Refining the control system of the DarkAero 1 prototype remained a primary focus for the team in October. Installing and testing the pitch trim and flap actuation progressed, and the canopy latch mechanism was refined as well. 

Control System Refinements
After building up the control system, a few areas were identified that generated free play and compliance between the control sticks and the control surfaces, so the control system was disassembled for refinement and installation of other upgraded hardware.

A prototype version of the control stick mount was previously manufactured using several sections of carbon fiber plate and carbon fiber tubing. These parts were bonded together to develop the basic shape of the mount and to test out the stick position and motion. The early concept provided insight that enabled the development of an airworthy design with improved fit, manufacturability, and strength. 

The new design is CNC machined from a single section of aluminum, consolidating seven parts into one. Despite the new mount being slimmer, its single piece design is stronger and can handle forces well beyond what the pilot can generate. A fair amount of time was spent exploring a 3D printed version of the stick mount made from carbon filled nylon, but the strength values did not meet limit control forces with an acceptable safety factor. Every time hardware like this goes through design iteration, more ideas for improvements arise. Naturally, new ideas for improving the stick grip and stick mount have already surfaced, but the DarkAero 1 will be flown with the hardware shown here.

Additional control system work included designing the travel limit stop for the control stick. This component provides a solid structure for the control stick to stop against and prevents potential damage to the rest of the control system if large forces are input into the stick. The stop will be 3D printed as a single unit that can be mechanically fastened in place on the armrests. Since the stick travel may change from lessons learned during flight testing, the stop was designed to be easily modified and swapped out.

Pitch Trim
The trim system on the DarkAero 1 is used to reduce control stick forces as power is increased or decreased and as the airplane changes configuration. An internal spring system was originally planned for trim, but an external trim tab was selected for the prototype to reduce the amount of iteration required to achieve a workable trim system. 

The Vertical Power VP-X Circuit Breaker System in the DarkAero 1 has a built-in pitch trim control that allows the hat switch on the control stick to move the trim tab through a linear actuator. An off-the-shelf trim tab and actuator were purchased for evaluation, but after some initial testing, this trim system was rebuilt with a number of new parts that were made in-house. 

The rebuilt actuator and tab were installed on the elevator and are now ready for flight testing. An aerodynamic cover for the actuator will be fabricated in November.  

Flap Actuation
The DarkAero 1 uses split flaps to enable reduced approach speeds and achieve steeper approach angles during landings. The flaps are actuated manually via a handle located between the pilot and copilot that is mechanically linked to the flaps.

Much of the flap actuation mechanism had been built up previously, but fabrication and installation of the remaining flap mechanism hardware had been on pause as the primary flight controls were being installed and refined. Flap mechanism work advanced in October with additional linkages and hardware being designed and fabricated to move the system to a testable state. This hardware is in the process of being installed, and initial testing of the flap system is planned for early November.  

Canopy latch
Work continued on the flight test canopy latch mechanism that was designed in August. A unique functional requirement for the prototype canopy is the ability to be jettisoned for emergency egress. In that scenario, the test pilot would pull the canopy jettison handle which would disengage four pins that secure the front end of the canopy. A flight test specific canopy latch was designed to allow the canopy to separate from the aircraft without interfering with the jettison mechanism. 

The flight test latch was recently modified to unlatch the canopy by sliding the exterior handle rather than twisting it. Although the twisting handle design created a smaller penetration in the airframe, it was more complicated and slightly heavier to implement compared to the sliding handle. The parts for the sliding handle design were fabricated, installed, and tested. The system functions as intended, allowing the canopy to be jettisoned by the pilot in a single motion.

Aerospace Mold Making Course
Session 7 of the DarkAero Aerospace Mold Making Course was held in October. Students' mold and tooling applications in the latest session ranged from rocket parts to performance motorsports components. A variety of mold manufacturing approaches were covered including CNC machined molds, composite gel coat molds, and moldless construction. 

The last session of the Aerospace Mold Making Course for 2023 will be held December 8-9. Prices will be increasing for all course sessions starting January 2024 to reflect the increased value offered through new demonstrations and process guides that have been added to the course. Sign up for the course using the link below: 

Sign up for the DarkAero Aerospace Mold Making Course!

Aerospace Composites Course
One of the topics covered in the DarkAero Aerospace Composites course is how to combine metal hardware with carbon fiber components in an assembly. This challenging material combination can potentially result in galvanic corrosion. The latest article released on the DarkAero Knowledge Base goes into more detail about the mechanisms behind this phenomenon and highlights the techniques that were used to prevent galvanic corrosion on the DarkAero 1:

What is Galvanic Corrosion? How is Galvanic Corrosion Prevented?

The next session of the Aerospace Composites Course will be held November 10-11.

This session has filled up quickly, but there is still one spot available. Sign up using the link below: 

Sign up for the DarkAero Aerospace Composites Course!

YouTube
The latest DarkAero video, which went into more details on the aircraft control system, was released to the public in October. A follow up to this video is being planned that will discuss the function of the flaps and trim. Stay tuned for its release!

Looking Ahead
In November, the DarkAero team will be working to conclude efforts on the primary and secondary flight controls as well as wrapping up a few remaining tasks on the engine, landing gear, and cabin. The list of outstanding tasks on the DarkAero 1 prototype has been shrinking, and the team focus will soon transition purely towards ground tests, taxi tests, and ultimately flight testing.