Dynon D6 or Gemini PFD for b/u?

Been debating the merits of the two as a back up attitude source. Primary is all G3X (sitting in the boxes, plus the TT GX).

Only reason for considering the D6 is to take advantage of the AOA functionality of the Dynon pitot that's hanging off the wing.

What say the experts?

Depth?

If depth is an issue the D6 is much deeper than the Gemini. I have not seen a Gemini yet but looked at the specs to compare.

AOA is really nice to have and if you're already plumbed for it that's a bonus.

Neil

AllThumbs said:

If depth is an issue the D6 is much deeper than the Gemini. I have not seen a Gemini yet but looked at the specs to compare.

AOA is really nice to have and if you're already plumbed for it that's a bonus.

Neil

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The d6 is about 11" deep. The Gemini is less than an inch and a pound or so lighter. I'm bias since I've already purchase a Gemini PFD. Since I already had a Trutrak ap, it was a no brainier for me. It kept the number of vendors on my panel to a minimum.

The D6 has space for it's own stand alone internal back up battery. If you are going to bet the farm in IMC with non TSO glass, you might do well with both a D6 and the Gemini ( 2 back ups)

F1R said:

The D6 has space for it's own stand alone internal back up battery. If you are going to bet the farm in IMC with non TSO glass, you might do well with both a D6 and the Gemini ( 2 back ups)

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You have to put that in context of the total system design. The Gemini is the fourth EFIS in my panel. I have two AFS 4500 and an AFS 3400. The Gemini is truly just a backup and a tie breaker if one of th e AFS screens run amok.

There are many solutions to solve the electrical backup scenarios.

In IMC, I don't think I would want either the d6 or the Gemini as a PFD.

rleffler said:

The d6 is about 11" deep. The Gemini is less than an inch and a pound or so lighter.

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Just to keep the facts accurate, the D6 is 6.85" behind the panel, not 11". It weighs 1.56 lbs. TruTrak doesn't publish weights in their install manuals so I can't tell you how different that is. The TCW backup battery weighs 1.5 lbs while ours is 6oz, so if you are backing up your Gemini, the weights are likely identical.

The D6 and the Gemini are pretty different products. The D6 has the ability to display attitude, airspeed, altitude, turn rate, vertical speed, and actual magnetic heading. These functions all work the way you'd expect from the gauges in a standard 6 pack in any airplane you have flown.

The Gemini does not display attitude or heading. The display of attitude is actually vertical speed and turn rate, and is limited to lower bank and pitch angles. The display of heading is GPS ground track. The D6 has no attitude restrictions and is fully aerobatic. It is also proven over time and temperature, with thousands sold and a fully specified temperature range from -20C to 50C.

As mentioned, the D6 can also do AoA if you have our $200 pitot probe (which also works as a standard pitot), and it can generate audio alerts for critical AoA. It can also be the encoder for your transponder.

Additionally, the screen on the D10A is much bigger and has excellent off-axis visibility, which is critical if it isn't in front of you. The D6 screen is fully dimmable for night flight, all the way down to about 1 nit. The D6 also includes everything you need to update the firmware right in your plane in the standard price, and has an internal back up battery that goes right inside instead of needing to buy a much more expensive external battery. In fact, when you add it all up, the prices are only $5 different.

Both Dynon and TruTrak make good products, so you'll get a useful, quality product either way. It's just important to know what you're purchasing for your backup and what it's features and limits are, and if they fit your needs for your aircraft's mission.

Good luck with your decision!

--Ian Jordan
Dynon Avionics

All Depends What You're Comfortable With

rleffler said:

You have to put that in context of the total system design. The Gemini is the fourth EFIS in my panel. I have two AFS 4500 and an AFS 3400. The Gemini is truly just a backup and a tie breaker if one of th e AFS screens run amok.

There are many solutions to solve the electrical backup scenarios.

In IMC, I don't think I would want either the d6 or the Gemini as a PFD.

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I'm presently using a TruTrak ADI as my primay attitude instrument, backed up by a turn coordinator and whiskey compass. I'd love to have just one EFIS, But my next move is a WAAS GPS, and then a Gemini to replace the ADI. The downside of my simple setup is that I don't have the flood of info that multiple EFIS's would give. On the othe hand, I'm pretty well aware of exactly where I
am while in IMC, and what ATC will look for me to do next. The upside to a simple setup is that very little button pushing is needed for precision and non-precision approaches, so nearly all of my attention is focused on just just flying the plane. I tend to like to see students do the same.
Terry, CFI
RV9A N323TP

