Electrical problem

[Guest terry]

Hi all, Got a problem can anyone help. I fly a thruster t500 with a 582. No thats not the problem On a flight yesterday my volt meter and water temperture gauges started to malfunction causing some minor concern. When I cut back revs the temp and volts drops and when I increase the revs the dials go hard right. Is it an electrical short or a rectifier problem, I don't know. I've uncovered all joints and connections at the engine end if you like and can see no obvious problem. I thought I'd ask the question. All other gauges are working correctly.

 

 

[kfowler]

what other engine gauges do you have

 

 

[Guest terry]

thanks Kfowler, egt , rev counter, air speed indicater, altmeter

 

 

[kfowler]

does the rev counter still read ok

 

 

[Guest terry]

yes rev counter works fine

 

 

[kfowler]

if you own a mulit meter very carefully start the engine and check the voltage at the battery with the engine at idle with the wheels choked hand brake on some in the plane with the brake rev the engine up and read the voltage at the battery if the voltage goes over 14.5 volt it the rectifier or regulator not shore what the voltage should be set at 14.5 or there abouts the volt meter in your plane should go up to 16 volts if the volt are ok iwould check the gauge earths temp gauge earth under dash

 

 

[wanabigaplane]

Failed regulator ?

 

These symptoms would be an indicator of your voltage regulator having failed. The most common type of regulator seems to fail in a mode where full voltage is applied from the alternator, and the voltages can be very destructive indeed !

 

Normally the battery will protect your electronics from any high voltage excursions. If the regulator fails, the equipment will survive until the battery electrolyte boils off. Higher than normal battery voltages, or electrolyte boiling off more quickly than usual is the first sign of regulator failure. For this reason, a battery electrolyte level inspection should always be a part of you pre-flight inspection.

 

Jack. :):)

 

 

[vk3auu]

I had a similar problem a few years ago with the voltage regulator on a 503 powered Gemini. The battery case was transparent and you could see that the cell at each end was kaput. It was receiving raw AC from the alternator.

 

David

 

 

[Guest terry]

Hi guys, Thanks for your help Problem fixed. I bought a new rectifier and while I was installing it discovered how the original earth had been installed. I didn't think it would be good enough and so wasn't surprised the rectifier wasn't the problem. I pulled the earth out, re ran it to a different and more appropriate place and bingo every things fine. Don't know how it worked for so long. Having fixed the problem back into the air ten minutes later. gee it was good

 

Regards Terry

 

 

[facthunter]

Meters etc. going crazy.

 

As has been mentioned, a battery in good condition will limit the voltage, to about 14.5, provided the terminals are in good condition, as well as the earth wires. The easy way to test a battery is to apply a high charge rate for a brief period, (especially if the battery is slightly discharged) and see if the battery will take it. (High amperage) If it doesn't ,it is partially,or fully open-circuited, ie damaged by plate breakage.,(old age or dropping) or has sulphated by being left discharged for a while.

 

The battery is an oft-neglected part that can cause serious consequences. Especially with digital instrumentation/engine management.

 

IF the voltage regulator is malfunctioning (high) the battery will use too much water. An ammeter in the charge circuit, should drop back after a while indicating that the voltage regulator is responding to the rising battery voltage. N....

 

 

[Guest AVU]

Hi gang.

 

Just a observation on my part. A Rag and Tube type A/C (Thruster - Drifter) and the like should have a good earth/negative return from the battery to the engine. Aluminimun is not a good conductor, changing from aluminium to chrome-molly and back. The difference in dis-simular metals can, and will, set up electrolises. I mean corrosion, and hamper the earth return to the battery. Hence a 6mm earthing lead from the battery to the engine should overcome any problem with burned out components.

 

Cheers.

 

Steve

 

 

[vk3auu]

The earth connection to the regulator should also be included in the heavy wiring. If the earth to the regulator is poor, the regulator will not function correctly.

 

David

 

 

[facthunter]

Conductor.

 

Just being a bit pickey, Aluminium IS a GOOD conductor. It is used as an alternative to copper ,commonly where cheapness and lightness is a factor. Some starter motors have aluminium windings, and some welders also. To utilise Al wiring in A/C is sometimes considered for weight advantage but the difficulty of joining fine stranded wire, and corrosion are possible problems. With metals, if the metal is a good conductor of heat, it will also be a good conductor of electricity. Interesting that.. If the connections between dissimilar metals is the issue, then that point is valid, but the problem would be caused by a poor contact existing and the presence of an electrolite ie salt water etc. Nev...

 

 

[vk3auu]

It is often difficult to get a good contact between aluminium and other metals because of the oxide film on the ally. It is almost impossible to get a contact with aluminium if it has been anodised.

 

David

 

 

[facthunter]

Good Contact.

