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I am installing my flap switch in my Stol CH-750 with dual sticks and a center mounted throttle and I am trying to decide what type of flap switch to install and I am looking at two different paths.
-The first way is to use a switch that is OFF in the center and MOMENTARY on in both the up and down position.
This would allow me to put the flaps down and up as much as I needed , which allows me to slowly bring the flaps up in a go-around. BUT, I have to have my hand on it the entire time the flaps are coming up.
-The second is a switch that is OFF in the center and ON in the up position and MOMENTARY on in the down position.
This would let me put the flaps down as much as needed and in a touch and go, I would simply switch it UP and the flaps would retract and the flap motor limit switch would stop the flaps in the up position.
Which is the best way to go?
Hi Jeff, thank you for the reply and schematic. I may not have the correct idea of the switch connections according to your schematic. My motor has internal limit switches for sure. I bought a switch that has 3 prongs, so, it looks like my switch will not work. I haven't got to the stage of hooking it up so I didn't realize it yet :) .
You schematic will be a big help, thank you!
Update... Below, Jeff posted a 6 terminal switch that should work. The one I posted above should be disregarded,
I owned a Grumman Tiger for five years in the 1980's and it is a wonderful airplane. The Tiger (and all the Grumman/Gulfstream single engine planes) use a flap switch exactly like what you describe - center off, down spring loaded back to off, up locks in place. The arrangement works wonderfully, in my opinion. The electric flap retraction is slow enough that the plane tends to accellerate at a pace that matches up with the flap retraction pretty nicely, it went well every time I did it. If you do think you might be retracting flaps faster than is safe, all you need to do is put the flap switch back to the middle for a moment to stop the flap retraction. Once you have gained a bit of speed you can then pop it back into the flaps up position and let it finish the job on its own. The "stay in the retract position" function is also very nice during touch and go landings, just pop the flap switch to up and let it do it's own thing while you reset the trim and scan the departure track, then do a no flap takeoff.
Grumman did publish one caution that would be relevant to this discussion -- if, while extending the flaps, the pilot jerks the finger off the swich and lets it snap back to the center "off" position, there is a chance that inertia will carry the switch handle through the "off" detent and pop it into the flaps "retract" detent. Once in that "retract" detent it stays there so you can end up with your flaps retracting without your being aware of it.
The Grumman solution was to direct the pilot to PLACE the flap switch back to the middle "off" position rather than let it SNAP back into position. I think this would be a wise procedure to use in a Zenith equipped with such a switch. The problem gets more possible, by the way, if you have a flap shaped handle (which adds extra mass to generate extra inertia when letting the switch snap back to the middle) attached to the flap switch toggle as shown in the photo that accompanied the initial post for this discussion. The Grummans have a flap shaped handle attached to the toggle also, as do the big planes I flew in the military and airline - it is a good way to confirm by feel that you have the correct switch, I like it and plan to give my flap switch that style of handle. I plan to give the landing light switch(s) a special shaped handle also so one can confirm the right switch by feel. Being able to grab, confirm and operate the flap and light switches by feel can be very convenient in challenging approach situations.
Bob, thank you for the very informative post! You discussed some very important details about the switch operation. I didn't think about the simple act of just placing the switch back to the off position in a go-around and stopping the flaps from going up to fast. Thank you again!
I think either flap switch will work just fine. I flew with slats for a while, but most of my experience has been without slats. The "slat people" comment quite a bit that "they hardly ever use their flaps," so you'll be fine whether you deploy the flaps or not! Haha! If you go the "slatless" route, you'll find you DO use the flaps a lot more, but it is no big deal in a go around because the 750 will climb just fine with full flaps deployed! In fact, it's another one of those weird-but-fun things you can do in a 750: do a full-flap take-off - the darned thing goes up like you're in an elevator! :>)
For the above reasons, that's why you'll be be fine whichever flap switch appeals to you!
P.S. ... It's past time that I fly up again to check on your build! :>)
John, I hoped you would chime in! Thank you for the info. I will not be using slats, so I will using some flaps then.
I will be using the up ON switch then, makes more since to me!
I hope to have my first engine run in a month, maybe you could fly up around this time and give it a good eyeball! I would love to see ya!