Redundant Receiver Installation

[Dirt Doctor]

I have had lots of "altercations with the ground" but only one from electrical failure and that was a bad Hitec 5955 that stuck in a locked position. That locked position caused the plane to go into a full right roll that I couldn't overcome but I did get the plane pointed away from the parking lot! That servo was on the outside of a two-servo right wing - I guess the other 5955 could not overcome the pull of the bad servo. My setup was a JR 12X with one 2.4 1221Rx - with two batteries going into a Smartfly power expander. Upon inspection of the "carcass" everything worked except that bad Hitec 5955!

The only other electrical failure(s) was due to the battery becoming unconnected due to not securing it correctly (in my early flying days)

The bottom line is that electronics, especially receivers, have become very reliable in the past several years!

 

[JimD]

Doc,

As I think back, most in flight failures I have witnessed are in one of two groups. Servo failure is #1 (usually a broken wire), and battery failure is #2 (usually a broken wire or weld of cell interconnection). A distant #3 is poor installation or poor maintenance. Amazing how well our current electronics work in spite of our best efforts to sabotage them!

Agree that actual receiver failure is very rare.

 

[Robotech]

In the case of the flying half the controls, it will feel sluggish but it is fully flyable.

 

[Pistolera]

I run a very similar setup in my 42% Raven....dual 6014HS receivers, two 5200mAh batts...only they go thru a Fromeco Wolverine switch, so they will both have power should one batt fail.

I have all servos setup for failsafe in neutral position, throttle at idle. If one Rx fails, then the "dead" side of the plane should not be fighting control from the "live" side. It will be sluggish, but should be controllable, at least to steer it away from people and/or land it. Of course, I will either have a throttle and no rudder, or a rudder and no thottle, as I have these two channels on separate Rx's.

Been flying this setup for over a year with no problems....but I have yet to fly it when one side fails. It works fine on the ground though!

 

[thurmma]

@Pistolera I have my two rudder servos split between my rx's. That way if one does fail I will have at least half of my rudder throw to work with. I am using the SWB servo tray, not a direct connection between the servos.

 

[Pistolera]

Should work OK then. I have 3 rudder servos, direct linkages, so all plugged into one Rx. I sent an email to SWB asking about getting just their self adjusting links/cable/pulleys....but he would only sell them if I bought the tray. Even though my 3-servo setup is dimensionally the same.

 

[Wacobipe]

Wacobipe...Failure is always a possibility...that said, is there any way of decreasing the possibility of catastrophic failure?

After four plus decades of flying R/C, the failures I have witnessed (discounting pilot error) are either some type of power failure or some type of signal reception failure.

Having two batteries and two receivers seemed like a simple way to address these points of failure back in 1998...fortunately, I never had to test the ability of the plane to fly on just one receiver.

One of the reasons I decided to stay with this system for my giant scale 2.4GHz setups was the "brown out" issue that seemed to be an problem early on. By limiting the number of servos attached to the receiver, we reduced the amount of total maximum current draw and subsequent voltage drop thus decreasing the possibility of a brown out. (BTW, I make no claim of being an electronics wizard, just trying to state what seemed apparent to me) Another thing we did was to put the throttle on one receiver and the choke on the other so in the event of a receiver failure the engine could be shut down either by throttle or by choke.

As I stated at the outset, this is a low tech way. The PowerSafe receiver system does these things in a more high tech way and I like what they have done with this design.

As for controlling a plane with one elevator, and/or one aileron, or rudder and no ailerons...I have done this because of servo failures and/or control surface structural failures. It is amazing what will fly, imperfectly for sure, but still fly and make it back to the runway. Teaching beginners to fly (and flying the planes they constructed) gave us plenty of unexpected moments. If you want to sharpen your reflexes, spend some time on a trainer cord!

Thanks for the insight!

 

[vatechguy3]

This is a question that has confused me for some time so this provides me a perfect opportunity to try to better understand. I totally understand the setup...what I don't understand is that in the event of a receiver failure you end up with a 1/2 controllable aircraft, which seems to me not much better than one with no control and in fail safe mode. I can't believe either one is coming home in one piece...am I wrong?

I fly JR and now use their Powersafe receiver which takes 2 separate battery inputs directly into the receiver. I use no switches, and just plug/unplug batteries every flight. This provides no redundancy if the one and only receiver fails, but is as redundant as I can get without a drastically larger investment and a lot more electronics (that could fail).

This is an interesting topic and one I've never found a suitable solution to...so I am hoping to learn here.

A half controllable aircraft can still be landed safely.
i have landed a 35% carden myself when it experienced a receiver issue.
it was difficult at best but doable.

Tony

 

[vatechguy3]

Should work OK then. I have 3 rudder servos, direct linkages, so all plugged into one Rx. I sent an email to SWB asking about getting just their self adjusting links/cable/pulleys....but he would only sell them if I bought the tray. Even though my 3-servo setup is dimensionally the same.

That doesnt sound like Scott.
you could always make your own. I used to have this setup in my old 40% carden 330 before i moved to a push pull tail mounted rudder servos.

Tony

 

[Pistolera]

Tony....do you have a drawing, or schematic of the cable and pulley routing? I've never examined one and it's hard to see in any photos I've seen.