Brent,

I suppose I should have been more specific - I assume that pilots of experimental aircraft will exercise sufficient judgment not be flying into thunderstorms, and thus the likelihood of in-flight lightning strike is nearly nil.  Not absolutely nil, naturally, but approaching or below the likelihood of vacuum failure, which is fairly common.  Of course, perhaps I should not make such an assumption given that a very famous pilot died just last year flying his Bonanza into thunderstorms.

Absent thunderstorms, we will simply have to agree to disagree.  Vacuum pumps and vacuum-operated artificial horizons are notoriously fallible, and a poor vacuum can give insidious symptoms causing catastrophic results.  While there have been some experimental EFIS units (notably one you mention, also the original pioneer Blue Mountain) which had early individual failure rates much higher than vacuum equipment, still the likelihood of two or more going down simultaneously is rather rare.  In my personal experience my TSO Garmins failed just as often as my experimental equipment - anecdotal evidence, to be sure, but 3 TSO failures in 600 hrs not counting vacuum pump failure and attitude indicator partial failure ("lazy" attitude, "sort of" working).

None of this absolves individuals contemplating use of experimental equipment from the burden of research to draw their own conclusions about reliability.

Your statement that TSO is required for legal flight is simply untrue.  If you wish to dispute this, please feel free to point out the section of the FARs that you believe says otherwise (it does not exist, but knock yourself out).  I don't expect to convince you of that; it seems that there are some folks who have made up their minds and aren't interested in anyone else's opinion.  That's fine, you are entitled to yours.  I, like many, have reviewed the pertinent FARs along with (among others) my mechanic who was a chief avionics safety inspector for a major airline.  For the type of flying for which Experimental aircraft are authorized there is no such rule stating that each piece of equipment must be certified to pass TSO.  The altimeter must, or pass the test for equivalent accuracy (performed during the annual pitot-static check).  Doesn't mean it's a bad thing, only unnecessary for legal flight.  Just as you admonish people who are not engineers (I too was a software engineer by trade) to form unwarranted opinions about avionics, you too should not consider yourself an expert on FARs simply because you build avionics.  Glass houses, etc.

Blocked pitot or static tubes are no longer a killer for correct attitude indication on any of the three leading experimental EFIS units (GRT, Dynon, MGL).  May also not be on others, haven't kept up.  Of course, you will not get accurate airspeed with either blocked and will not get accurate barometric altitude with static blocked, but that would happen irrespective of the type of avionics you use.  However, you will still have accurate horizon, and GPS can provide altitude and ground speed which, combined with a pilot's knowledge of their aircraft power settings, etc. should enable you to fly safely to landing. 

At the end of the day, you are putting your own life on the line.  If you feel more comfortable with spinning gyros, by all means load up.  However, if you feel you have done your research and would rather replace that vacuum pump for a second alternator to prevent power-out and ditch the gyro for a small self-contained backup EFIS, then your odds of total failure will ultimately be about the same - just different causes.


Fly safe!

Bill


On 01/-10/-28163 02:59 PM, Brent Regan wrote:

Bill speculates:
<<Given that two EFIS units with battery backup are more reliable than a single vacuum pump, your argument that people must have "TSO'd" equipment is logically ridiculous - especially if they also have as part of their panel an independent 2-axis autopilot.>>

The primary assumption here is false. It is not "given" that "two EFIS units with battery backup are more reliable than a single vacuum pump". Analysis and data show the opposite is true.

Having designed several Certified EFIS systems and sensors (AHRS, Air Data, Magnetometer, OAT etc.) over the last 15 years and shepherded those systems through DO160 certification testing I can say with the confidence of having empirical  data (Remember that one test is worth a thousand expert opinions) that I would NOT fly behind a panel that had ONLY electronic gauges, regardless of their certification level or lack thereof. Even the Starship, with a million dollar 17 tube Pro Line 21 integrated avionics suite, STILL has a mechanical Airspeed, Altimeter and AH.

Regan Designs was the first company to design equipment that passed the DO160 Lightning Induced Transient Susceptibility (section 22) and Lightning Direct Effects (section 23) requirements introduced in 2004.  Hamid engineered several test articles that he then subjected to simulated lightning strikes in a certified laboratory.  Based on those tests I can say with a high level of confidence that most GA certified EFIS and likely all experimental EFIS systems will not survive a proximal lightning strike, let alone a direct strike. Same goes for experimental autopilots. And that is considering just 2 of  26 sections. There is also Shock, Vibration, Temperature, Magnet Effect, Voltage Spike, Operational Voltage, RF Susceptibility, ESD,  etc. etc. etc.

One transient event can take out most of the digital electronics wired into the aircraft. A battery back up won't do any good if your EFIS is fried.

Here are some additional reasons for a spinning mass backup to an EFIS.

1) Compelling disaster. If your EFIS starts to roll (e.g. due to a long climbing departure turn), you feel compelled to follow it to your doom. Having a familiar AH in you scan will help you keep you wings level.
2) Different physics. Spinning mass and MEMS gyroscopes work on different principals and physics. The set of events that will kill both is small and most of those involve the pilot not surviving either.
3) Old faithful. Most of us learned to fly with an AH. The response to and AH display is nearly reflexive and may save you life during a helmet fire.

Some words on TSOs. TSOs are the Technical Standards that equipment must meet to to be considered as equipment on aircraft. Therefore, in order to have an "altimeter" in your aircraft you must have an instrument that meets the TSOs for an "Altimeter". You can either let the instrument manufacturer do the testing or, as an aircraft manufacturer, you can do the testing, and document same. Why? Imagine you took a rock and printed "8,250 feet" on it. You then "install" it in your aircraft and claim it is an altimeter as it will tell you your altitude during certain conditions of flight. One of those conditions must be that you are actually flying at 8,250 feet MSL. To prevent this type of thing the FAA has established standards that a device must meet in ordered to be qualified to function as a required device. See FAR 21.601.b.1.

So, Bill's statement that "...(the) argument that people must have "TSO'd" equipment is logically ridiculous..." is false. You MUST have at least one of each of the required instruments and they MUST meet the TSO. You can call it ridiculous, but it does not change the fact that it is the law.

Bill also postulates that " Experimental EFIS units work acceptably with either good pitot-static input or GPS input, removing the single point of failure in steam gages.". This statement is non sequitur. The most common Pitot Static problems are blocked ports (insects or ice), leaks or water in the lines, any of which will produce a similarly wrong reading in either the steam or electronic display. Redundant sensors are fine ONLY if you have a method for differentiating good data from bad data.

FWIW, Being a good pilot, as I am sure Bill is, does not make you a good engine mechanic or good at failure analysis. You can take or ignore the advice of those with experience. Fred has put a lot of thought into his system and has reduced the likelihood of a catastrophic electrical failure. Now if you could only do the same for rocker arms.......

Regards
Brent Regan