Classic Threads . . . on the virtues of vacuum systems

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 . . . 
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     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 . . .

Comments and alternative views welcome!