 

Good point there. I think anodising is a modified oxide with dye added for appearance. You would have to mechanically remove it, in the area where the contact is required. (pretty fiddly). I guess the point is ,that when an instrument goes wild ,check ALL connections before blaming the instrument. The only satisfactory way to do this when the part is in a corrosive environment is to undo the screw/bolt and check all the surfaces for cleanliness. What about crimp joints ?(I hate them), but they are used everywhere. cheers Nev..

 

 

[Guest AVU]

Hi again gang.

 

In my experience with the rag and tube A/C after a couple of years (2 or 3) and approx 200 hrs flight, the joints, where al the important bits hang from including the pocockpit, become somewhat bedded in. and if you pull a joint apart for inspection you will see what I mean. If your battery is behind the cockpit and the airframe is used as a earth return the ("used current") will have to flow back to the battery via bedded in joints. I've experienced a large drop in current via the airframe. with dire results on instruments (electrical). Since fitting a 6mm earth wire directly back from the battery to the engine and an axilary earth to the airframe no more problems.

 

Cheers.

 

Steve

 

 

[Yenn]

There is a technique for getting good electrical connections with aluminium.

 

Thoroughly scuff the contact area and apply BP Energrease LE or a similar conducting air sealing material. Use Bellville washers to apply a constant pressure on the connection. The grease is as specified in the Thruster handbook.

 

 

[Flyer]

Nothing wrong with aluminium as a conductor. Its cheaper and lighter than copper and is what overhead power lines are made from. As has been stated, the oxidising or anodising (2 different things) layer makes getting a good contact difficult. The way to get through the layer is to scrape it off with a file, sandpaper, steel wool etc and all will be well. watch for corrosion in that area though.

 

A point on batteries. A cooked regulator will deliver whatever voltage it likes to a battery regardless of what state the battery is in.The battery will not regulate the voltage, only smooth out the ripples. A good battery will soon be turned into a bad battery by a regulator pumping 18 volts into it and boiling it dry with obvious results. Suzuki motorcycles were GREAT at doing this...ask me how I know.....:yuk:.

 

Phil

 

 

[storchy neil]

how do you know you said ask or should i have not asked this do i need a coffe and a packet of smokes how mutch flying time will i lose

 

 

[Flyer]

distorted buggered battery (was brand new) under seat, and an overflow line that spewed battery acid over the swing arm.....and a hundred dollars or so for new bits from memory

 

 

[facthunter]

Overcharging.

 

Flyer, I didn't say that a battery would regulate the voltage, I said that it would LIMIT the voltage. Of course, if you want to put monster amps into it, it will boil the acid out of it pretty quickly, and it is then ineffective. The first indication of a regulator failure in the manner that we are discussing is a high charge current, not a high voltage. If you remove the battery from the circuit, in these circumstances (with the engine running) the system will overvolt and the filiament bulbs in use will blow and voltage sensitive components may suffer. In an aircraft, the battery charge situation should be monitored as I think I mentioned earlier. A lot depends on it, really, much more so than in your bike (though I can understand that you were not happy) Nev...

 

 

[storchy neil]

ug o new i should have put my fingers in me pocket new that some how it wold not be nice neil

 

 

[Guest AVU]

Hi Gang.

 

Re: Electrical connections, via aluminium tubing, in rag and tube A/C. My findings have been that conductivity in aluminium tubing used in earlier A/C have been lacking in a number of places.

 

1) Used in situations where the tubes, bolted on to another metal, like s/s brackets via an A/C bolt to keep them together. 3 different metals with different current potentials

 

2) Onto chrome-molly. Another metal (different current potential) back to aluminium tubing.

 

The overall connections are made to use the shortest way for the (return current) to get back to the "current" suppier namely the battery.

 

The battery which gets it's power supply, via the engine, regulator and rectifier.

 

Let's take this back a step or two, and set up a system that is (Ridged) by tighten it up to the point whereby they do not flex, (Ridgid) and cannot move it makes for a great earth return. But the joints should be flexible, the airframe should have some movement in the joints. They would come apart quite quickly with dire results.

 

I remember when, as a young un, the story about a tree that would not bend with the storm.

 

This flexing in the tubing pay's a penalty. It allows the metals to build up a barrier between the contact points (the part where the bolt joins the the bits together) the buildup of this resistance can be drastic. Sooooo earth return can and will be greatly reduced. We can of course file or sand back the anodised part of our aluminim tubes and reduce the dia. of our tubes and maintain a good earth, before the flexing starts.

 

There is no offence intended to the advise given by the members that 'qualified' the properties of aluminium and the electrical potentials it possesses, it is a great material, easy to use and work with.

 

The trick that worked for me (and still works) is to install a cable from the battery (earth cable) back to the engine.

 

Tip: If you service your own Rag & Tube A/C do not keep on tightening the bolts on the tubes (snug fit) or you will crush the tube from the top to the bolt hole creating a crack.

 

Cheers.

 

Steve.

 

 

[facthunter]

Earth return.

 

I'm with you, AVU. & 2 very flexible earth straps across the engine mounts. Unless you want red-hot throttle & choke cables, when you hit the starter. N...