Flap up limit stop switch

[gasman]

Originally Posted by decathlon737

I'm about to install a micro stop switch in the flap system to stop motor from running in case I forget to turn it off on my Infinity grip. My question is, once the switch trips and opens the circuit, how do I restart the motor downward with the circuit open? Seems one would need both circuits closed before the motor would operate again. Probably is simple but I'm drawing a blank on this one. Thanks in advance.
Bill Woods
RV8 QB
IO 360 A1B

have a light that will tell you that power in applied to the flap motor? KISS... Are you worried that you will hold the switch on too long?

Van used this type of drive unit so you would not have to install limit switches.

[vlittle]

Originally Posted by gasman

have a light that will tell you that power in applied to the flap motor? KISS... Are you worried that you will hold the switch on too long?

Van used this type of drive unit so you would not have to install limit switches.

The idea of the limit switch is that if you have to dump flaps for a go-around, or after touchdown, you can flip the switch [an (ON)-OFF-ON] type and let the flaps come up on their own without holding the switch in the UP position. This frees your right hand for other useful functions.

I had a flap light that showed me whenever the flaps were running, but this was not good enough to prevent me grinding the gears out of the flap motor mechanism. I suppose that if I had installed the flap motor properly this may not have happened. Nevertheless, the flap limit switch for the UP position is very useful, for the reasons stated above. Some Cessnas work this way.

I also used the same limit switch to build a "Flaps Deployed" alarm that provides an audio tone whenever I exceed Vfe with the flaps extended. In my 9A, Vfe is only 78 knots, so you have to be careful.

I haven't commercialized the flap speed warning alarm, but it involves a microprocessor listening to the Dynon output stream. One could also use a pressure switch on the pitot/static system, but that's more complex.

V

[az_gila]

Originally Posted by vlittle

The idea of the limit switch is that if you have to dump flaps for a go-around, or after touchdown, you can flip the switch [an (ON)-OFF-ON] type and let the flaps come up on their own without holding the switch in the UP position.
.....
Nevertheless, the flap limit switch for the UP position is very useful, for the reasons stated above. Some Cessnas work this way.

IV

This is exactly the operation of the flap switch in my Grumman Tiger... and is quite convenient as Vern says.

gil A

[Rivethead]

Vernon Littles' Schematic exactly shows the wiring for the switch. At first I didn't get it but after giving myself the two minutes of attention it needed it exactly shows the wiring I've been trying to describe all afternoon. In that schematic the micro switch is completely removed from the up flap circuit allowing it to reset itself as a closed circuit for it's next use. The diodes are a nice touch.

[Walt]

The hardest part of this is the installation and adjustment of the switch. Pretty hard to get it adjusted so the flaps stop exactly when they should. To soon and they are not retracted all the way, to late and the motor continues to run (except now you are not aware of it). These style micro switches are not really designed for precision adjustment and repeatability. Personally I like my flap switch just the way it is, it's simple and easy to get to with my thumb while my hand is on the throttle. Just my 2c.

[az_gila]

Originally Posted by Walt

...
These style micro switches are not really designed for precision adjustment and repeatability.
....

Similar switches are used for the retractable gear in many (most?) certified aircraft....

gil A

[Walt]

Originally Posted by az_gila

Similar switches are used for the retractable gear in many (most?) certified aircraft....

gil A

True enough, and I didn't say they weren't reliable but it's the adjustment that is the problem for the RV. On most retract these switches are activated by the break over of the drag links or some variation which is far from a "fine" adjustment. Trying to get your flaps to stop at exactly "0" degrees (I don't want my flaps at 2 or 3 degrees at cruise) is a different matter than a gear activated switch. If you've done it and it works for you that's fine but for me it just seems like more stuff that really isn't necessary.

[gasman]

Originally Posted by Walt

The hardest part of this is the installation and adjustment of the switch. Pretty hard to get it adjusted so the flaps stop exactly when they should. To soon and they are not retracted all the way, to late and the motor continues to run (except now you are not aware of it). These style micro switches are not really designed for precision adjustment and repeatability. Personally I like my flap switch just the way it is, it's simple and easy to get to with my thumb while my hand is on the throttle. Just my 2c.

If you need it, you could time it out with a time delay relay. The flaps go all the way up, the clutch slips.... the relay counts down a second or two then shuts off. You could get away with a correct size capacitor instead of the relay....................................

[az_gila]

Originally Posted by Walt

True enough, and I didn't say they weren't reliable but it's the adjustment that is the problem for the RV. On most retract these switches are activated by the break over of the drag links or some variation which is far from a "fine" adjustment. Trying to get your flaps to stop at exactly "0" degrees (I don't want my flaps at 2 or 3 degrees at cruise) is a different matter than a gear activated switch. If you've done it and it works for you that's fine but for me it just seems like more stuff that really isn't necessary.

Walt... it's just a matter of making a fairly solid mount for the switch (solid, not heavy.. ...).
The end flap positions (up and down) on my Tiger are set by microswitches bolted onto brackets that have slotted holes. They are activated by the traveller on the flap drive motor worm drive.
I believe this is fairly typical, and should be easy to replicate on a RV. These switches are built to activate at a consistent mechanical position.

gil A

[vlittle]

Originally Posted by az_gila

Walt... it's just a matter of making a fairly solid mount for the switch (solid, not heavy.. ...).
The end flap positions (up and down) on my Tiger are set by microswitches bolted onto brackets that have slotted holes. They are activated by the traveller on the flap drive motor worm drive.
I believe this is fairly typical, and should be easy to replicate on a RV. These switches are built to activate at a consistent mechanical position.

gil A

The secret to getting a fine adjustment is to use a large lever switch (such as the one in the schematic) and fabricate a mount that places it a long way out on the actuator arm of the flap. A fraction of a degree then has a lot of linear travel, making it easy to adjust and repeatable. I wish I had a photo, sorry.