Progress on the DarkAero 1 prototype continued in March, with the team focused on installing and testing the main landing gear retract system. The nose gear drop test was set up along with tests for the fuel system sump tank. Additionally, the prototype was moved to the new pilot production shop to allow systems work to be wrapped up in a single location rather than spending time traveling between the shop and the hangar.

Main Gear Retract System Installation and Testing
After the main landing gear retract hardware arrived, work commenced on assembling and installing the retract mechanism into the airframe. Mounting holes were drilled through the inner trunnion frames to receive fasteners for the retract gearboxes. Once installed, it was possible to connect the retract motor to a battery and test the retract motion. The actuation mechanism functioned as intended, and the test helped confirm the fit and function of the main landing gear as they move through their retract path. 

Brackets were installed on each gear strut to interface with the latches that secure the struts in their up locked position while they are retracted in flight. The locks prevent the gear from being pulled down from their retracted position during high G-load maneuvers. A separate set of brackets were also installed on the struts to interface with a set of gas springs. The gas springs allow the gear struts to overcome gravity and aerodynamic forces and move into the down locked position during an emergency extend event. 

Retract Electronics Bench Testing
The majority of the landing gear electrical system was recently built up and tested. Portions of the landing gear electrical system were tested throughout the landing gear development process, but these early tests did not include a fully connected system that would simulate operation in the airplane. The latest testing included a verification of the landing gear control module that was assembled in February. 

The tests were able to simulate full retract and extend cycles including the operation of the lock solenoid that is used to disengage the gear locks prior to engaging the drive motors. Several changes were made to the gear logic code which allowed efforts to shift to installing the control modules in the airplane for final retract ground testing. 

Nose Landing Gear Updates and Testing
Taxi testing and a preliminary round of drop testing revealed aspects of the nose landing gear that could be improved. This led to several of the nose gear components being redesigned. The redesigned parts were outsourced so their manufacturing could proceed in parallel to other work on the prototype. The updated parts arrived in March, and they were assembled with the rest of the nose gear for testing. 

The new strut bottom bracket design included several improvements with the most notable being a reduction in part count. This was achieved by integrating the forward clamping bracket into the main structure. The new design also incorporates provisions for a nose wheel centering device which will eliminate the centering guides which were originally designed into the nose gear doors.

The nose gear fork was also redesigned. The new design incorporates several important updates including improved manufacturability, tow bar mount points, stronger interface between the fork and the pivot pin, and increased tire clearance. The changes are weight neutral.

The nose gear drop test rig has been assembled using the latest nose gear components. Portions of the rig were CNC machined to accurately locate the engine mount and drag link mount relative to each other. The test rig is mounted to the building structure, allowing it to pivot in a controlled manner all the way to the ground. The testing process will simulate the worst-case landing loads specified by FAR Part 23. The drop testing has been scheduled for early April, and the results will provide valuable insights into the durability and reliability of the new nose gear components.

Antenna Work
An experimental dipole antenna for transmitting and receiving communication radio signals was fabricated. Communication signals have some of the longest wavelengths used in general aviation, and consequently require some of the longest antennas. The design intent has been to conceal these antennas within the fuselage. 

This latest design for a concealed antenna came out of successful tests on a basic version of the dipole antenna that was fabricated from copper foil strips soldered to the inner and outer conductor of a coaxial cable. The version of the antenna shown here was built with a PCB that was fabricated to adapt a coaxial port to two conductive tabs where 1/2” copper foil could be attached. This design was cost effective, easy to fabricate, and offered location flexibility on the airframe compared with off-the-shelf versions of this antenna. 

Mounting locations under consideration include the inside of the airframe under the fiberglass canopy fairing and on the exterior of the airframe on the belly. These locations position the antenna in a more horizontal orientation, which reduces its ability to send and receive the vertically polarized signal of the COMM band. However, after conducting tests in these locations with positive results, this antenna design will be assessed further during flight testing. A backup radio will be present in case these tests yield unacceptable results. If satisfactory performance cannot be obtained with this design, it will be replaced with a traditional whip antenna.

Fuel Sump Tilt Testing
After discussions with test pilot Sean, it was decided that ground tests would be necessary to validate the fuel sump's functionality. These tests will include verifying the sump check valves and identifying any potential leak points. The draining capabilities of the sump tank drain port will also be quantified. Conducting critical system tests on the ground is essential to identifying potential failure modes before engaging in higher-stakes testing scenarios.

Aerospace Composites Courses
Sessions 15 and 16 of the Aerospace Composites Course were held in March. Student projects ranged from kit aircraft components to the fender for a NASA lunar terrain vehicle. It has been fun working with students to overcome challenges they are facing with their composite projects. 

The next two course sessions will be held on April 28th-29th and May 19th-20th. Sign up for one of these sessions using the link below: 

Sign up for the Aerospace Composites Course!

The next session of the Aerospace Mold Making course will be held on April 20-21st. This course complements the Aerospace Composites Course by teaching the fundamentals of building high quality tooling which is a requirement for creating high quality composite parts. 

Sign up for the April session of the Aerospace Mold Making course by using the link below: 

Sign up for the Aerospace Mold Making Course!

YouTube
A new YouTube video was released detailing the latest progress on the main landing gear retract system:

Why we designed our own retractable landing gear

YouTube videos are released early for paid tier YouTube community members. In addition to early video releases, pictures and behind-the-scenes design discussion are shared to the YouTube community throughout the month, allowing for more frequent updates in between video releases. To see the very latest updates on the project, become a channel member at the link below:

Become a DarkAero YouTube Community Member!

Visit with Senator Agard
Earlier this month, the DarkAero team was privileged to have Wisconsin State Senator Melissa Agard visit the shop. The team presented their vision for DarkAero, and Senator Agard facilitated introductions to influential leaders in the Madison area. These connections will prove to be extremely beneficial as the company expands its team. Senator Agard was eager to offer support, encouraging the team to remain in Madison and bring more technical jobs to the community.

Looking Ahead
Next month, the team will be focused on completing the nose gear drop tests, installing the remaining landing gear hardware, testing the gear retraction and extension operation, and tilt testing the fuel sump tank. Additionally, sessions of the Aerospace Mold Making Course and the Aerospace Composites Course will be held towards the end of the month.