The new year brought along with it new areas of progress on the DarkAero 1 prototype. Canopy tasks were the primary focus in January. Milestones achieved over the past month included bonding the new canopy acrylic into its composite perimeter structure and revising the canopy hinge mechanism.

Canopy Design
One of the larger remaining tasks on the DarkAero 1 prototype involved integrating the clear canopy acrylic into its perimeter structure. Although the canopy has been shown installed on the aircraft in earlier photos and videos, it was always either trial fitted or temporarily held in position. This was because the integration of the canopy with the airframe was dependent on several design details that had not yet been finalized. These details included the canopy seals, reinforcement structure, hinge mechanism, jettison mechanism, and latch mechanism. All of these items were refined over the past month.

Aft Canopy Seal
The canopy of the DarkAero 1 requires seals around its perimeter to prevent unwanted air leaks from entering the cabin while in flight. The perimeter seals also prevent rainwater from entering the cabin both in flight and while parked on the ground. A portion of the sealing solution is formed by a lip attached to the canopy fairing that bridges the gap between the canopy fairing and canopy frame and interfaces with the aft edge of the canopy perimeter structure. The lip was built by placing the canopy fairing back into its mold and then bonding in foam sections that were contoured into the shape of the lip. Fiberglass “tapes” were then added on top of the foam sections using a wet layup and vacuum bag process. In production, the lip will be co-molded with the canopy fairing during the canopy fairing infusion process.

Canopy Bulkhead
The canopy assembly includes a bulkhead to give additional strength and stiffness to the structure and to more precisely maintain the shape of the structure during assembly operations. The canopy bulkhead was manufactured by first infusing a flat sandwich panel with fiberglass skins and a foam core. The canopy bulkhead was then CNC cut from the sandwich panel stock, resulting in a tight fit with the molded canopy hoop. The canopy bulkhead was built with a bottom horizontal member for added rigidity during assembly, but this will likely be removed later to reduce weight and allow for better aft baggage access during flight.

After proper fit and alignment was confirmed, the canopy bulkhead was bonded to the canopy hoop. The canopy fairing mold was used as a matched assembly fixture during the bonding operation. This helped maintain a tight interface between the parts as the bonded assembly cured. The components were allowed to cure enough for handling before a final post cure was performed in the oven.

Canopy Longerons 
Longerons were CNC cut from solid fiber-reinforced phenolic plate and bonded along the sides of the canopy frame. The canopy frame mold was used as a fixture to help maintain correct geometry as the assembly cured. The canopy longerons provide additional stiffness for the canopy frame and serve as an attachment location for seals along the sides of the canopy frame. They also provide a versatile mounting location for hard points if additional side latching mechanisms are ever added to the canopy frame. 

Canopy Frame Assembly
After the lip and bulkhead were installed in the canopy fairing, the canopy hoop was cut free from the fairing. It was then possible to fit up the canopy frame, hoop, and fairing on the fuselage and establish the desired alignment between these components. Once the proper alignment was achieved, the canopy frame and hoop were bonded together to close out the canopy frame assembly. After cure, the canopy frame assembly was removed from the fuselage and inspected. Assembling the canopy frame was challenging, but a few changes were identified to make the assembly process more robust and simplified for DarkAero 1 builders. 

Canopy Acrylic Installation
The new canopy acrylic that was manufactured by Airplane Plastics was trimmed iteratively to final dimension by repeatedly marking, trimming, and fitting the acrylic into the canopy frame assembly until the desired fit was achieved. Two prototype canopies were originally manufactured by Airplane Plastics. The second canopy will be trimmed to the same dimensions as the installed canopy and then sent back to the Airplane Plastics to be used as a template to enable future canopies to arrive trimmed closer to final shape, eliminating the iterative trimming approach that was required on the prototype.

The canopy acrylic was trimmed leaving an inch wide section of stock around the perimeter to serve as bonding area between the acrylic and the composite canopy frame. Clecos were used to hold the acrylic in place and pull it tight against the canopy frame. The placement of the canopy into the canopy frame assembly was performed on the bench, but once the canopy was clecoed to the canopy frame assembly,  the overall fit had to be confirmed with the fuselage. Even though all the composite components were manufactured using CNC machined molds, there was still a concern of tolerance stackup from all of the parts being assembled together. Additional time was dedicated to confirming the full canopy assembly fit correctly into place on the fuselage. Once the fit of the canopy acrylic and the canopy frame assembly was dialed in, the acrylic was bonded in place. This step marked an exciting milestone in the prototype construction, given the history of effort that went into canopy development. 

Hinge Mechanism
Another project completed over the past month involved redesigning the canopy hinges, which were originally incorporated into the instrument panel’s center structure. Modifications to the instrument panel were required to move the hinges outboard. The original design intent was to reduce part count and weight. Although this objective was accomplished, the original design was difficult to assemble and lacked rigidity. After moving the canopy hinges to the outside walls of the instrument panel, the mechanism was much easier to assemble and significantly more stable. It also allowed for incorporating hard points for the canopy jettison mechanism. 

DarkAero Aerospace Composites Course
Another session of the DarkAero Aerospace Composites Course was held this past month. Those who attended went through two days of instruction ranging from technical theory to hands-on demonstrations centered on building a small wing section. The material covered in the course shares aspects with the training and instruction that will be used to build a skilled workforce to manufacture DarkAero 1 kits in production. The next three sessions are already fully booked! The next open session is April 29-30, 2022, but this session is filling quickly as well! If you are interested in securing your seat, more details can be found at darkaero.com/courses. 

YouTube
In January, we released a video that discussed the full assembly of the DarkAero 1 and included an overview of the high level tasks remaining before flight testing. Check out the video below:

DarkAero 1 - Full Assembly Discussion!

Looking Ahead
In February, work will continue to finish the canopy hinge mechanism, jettison mechanism, latch mechanism, and canopy seals. In parallel, we will be working on completing remaining tasks with the landing gear.