Thursday, March 01, 2007

Avionics Upgrade - Part 5

Before we start dismantling the panel there are a few things that must be kept in mind prior to starting a project of this magnitude.

The first and foremost is keep the project organized. I cannot stress this enough. There are many specialized springs, spacers, switches and pieces parts that come out easy and are essential for reassembly. Not everything can easily be replaced either. And if they can, be prepared to pay a pretty penny. A good example on 36G is the electric trim switch. It is small and easy to remove; however, if you lose or damage it get out your checkbook. The cost of this one switch is nearly $700!

The second is to take pictures of everything! Use a digital camera or disposable, but document all key components of whatever you are taking apart. Don't expect to rely on an aircraft maintenance manual or illustrated parts guide to tell you everything you need to know -- it won't. Aircraft manuals typically do not get into the detail required to put things back together. Take pictures of the switch locations, all placards, unique mounting assemblies, etc. Trust me on this one...You cannot have too many pictures.

The third, and in my opinion most important, trick of the trade is to keep all of the parts of each section disassembled together in small sealable containers and clearly label what is stored in them (e.g. Pilot Instruments, Pilot Switch Assembly, Circuit Breaker Panel, etc). Most parts are small and often look alike. It is critical that you keep them separated. You can use anything that tightly closes. My preference is to use small Ziploc sandwich bags and/or Rubber Maid reusable hard side containers. They are cheap and seal tightly. If they fall off of a shelf they generally will remain closed. The Rubber Maid containers are very nice because they are also stackable. What I do is use the Ziploc bags to store small parts, put those bags in the Rubber Maid containers and then stack them in a location close to the work area in case I need them.

Ok, we have a plan, let the project begin!
It can be a daunting task to tear into an aircraft panel, but it isn't as difficult as it looks as long as you take your time. The tools required are generally not much more than a Phillips screwdriver and some wrenches. The easiest way to approach the project is to figure out how it was put together in the first place. In most GA airplanes, the pilots instruments are the last to be installed. Mooney installed the panel from the right (copilot) side, then the avionics, then they pilot panel and finished off with the glare shield. To remove the pieces the most straightforward way to do it is to start on the left (pilot) side and finish on the right (copilot) side.

The first component to remove on 36G is the glare shield. This is easy enough. A couple of screws and it slides out. This opens up access to the panel from the top making it easier to see how everything fits together. The next step is to carefully remove the pilot instruments. I like pulling the indicators on top since they are easy to reach and work down. I start with the Artificial Horizon (36G's Flight Director) since it is a $8,000 part! NOTE: It is important to seal the vac hose inputs with caps or tape. You do not want dust to get into the AI. I then remove the Altimeter, avionics indicators, airspeed, etc. until all of the 3" parts are removed and secured. After the large parts are removed, this frees up access to all of the other supporting pieces such as fuel gages, switches, etc. These parts are generally easy to remove. The final step in removing the pilot panel is to remove the main panel mounting screws.

As you can see above, the panel is nearly removed; however, the gear switch is riveted onto the panel. I had to drill 4-rivets and the panel was finally removed! NOTE: Make sure and label the gear switch! You need to know which way is down.

After the pilot panel is removed, the project moves into the main avionics stack. Generally speaking, the main riser bars in most radio stacks are mounted to the main structure. A few screws will loosen it up and it can be pulled forward. The wire backplates can then be removed and the entire assembly can then be removed. It is a bit difficult to see in this picture, but I put arrows around the 8 or so screws that needed to be removed to remove the entire radio stack in 36G.

The final removal step is to disassemble the circuit breaker panel. This panel is designed to be slid forward and aft, but it isn't easy to remove. It takes time to do this one right. First remove the CB panel mount nuts, then the gauges, then the switch, then drill the rivets holding it to the airframe, and it's out!

The level of difficulty of the disassembly process is a 2 out of 5. The key is to take your time, label your parts and don't break anything. I completed this entire project in about 3 hours.

As you can see above, 36G is now at the point of no return. We are 100% committed to finishing the project. She's grounded until we do. Next we'll talk a bit about prepping the parts, removing the unused wiring and getting her ready for equipment installation.