In November, main landing gear modifications were implemented on the DarkAero 1 prototype to enhance performance during nose-high landing scenarios. Contract projects fulfilled through DarkAero Services continued to progress last month as well, with more airframe deliveries completed.

DarkAero 1 Landing Gear
The main landing gear struts are built up from an assembly of molded carbon fiber segments combined with CNC machined aluminum components. The main length of the strut is carbon fiber and has a hollow tapered cross section. The top and bottom ends of the strut are CNC machined aluminum, and these pieces are both bonded and bolted to the carbon strut. The bracket that interfaces with the shock and drag links is also CNC machined aluminum. The strut design worked well during the first two phases of drop testing, but performance limitations caused by the strut geometry were uncovered early in the third phase of drop testing, which led to a number of design modifications. 

One of the more invasive modifications involved extending the struts to change the pivot location of the trailing links. This required cutting off the existing strut ends and bonding in a carbon fiber extension. The extension was made from molded prepreg carbon fiber and the corresponding molds were directly machined in-house from high temperature tooling board. The extensions were molded in two halves and joined together through a double lap joint made from additional prepreg carbon fiber segments that were water jet cut to final dimension from plate stock.

New aluminum strut ends were CNC machined, and these will be both bonded and bolted into the molded strut extensions. Joining metal to composite is more challenging than mating composite to composite due to differences in physical properties between metal and composite. The metal-to-composite joints in the gear struts were identified as a potential area that required extra scrutiny during testing. Cutting off the lower ends of the struts provided an unanticipated but valuable opportunity to evaluate the joints that secured the machined strut ends. After over 100 landing gear drops, the cross section of the joint remained intact with no indication of degradation. The cut off strut ends will be further torture tested through thermal cycling to gain more valuable data on their durability. 

The new strut end design follows similar architecture to the original design, with the machined ends being both bonded and bolted into the molded end of the carbon fiber strut. A simple assembly fixture was constructed to ensure alignment between the original strut and the new components during the assembly operation.

Even though the struts were extended in length, the modification was weight neutral due to more efficient material utilization and a more refined design. The modification to the strut led to updating the trailing links to maintain the same amount of travel. The new trailing links were machined in-house.

Additional reinforcement material was laid up inside the landing gear wheel well to strengthen the connection between the trunnion frame and the surrounding fuselage structures. These modifications will be validated in December as nose-high attitude drop testing resumes.

DarkAero Services
In parallel to DarkAero 1 development, contract engineering and manufacturing projects have continued to be fulfilled. While the specific details of these development programs are not public information, DarkAero’s involvement has ranged from design for manufacturing, CAD modeling, and trade studies all the way up to manufacturing multiple airframes and performing structural validation testing. Multiple aircraft development programs are underway, with shipment of multiple airframes occurring in November.

Contract manufacturing work will continue to be scaled up in the coming months with more customer orders coming through and additional development programs coming online. The need for even more engineers and technicians at DarkAero has scaled as well, and open positions are available.  If you’re passionate about aerospace and want to design and build new aircraft, check out the DarkAero Careers page and apply today! Interested candidates can also inquire at careers@darkaero.com.

Looking Ahead
Nose-high attitude drop testing will resume in December once the modifications to the main gear struts are complete.