Hey Fred,

There will always be at least as many opinions as there are pilots (and probably more, since at least a few I've met have displayed some MPD tendencies...).  With over 1500 hours in military jets (fighters, trainers, forward air control) as well as an additional 1000 hrs in spam cans, I have had numerous failures of flight instruments - both traditional TSO'd and experimental / electronic.  While the "more instruments / more technological varieties" is certainly true, as in all things aviation it comes with added expense, weight, and complexity.

Modern electronic EFIS systems properly installed with backup batteries and internal automatic isolation circuitry are about as fail-proof as a single piece of electronic equipment can get.  While certainly not failure-proof, the likelihood of two, or even three, simultaneously going Tango Uniform are far less than losing the sole (or dual) vacuum powered Attitude Indicators in your typical rental IFR plane, all of which fail if the vacuum pump fails (a fairly common occurrence relative to the universe of possible failures).  That vacuum mounting pad can be used for a backup alternator, providing pilots with a choice.

Every pilot should weigh their mission and budget against their personal tolerance for risk.  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.

Experimental EFIS units work acceptably with either good pitot-static input or GPS input, removing the single point of failure in steam gages.  The likelihood of two battery powered EFIS units (each with it's own ADHRS) plus, for example, a TruTrak or Trio autopilot all failing during IFR flight is far less than the "best" IFR equipped airplanes of only 20 years ago.  Is that enough?  Maybe, maybe not - but pilots should make decisions based on factual information about risk, not emotional "absolute" claims that "Experimental Avionics are not safe."

Fly safe,

Bill Reister



On 01/-10/-28163 02:59 PM, Frederick Moreno wrote:

Brent has written much on this topic including "In my "Glazed and Confused" presentation on "Glass Cockpits" I say that flying an aircraft with a non-certified, non TSO'ed glass standby (Dynon et al) is like jumping out of an airplane with only your main parachute and your standby plan is the fact you are wearing real soft socks."   I concur.    When I was young and stupid (not long ago) I had thoughts of long overwater (think trans-Pacific) flights.  I also have experience with failure modes assessment analysis (FMEA) which frequently shows up failure modes easily over looked.  After reviewing various electrical and instrument configurations I arrived at a system design which is shown in simplified form in the attached sketch.  It consists of two alternators, two batteries, four busses, and a lot of opportunities for cross tie.  I use dual Chelton screens, with PFD off the essential buss (many sources of power), the MFD off of the avionics bus (which has many sources of power), and back up electric attitude  indicator (on essential buss), turn and bank (essential buss) and air speed and altitude indicators.   You show me the failure and I can show you the automated or manual work around.  And critical stuff is all double protected with circuit breakers and surge arresters (not shown).   But even this diagram is not as safe as it could be.  What about something simple like: a battery relay decides to go flotch?  (One already has done so.)  That causes a main bus to go south forcing you to a cross tie solution, not ideal.  So not shown are by-pass switches and fuses around the relay solenoids I added "just in case" to provide redundancy on all supply routes.    I have a mechanical and electrical fuel pump.  And I have an electronic ignition and a magneto.   Two of everything, independent power modes, independent pathways, cross connects, multiple layers of electrical spike and surge protection and independent and different principles of gyroscopic display and  electrical power supply.  Now one begins to achieve realistically (and defensible) high levels of reliability.     If I could only achieve the same with the pilot.   Fred Moreno