I think Ian posted a pretty fair comparison.
I have a D6 as a backup, and I've flown approaches under the hood using just it and a hand held nav, it can be done.
While the Gemini appears to be a nice product, it would be much harder to use it for an approach without the ground track info, so I would consider a battery powered gps (to get the ground track info to the Gemini) mandatory if you go that route. Also since it is a backup the TT external battery is needed, just as the internal battery in the D6 is an option you should get. Once you add in these things the cost and weight are pretty much the same. You have to figure out where to put the TT battery.
As pointed out, at this time the Gemini does not display true attitude - it will settle down into showing nose level when you are in slow flight, nose high with no altitude change. Just as long as you're aware of this, it works okay; I've used the TT ADI (same principle) and it is quite flyable.
Gemini is new, no track record. TT has promised an upgrade to a "real" attitude display but can't say when, and it will cost you to get it (either you have to pull it and send it back, or buy a gizmo for loading new software).
If it were me, right now, I'd go with the D6. The big but is: if I was also going with a TT autopilot, I might wait for the Gemini/autopilot all in one box, and then look at the total costs going either way. Mindful that this would also reduce redundancy. Life is complicated!

The Gemini can act as a standard directional gyro without a GPS. It just needs to be set just like a normal mechanical DG. Most people wire them to a switch so they can pick from one of the many typical GPS's as a track source. My future panel will have two battery backed up GPS's and one 430w. Odds are there won't be a need for a backup to the track info.

The backup battery argument is debatable since the Gemini can use just about any backup battery including the one that most people would have installed for a G3X anyway (or other EFIS that does not have a built in battery).

Some people don't have room for a D6 as a backup....

People have been flying TT ADI's for years as backups in IMC. The velocity vector display apparently works pretty good. Some even claim it is better.

Yes if you get completely out of shape most likely the Gemini is not going to help much....but you are not suppose to be doing aerobatics in IMC and if you are I doubt even the D6 would help you.

The Gemini has .4lbs printed on the back of it.

D6 Overall Depth Including Connector and Wiring?

dynonsupport,

The D6's 6.85-inch depth is from the rear of the front bezel (front of the panel) to the back of the air port receptacles, correct? When the D-sub connector is plugged into the D6 with all its wiring, the total installation depth required behind the panel stretches out to about 9 inches, correct? Given that the air lines must also be connected, is there a right-angle D-sub adapter, or D-sub connector, available which would reduce the required depth behind the panel somewhat? If so, by how much?

Thank You

Can't answer your question exactly. My RV10 has 11" from front panel to sub-panel, and the D6, wires and pitot, AOA, and static tubing, fit in that space easily.

No one else answered part of the original question: yes, the D6's AOA works, and can be wired to give an audio tone warning to your audio panel as well as the visual representation. If you already have the dynon pitot it's a consideration.

If I were considering the Gemini without a battery powered GPS, I'd want to know how well it works as a DG. IF the drift is a few degrees in 15 minutes, that's great. If drift is a few degrees per minute, I'd really want that GPS.

Other question is off-angle viewing, how is it? Since we're talking about back up in IMC, sunlight readability is not an issue!

Since this device is my last line of defense, I'd really like it to have its own standby battery. Who knows? A failing main EFIS might take out its battery with it. Risk analysis is not easy, and we can't guard against everything.

So I'd change my recommendation to be: if space is not a consideration, go with the proven D6 and get the AOA "for free" since you have the pitot tube.
If panel space and depth are an issue, go with the Gemini but get the backup battery and a battery powered GPS wired into it.

BobTurner said:

If I were considering the Gemini without a battery powered GPS, I'd want to know how well it works as a DG. IF the drift is a few degrees in 15 minutes, that's great. If drift is a few degrees per minute, I'd really want that GPS.

Other question is off-angle viewing, how is it?

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I can answer both these...

The Gemini has a function where you can tweak the precession. I was able to tweak mine to the point where it only processed 5 degrees in 30 minutes. It also has an easy one touch method for setting the DG to a known heading making it easy to keep aligned. Works just like a mechanical DG only with much better performance.

The off axis viewing of the Gemini does fall off sharply after about 30 degrees. I would not use this as a backup if you cannot put it in that viewing range of the pilot. The sunlight readability of the Gemini is excellent.

I am resurecting this thread so I can say I told you so, specifically that anytime you bought a new technology you were a beta tester. Trutrak is a good company and I'm sure they will get the bugs worked out, but there is a recall out on the Gemini.

Bob,

I can only assume you are talking to me.

I know there is a firmware update available or soon to be available for the Gemini, this is old news. Anyone with any sense that buys a product with version 1.01 firmware should know that they can expect many updates over the first year of the product's life.

Take a look at the manuals for most every EFIS on the market today and look at how quick and how often they ALL have had to come out with updates for their firmware. Some are feature enhancements but many others of them are bug fixes.

One of the reasons I bought the Gemini now is so I can help TT in their efforts to make this product great. I have no need in my current panel for a backup PFD so I don't care that there may be a few bumps in the road on its development. I would be concerned only if TT did not come out with new firmware revisions.

Oh and Bob, I like being a Beta Tester it is a big part of the fun for me. Got a full panel of Dynon gear and have been a big supporter/beta tester for them for years....they have issues just like everyone else. The day you show me a perfect system, I will be amazed.

