| Jeff and Colyn make the strong point about reliability of the backup. I guess it is just my naiveté but I am just not familiar enough with what it takes to get a TSO rating on an instrument except that once it gets it, the price goes way up. I think the issue is are we more comfortable with old (not necessarily outdated) technology vs new technology. I don't think anyone would advocate vacuum driven instruments as more reliable than electric yet they are certainly TSO'ed. Yet Glass panels of all types would seem to conjure up uncomfortable feelings even though there are plenty of certified versions available! I believe the key is redundancy of all critical systems. Marv was kind enough to post my panel schematic and I have a vertical row of AI, ASI, Alt, and VSI to complement my Chelton (besides the Garmin 480). The pitot static ASI, Alt, VSI are clearly independent. So the goal is to find a reliable AI with independent power to save the day when the rest of the panel goes dark in night IMC (where I should never be anyway).
The analogy to medicine is most appropriate. Doctors use FDA approved medications for off shelf indications all the time. And as a surgeon we frequently employ implants for noncertified uses when in the physician's judgement the patient would so benefit. Accordingly, this is precisely why I am posing the AI question to the lml who in my opinion, have the combined experience and insight to make a recommendation that one or another attitude indicator, be it TSOed or not, is a safe option for a backup ( or until my Chelton PINPOINT arrives, a primary instrument).
As an aside, the attach link from BlueMountainAvionics (admittedly not an unbiased source) seems to suggest that while TSO'ed equipment may be desirable, it is not required for IFR in an experimental so long as the required instruments perform the tasks specified by the regs .
We fly homebuilt plastic airplanes with modified experimental motors and have faith in the building community to give each other advise based on the reputation of the suppliers we use, the products they produce, and the mission for which they are meant.
So at the end of the day what I am going to do? If the Trutrak does not arrive (I am flying with their autopilot so I should probably trust their AI), I will buy the new 2 1/4" mid-continent AI with battery b/u you all have highly praised.
thanks again
Joe Neustein I
would
greatly appreciate feedback from the LML on the advisibility of using either
of these AI alternatives and whether or not one could depend on them for IFR
flight (disclaimers by the manufacturers notwithstanding) given the
configuration of the rest of the panel which includes a Garmin 480.
Dr. Joe, Great question. Why would you want a backup AI? Aswer, because of an emergency requiring you to fly on a backup system in IMC conditions. Obviously when it happens to you, you will be breathing very deeply and the seat cusion will have disappeared up the through the seat of your Levis (I have had this happen more than once while IMC with my three screen Chelton system). Next question: Do you want an experimental attitude system being your only backup or do you want a TSO'd unit? Third question: when you perform surgery on a patient do they get the tried and true procedure or the new stuff they are doing clinical trials on? What is more risky? Last question? Will you be flying lone or putting your family in the aircraft, too? Your assumption of risk will be borne by your passengers as well. Mind you this is all tongue and cheek but analyze the risk. I put a TSO'd AI in as my backup as well as a TSO airspeed and altimeter. My Levis thanked me. Talk to Kirk Hammersmith-- he can set you straight on what has to be in the aircraft to be IFR certified. Just because the aircraft is experimental does not mean you do not have to meet some regulatory requirements, ie. you need a magnetic compass and a transponder as well. Best Regards, Jeff Edwards LIVP |