Andres, I've had your melted lens on display in my office for a while
now.  Let me know if you'd like it back.  It's a great conversation
piece!

Dave Saylor
AirCrafters
140 Aviation Way
Watsonville, CA 95076
831-722-9141 Shop
831-750-0284 Cell



On Fri, Jan 20, 2012 at 6:42 AM, Andres Katz <bu131@swbell.net> wrote:
> I have been struck while flying twice, once it melted the lens on the iv-p
> and blew open the wing extension, the second time in a 737 landing in dfw,
> Once in a million? I guess I am unlucky
>
> Sent from my iPad
>
> On Jan 20, 2012, at 7:06 AM, Gary Casey <casey.gary@yahoo.com> wrote:
>
> Just a quick comment on the redundancy issue.  I read the comment that a
> vacuum system is not a good candidate for a back-up because of the known
> poor durability of most vacuum pumps.  But that doesn't by itself reduce
> reliability.  What happens if one has two electronic systems and both get
> disabled by a lightning strike?  Say there is a one in a million chance of
> getting struck by lightning and there is a 1 in 2 chance that both systems
> will be disabled.  That says that there is a 1 in 2 million chance that you
> will have a really bad rest-of-the-day.  Now put in a vacuum system that
> will absolutely not fail as a result of a lightning strike.  There is, say,
> a MBTF of 500 hours for the vacuum pump(I think it is more like 1,000
> hours).  It will take maybe 30 minutes to get on the ground after the
> lightning strike takes out all the electronics.  What is the odds of the
> vacuum system failing in that 30 minutes?  Presumably 1 in 1,000.  So the
> odds of the electronic system failing AND the vacuum system failing in the
> next 30 minutes is 1 in a million times 1 in a thousand, or 1 in a billion.
>  You only need the vacuum system to keep working for the time it takes you
> to get to the ground.
>
> So the all-electronic system will have a 1 in 2 million chances of killing
> you, while the combination of an electronic primary and the not-as-reliable
> vacuum system has a 1 in a billion chance of killing you.  500 times better
> than the all-electronic system.
>
> That's why I have an engine-driven vacuum pump and a vacuum AI in mine,
> along with the electronic EFIS.
> Gary Casey