![]() |
If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
|
#1
|
|||
|
|||
![]() "Greg Reid" wrote in message om... I've installed a 12-gallon fuel cell aux tank in the tailcone of my 4-place conventional low-wing plane -- intended for go-fast trimming when flying solo more than for its extra fuel capacity. As you know, a typical 4-place is terribly nose-heavy with only front-seat passengers and no baggage. The tank would be emptied if flying with a full load of passengers and baggage. Greg, Thats a bunch of weight and complexity to add for trim fiddling. I can see the benefits but think that a fixed/removable ballast bar bolted to somewhere around the rudder post weighs less, is less complex, gets you 90% of what you are looking to achieve and has no failure modes that would be critical to flight. Make a bar for solo, one for 2 up. Some certificated gliders and helicopters do it this way. But I'm afraid it might be too simple.......... Scott |
#2
|
|||
|
|||
![]()
Hey guys, thanks for all of the commentary/concern ... and sorry I've
been remiss in responding until now. Thanks in particular to Bruce for going the extra mile and a half in actually hooking up and testing to see if you can pump backwards thru a typical Facet pump (nope). A simple "gear motor" mentioned elsewhere is what I need, I suppose, so that the single pump could pump both ways (with polarity reversed). I could add an on/off valve (manual or electric solenoid) to complete the single-pump-and-single-tube hookup. Such gear motors are typically found in cheap hardware-store siphoning pumps that let you drain or fill your auto crankcase via the dipstick tube (turned by an electric hand drill). I wonder if I can find one of aircraft quality somewhere. I did find the ppavionics site mentioned. That's the link I mentioned having found (and then temporarily misplaced) earlier. They've got a Facet pump model that contains internal valving to prevent flow in either direction when off. So they could be used for a two-line and two-pump setup for "fill" and "drain". I found some other stuff on their site that seems "interesting", and wrote them (no response as yet). (And no, I have no financial or other interest.) I just want to assure you all that even when the aux tank is full, I'll still be within rear CG limits ... barely. I wouldn't really CHOOSE to take-off or land (or do intentional stalls) at that rear limit, but it WILL be possible to do so safely. I'm currently leaning towards the obvious two-line and two-pump arrangement, but am still on the lookout for a lighter/simpler alternative using a single line and single pump. As I mentioned earlier, it's easily possible to use a single line and a single pump to fill and drain (with the pump always running in its normal mode) by using a stacked selector valve as used with a fuel-injected engine, and a bit of fancy cross-plumbing of the valve ports. This is basically trading the expensive selector valve for the second pump and line. It might be a little lighter and somewhat less complicated. Someone else suggested much earlier using a single pump to fill and a "bypass valve" to drain by gravity. That's an excellent and simple solution -- if I could trust that gravity alone will drain the tank within a reasonable length of time. I need to do a simple experiment to find out. Thanks again for all the comments, Greg |
Thread Tools | |
Display Modes | |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
Hot weather and autogas? | Rich S. | Home Built | 33 | July 30th 03 11:25 PM |