini when available , a vacum attitude indicator and a compass.

My major concern is a lightning strike and I don't know how well any of the EFIS systems will do with a direct strike.

Although I end up adding a vacuum pump I have a simple electrical system no second alternator. This is complemented by an IPad and handheld radio.

Niko
 
airguy said:
Simple. The primary, since it's the one you use most often - until you have the first reason to distrust it - which is why you have the secondary. If the primary is confirmed faulty then power it down, ignore it, and go with the secondary.
Click to expand...

The question is when you are in a IMC and the two EIFS is going to disagree in terms of attitude data, which one are you going to trust? Likewise the electrical melt down does not necessarily mean only loss of electric power. It has happened before and the chance of it happening again still exist.

I was on the path of having an EIFS as my redundant instrument when by luck I read a report of a certified GA plane that lost all electrical system and was left without any instrument.

The question that I ask myself, what is the benefit or trade off of having another EIFS as my back up?
 
If the two EFIS disagree, you can use the whiskey compass, altimeter, VSI, and airspeed indicators to see what indications make the most sense based on the two different attitude displays. If attitude fails on an EFIS it does not necessarily mean that the other sensors have failed (although the attitude could be bad because one of the other sensors is in fact bad). Some combination of the data hopefully will make sense. :)
 
I have the dual cheltons with single ahars as my primary with full size round airspeed, altimeter, and trutrak adi right below. Also have an sl-30 and garmin 496. The 496 provides gps to the trutrak adi, so with a total power failure I have the airspeed, altimeter, adi with battery backup and the 496. This gives me the same capability as a full 6 pack of instruments along with the 496 to fly an approach.

For my instrument check ride this past fall, my examiner failed the chelton ahars simultaneously with the autopilot. This left me hand flying the ils using the round backup gages and the sl-30 to minimums.

If I had to do it again, I would replace the cheltons with a grand rapids or dynon dual screen system with a garmin waas gps (lpv capable gps). I absolutely love the backup gages ... independent of software, electrical, etc failures, and easier to fly than the standard 6 pack.

Aaron
 
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