I need a fresh look and an expert opinion on my new panel composition. I fly a lot of IFR and am in the middle of a complete interior redo of a 6A, including a new panel. I bought a 2 screen G3X Touch, the 305 autopilot head with blue button, and a TCM backup battery. I also got second ADAHRS in the belief that, with auto reversion, it would give me redundancy I need in case of a ADAHRS failure and avoid the expense of a backup AI. Please weigh in and tell me if this is a good plan, or if you see a hole in the plan and think I still need an independent backup AI. If the latter, why? Thanks in advance for the input!
Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Do I still need an independent backup AI?
- Thread starter cccjbr6
- Start date
N941WR
Legacy Member
The answer to you question is, No, you do not need (by "need", one is not required.) a backup AI. However, my recommendation is to put in a Dynon D1 or D2 Pocket Panel because they are not tied into your pitot or static systems and the internal batter will last four hours.
The internal battery is the same reason I recommend you install a good handheld GPS (not an iPad) that is constantly charged by the aircraft system. Then, if you have a total electrical failure, you can aviate and navigate.
Practicing with those two units is critical to your survival.
The internal battery is the same reason I recommend you install a good handheld GPS (not an iPad) that is constantly charged by the aircraft system. Then, if you have a total electrical failure, you can aviate and navigate.
Practicing with those two units is critical to your survival.
Last edited:
WhiskeyMike
Well Known Member
Please share your thinking as to why an IPAD or other tablet device (with built-in GPS, and running Forefligh, Garmin Pilot, etc.) is not desirable for this purpose. A tablet can be easily rigged so that it?s charged by the plane?s electrical system while in flight, so there must be some additional criteria you have in mind. Thanks in advance for your feedback ?
FORANE
Well Known Member
I for one vote for a backup AI. I have experienced an EFIS roll inverted in IMC. I have heard from others who have experienced the same - even with a late model modern dual ADAHRS system.
avionicsr
Active Member
Backup Attitude
Absolutely YES, you need an independent backup Attitude, Altitude and Airspeed. We install one in every IFR panel we build. I understand this is an experimental, but we build all our panels using Part 23 guidelines, and in that application, it is required.
The reason is, even with two AHRS and an independent backup battery there is still the very, very slim potential for a common software problem to cause all displays and/or AHRS to reset. I've flown the G3X and G3X touch systems for about 300 hours total, and never had it happen, but the potential exists. That's why we use an independent Attitude, Altitude, and Airspeed. We typically use the Mid Continent MD-302 SAM or the Dynon D6. These units both have (option on the D6) an internal backup battery, and operate independently of the G3X system.
The big benefits of the MD-302 that the D6 doesn't have;
The MD302 will auto set its baro setting from the G3X and is auto dim. It is a Part 23 certified product, so it is very expensive.
Absolutely YES, you need an independent backup Attitude, Altitude and Airspeed. We install one in every IFR panel we build. I understand this is an experimental, but we build all our panels using Part 23 guidelines, and in that application, it is required.
The reason is, even with two AHRS and an independent backup battery there is still the very, very slim potential for a common software problem to cause all displays and/or AHRS to reset. I've flown the G3X and G3X touch systems for about 300 hours total, and never had it happen, but the potential exists. That's why we use an independent Attitude, Altitude, and Airspeed. We typically use the Mid Continent MD-302 SAM or the Dynon D6. These units both have (option on the D6) an internal backup battery, and operate independently of the G3X system.
The big benefits of the MD-302 that the D6 doesn't have;
The MD302 will auto set its baro setting from the G3X and is auto dim. It is a Part 23 certified product, so it is very expensive.
N941WR
Legacy Member
First, a little background. I'm a life time IT guy and have had to support these units, Apples, Microsoft, etc.
Reasons:
1. The operating systems are unpredictable. They are designed to do more than just provide flight information and are subject to viruses. Because of this, they can run slow, crash, operate erratically. Even if you have antivirus software on them, something will get by.
2. The hardware is unpredictable. Remember, these were designed to be used in an office or home environment. They may or may not work in an airplane. Most do work, which is a good thing. However, each of our planes are different and at altitude, they could have issues due to the thin air that is supposed to provide insulation from one component to another. That's why airplanes with turbocharged engines have pressurized ignition harnesses.
3. Battery life on these things seem to die fairly quickly. So while you might think you have four hours of battery life, you might be down to an hour or less, when you really need it.
4. They are constantly changing the form factor. Thus, you design your panel and wire in brand X notepad and two years later, it goes Tango Uniform. Now you have to either buy a replacement on eBay or rewire your panel and replace the cool snap-in holder you installed for it. Oh, and by the way, the new replacement unit is a completely different size so you will have to redesign your entire panel. (Note, my Garmin 496 is also considered obsolete; however, I can buy a replacement that has been lightly used. Good luck finding a "lightly used" tablet.)
