Copalum splices are used to connect copper to copper, copper to aluminum or aluminum to aluminum wire.
We use copper and aluminum wire in aircraft for power feeder lines (generator power lines to provide the aircraft with electrical power).
The copper wire is relatively flexible, very heatresistant and it is a very good conductor. Aluminum on the other hand is very light and for aircraft, this is a important factor.
With these material properties most manufacturers choose copper wire for the engines, these are considered hot and high vibration areas and not well suited for aluminum, the aluminum usually runs for the majority of the length of the aircraft to save on weight.
Because the aluminum wire is not as good a conductor as copper, the conductor thickness (AWG size) must be thicker than the copper wire to maintain the requirements of the wire for the power that needs to be put through the wire.
The copalum splice is a way of crimping copper to copper, copper to aluminum or aluminum to aluminum.
The die sets used for copalum crimps are:
Gauge 8: head 69066, die set 68006
Gauge 6: head 69066, die set 68007
Gauge 4: head 69066, die set 68008
Gauge 2: head 69066, die set 68009
Gauge 1/0: head 69066, die set 68010
Gauge 2/0: head 58422-1, die set 68011-1
Gauge 3/0: head 58422-1, die set 59877-1
Let's look at some power feeder lines on a 737pg. For the purpose of this demonstration let's say that the aircraft effectivity is 001.
U can see that there are three power feeder lines coming off the generator, the first section is a copper gauge 6 wire, it then goes through a engine firewall disconnect area. This leads the power feeder wire into the pylon area where the wire thickness becomes thicker, gauge 4.
The wires then pass through the wing disconnect area where the wires sizes step down to 6 again. The wires are then fed through the pressure seal, behind the pressure seal the copper gauge 6 wiring is spliced with factory copalum splices to the gauge 4 aluminum wiring.
Here u see these manufacturers copalum splices right behind the pressure seal as indicated on the schematic.
The wires then run a long length through the aircraft to a generator circuit breaker.
The generator circuit breaker is controlled by it's generator control unit. For now it suffices to say that with flightcrew selections and generator control unit inspection on the quality of the electrical power, the power can be selected on a variety of electrical busses.
The gauge 4 aluminum wires connect to the generator circuit breaker with copalum terminals.
The generator circuit breaker is actually a heavy duty 3 phase relay that can connect the electrical power to the electrical busses.
Most large passenger aircraft have generators on their engines and on a onboard Auxilliary Power Unit (APU).
With multiple generators, load shedding systems, DC power from batteries, AC power from a battery inverter large aircraft should allways have sufficient electrical power to power their most important systems.
So let's say that a gauge 6 copper wire has been damaged, it chafed against structure, shorted out and a piece is burned away.
Let's also say that the wires burned out on a outstation with very limited recources available and that we have to go there to repair the aircraft.
We now have to find out if we are allowed to repair this wire or if we have to replace the wire. We go to the Standard Wire Practices Manual (SWPM) 20-10-13 to see if this is repairable.
Looking at the general info section usually tells us where we need to look, this saves us reading the whole index to find what we need.
We find the table II
Quickly back to the index to find the page number.
In this paragraph we find the damage limits, in our case any damage to the conductor requires repair with a splice.
The SWPM refers us to 20-30-13 for the repair procedure.
The general conditions apply to all wiring repairs and are found in paragraph 1
Wire repairs are permanent unless stated otherwise in the applicable repair procedure.
For example, according to the general conditions at this time, a wire repair with a splice can be a permanent repair, however if the splice is on a engine, the repair is by definition a temporary repair and the wire must be replaced within 500 flight hours.
Our damaged wire is not damaged on the engine however and we are therefore not bound to this time limit.
According to the general conditions it is recommended to replace the wire but in our case that would be very time consuming and may be impractical especially if this happens on an outstation.
In this case we will opt for repairing the wire with a splice, according to the general conditions there are many requirements to be met.
For example, a maximum of three splices in any standard wire, the temperature grade of any of the materials used must be equal or higher than that of the wire, if the repair is in a hot section the temperature grade must be grade D, if a segment of wire is put in it needs to be the same partnumber as the damaged wire etc. etc. etc.
READ this section carefully before starting ANY wire repair on a aircraft.
Now we are armed with the SWPM that we are allowed to repair the damaged wire but we aren't there yet.
We need tools, splices, gauge 6 copper wire, shielding material, etc etc.
So let's find these materials in the manuals.
To get the wire we go back to the Wiring Diagram Manual. I see that the wire number is W142-002-06.
