Progress on the DarkAero 1 prototype continued in April with work on a number of systems tasks. This work included details on the fuel system, electrical system, and landing gear system. The design and installation of the seatbelts also moved forward. Significant progress was made on the new pilot production shop as well.

Fuel System
A number of outstanding tasks were completed on the fuel system of the DarkAero 1 prototype. The hardware to mount the fuel sight gauge was installed along with some of the plumbing that allows air to vent from the sight gauge. The manifolds that unite the fuel pumps were updated to incorporate a number of necessary changes that were identified in the process of manufacturing the first set of fuel pump manifolds. A small 3.5 gallon header tank was purchased that will be used for the first engine start and initial taxi tests. This tank will allow the engine to be run without introducing fuel into the wing tanks and sump tank. Keeping fuel out of the wing will simplify removing the wing from the fuselage since this will need to happen a few more times before the first flight. The test tank will sit in the copilot seat and be supported by a simple cradle. 

Electrical & Avionics System
Wires from the engine compartment must pass through the firewall to connect the engine to the avionics that sit aft of the firewall in the center tunnel electrical box. The interface that allows the wires to pass through the firewall was fabricated and installed. The interface consists of a connector plate made from a rectangular stub section of firewall heat shield with round Mil-Spec connectors mounted to it. The connectors allow the engine wire harness to be rapidly split at the firewall to simplify removal of the engine for service. 

After the firewall connector plate was completed, a series of fit checks were conducted with the center tunnel electrical box to confirm the amount of clearance between the wire harnesses and surrounding structure. The motion of the wire harness that runs from the center tunnel electrical box to the instrument panel was studied as the canopy was opened and closed. This length of harness incorporates a bent segment to allow it to pivot without straining the wires in the bundle. This detail has been an area of interest, given the unconventional hinging instrument panel. The testing allowed the total motion of the harness to be demonstrated and proven within acceptable limits. 

The mount bracket for the GPS antenna was fabricated and installed inside the new glare shield. The mount was constructed from an infused panel structure and secured in place with Click Bond nut plates. The bracket was designed for the current in-cockpit antenna but was also designed with mount points to allow for a Garmin WAAS GPS + XM antenna. Testing is required to validate this location for both antennas. 

Additionally, a cover was fabricated to close off the aft face of the main landing gear wheel well and protect the aft electronics plate that sits behind it in the tail cone. This cover was also cut from infused panel material.

Main Gear
The main landing gear retract system has steadily been coming together in parallel to other system work. 

The locks to constrain the main landing gear in their retracted and extended positions were recently machined and installed. The lock system is built around a latch mechanism integrated into each drag link mount. The latch has two “hook” features that interface with corresponding pins on the landing gear. The down lock pin is located on the upper drag link and the up lock pin is located on the gear strut. As the gear cycles to the limits of its retract or extend motion, the latches catch the pins to automatically lock the gear into position. They are unlocked via solenoids that are commanded by the gear logic to swing the latches open before the retract motors turn on. The latches are mechanically coupled to the same system used to manually extend the gear in the event of an electrical failure. This design concept was developed and tested on the nose gear and the basic architecture was replicated in the main gear design.

The main gear struts retract through an electrically driven gearbox. The torque to actuate the struts up and down is transmitted to the strut through a large spur gear mounted on each main gear trunnion. These spur gears were machined and installed on the landing gear struts. Carbon fiber covers that enclose the large spur gears were also fabricated. The gearbox that drives each spur gear will be machined and installed in the upcoming weeks.

Seatbelts
The DarkAero 1 will utilize 5-point harnesses for the pilot and copilot safety restraints. Each harness includes a lap belt, shoulder straps, and a center belt that passes between the legs. They will be attached to the airframe through brackets bolted into hardpoints in the seatback bulkhead and aft baggage bulkheads. Crow Safety Gear was selected as the manufacturer for the prototype seatbelts. Crow has supplied two test harnesses to be used to establish optimum seat belt arrangement and dimensions. The test harnesses will also be used to establish a standard harness option for DarkAero 1 builders to simplify their kit construction process. 

Wing Attach Interface
This past month, modifications were made to the interface between the wing and fuselage on the prototype aircraft. The wing of the DarkAero 1 is structurally attached to the fuselage with four bolts that tie into hardpoints at the root of the wing. This bolted joint was designed in the CAD world, but some alignment challenges were identified once the wing and fuselage were first brought together on the prototype. The design of this interface was refined to simplify the wing installation process and eliminate alignment problems. The interface was rebuilt and the bolt holes were match drilled with the wing and fuselage joined together to ensure alignment. These modifications were accomplished with the airframe positioned inverted to provide better access to the wing attach points. 

Pilot Production Shop
Significant progress was made over the past month on the build out of the new DarkAero Pilot Production Shop. The stud walls that were constructed in March are now covered with drywall and fresh paint. The air conditioning system was installed as well as LED lighting for the office and shop areas. The bathroom and kitchen areas were completed and drop power was wired in, extending from the ceiling throughout the shop area. Ceiling fans were installed to work in conjunction with the heating system, which is now up and running. However, the heat will not be used much until next fall since the weather is starting to warm up in Wisconsin. A few small tasks remain in the space, but the construction work is nearly complete. Once the build out is complete, the next phase of work will involve moving equipment from the legacy hangar into the new building. A video tour of the new space will be released once it is fully complete.

A number of pictures and videos highlighting behind-the-scenes progress at the new shop were shared in the DarkAero YouTube Community:

YouTube
A new YouTube video was just released covering several of the projects leading up to the first engine start. An early release was made available to DarkAero YouTube Community Members in April, and the public release is now available here: 

Aerospace Composites Course
Two more sessions of the DarkAero Aerospace Composites Course were held in April. Students have been attending with goals of learning composite design and manufacturing for a broad range of applications. These applications have included experimental aircraft, eVTOLs, drones, UAVs, boats, electric vehicles, motorsports, bicycles, and military hardware. The courses continue to fill up as interest remains high. Starting in May, sessions will be held in the new building which will offer an improved experience for students.

Click here to reserve a seat in an upcoming session of the Aerospace Composites Course!

Looking Ahead
In May we will continue wrapping up systems tasks with the goal of performing the first engine start! Activity will also start to ramp up at the new shop space.