5. Can you read it in our cockpits? Some I have tired are so dim, they might as well have stayed in my flight bag.
Don't get me wrong, I like tablets but with my SkyView, D1, 496, etc. I simply don't feel the need for a "non aviation" device being pressed into service.
PS. How many people who fly with a tablet for "backup" leave it on a screen displaying an AI when they fly? Should the primary EFIS go dark or turn upside down, that would be a bad time to have to start fiddling with your tablet to bring up the appropriate screen.
Last edited:
Chris is already aware of our position on this, but here is a link to our previous post on this subject for reference.
Backup Instrument Posting
Thanks,
Steve
Backup Instrument Posting
Thanks,
Steve
N941WR
Legacy Member
Positive outcome
Even with my comments above, this husband and wife team were able to land their Cessna after a total electrical failure using their iPad.
The article mentions "iPads", so maybe they had two aboard and not one.
While this happened at night, there is no indication if they were in the clouds or VFR. Two people would surly be a big help so one could fly and one could pull up the proper page on the iPad(s).
The other thing that bothers me is that they forgot to drop the gear and bellied it in.
It would be nice to hear their full story; did they have the iPad displaying the flight information or did the passenger have to bring it up, etc.
Still, I think the very simple Dynon Pocket Panel, which is designed specifically for this task, would be a better option.
Even with my comments above, this husband and wife team were able to land their Cessna after a total electrical failure using their iPad.
The article mentions "iPads", so maybe they had two aboard and not one.
While this happened at night, there is no indication if they were in the clouds or VFR. Two people would surly be a big help so one could fly and one could pull up the proper page on the iPad(s).
The other thing that bothers me is that they forgot to drop the gear and bellied it in.
It would be nice to hear their full story; did they have the iPad displaying the flight information or did the passenger have to bring it up, etc.
Still, I think the very simple Dynon Pocket Panel, which is designed specifically for this task, would be a better option.
deej
Well Known Member
Nearly always in my case. My iPad is the third AI on my panel, running WingX and linked to a Skyradar ADS-B receiver with the Levil AHRS unit attached.
First AI is a GRT HX with one AHRS, and second AI is a GRT Mini-X with built-in AHRS.
Plane has dual redundant electrical buses.
The chances of all three AI devices failing within the same flight is small enough for my comfort level.
-Dj
Brantel
Well Known Member
I had a triple screen G3X system with dual AHRS units and still had a totally standalone separate backup EFIS (TT Gemini then a Dynon D6). The latest version of my panel swapped the triple screens for one 10" Touch but kept the backup EFIS. I eventually plan to add the 7" Touch to the co-pilot side but I will keep the backup EFIS.
I totally agree with TeamX's position on this subject!
I totally agree with TeamX's position on this subject!
Last edited:
Although there is nothing wrong with having redundant devices/systems from different manufacturers, it is not necessarily true that it eliminates common-mode software errors. Experiments done by software safety researchers (ref. Leveson, et al.) demonstrate that n-version programming quite often results in the same "errors" in design and implementation by completely independent teams (given the same requirements). This is quite a controversial result, but it appears to be the case based on research into software systems safety.
avionicsr
Active Member
As we all know, nothing in aviation is an absolute guarantee, but the likelihood of two independent systems suffering a failure that causes a reset at the exact same time is significantly lower than that of a single system resetting.
Rather than getting wrapped up in the miniscule details of software, research, and hardware, the point being made here is:
Due diligence in providing a safe, IFR platform means following the part 23 guidelines and providing an independent Attitude, Altitude, and Airspeed powered by an independent power source (independent backup battery is acceptable).
I personally, will not put myself or my family in a glass panel aircraft in IFR conditions, either certified or experimental, without a panel mount backup basic flight instruments with an independent power supply. Whether that backup power supply is an internal backup battery or pneumatic and vacuum makes no difference, as long as it's independent.
I'm not arguing that point. I have a backup EFIS myself, and both primary and backup have backup batteries, plus one is on the E-buss, primary has external ADAHRS, backup has internal/external, etc. (Skyview primary, D6 backup).
I was only pointing out that the na?ve approach of insisting on different manufacturers on the basis of n-version programming isn't necessarily grounded in facts, based on research into safety-critical software development.
I was only pointing out that the na?ve approach of insisting on different manufacturers on the basis of n-version programming isn't necessarily grounded in facts, based on research into safety-critical software development.
I look at redundant same-brand EFIS screens as simply a convenience in the case of something like a display failure. Likewise, electrical bus faults do happen and so some sort of backup power supply is a given.
However I agree that a totally independent standby attitude source, if you fly lots of IFR, is a very good idea.
From a risk assessment perspective, the chance of a common fault causing multiple display failure in IMC is certainly rare. However the consequences are extreme if there isn't an independent source!
However I agree that a totally independent standby attitude source, if you fly lots of IFR, is a very good idea.
From a risk assessment perspective, the chance of a common fault causing multiple display failure in IMC is certainly rare. However the consequences are extreme if there isn't an independent source!
