alasdair

I had an issue yesterday flying my CARF Lightning on a Spektrum DX18.

I carelessly nudged the wheelbrakes on slightly, allowing all the air to escape (one big air cylinder).
Yes I know I could fit a second cylinder, but the other option is to program the Tx so that the brake valve works (opens) ONLY when the gear is down.

I have spent hours reading the manual and fiddling with the p mix parameters but I have not been able to get it to work.

Anyone able to offer detailed advice?

Len Todd

Set up the mix so that when the gear switch is in the gear down position, the mix is active. Then set the % for the gear channel to the brake channel mix. Probably 100% to 100%.

But seriously, only one can? Also, it sounds like you do not have a good proportional brake valve. You might take a look at an Ultra Precision 1 brake valve. I pump up the brake tank, which is very small, about once every 20 flights or so. Sounds like you got one of those cheap electronic brake valves that takes a whole tank of air for one stop. a UP1 will stop that and would preclude the problem you experienced, even with one tank!

RAPPTOR

My Feedback: (41)

Feed brakes, from gear air ,only when down

quist

My Feedback: (198)

I have my brake valve air supply coming from my gear door open supply line. Works great.

stuart_80

Alasdair,

On my Ultra Flash I have one air tank. I have a program mix that mixes down elevator with the brakes, but only when the gear switch is in the "DOWN" position.
My retracts and brakes are actuated by a mechanical valve & servo

I cannot not get my iPad to post photos on here, but if you PM me your email, I can send them. It's just some screenshots of my Tx screen showing the mix. It's the JR DSX-12, but hopefully it gives you the idea

Nice to see you at the weekend
Stuart McCallum

i3dm

My Feedback: (51)

you can also do this trick - when gear is in UP position:
mix brakes --> brakes with -100% / -100%
this will leave the brakes channel comptely off, at 0% position (middle of travel). then add offset to move as you like to be at lets say -100%.
Done! permanent -100% on brakes channel with ease, when gear is up.

alasdair

That is a great idea. I'll do that from now on.
I didn't build this jet with just one air tank and the two Jet Tronics valves, a double for gear and single for brakes.
I bought it second hand, and to be fair this is the first time I have had this brake problem in 8 years.
I started with a Weatronic dual Rx with GPS controlled by a JR 388S but changed to a Spektrum DX18 with AR12020 when they came out.

changing the air supply will do the job, but I would still like to learn more about programming the DX18.
Is there a source of detailed step by step instructions (e.g. website)

i3dm, I have tried to fit those numbers into a Mix but it doesn't work and I have no idea what they do, which doesn't help.
Are the workings of these mixers explained ANYWHERE?

alasdair

isn't there a "DX18 Programming for Dummies" available????