Progress on the DarkAero 1 prototype continued in January. Applying primer to the airframe was wrapped up, work on the main gear retract mechanism resumed, and the landing gear logic was refined.

Primer
Applying primer to the airframe started in late fall, and the final primer coats on small parts were completed in January. The last parts to be coated were the control surfaces, canopy frame, cowling, and access covers. In total, just under four gallons of primer were consumed, with around half of that actually landing on the airframe when accounting for practice sessions, overspray, and material sanded off. Afterward, everything was reassembled to verify the fit between mating components. The airplane will be test flown in its current gray primer state, and a final paint scheme will come after testing. 

In parallel to primer, experiments were conducted using UV resistant clear coat. After a series of tests on scrap parts, the flaps were used as a trial part for exploring clear coat on the prototype. Further testing is required to dial in the application process and validate the longevity of the clear coat. 

Main Landing Gear Retract Mechanism
Progress on the main landing gear actuation system has been moving forward once again. The basic design had already been established, but it needed to be taken to the finish line. This required a solid block of time to focus on the design, and that opportunity came after primer was finished. 

Much was learned from the three iterations on the nose landing gear actuation system, and these lessons were incorporated into the main gear. The main gear is retracted by an electrically driven gearbox, just like the nose gear.  The basic motion with a gear drive is straightforward, but the major challenge comes in addressing edge case scenarios if something fails. Solutions to these edge cases were established, and the design matured enough to allow ordering hardware and raw materials for the gearboxes. 

The primary logic for controlling the landing gear motion has been complete for some time, but additional testing was required to address a few potential failure modes that were identified. The bulk of this work centered on refining the encoder logic. An encoder on each retract motor tracks the position of each gear strut as it moves through its range of travel. This enables throttling the motion of the strut before it reaches its travel limits. Logic was written to handle a scenario in which the encoder hardware fails, and this same logic was expanded to serve as a jam detector to prevent the retract motor from continuing to drive in the rare event that the strut is blocked or jammed. This will be especially important to have in place while testing the retract mechanism on the aircraft where a wide variety of retract conditions will be studied. The jam detection code will minimize the risk of damaging the airframe and retract hardware while testing failure scenarios. 

Nose Gear Modifications
Several modifications to the nose gear are being implemented based on observations made during taxi testing and other landing gear ground tests. The centering mechanism for the nose gear is being relocated from the wheel well to the fork. The interface between the nose fork and its pivot shaft is being modified from a press fit to mechanically fastened. Additional modifications include dedicated tow bar mount points and hard stops that limit the steering travel of the nose fork. These design changes were necessary to avoid potential anomalies during flight testing, and they will also improve the function of production units. 

Aerospace Composites Course
Session 14 of the DarkAero Aerospace Composites Course was held in January. A longer demonstration of ultrasonic testing was included in this last session, led by guest lecturer John Register of RCON NDT. The infusion demonstration was carried out using the elevator skins of the DarkAero 1 as an example. The next course session will be held on March 3-4, and it will include a new module on machining composite materials. More guest lectures are planned for future sessions, and these will be filmed and added to the online version of the course, which is offered with unlimited access once enrolled in either the in-person or online version of the Aerospace Composites Course.

Learn more and sign up for the Aerospace Composites Course here:

DarkAero Aerospace Composites Course

Mold Making Course
The next session of the Mold Making Course will be run on February 23-24. This course was born out of interest from students who attended the DarkAero Aerospace Composites Course and expressed interest in developing a deeper understanding of building tooling to create their own composite parts. The two-day course provides a foundation of knowledge and hands-on training that prepares students so they can design and manufacture their own molds to make high-quality composite parts! 

Learn more and sign up for the Mold Making Course here:

Mold Making Course Sign Up!

YouTube
A new YouTube video was released in January, discussing the details and lessons learned during the painting project. The video can be viewed at the link below:

Looking Ahead
In February, we will be manufacturing the hardware for the main landing gear retract mechanism, installing the seatbelts, and continuing to wrap up the last bits of systems work on the prototype aircraft.