My comment was to no one in particular. But the original post asked about backup equipment, and my original reply was that older established gear might have fewer (not necessarily zero) problems than the newest, just out stuff. You just said the same thing. But you said everyone knows this, I'm not so sure about that. It's just one more thing to consider for the flight instrument you want to work when everything else doesn't.

BobTurner said:

I am resurecting this thread so I can say I told you so, specifically that anytime you bought a new technology you were a beta tester. Trutrak is a good company and I'm sure they will get the bugs worked out, but there is a recall out on the Gemini.

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From your subsequent posting, it appears that what you meant and what you said may not be the same. "I told you so" just offends people and doesn't add value to the discussion.

I have a different opinion that is not specifically related to the Gemini. I'm an IT guy and deal with software issues all the time. It doesn't make a difference if the product is brand new or several years old. Another prominent EFIS vendor released three updates last week. Does that make the product less safe?

I applaud and support vendors that once they find a serious bug that release a fix promptly. I'd rather have a vendor that actively supports their installed base than one that just releases quarterly releases regardless of the significance of the bugs fixed. Additionally, many of the EFIS vendors prefer that you not fly IFR on the most current release unless it's been in the field for awhile.

What it comes down to is not the specific vendor products that are picked, but the total system design and how that product is used in the total system design.

In my particular case, my system design has two EFIS and one slave monitor in the panel. I'm not protected if there is conflict between either EFIS, the dual magnetomers, or the dual ahars. I needed a tie breaker from a different vendor to function as a back up device or as a primarily device should there be a problem with the primary EFIS vendor's code. The system design can tolerate any single failure and in some specifc functions multiple failures.

The issue as hand is more of release management and reliability and how do you manage that in your aircraft. What are the inherent risks to flying with a new release? How do you choose to mitigate these risks? As long as the PIC understands all the risks, they can be managed sucessfully.

The answers to these questions are going to be different for each of us. The answers to these are also more important that whether or not you are using Vendor's A new product or Vendor's B more mature product. All of us flying with modern avionics are now software risk managers whether we like it or not.

If you are going to be at OSH, be sure to stop by the RV-10 HQ in Camp Scholler late afternoon or early evening. We can continue friendly dialogue on the subject there while consuming some adult beverages.

bob

When the primary EFIS dies, the back-up becomes the primary. If the original poster is thinking about IFR then my recommendation would be to go with a back-up system that has significant history and substantial debugging, in this particular case that would be the Dynon D6. In IMC you certainly do not want to be a "beta tester".

In the Experimental category many believe that the latest gee-whizz doodad must be the best. Personally I prefer a proven track record for crucial componentry.

I remember the software guru telling me stuff about 10 to the minus 9th reliability of his machine code in the first synthetic vision. Names left out to protect the guilty... think Alaska.
Coming home in the company plane one night, the screens all go dark just prior to crossing Grand Canyon. Pitch black.
Turned on the 496 Garmin and hit nearest. Clicked 7 times and turned on the lights behind me in Utah. Motel felt just great. Continued on in the morning.
Now, the marketing department had concerns about my Garmin riding along on the glare shield after that in it's little bean bag mount. But I said screw it... software might be really cool when it is running... but it sucks when I am up there at 9K ft. in the black... and the code writer is home having sex.

I fly my plane IFR almost all the time since I have upgraded my panel, I decide to go with Dynon D-6 instead of TT Gemini, because D-6 give me accurate attitude, airspeed, altitude and heading, when TT Gemini from what I have read here works OK for attitude it sucks for altitude, so if you really need a complete 6 packs backup and not just an attitude indicator, go for D6.

I have a TT GX and I think is the best autopilot I have flown with, so every company has their best product where in others their are not so great.

Just my two cents!!!

AirbusPilot said:

I fly my plane IFR almost all the time since I have upgraded my panel, I decide to go with Dynon D-6 instead of TT Gemini, because D-6 give me accurate attitude, airspeed, altitude and heading, when TT Gemini from what I have read here works OK for attitude it sucks for altitude, so if you really need a complete 6 packs backup and not just an attitude indicator, go for D6.

I have a TT GX and I think is the best autopilot I have flown with, so every company has their best product where in others their are not so great.

Just my two cents!!!

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I'm not sure where you heard that about the Gemini PFD. That hasn't been my experience, nor do I suspect it has been the experience of many others.

My TT Gemini works perfect in altitude. always matches the other two indicators.

Airspeed and attitude are a match as well.

Seems like most people are posting "from what I have read" about the Gemini PFD.

Like the previous posters, my REAL LIFE experience with the Gemini PFD has been terrific. Yes, initially, the software needed tweaking. That's been done and the instrument is rock solid.

My readings are all spot on or very close to what my other instruments are reading. I use the Gemini PFD as an inadvertent IMC tool as my instrument rating does me no good without a fully IFR equipped aircraft. I chose not to go that route.

I would be confident in the Gemini's ability to get my butt out of the soup safely.