We go to the wire list in the WDM and find that for our effectivity (001) W142-002-06 has Wire Type Code CQ (WTC CQ).
With this code we go back to the SWPM, chapter 20-00-13.
In the wire type codes section we find the WTC CQ.
The wire we need is BMS13-58T01C01G0. This is high temperature resistant wire.
If this wire isn't available we can use a alternative wire.
Alternatives can also be found in the SWPM under 20-00-14.
Now we have the wire, let's find the copalum splice.
We go back to the SWPM to chapter 20-30-13 like the repair procedure mentioned.
Because the wire was burned out, we need to cut out a section of the damaged wire, insert a splice to the aircraft wiring, then insert a new piece of wiring into the splice, cut that to length and terminate that wire into the receptacle D5124J.
In the partnumbers section of SWPM 20-30-13, we find a partnumber table for our splice. For this repair we need splice 277158-1.
This splice connects a size 6 copper to a size 6 copper, or a size 6 copper to a size 4 aluminum or a size 4 aluminum to a size 4 aluminum.
In the section 'necessary materials' of this chapter we find the partnumbers of some of the other materials that we need.
Release agent, solvent, heat shrinkable sleeve, insulating tape and or PTFE tape.
Let's take the heat shrinkable sleeve as an example here, we can order the temperature grade D but if that is not available we need to know if we can use a lower temperature grade. (the temperature resistant grades run from A to D, A being the lowest temperature resistant and D the highest).
Typical high temperature areas can be found in chapter 20-02-20.
And even though our repair area is NOT high temp, one of the requirements for this repair was that the both the insulating materials and the splice must have the same temperature grade as the wire and the wires temperature grade was high temperature resistant.
So the temperature grade to be ordered is grade D.
Same goes for the isolation material, in this case we will use PTFE P-422 tape and a cold shrinkable sleeve.
Now that we have the partnumbers of all the materials we need to have the tools also.
We go back to the copalum splice repair procedure.
The Head is a hydraulic press that can hold the Die Set. The partnumber of the Die Set that we need is 68008 and there are three types of Head that can house this Die Set.
It doesn't matter wich Head we use so we find the one that is easiest available to us.
The head is connected to a hydraulic press, the press uses compressed air to pressurise a hydraulic tank wich in turn pressurises the Head with the Die Set in it.
Different Heads need different pressures to operate.
The power pump must deliver enough pressure to correctly crimp the splice but not too much for obvious reasons.
So now we have all the partnumbers that we need. Ideally we would get all this stuff before we go to the outstation but in some cases it takes some time for the materials to be ordered and received.
For this time, we take the materials and the tools with us.
The wire that we take with us is the same partnumber as the damaged wire.
BMS 13-58 Type 1, Class 1, Gauge 6 (BMS13-58T01C01G06).
We strip off 0.69th of an inch.
The wire has different layers of insulation.
The power pump is hooked up to a compressed air source.
The Head is connected to the power pump. My colleague opens up the Head.
The Die Set that is in the Head is not the right one, we take the correct Die Set out of our Die Set Kit.
To remove a Die Set from the crimp Head, my colleague has to loosen two allen screws.
The first one releases the indentor Die.
To loosen the second allen screw we need to activate the power pump and press out the nest Die.
We insert the correct Die Set and close the Head.
At this time some release agent can be used on the Die Set.
The splice is put in the Die Set, the wire is inserted in the splice and the splice crimped.
The splice is removed from the crimptool and inspected.
We do the same on the other side of the splice and inspect the splice further.
We use the PTFE P-422 high temperature resistant tape to build up thickness for the coldshrinkable sleeve.
The coldshrinkable sleeve is put over the splice.
By pulling the plastic strip out from the middle of the coldshrink, the cold shrinkable sleeve retracts tightly over the splice.
Now the splice is complete.
When making a copalum splice, the splice should not be cracked, the indent mark should be clearly visible and not bent, the crimp should be in the correct place on the splice and the crimped splice size should be correct.
Copalum splices and terminals are designed especially for solving the inherent problems of terminating aluminum conductors. These connectors are terminated to stranded aluminum wire using a "dry crimp." This technique eliminates the need for an inhibitor agent to break down the highly tenacious and inert oxides that form on aluminum conductors.
This section covered the use of the copalum crimptool (for splices, this tool can also be used on copalum and aluminum terminals), the other end of the wire is to be connected into a receptacle and for this we can use a hydraulic hex tool or a pneumatic indent tool.