The main landing gear remained a key focus in September as progress continued on the DarkAero 1 prototype. More machined landing gear components were manufactured, and we were able to proceed into building the mounting structure to join the landing gear to the fuselage.

Main Landing Gear
Several outstanding CNC machined components in the main landing gear system were milled this past month. These included the drag link mounts and the main gear strut bottoms. The drag link mounts structurally tie the drag links into the airframe while the strut bottoms allow the trailing link suspension to pivot on the ends of the gear struts. 

The strut bottoms also establish the wheel camber and toe-in geometry, which is important for acceptable aircraft ground handling characteristics. The strut bottoms challenged us since they had several unique requirements. They are made from aluminum, but they are structurally joined to the carbon fiber gear struts. Machining these parts required some planning due to their shape and dimensional tolerances. Their geometry led us to consider outsourcing them as 5-axis parts, but we eventually came up with a strategy to complete them in-house on our 3-axis mill.

The alignment of the components in the strut assembly is ensured through the use of an assembly fixture that we built this past month. We were able to move forward on assembling the gear struts, but we were slowed by some manufacturing hurdles with the carbon fiber piece at the top of the gear strut. The geometry and composition of this part made it difficult to mold so we are working through some fixes including experimenting with some alternative cloth weaves, different molding techniques, and a redesign of the component. 

The main gear assembly is joined to the airframe through a molded carbon fiber structure called the main gear trunnion frame. This structure is somewhat like the “pelvis” of the airplane since it supports the gear legs. A large portion of our work this past month centered around designing and building the mold for the trunnion frame and then molding the trunnion frame itself. We originally approached the design of the trunnion frame as an assembly of 2D flat panel sections that would be CNC cut from a bulk panel. However, we eventually concluded that a molded structure would be a better solution, both structurally and for manufacturing. The drawback of a molded structure was that it required us to design and build a mold. 

The mold for the trunnion frame was built from MDF and directly machined to final geometry on our CNC router. This approach was a departure from our standard production mold making process that involves first building a mold pattern from tooling board and then forming a final mold using the mold pattern. We decided not to go straight into making the production mold for this component because we identified a few features that might change once we work through installing the part in the aircraft. MDF offered a quick and cost effective approach to test these features before building the production mold. 

Once we built the mold, we were able to make the trunnion frame through the standard infusion process we have used for the rest of the composite airframe components. There are a few access holes we will add to the trunnion frame that we will finalize as we work through assembling the landing gear into the airframe.

In addition to making the machined and molded landing gear components, we were able to source and purchase the rest of the purchased components in the landing gear system. These parts include fasteners, spur gears, and hardware for the retract mechanism.

The remaining tasks for the landing gear will be to assemble the gear struts and join the trunnion frame to the fuselage. Each main gear strut utilizes an electric motor and a gearbox connected to the strut to drive the retract motion. We will be machining and assembling the retract gearboxes in the next few weeks.

Knowledge Base Updates
Version 1 of the DarkAero CAD Library was published to our Knowledge Base this month. This library provides links to our publicly available CAD models. The objective of creating this library is to provide a central source for 3D models of commonly used aircraft hardware and accessories in kit build projects. The CAD models can be accessed in your web browser via Onshape cloud CAD without creating an Onshape account and can also be downloaded as STEP files for use in your own CAD program. We are adding to this list all the time so check back in the future for more files and updates. Check out the DarkAero CAD library by visiting the link below: 

DarkAero CAD Library

YouTube
We filmed and released another YouTube video documenting recent progress on the DarkAero 1 prototype which can be viewed here:

Why So Many Parts? | DarkAero Shop Vlog | September 4th, 2021

Another video is currently in progress and will be released in the first week of October.

Keegan & Sarah's Wedding
These monthly updates have remained strictly focused on the DarkAero 1 progress, but a big event occurred last month that is worth announcing: Keegan and Sarah celebrated their wedding! Sarah and Keegan have been together since before the start of DarkAero, and she has supported the project all along both behind the scenes and on the front lines in the shop, at AirVenture, and in our videos. After the wedding, Keegan and Sarah were able to take some time away from work and enjoy their honeymoon in Hawaii. 

Looking Ahead
We are looking forward to assembling and installing the main landing gear in the fuselage in October. Also, we are excited to host the first session of the DarkAero Aerospace Composites Course coming up on October 22-23.