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Date: Tue, 10 Feb 2009 00:50:05 -0500
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From: David Standish <carbonflier@bresnan.net>
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Subject: Re: [LML] Legacy Canopy Down & Latched Indication
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Valin & Allyson Thorn wrote:
>
> Hey Legacy pilots and builders,
>
> There have now been two Legacy crashes, including the loss of a fellow 
> pilot, apparently from canopy openings on takeoff. I’m sure we’d all 
> recognized even before these losses that the standard Legacy canopy 
> latching system can easily mislead a pilot that it is closed but not 
> be latched down. And, with these great visibility bubble canopies, but 
> hot green house effects, the canopies are usually propped open on the 
> ground and not closed and latched until just before takeoff. This 
> makes it fairly likely that every Legacy pilot at some time, with 
> fatigue or distractions, may not latch the canopy down before takeoff…
>
> Given this probability of occurrence, we’ve been planning to use 
> simple micro or proximity switches on both the canopy and the latch 
> mechanism to control an indicator/light on our instrument panel as a 
> secondary and hard to miss canopy configuration indicator. It would be 
> red whenever the canopy is not down OR not latched. I haven’t yet 
> decided if it would be good to have it green when the canopy is down 
> and latched.
>
> Anyway, I just wanted to share this with other pilots and builders 
> that are thinking about how to mitigate this in flight canopy opening 
> risk after the second accident from this (apparent) root cause. This 
> kind of set up should be a very easy retrofit for flying Legacy 
> airplanes, too.
>
> Valin Thorn
>
> Legacy
>
> Houston, TX USA
>
> http://www.starflight.aero/legacy/
>
> P.S. Also, if you do the mod we worked up a few years ago that props 
> the canopy open when you unlatch the canopy (so you can get your 
> fingers under it to open it) you get another more clear indication 
> that the canopy is not latched… Don Barnes has this info on his website:
>
> http://www.lancairlegacy.com/tips_canopy_fixes.html
>
On the door of my IV a contactor closes when the door is in the closed 
position a micro switch detects the door latch position so that the 
circuit is complete when the door is properly closed and latched. This 
circuit powers a micro relay that opens when the door circuit is 
complete and closes when the door is open or unlatched. The relay in 
turn powers a red annunciator light near the middle of my scan on the 
panel near the gear lights. This would probably work great on the Legacy 
canopy.

David