No, but certainly if some instruments give “misleading indication in pitch and roll at low speed” it will do so whatever regime you fly under. Besides, I may very well fly NVFR for instance. Obviously the LAA have some standard of how things should be displayed. Chances are, this standard may even be well thought through 
and therefore worth adopting.
LeSving wrote:
What exactly is “an accepted screen layout” ?
I would think they’re talking about attitude, altitude, speed, etc. – the basic indicators on a PFD. There is not that much variation in this in the certified world. Even G1000 follows the same basic layout. I don’t know how crazy you can get with MGL.
LeSving wrote:
Mission: VFR, fun flying, some basic aerobatics, burger runs (or “waffle runs” around here), and an occasional longer trip.
For example, why install four independent means of determining altitude (two altimeters, GPS, and glancing out of the window), or two artificial horizons when the real one needs no battery?
I haven’t seen a Onex close up, but from the description it would benefit from chucking out all that is not essential, and drilling holes in everything else.
Jacko wrote:
For example, why install four independent means of determining altitude (two altimeters, GPS, and glancing out of the window), or two artificial horizons when the real one needs no battery?
You are right of course, and there is a bit of “because I can” into this, I have to admit, and gadgets are cool. But from a more practical point of view, an EFIS is much simpler to install than a whole bunch of individual instruments. It’s also much lighter.
What is required for VFR is (according to the current regulations, non-part-NCO for experimentals):
Then for NVFR I need additionally:
Then for IFR (in addition to the above)
A typical EFIS (+ one extra altimeter) will give you the minimum required instruments for IFR. And since this is the easiest (and lightest) thing to install, why bother with anything else?
No matter how you look at this, no matter how capable the EFIS is. A single EFIS IS and always will be an all eggs in one basket configuration. A typical modern EFIS system can have every single instrument included, flight, engine, navigation and autopilot. The newest transponders are headless, unusable without an EFIS. This is very different from a traditional system. Even the simplest of traditional systems are fully “redundant” (in the sense that one fault in one instrument does not make you lose every single instrument). I’m simply wondering about what a minimal redundancy should be like. Is SD on a pad enough for instance. Would anyone else consider this enough, or is it just me?
It’s not that I need a full autopilot IFR configuration with dozens of gyros for anything. Those things just come along with the ride on each EFIS. They are there by default whether you want them or not.
Oh could you fly experimental VFR night? That changes a lot in instrumentation needs, but for VFR day in a basic fun plane, I’d rather be so current not to fear a complete dark panel and I think this is quite achievable in the Onex, based on what I have read.
But then again you could reuse any equipment in your RV-to-come and proficiency in an avionic suite isn’t a bad thing either. So if you plan to reuse equipment, an EFIS/EFIS solution could be the most efficient setup in the long run.
I wasn’t talking about the relative MTBF of EFIS versus “steam”. I was talking about the dissimilar nature of the two technologies which eliminates common mode failure.
We could have two EFIS systems with a 10e6 MTBF each but a common failure mode. Or one EFIS with 10e6, plus a conventional instrument with “only” 10e4 but unrelated failure modes. Which combination is more reliable?!
So personally I would prefer one EFIS and one conventional (even if theoretically less reliable) instrument.
If planning to fly night VFR then I would want to equip to IFR standards, as NVFR can become IFR any moment.
But if VFR only, just go with whatever looks coolest and is most usable.
An argument in favour of a conventional ASI in primary field of view might be that some people find a needle and dial easier or quicker to check during an aerobatic sequence.
mh wrote:
but for VFR day in a basic fun plane, I’d rather be so current not to fear a complete dark panel and I think this is quite achievable in the Onex
Agree, and I think that simply must be one basic “spec”. The RV-4 will essentially have the same " mission profile" only with a larger envelope, particularly regarding travelling.
ortac wrote:
I wasn’t talking about the relative MTBF of EFIS versus “steam”. I was talking about the dissimilar nature of the two technologies which eliminates common mode failure.
I understand that, but it would mean having two different engines in a twin with low MTBF is better than having two equal engines with high MTBF. This is simply not the case. When you have a number for MTBF, you also have knowledge of the failure modes, and for two identical engines they are the same. Going from mechanical to solid state electronics usually increases the MTBF by an order of magnitude or more. The same failure mode happening at the same time is so small that it is not worth thinking about. What is more important is true parallel systems, duplication of everything and possibility to isolate one system from the other.
I have had one ASI failure. It was due to blocked static port, and I didn’t notice anything wrong before climb out and the speed was all over the place. No backup except a separate pitot would have helped. But I had GPS, so I just turned back and landed without any problems. I could have landed without GPS also, but with a much higher heart rate I guess
Seems like most people agree that a black panel in a basic VFR aircraft is no big deal, so I will go for that and equip it the way I can practical and cool
LeSving wrote:
I understand that, but it would mean having two different engines in a twin with low MTBF is better than having two equal engines with high MTBF. This is simply not the case. When you have a number for MTBF, you also have knowledge of the failure modes, and for two identical engines they are the same.
The failure modes are the same, but the failure causes are not the same (unless you run out of fuel), so the situation is completely different compared to twin EFIS where the same cause (e.g. a database problem or electrical systems problem) could cause both units to crash simultaneously. But of course you understand this, so I don’t really see your point?
Airborne_Again wrote:
The failure modes are the same, but the failure causes are not the same (unless you run out of fuel), so the situation is completely different compared to twin EFIS where the same cause (e.g. a database problem or electrical systems problem) could cause both units to crash simultaneously. But of course you understand this, so I don’t really see your point?
I don’t have a specific point about this, I simply disagree. A database or electrical systems problem is no different in principle than contaminated fuel, leaking fuel tank or wrong oil filled at the latest oil change. If the electrical system is the bottleneck, then you fix that problem with two independent buses, or for instance by using something like this:
I was wondering about how far I should go with redundancy with an “all eggs in one basket” EFIS system in a “for fun VFR” aircraft. It seems to me the majority agrees there is no need to do anything basically, and I agree as well. Making it practical and nice is more important.
