Progress continued on the DarkAero 1 prototype in August, with efforts focused on testing and small remaining systems tasks. These included improvements to the landing gear retract system, refinement of the canopy jettison system, and heat shielding remaining exposed areas in the engine compartment. Efforts are also underway to bring on additional technicians to accelerate progress on the DarkAero 1 prototype and support increasing demand for DarkAero Services. 

Canopy Latch/Hook
One of the main projects in August involved creating a flight test version of the canopy latch mechanism that functions automatically with the canopy jettison mechanism. The production intent canopy latching mechanism was previously developed and installed. It includes two latches at the aft corners of the canopy frame that automatically engage once the canopy is closed. This is still the intended design for production, but a different latch was required for flight testing. 

A unique functional requirement for the prototype canopy is the ability to jettison for emergency egress. In that scenario, the test pilot would pull the canopy release handle to disengage four pins that secure the front end of the canopy. If the production intent canopy latch mechanism was used, it would need to be disengaged at the same time that the canopy release handle was pulled. This additional pilot workload and complexity would not be ideal for rapid egress. Additionally, the production latch did not include a mechanism to guide the canopy up and away from the aircraft if it was released in an emergency.

This led to the design and fabrication of a flight test specific canopy latch mechanism that only required the test pilot to pull the canopy release handle to jettison the canopy. It's also designed to prevent the canopy from sliding back into the test pilot by guiding the canopy up and away from the aircraft.

The new latch is located at the top center of the canopy. The canopy is opened from the outside by twisting an external handle that disengages a spring loaded latch. To exit from inside the aircraft, the same latch can be disengaged by pulling back on a small handle. The canopy automatically latches with this mechanism. The geometry of the latch prevents the canopy from sliding back into the pilot, but it still allows the canopy to be jettisoned when the release handle is pulled.

The new latch is mounted on the canopy fairing which required additional structure to be added to stiffen the fairing to support the latch loads. The next steps will include installing the latch mounting structure and then installing the latch itself. 

Firewall Heat Shield Extension
In the DarkAero 1, a stack of titanium and ceramic blanket covers the forward face of the firewall bulkhead to create a fire barrier that protects the occupants of the aircraft in the rare event of a fire in the engine compartment. There is a cutout in the firewall that allows the nose gear to retract through the firewall and into the nose gear wheel well, but this cutout also creates a gap in the heat shield that could allow flames to reach the unprotected walls of the wheel well. The cutout can also interfere with the engine cooling when the nose gear is extended as air passes through the nose gear wheel well instead of through the exhaust tunnels as intended. 

An extra portion of heatshield was added to enclose the nose gear and prevent fire from reaching the wheel well. The challenge in creating the addition came in conforming the heat shield to the contours of the nose gear mounting structure while not interfering with any surrounding engine hardware. A prototype version of the added heat shield section was mocked up in thin aluminum, and this design will be converted to a titanium version in September. 

Landing Gear Updates
The wiring for the nose landing gear was updated to a routing that was suitable for flight testing rather than just ground testing. This involved extending the wiring harness for the nose gear motor so it could route through the nose gear wheel well and into the cockpit. The harness was updated to include a bulkhead fitting to allow it to pass through the wall of the nose wheel well which was modified to accommodate this fitting. 

Control Surface Correction
A small but important issue that was recently addressed was a misalignment in one of the elevator hinges. The inner and outer elevator hinges were installed in alignment with each other, but there was a slight amount of interference in the middle hinges that made elevator installation difficult, and it created a risk of binding in the elevator motion. This was corrected by realigning the middle hinges to eliminate the interference and allow smooth motion of the elevators. The root cause of the misalignment was identified and a plan was established to correct the assembly process for production kits to prevent misalignment in the future. 

HS/VS Load Testing
The first set of load tests on the horizontal stabilizer (HS) and the vertical stabilizer (VS) were conducted last month to validate the mechanical integrity between these structures and the fuselage. The series of tests were established after discussions with the test pilot, and they are meant to simulate worst case conditions on the VS and HS due to asymmetric aerodynamic loads, cross winds, and gusts. 

The test rig is made up of two custom machined cradles that interface with the tips of the HS and VS. Load is applied to these structures through a cable and turnbuckle that span between the cradles. The force applied to the test fixture is measured with a load cell connected in line with the cable and turnbuckle. The initial testing focused on simulating worst case side loading on the VS, and the results validated the bond between the VS and fuselage. The next set of tests will increase this load further on the VS to complete the proof loading. Additional tests will also be performed on the HS to specifically validate its bond with the fuselage. The HS test will involve inverting the fuselage and adding a distributed load across the underside of the HS. 

YouTube
In August, a new YouTube video was released discussing some myths and misconceptions about carbon fiber. The airframe of the DarkAero 1 is built primarily from carbon fiber composites, and the mechanical properties of this material contribute to making the aggressive performance targets of the aircraft possible. Carbon fiber is an appealing material choice for aircraft, but it can be complicated to design and work with, and naturally there are some misconceptions surrounding this material. The video, which seeks to clear up some of the most common misconceptions, can be found at the link below: 

Aerospace Mold Making Course
Session 6 of the Aerospace Mold Making Course was held in August. Students who attended included both hobbyists and professionals, and their applications ranged from kitplanes to unmanned aerial vehicles. The course covered techniques for mold design and manufacturing that ranged from moldless prototyping methods for one-off designs to CNC machined molds for mass production of composite parts. 

The next session of the Aerospace Mold Making Course will be held on October 13-14. Sign up for the October session using the link below:

DarkAero Aerospace Mold Making Course

Aerospace Composites Course
The September session of the Aerospace Composites Course is sold out! The next session will be held November 10-11. Sign up for the November session using the link below:

DarkAero Aerospace Composites Course

If you’re interested in accessing the course immediately and want a more convenient option that doesn’t require travel, an online version of the course is available. The online version covers the lecture portion of the in-person course, and is continuously updated. Last month, a new module on ultrasonic non-destructive testing of composites was added.

The online version of the Aerospace Composites Course can be found at the link below: 

DarkAero Online Aerospace Composites Course

Expansion of Team
This fall, DarkAero will be bringing on additional team members to support work on the DarkAero 1 prototype and to expand capacity for composites manufacturing services. We are seeking technicians with hands-on skills and attention to detail. If you, or someone you know would like to apply, please reach out at careers@darkaero.com. 

Looking Ahead
In September, the team will be focused on wrapping up the new canopy latch system, performing additional tests on the fuel system, completing load testing on the HS and VS, fine tuning control system, and performing more tests on the landing gear.