The main landing gear downlock is the simplest of the hydraulic mechanisms on the Swift to rebuild, but it still is best accomplished with a copy of the Swift Hydraulic Manual. It may be purchased from the International Swift Association, Athens, TN. In it are parts breakdowns and step-by-step instructions for the overhaul of all of the Globe Swift hydraulic components. The Swift Association also has a Parts Store which sells pre-packaged seal kits for the various hydraulic components. I have listed for your reference the kits that I purchased when I began my hydraulic rebuild project, but check with the Parts Store representative when you make your order.
Downlock seal kit: S-148
Actuator seal kit: S-147
Adel Gear Strut seal kit: S-145
Adel Gear Strut bolt & bushing kit: S-144
Flap Cylinder seal kit: S-150
Tailwheel Strut seal kit: S-149
Brake Master Cylinder seal kit: S-151
I am writing these maintenance articles to make it a little easier for individuals to rebuild the Swift hydraulic components. This is NOT intended to be comprehensive or step-by-step advice about how the rebuild of these components should be completed. In order to accomplish this work you must hold either an A&P or AI certificate or you must be supervised by an individual who does and you must have in your possession the manuals and tools necessary to accomplish the task. I do not discuss all of the steps shown in the hydraulic manual. This is not considered to be preventative maintenance.
The downlock is located in the landing gear wheelwell in the narrow area occupied by the landing gear strut when the gear is retracted. It is bolted to the landing gear actuator in a way that prevents the gear from retracting once the downlock is engaged at full gear extension.
The easiest way to remove the downlock from the wheelwell is to remove the entire landing gear actuator with the downlock still attached to it. You will need to disconnect and cap two hydraulic lines leading to the actuator. Capping is required so that the hydraulic reservoir on the engine compartment firewall does not drain all of it’s fluid through the open line. Very messy. Be sure to have plenty of rags available to mop up the hydraulic fluid that will spill as the lines are disconnected and capped. Even if you disconnect and cap the lines at the reservoir, you will still have the full lines from the reservoir to the actuator draining fluid. Expect a mess.
The Manual Page
The Hydraulic Manual provides a parts breakdown of the downlock, a cut-away drawing of the downlock assembly and the steps needed to disassemble it and replace the internal seals (o-rings). The Swift Association Parts Store sells rebuild kits for each of the Swift Hydraulic assemblies. A downlock rebuild kit contains all of the seals to rebuild both landing gear downlocks. The photos below show what the downlock looks like when it is taken apart for rebuild.
When replacing the seals, it helps to coat the o-rings with a small amount of hydraulic fluid to allow them to slide into position a little easier. it also helps to do this when reinstalling the piston into the downlock body, making it easier to keep from shaving the o-ring as the piston slips into the downlock body.
Be sure to reinstall the check valve balls in their proper order beneath the spring as shown in the diagram and photo.
Once the reassembly is complete, set the downlock aside, enclosed in a sealed plastic bag until it is time to bolt it onto the actuator assembly for installation in the wheelwell.
It is very important when rebuilding hydraulic components to keep everything as clean as possible. Any foreign material introduced into the assembly could easily cause erratic operation or accelerated wear of your new seals.