Common causes where to look.....

[IceAge]

I hope someone can point me in the rights direction regarding fault finding on electical system on 582....... What are the 'common' places to look for shorts without stripping all electrical wiring.

My problem is that I have serious problems with comms due to a short somewhere which I cannot find. My rationale is that the radio and intercom system work 5/5 when the engine is not running. The moment I start the engine I hear incoming conversations at 5/5 but the moment I push the ptt the system makes the weirdest noises and my conversations are less than 1/, ie. totally unreadable. I have had the intercom system serviced as well as the headsets. I have also tried to the system by removing the intercom completely, ie. plugging the headsets directly to the radio (pilot iii) and the same happens when the engine is running. I have also tried with both the V-Rabbit antenae as well as the standard on that comes with the radio with the same result.... I have also eliminated any power source to the radio which normally charges from the standard 12v charger that yeasu provides...........

My conclusion is thus that the only other problem I can think of is that there must be a short causing the issue and thus my question to pilots who have been there before where is the most common places to look for shorts......

Any constructive advice will be highly appreciated as I cannot fly my trike without comms.......

Thanks
Deon

[nicow]

Do you use the right spark plugs and suppressors?That sounds like a spark plug,plug wire or suppressor problem...

[Slabfish]

Deon,we are going through the same scenario at the moment with the Jora we just sold to Deon in Barberton.
What happened is that I thought I had a voltage regulator problem and it was replaced with one from the agents the day before I left Paradise Beach on the delivery flight to Barberton.
I was disgusted in the fact that my coms had gone from perfect before to the same as you`r describing .
The new owner had first fitted a capacitor and now bought new expensive headsets but the problem persists.
After a lot of thinking I came up with the following.
1. The old voltage regulator was bought as a pirot part from somebody else than the agent when the aircraft was built as the agents never had stock. This regulator had a big capacitor visibly built in. Whereas the new one we got from the agents now was the Rotax regulator with no viable cap .
2. When fitting the new regulator I noticed the wiring was different. I phoned the agents and was given the correct way to do the wiring---but they instructed me to fit a earth wire from one of the new regulator`s wires to the engine block, which I did.
Now after a couple of weeks of picking up the problem and thinking about it I came to the conclusion that the only thing that changed since the coms where working well was the regulator and importantly --- the added earth wire !!
So I told Deon to remove the earth and or I will send him the old regulator to try.
This has not been done yet but I have a feeling that we are going to get a surprise when removing the earth wire as the old regulator had no earth wire and this is the only variable since before when the coms where working perfect before the change.
All this said, I hope you can see what I`m getting at here, think you must start looking at your regulator if there is an earth fitted or not ?
Hope you come right as it is a very frustrating problem to not have descent coms.
Regards
Clem

[IceAge]

Hi Gents,

Thank you for the feedback I will check and see...

1) Nico I only use the recommended rotax plugs which has never caused any problems before and I have not replaced in a while now either, ie. replaced at 200 hours and trike now about 215 hours. However, the rke did stand for a a few month (four to be exact) during my conversion and hour building on the Savannah hence it could be that there might be a problem there. I will remove, check and replace the plugs if required and also check all the plug wires in the process.
2) Clem I have not replaced any parts as yet but as mentioned above due to the trike standing for a period it could be that the regulator is faulty. I have heard of electrical faults occuring due to non use before but have not experienced it first-hand yet.

Maybe soething else that could have caused a short was the fact that I washed the trike before flying and there could have been some moisture in the connections/components at the time of testing. This has however never been a problem in the past but in my view worth investigating.

Thanks for the feedback.

Fly safe
Deon

[salem]

I have the same problem except that I can hear and transmit 5/5 while idling but the moment I increase the revs I can still hear what others are saying 5/5 but cannot hear myself when I transmit. This makes it difficult to diagnose with the 582 running at high revs. IceAge please let me know what you find.

[John.com]

This is a very good source: Rotax Aircraft Engine Electrical System Troubleshooting

Good luck!

[mulderpm]

IceAge, it is always very difficult, if not impossible, to fault find using written descriptions, but I can share my thoughts/guidelines.

Mostly the cause of the problem with radio interference is either from the electrical side or from the air interface side.

Regarding the electrical side the golden rule is that all earthing/electrical air frame connections, must be as short as possible and all to one single point, or to as few as possible. This prevents earth loops and thus electrical interference.
1) Make sure your battery negative is electrically connected to the engine block. This is done by means of a thick cable (8mm²) from the battery negative to the engine block.
2) Make sure your engine block is electrically connected to the airframe (engine mount). This is done by means of a flexible copper braid which bypasses the rubber mounts of the engine.
3) Make sure your radiator is electrically connected to the airframe. This is done by means of a flexible copper braid which bypasses the rubber mounts of the radiator.
4) Make sure that there is a thick (6mm²) wire between your engine mount earth point and your instrument panel earth point. Connect all your internal instrument earth wires to this point in the console and do not connect this to the airframe at this point (only at the back engine mount point).
5) Make sure your radio antennae base is well connected to the airframe. Make sure the screen of the RG58 coaxial cable is well connected to the base/airframe of the antennae.
6) All earth points must have as low as possible resistance between each other, not exceeding .5 Ohm.

Also, make sure your spark plug caps are resistor type (5K written on cap) and that you use resistor type spark plugs, (BR8ES.

Regarding the radio side the golden rule is that the Standing Wave Ratio (SWR) must be as low as possible. This is a measure of the impedance matching of the load (antennae) to the characteristic impedance of a transmission line (coax) or in other words, is the ratio of the forward power to the reflected, reverse, power. All our installations are 50 Ohm impedance antennae systems. To measure the SWR one should connect an SWR meter between the antennae coax and the radio and push the Push To Talk. The length of the antennae determines its impedance and therefore the SWR. The closer to a 1/4 wavelength (600mm) the closer to 50 Ohm. If you cut the antennae wire to 596mm it should be perfect.

All cables of the intercom system must also be well screened and decoupled (ferrite beads) to prevent any Radio Frequency interference from entering via the cables. If your intercom gets its power from the aircraft, make sure it is earthed at the earth point in the console mentioned in (4) above. It will also help to move the antennae as far as possible from the intercom system.

Hope this helps.