We were discussing the relative merits of vacuum systems versus electrical systems and whether or not one was being foolish by choosing to put all his/her instrumentation eggs in the one electrical basket. One reader cited a case where a pilot flew a single engine airplane into convective conditions, took a strike. As with all dark and stormy night stories with happy endings, this one had its hero . . . a vacuum system that continued to power gyros after the electrical system was toast. This anecdote was offered as compelling data in favor of retaining the electrical independence of vacuum systems. We'll pick up the thread here where I am questioning the value of the data cited. Why would one go off to do research and development in an environment KNOWN to be a strike risk with an electrical system NOT proven to be resistant to strike stresses . . .-------------------------------------------------------------------- The key phrase here was in the second paragraph: " . . . PURPOSELY flown for the past several summers into developing vertical clouds as a part of R & D." Why anyone would do that in this kind of airplane is beyond my comprehension. We've all seen the 4-engine, turbo-prop airplanes they fly into hurricanes on the Weather Channel. I've seen numerous programs on aircraft versus nature studies where pilots went into thunder storms WANTING to take a strike. Bob, I have to disagree. That the pilot PURPOSELY flew into clouds is, in my opinion, not relevant in the least. Is a lightning strike from clouds I flew into on purpose any different from a lightning strike from clouds I inadvertently flew into? How is it not relevant? When I write up a plan to do anything out of the ordinary in the way of flight testing, lots of people take an intense interest in what I'm asking both pilot and airplane to do. Just a few months ago, I wanted to mount a new laser altimeter in a flight test Bonanza and get performance at 15-100 feet off the water over some large, local lakes. Got shot down because the safety folks didn't want to take an airplane that close to the water and a long way off shore . . . now, if I'd consider moving the experiment to a twin turboprop . . . my test budget wouldn't accommodate the change of machines. I think anyone that chooses to go into convective conditions (I presume he was on an IFR flight plan and got weather briefings) when the airplane is not equipped to deal with conditions that are KNOWN to reside there, the pilot is multiplying his risk by several orders of magnitude . In the case cited, he DID have vacuum gyros and the day ended on a happy note. I presume his safety committee deemed the action to be relatively low risk and his experiences bore out that assessment . . . I am truly happy for him . . . I don't think my safety committee would have bought into it. How is the experience you cited relevant to our discussion? How do we know that if he'd been equipped with a modern electrical system with multiple power sources for electric gyros that his day would have ended any differently? Bowing at the altar of vacuum systems based on anecdotal information is not good engineering. Flying into stormy conditions in a poorly equipped aircraft is not good piloting. I have never found it difficult to avoid flying into convective activity and I don't plan on needing that protection in the future. If there are builders who embrace the same operating philosophy for their airplane, my assertion is that there's no reason for them to enjoy "benefits" of vacuum systems while being deprived of the benefits of all-electric systems. Are electronics designed to protect against inadvertent lightning strikes but not purposeful ones? Of course not . . . What DIFFERENCE does it make whether the pilot purposefully flew into clouds or not? The original poster had a very valid point that, in your prejudice against vacuum systems, you ignored using this rather flimsy argument. A lightning strike is much more likely to affect electrical systems than vacuum systems. The difference was he wanted to be there and took pains to make it happen. He took the hit and survived. For myself and I believe for most builders, we take pains not to be there and probability of taking the hit is very close to zero. We all know your prejudice, Bob, and you have given a series of consistent and well thought out arguments for your favor of electrical systems over vacuum systems. Prejudice . . . ???? Really? Let's see. Webster says: 1 : injury or damage resulting from some judgment or action of another in disregard of one's rights; especially : detriment to one's legal rights or claims Nope. Nothing here. 2 a (1) : preconceived judgment or opinion (2) : an adverse opinion or leaning formed without just grounds or before sufficient knowledge b : an instance of such judgment or opinion c : an irrational attitude of hostility directed against an individual, a group, a race, or their supposed characteristics