Mailing List lml@lancaironline.net Message #5392
From: Bill Hogarty <hogarty@home.com>
Subject: Re: 12 volts vs 24 volts
Date: Wed, 03 May 2000 07:47:41 -0700
To: <lancair.list@olsusa.com>
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IMHO, I do not believe that it is necessary to go to a 24 volts system just because you have a
500 watt hydraulic pump for the same reason that you do not go to a 24 volt system because you
have a 1200 watt starter.  As I understand the logic here, the alternator should be sized based
on the basis of "constant use" equipment and in my opinion, the hydraulic pump should not
qualify as constant use equipment.

Although I have not flown my L-IVP yet, I have completed the retraction tests and have noted
that the hydraulic pressure remains at 950 PSI in the system for over a week. (after I repaired
a few bleeding fittings); although this was with the gear down.  I did leave the pump on with
the gear up for about an hour and noted that the pressure was constant but I was reluctant to
leave the aircraft on the jacks for any longer period without the gear being down.  Maybe some
flying IV owners could tell us how often their pumps cycle in flight.

Even with the pump switched off to simulate pump/electrical failure, the gear falls nicely when
the gear handle is lowered although I was surprised to find out just how many strokes of the
emergency hydraulic pump handle  were required to get the mains to lock down.  Is this normal?
Comments would be appreciated.

Regards, Bill Hogarty N499R




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