The landing gear drop test campaign for the DarkAero 1 prototype continued in June, and load test plans were finalized for the tail and empennage structures. Contract engineering and manufacturing projects were fulfilled alongside airframe testing, and growing the team remained a top priority. 

Landing Gear Drop Testing
Over the past month, landing gear drop tests progressed through increasing drop heights at the full target weight. The aircraft was dropped in a nose down attitude to simulate a level landing with inclined reaction loads.

Inclined reaction loads are the sum of vertical ground impact forces and horizontal drag forces from spinning up the wheels during landing. Horizontal forces had previously been generated during nose gear drop tests by spinning the wheel assembly, but this method was not used for the full airframe drop test due to the complexity that would have been introduced in trying to spin all three wheels simultaneously. Pitching the nose down during drop testing achieves a result similar to spinning the wheels by generating loads that contain both horizontal and vertical component forces relative to the airframe. Platforms were built under the main wheels so that all three landing gear would impact simultaneously in the nose down drop attitude. Additional test points are planned to simulate nose high attitudes with the main gear contacting before the nose gear, with the most extreme pitch attitude representing stalling the airplane onto the runway. 

The higher drop heights provided more insight into the shock travel and rebound damping. Initial test results were shared with the shock manufacturer to better inform the baseline shock pressure and damping parameters. Another lesson learned through drop testing was that the tires that were initially selected for the main gear were excessive in their load capability, and the tire pressure was run unnecessarily high. The main gear tires were swapped out to a model better matched to the airframe weight and better optimized to operate at lower pressures. Lower tire pressures will enable better impact energy absorption for typical weights the DarkAero 1 will operate at. 

Data obtained from accelerometers attached to the airframe showed the loads experienced by the airframe during drop testing were higher than initially predicted. Prior to advancing to the next round of drop tests, the team elected to install additional reinforcement plies in the highest stress areas where the landing gear interface with the airframe. These modifications will help increase the structural safety margins and better transfer loads from the landing gear to the rest of the airframe.

Tail Load Testing
Additional testing that was agreed upon with the test pilot included a series of proof loads to validate the connection of the vertical stabilizer and horizontal stabilizer to the fuselage. This test campaign commenced previously in 2023, but the full range of test points were not completed at that time. Efforts resumed in June with the test plan for the remaining proof loads being finalized.

The test plan for the tail and empennage proof loading is guided by FAR Part 23.321 through 23.459, which cover flight loading conditions for aircraft design and certification. These cover the nominal balance loads required for steady level flight, increased gust loading conditions, and maneuvering loads at a range of flight velocities (flap speed, maneuvering speed, cruise speed, and dive speed). Because the stabilizer structures were validated prior to being permanently bonded to the aircraft empennage through individual static load tests, all load calculations were simplified to bending loads acting about the respective stabilizer-to-fuselage joint. 

The test bending loads will be generated through simple sandbag loading, similar to the methods used for proof loading the wing and stabilizer structures. The remaining test points will be explored in July once the airframe is through drop testing. 

DarkAero Growth
DarkAero has been growing to expand engineering and manufacturing services. The capability of the team at DarkAero has been increasing as new engineers and technicians have joined in on the DarkAero 1 and other aircraft programs supported by DarkAero. Additional capacity will be added to the manufacturing team in July, and interviews have continued to identify more engineers and technicians that are a good fit for the team. If you’d like to join DarkAero, check out the DarkAero Careers page and apply today! Interested candidates can inquire at careers@darkaero.com.

DarkAero Courses
The latest session of the Aerospace Mold Making Course was held in June. Students who attended included both hobbyists and professionals, and their applications varied from kitplanes to robots. The course covered mold construction methods ranging from prototyping methods for one-off designs to CNC-machined molds for mass production of composite parts. The curriculum of the course was recently expanded to include more hands-on demonstrations related to 3D-printed molds. 

The next session of the Aerospace Mold Making Course has not been scheduled yet, but the online version of the course is available for immediate access here: 

Sign up for the Online Aerospace Mold Making Course!

The DarkAero Aerospace Composites Course is also offered online, with immediate access available here:

Sign Up for the Online Aerospace Composites Course!

Looking Ahead
Main landing gear drop testing is anticipated to conclude in July, as well as structural load tests on the empennage. AirVenture will be held at the end of July, and the DarkAero team is planning to attend! The DarkAero 1 prototype will remain in the hangar to avoid delaying flight testing. An official announcement of DarkAero plans for AirVenture will be shared through DarkAero social media channels closer to the show.