Hi Ed,
re: no steam gauges
The concern over an all electric system is "common failure mode".
In other words, what takes out one system may be the same thing that takes out the other one.
In your installation you have added to that that you have the same brand equipment in primary and backup positions?
Also you may or may not have them on fully isolated busses.
So here are some of the failure modes you have to worry about:
- lightning causes a transient throughout the entire electrical system. This one can take out both busses and if you have a portable linked to one of your main systems (or not) it can take that out too.
- internally caused transient takes out everything on one bus. examples: alternator over voltage - yes you should have protection for that but it's not instantaneous. generally that kind of protection is designed to keep the wiring from melting down. will your equipment survive that? another example: high current short to ground. this can happen in a faulty motor (e.g. gear pump) ; chafed wiring etc. same issue with protection: your equipment may be dead by the time the breaker trips. another example: loose ground in your charging system causes spikes. I had this happen on my cessna. It took out 3 different Garmin units before I discovered it.
- software issue. some particular sequence of events gets your dynon's confused so you have to reboot. ....or some electrical mode turns out not to be well protected on you dynon's. Since you have the exact same model, they could go out at the same time. Will you still be right side up by the time they reboot AND the AHRS get re-oriented?
- chip and circuit failure. One issue that I think is completely under-appreciated by the consuming public is that chips fail. They contain tiny traces which are created by a combination of photo-lithography and chemical processes. One such trace can be a little thinner in one chip than another causing the chip to fail under certain operating parameters. Not all of these are caught in testing. It's a percentage game. The chip vendors try to strike a balance between the cost of testing and the cost of replacement. In the pc world what typically happens is there is a test run of many thousands of chips. Some percentage of those will have problems. The problems are analyzed and the masks or the process are tweaked. Then the first production run of millions begins. Some small percentage of those will fail in the field. Those failures are analyzed and the process is tweaked again. Part number 40 million will have a very small probability of failure, but it's still non-zero.
In combination with the chip failure problem is circuit failure problem. The dirty secret of digital electronics is that when they talk to each other, analog issues become significant. Therefore, digital circuits get tweaked by modification of capacitor and resistor values and other tricks to try to clean up the signals on the board until they are "good enough".
If you now consider that the entire production run of all dynon units forever is likely less than a test run of pc chips, you can appreciate where you are in the march to reduced defects with an aircraft product.
Last and not least, many people confuse probability and severity. Just because not many units fail doesn't mean that yours won't kill you if it does fail. Most high school girls don't get pregnant but the ones that do are not at all comforted by the fact that their chosen method of contraception "only" had a 1% failure rate.
A spinning mass AI is highly recommended. The upside of having one if you need it so much more outweighs the aesthetic downside of dirtying your panel with non-digital stuff.
Colyn
On Jan 13, 2012, at 6:26 AM, Ed Gray wrote:
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Here’s a question for Chris, Paul, and others with knowledge of L2 exhaust. My 360 with Superior IO 360 is ready for engine start up. The exhaust is a 4 into 1 built by Sonic Headers in Princeton, Mn. It is beautiful work and ceramic coated. Sonic provided me with a clamp to fit over the large pipe (collector exit). This will need to be fastened to the underside of the fuse in some manner, but I question whether it is necessary. The collector is bolted to two of the headers with stainless dogbones and 3/16 bolts. The headers are of course very solid on the block. The additional clamp would need to be rubber mounted to allow engine movement. I see no way the collector or any part of it can ever depart the plane. Is this clamp necessary?
I just have completed the install of a 2 screen Dynon Skyview system with ap and Dynon txpd with traffic, Garmin SL30 radio to give ILS presentation on the Dynon screen. I have no steam gage backups. With dual screens, backup batteries and dual ADHRS I feel that I have enough redundancy. Does anyone have input or comment? This plane may be one of the first with no round gauges anywhere.
Next issue, my battery is an Odyssy 650 (650 cranking amps) which has been sitting around for 5 years. It does not turn the crank fast enough for starting. Is 650 amps enuf for a 360 (8.5 compression). I probably need a new battery but don’t want to buy one undersized.
I really appreciate this website-very informative! I will post pics when the plane is together. Look for N360 ZG at Oshkosh!
Ed Gray, Dallas