Preconceived? No, post-conceived based analysis and observations of field history for a technology that has not materially improved for over 5 decades while the alternative technologies have steadily advanced. " . . . without just ground or before sufficient knowledge." Again, I don't think so . . .been working this stuff successfully for too many years to have ignored the facts and physics of the two technologies. But you can't completely dismiss the benefits of a vacuum system, and your attempts to do so with arguments like this simply undermine your credibility. I wonder: if someone comes up with a REAL good argument in favor of vacuum systems, are you going to be grown up enough to admit someone else might have a better idea than you? Never have dismissed the benefits of vacuum systems. They were absolutely fantastic in 1950 . . . they allowed us to go off and do things in weather with reasonable confidence that the flight would not end badly. But, that technology has been static while electronics continues to improve. Bob, you're a tremendously valuable resource to the homebuilder community. I've learned a lot here that will find its way into my aircraft. But your overt bias leads me to question everything you say is a bad idea, because I'm never sure if it's a bad idea for logical reasons, or because you don't like it and are trying to justify your bias to us with meaningless argument. Bias? I admit to being ENTHUSIASTIC about electrical/electronic solutions to problems but I object to being labeled as "biased" . . . just a few days ago I worked hard to talk a guy out of doing an elaborate electronic flap control system in favor of a more ELEGANT, failure resistant mechanical system. Which of my assertions is meaningless? Here are my assertions about vacuum systems: They have a high cost of ownership; they're bulky, heavy, and require a lot of maintenance compared to their electrical counterparts. Every time I've had to pull a panel down loaded with vacuum instruments, I had to take time and extra-ordinary care to make sure open hoses didn't take a contaminant . . . I then had to worry about getting everything tight when it went back in while trying to swing a wrench in a space dominated with a bunch of hoses. In this instance, I think that purposely flying into clouds is a meaningless argument. (The rest of your post might have contained factual information, but none of it addressed the original issue: "With all the drawbacks of vacuum systems... it still kept working when all the electron powered stuff quit.") I'd hoped that my line of reasoning was founded on how most of us operate our airplanes where lighting avoidance is a high priority thereby making the argument on those grounds moot. For example: do you plan to have any form of de-icing on your airplane? Hot prop? Boots? Wet wing? If not, why not? Do you plan to have radar? How about a ballistic recovery parachute? (Hmmm . . . I wonder if anyone has considered adding air-bags to their cockpit equipment installations.) As I mentioned in the post, none of our big airplanes have vacuum systems and they get struck regularly. If one is truly concerned about lightning susceptibility in a light aircraft then by all means, have a vacuum system. Personally, I'd find little comfort for having a vacuum system in my airplane if there were strikes going on all around me and the gyros were the ONLY system on board with any demonstrated degree of strike resistance. If a builder has reasonable and considered confidence that he can maintain separation from conditions where lightning is a hazard, then why suffer the premiums for an "insurance policy" that literally sucks while adding little if any value? The decision to add any kind of risk mitigation system your airplane has to be weighed against the magnitude of that risk. How you plan to use the airplane is a major component of risk calculation. To extol what may be the only virtue of a vacuum system (resistance to lightning strike) makes no sense unless you also make the effort to shield yourself against OTHER hazards to be found in the same clouds. In spite of the fact that many of the airplanes I fly around in are tested for survival in these extremes, I appreciate the fact that pilots I ride with work diligently to stay the hell out of such conditions . . . These questions (and others like them) require answers by the guy building the airplane with consideration as to how HE and the AIRPLANE are going to operate. Only then can one deduce what equipment configuration makes sense for convenience of operation AND risk mitigation when things begin to go badly. I've oft decried the reverence with which we repeat dark-and-stormy-nights stories and run off to arm ourselves against the same scenario without understanding how the event came to pass (so that we can avoid it) and knowing what tools are available to help us out instead of reacting in classic and perhaps ill-considered ways. Bob . . .