Up to now the vast majority of the actual building has had to do with the fuselage and wing structure. The systems team has been focusing mostly on requirements, design, and procurement. That all changed last week when the systems team installed the first wire bundle into the wings!!!
So what? A wire bundle? Big deal!!! Not so fast…before we got to the actual wiring part we had to go through a series of steps that everyone has to go through before they get to cut wire! Let me give you a brief overview that will be repeated countless times, and give the team countless headaches, before the airplane is ready to fly.
If you look back to the DR&O post you will see that the DR&Os call for wingtip lighting, a heated pitot system, fuel probes, and a roll-axis autopilot. Simple right?
System Preliminary Design!
You can also look at the preliminary design post and see what some of the decisions that we made to fulfill the DR&Os were. In it you will see that some of the decisions that we made were to go with the Dynon Skyview (autopilot servo and heated pitot) as our avionics system, to use capacitive fuel probes, and LED lighting for the position and anti-collision lights.
Systems Detailed Design!
We have not put together a post on this (and might not seeing as how detailed design is somewhat of an ongoing adventure when we discover changes that need to be made) but we did do detailed design for the components outlined above. Part of that detailed design involved figuring out where these components are going to be placed on the airplane and what are the electrical requirements for that component. We know where the distribution and ground buses (remember that this is a composite airplane!) are located so now we have enough information to make a wire!
Using the pitot heat as an example we know that we need power, ground, and a signal wire which carries an indication signal about the state of the pitot heat. Looking in the Dynon documentation we know that the power wires have to be able to carry up to 10 amps and that the signal wires have to carry almost no current. We then go to trusty AC43-13 and look up the required wire gauges for the appropriate length of wire run (15 ft) and the current. After looking up the wire gauge we cut the wire and LABELED!!! it at each end. I cannot stress the importance of this task as 4 months down the line when we try to figure out what each wire goes to it will be invaluable. The markings all correspond to something in the aircraft’s wiring schematics that we keep with us in the shop (that will get posted once the wiring is finalized…sometime before first flight).
Finally…making the wire bundle!
After we measured, cut, and labeled each wire we then bundled them together with aircraft-grade zip-ties (YES there IS such a thing!, they are made of a plastic that is non-toxic when it burns and it resists burning in the first plane…all important when you are putting around at 8,000 ft and 170 KTAS) and proceeded to stuff them into the wings. To get that done we ran some string through the conduits and then tied the wire to the string. I’d like to say that we just pulled and it all went smoothly but we had to repeat the process about three times before we got it right! Although now it all looks great!
After reading through now you have a better idea of why the wire runs are somewhat of an accomplishment. It means that we have a mature design that is ready for installation. These are also the longest wire runs on the airplane. The strobe synchronization wire runs from tip to tip at 23 ft long! Hopefully we can hook those all up correctly when the time comes!