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I had bad luck with a falcon altimeter, but anything U.S. made is EXPENSIVE!. Lee
MGL ASX-1. 2 1/4 combination airspeed and altimeter. Works good for backup to Dynon.
The Dynon has proven reliable over the last 550 hours, and your gps should have a page that shows all the traditional guages
I agree with Roger -- I had planned to put backup "steam gages" in for altitude and airspeed until I saw the GPS generated flight instrument display in my Garmin GPS 496. That is waaayyyy more info than you need to get a plane on the ground in the event your Dynon fails. Also there are now several i-phone based flight panel apps that take advantage of the sensing gyros in the newer i-phones and give you a full panel including gyro based attitude indicator and everything. I see no need for panel mounted backup instruments for the Dynon. That would give you the lowest weight and least expensive solution.
When all power is lost, and your garmin, which I have, fails, what do you do. I personally feel one instrument you need in your plane is a ASI. mechanical that is. Just my opinion. just to get the plane on the ground.
We are talking odds here. All normal power is lost. The Dynon has a built in battery backup that should last for the rest of the flight. The Dynon dies anyhow. The Garmin (at least the ones I am interested in and also the one I already own, the 496) has an internal battery that should also last for the duration of the flight and can give you GPS derived groundspeed, track and altitude. Groundspeed will be within a few miles per hour of airspeed unless you have roaring winds. If you have roaring winds you can compensate to mentally adjust the groundspeed to get the airspeed you want. OK, now the built in battery in the Garmin fails (in addition to the aircraft electrics, and the Dynon, all in the same flight) -- whip out your smartphone and use its internal GPS and the aviation app you have in the smartphone and THAT will give you GPS derived groundspeed, track and altitude. How many backups do you need? Plus, I like to know my machine well enough to fly it by looking out the window and feeling/flying the plane without reference to instruments - not a good thing to do all the time but definitely a good thing to maintain proficiency in.
Basically, we each need to settle on the equipment and capabilities that work for us, our preferences, our capabilities and our wallet's ability to buy more stuff. I freely grant the logic of your comment/suggestion, Jon, and felt the same as you initially. After playing with the GPS generated panel in my Garmin 496 (and even flying under the hood with only the Garmin flight display, the rest of the panel was blocked) I decided I did not need the weight and expense of backup mechanical flight instruments.
In 46 years of flying the only time I have lost airspeed indications it was due to clogged pitot tubes, once due to heavy ice accumulation and once due to a large bug that got rammed down the tube from an impact in flight. In both those cases, a mechanical or electronic ASI would be disabled. Both those events were in transport category aircraft with dual pitot/static systems and dual instrument displays. In the case of the ice, it overpowered both heated pitot tubes, in the case of the bug only one pilot's indications went bad, but then we had to decide which one to trust. GPS speeds do not need a pitot tube or static port.
I did consider using the kit provided pitot/static mast to feed a mechanical ASI and/or airspeed. That would provide redundant pitot/static systems since the Dynon panel will be using its own pilot/static information. At this point I don't think I will do that, but the idea has charm -- a totally redundant and independent ASI and altimeter with its own redundant pitot/static sources. Considering the low odds of needing it, I most likely will not do it, but the idea charms me -- I spent 38 years flying equipment with independent redundant systems. I will miss having redundant engines, electric systems, instruments, heating sources, etc etc etc but expect I will be fine without them.
That is the beauty of Experimental aviation, we can do exactly what we feel is best and then see how the experiment works.
How many backups do you need? Plus, I like to know my machine well enough to fly it by looking out the window and feeling/flying the plane without reference to instruments - not a good thing to do all the time but definitely a good thing to maintain proficiency in.
Many years ago, I was doing transition training to gliders, flying a Schweitzer 2-33. One day, the ASI was broken and I was due to fly solo, so I assumed the flight wouldn't happen that day. Instead, the instructor told me to get in the cockpit and get going. I said to him, "What about the airspeed? It's broken!" He said, "Aw, that's OK, just keep up some wind noise and your speed will be OK!"
He knew that the big, boxy 2-33 wasn't going to "run away with me" as it has tons of drag, and he also knew that it didn't need much airspeed to avoid a stall. Similarly, the 750 in normal flight attitudes won't reach a speed where you worry about something bending due to abrupt maneuvering, and you have to really, really make an effort to achieve a stall. Since I would venture that 90% of us are day VFR fliers within an hour or two of home base and since we know our planes intimately, I agree with Bob that little or no "steam gauge" backup is needed to an EFIS (MGL XTreme in my case). My independent iFly 720 GPS is waaaay more than capable and even my phone's iFly app is too!
That being said, if you're a "gadget freak" and want every possible instrument and backup installed 'til the panel can hold no more and you can spare the weight, that's OK, too, because it's your plane and you only have to please yourself! ;>)