This just in from my club. Thought it was worthwhile posting here. I only edited names:

Greetings:

I wanted to pass this important information along just in case you didn't know. I didn't, but then no novice flyers want to fly mode 1 so I've been spared the experiencee! This situation almost caused a crash at the field on a recent Saturday. Submitted by xx with some edits by xx.

As a result of a near-crash experience at the field recently, I've run some tests on the use of a trainer (slave) transmitter on a buddy cable. As is usually the case with most buddy box set-ups, the slave transmitter was on a frequency different from that of the master unit. I running some tests "after the fact" I found that the slave transmitter will only work (as a slave) when the crystal and battery are installed, so removing the crystal or battery doesn't solve the potential problem. If the on/off switch on the slave transmitter is inadvertently turned on, even though it's attached to the master transmitter via the cable, the slave transmitter will still transmit RF on its frequency. If someone were by chance flying on the slave transmitter's frequency at that moment, oops! We were very lucky that a crash was avoided! Thank goodness it was xx, whose very agile thumbs saved the day ... and his plane.

As a result of this sitatuion I found that if the slave transmitter is on a frequency different from the master transmitter, a novice holding the slave transmitter can cause a potential problem for someone flying on the slave transmitter's frequency by turning on his slave transmitter. (Would make sense to the novice to turn it on so it works, right?) To avoid this problem in the future I now have put red tape over the on-off switch on the buddy box and will instruct new pilots using the slave not to turn that switch on under penalty of severe flagilation or death, whichever comes first! DX7 anyone?

I don't know if this is true with all slave/master transmitter connections, but it certainly was true in this case. I was there at the moment of epiphany. Our thanks to xx and, of course, to Quickie xx for "exposing" the problem.

xx.

You sure the buddy box (slave) students box, whatever, wont work with the crystal out and or the battery removed? I thought with the trainer switch held to the trainer position all you were doing was using the gembals on the students box (the one the student holds) I sure at the old field I flew at we had a buddy box with out a crystal. Are you using JR?
Antway thanx for posting the important thing to stress.... as i did to my students "leave your box off"

How trainer functionality works varies from radio manufacturer to radio manufacturer. Your mileage may vary.

I just remove the battery from the buddy box to prevent anything like this from happening. This applies to all but JR buddy boxes because those need to have a battery in them in order to work properly.

Ken

Hi

I usually remove the crystal from the buddy box unless i know no one else is using that frequency.

Dosn't actually need its own battery either, i'm usually using futaba.

You can still teach people mode 2 if you are on mode 1 with a buddy box, have used ths method several times to allow people to have a go with a plane which is set up on a different mode to what they normally fly.

Simon

Could just have the student pull the frequency pin for the transmitter frequency... He needs to get in the habbit anyway.

Wasn't me. I just got the club e-mail. Here is a follow-up e-mail, and a very thoughtful one at that:

Guy’s,



It’s the responsibility of the (Teaching) pilot to understand how the Buddy Box system operates not the (Student) Pilot. It is the responsibility of the Teaching Pilot to make sure the system is working properly before handing over the Buddy end to the student. It is the responsibility of the Teaching pilot to ensure all of the throws are correct, the trims are centered to the master transmitter and that the throttle is set to a position that will not kill the engine once the system is turned over to the student, usually half throttle. The Student never touches the left stick until instructed to do so.



Buddy box types:

1) Purchased Buddy Box matching the Master Transmitter.

a. This system is pretty foul proof, no batteries, on/off switch and no antenna is supplied. No possible way to create a second RF signal.

b. There is one system problem with this scenario, if the master transmitter is a high end unit and complicated programming is used (Duel Rates, Expo, Mixing etc.) the buddy transmitter will not operate in the same manor. The buddy box will only function at full rates not the programmed rates of the programmed master transmitter. Maybe some systems will handle this situation now?

2) Borrowed Transmitter and Trainer cord (most common scenario)

a. This is probably the system in question, FULL FUNCTIONING TRANSMITTER! This is OK if the Teaching pilot knows how to set it up!

b. Remove antenna from Buddy Transmitter if possible

c. Ensure Transmitter is turned off and stays off !

d. Check Throw directions (Buddy Transmitter), Up is Up, Right Aileron is Right, Nose wheel and Rudder are correct ETC.

e. Ensure control surface movement matches Master Transmitter

f. Ensure Throttle is working correctly! Check to ensure the closed and open positions are correct! Check to make sure the idle trim is set to match the Master Transmitter.

g. Pre-engine start check: Flip the Trainer Switch on and off observing each function (control surface & Thorttle) does not move! If a surface twitches or jumps STOP and adjust the problem.

h. Everything checks OK ?

i. Start Engine, Ensure all function work properly (Teaching Pilot) responsibility!!!!!!!!!!!

i. Check throttle is set properly when Trainer switch is activated.

ii. Ensure engine well stay running at idle position, Buddy Transmitter.

iii. Buddy switch off set Buddy Transmitter throttle to half, do not allow Student to touch controls until plane is airborne.



NOTE: If the Plane Crashes it is 100% the INSTRUCTING PILOT’S Fault!!!!!!!!!!!!!!! . (not due to mechanical failure)

The instructor can resume control of the plane by the release of the trainer switch! The Teaching pilot must establish his recovery parameters, plane height, plane attitude before attempting the first flight.





If I’ve missed anything please fill in the blanks!



I hope this helps those to follow.



xx

I use the buddy box system and it works well. I take the crystal out of the slave {students} and place it in my trans. I hold the trainer switch in when student is flying and let go of switch if he goofs up

JR, Futaba, and Hitec will all work with the battery removed from the Buddy Box. Airtronics, on the other hand, requires a charged battery in the buddy box. Not sure about the crystal.

Our club has four buddy boxes, none of which has a battery or crystal. These are the boxes I use with any student training at our club, so even if the student does hit the switch, nothing happens.

Brad

JR Will NOT work without a battery in the slave. The cord connecting a JR master and JR slave does not carry power. I know this because i use exclusively JR products. I will not comment on any other system that I do not have first hand knowledge of.
However, i also know that JR will work as a slave without a crystal as I took the crystal out of my quatro and just left the battery in. It works fine as a buddy box. However, without the battery, nothing.

This doesnt make sense, I use the JR buddy box system and the slave does not have a crystal, how is it going to transimitt on that frequency with no crystal?

I've had no problems using the JR system and the JR does require a battery.

The JR slave/buddy can NOT transmit without a crystal or module depending on the model used. I've used regular JR transmitters as buddies as well as the Quattro trainer buddy. Both require batteries.

Futaba does not require batteries in any that I have used as yet. No xtal needed but OK to have if power switch is OFF. Anyone buddy with a 14MZ yet?

I've buddied an Airtronics but it's been so long I can't recall the circumstances.

correct
All JR's require a battery to be a buddy box. However, they do not require a crystal.

jr to jr the slave does not need a crystal only a battery . the crystal goes into the master

Bkdavy,
No, Airtronics do not require the battery in them to work as a buddy box. I've got 3 Airtronics buddy boxes (all I fly is Airtronics) and I have the battery and crystals taken out of all of them. It's JR that needs to have the battery in the buddy box to work.

Ken