In the last 20 hours of flying my Legacy I have now had 2 occasions
where the gear would not extend via the gear switch.  Flip
down....nothing.  Recycle....nothing.  Recycle...nothing.  Slow to 90
knots and prayerfully turn the gear dump switch...voila!  After landing
I can hear the pump running, so it's fine.

Both times this has happened I have been "on the road" (of course!).  I
have lifted off with much trepidation knowing that I might have to fly
home with the gear down...but then the problem goes away and the gear
works fine.

Seems to me I have a switch problem.  What say you?

Barry,

 

Probably not the switch.  Of course there would have been no reason for you to read the LNC2 e-mails over the last few years but the Legacy hydro-electric gear system is very similar.  So are the problems that can arise.  You might want to search the archives for LNC2 gear related issues.

 

Your situation might be related to the pressure switches, the pump shuttle valve installed backwards, damaged relays, back pressure faking out the pressure switch so that it thinks it has reached the right pressure, pressure switches not set high enough, etc.  But, probably not the switch that controls the relays.

 

From your description, it does not sound like you are following the emergency gear down check list.  If you don't pull the breaker(s), after the pressure is relieved the pump will continue to run until the cows come home - this is not good nor is it applying any pressure to the actuators and, if it is wired correctly, might even cause the pump thermal circuit to open the selected relay but apparently that is not the case.

 

When this happens in flight have you just tried to momentarily crack open the dump valve and return it to the closed position to relieve the possible back pressure while the gear switch is in the down position? 

 

When the pump is running does your "gear in transition" light come on?  If so, when you opened the dump valve (assuming you did not pull the breakers) did the light come on?