Drop testing the main landing gear for the DarkAero 1 continued in September, with the second test configuration reaching completion. Training new team members and completing contract work continued in parallel as well.

Landing Gear Drop Testing
Drop testing the DarkAero 1 landing gear has been broken down into several phases to simulate a range of different types of hard landings. The first phase tested level landings with all three landing gear contacting the ground simultaneously with both ground reaction loads and drag loads applied to the landing gear. This phase concluded in July. The next phase, which was completed in September, simulated level landings with only the main landing gear contacting the ground. Just like during the first phase of testing, both ground reaction loads and drag loads were applied to the main gear. However, the second phase of testing built upon the first by stressing the main landing gear much harder. Since the nose landing gear remained clear of the ground and absorbed almost no impact energy, the full magnitude of landing loads were transmitted through the main gear.

Although the second iteration of the trailing link design performed better than the initial design, a third iteration was developed with larger diameter fasteners to provide increased structural margins during hard landings. The new design was CNC machined in-house on the Tormach 1500MX. Maintaining engineering, manufacturing, and testing under the same roof has enabled a tightly coupled feedback loop allowing designs to be quickly refined and optimized based on how they actually perform.

Further discussions with the shock manufacturer led to a third iteration of the shocks being implemented and tested. The third shock had changes to the internal valving to increase damping at high impact velocities. 

Areas of the airframe were also reinforced prior to completing the highest drop heights. After all the modifications and changes were implemented, the airframe was taken through progressively increasing drop heights until the peak target drop height was reached. Inspection of the airframe after the highest drop height as well as reviewing video and accelerometer data allowed the team to deem the second phase of drop testing complete. Over sixty drops of the airframe have been conducted to date.

The next phase of drop testing will explore the behavior of the main landing gear in a nose high attitude simulating a landing similar to stalling the airplane onto the runway.

Side Load Testing
Planning and setup for side load testing of the landing gear has proceeded in parallel to drop testing. The landing gear will see side loads during crosswind landings if the aircraft touches down at an angle relative to the runway centerline or if the airplane is drifting sideways as it lands. Guidelines for side load conditions are established under FAR 23.485.

Applying side loads in the same direction to both landing gear is a common test method for light general aviation aircraft as it directly mimics a crosswind landing. This method of testing is necessary for aircraft with single piece “bow” type landing gear to prove that the landing gear and mounting structure can withstand the side loads. Side loading both landing gear in the same direction requires a fixture to constrain the fuselage and react against the side loads.

To simplify the side load test and eliminate the fuselage fixture, the landing gear on the DarkAero 1 will be pushed and pulled against each other, generating side loads in opposite directions. This test method is possible with the DarkAero 1 landing gear because they are integrated into the airframe, so each main gear assembly and mounting structure behaves mostly independent of the other. Although the test will look different than a crosswind landing, the test will still generate equivalent side loads. Analysis and simulations were conducted to characterize the stresses generated under this test method to establish that it is more conservative compared to side loading both landing gear in the same direction. A hydraulic jack will be used to push the landing gear apart and generate outboard acting loads, while a simple come along will be used to generate inboard acting loads. 

DarkAero Team Growth and Development
The engineering and manufacturing capacity of DarkAero has been expanding as new engineers and technicians have been brought on board and trained. With additional team members designing and building hardware, quality standards have been further refined in the environment of manufacturing at scale. These quality guidelines and procedures are part of the foundation for AS9100 certification.

The team continues to grow, and open positions are available for talented engineers and technicians who want to design and build new aircraft. If you’re passionate about aerospace and want to be part of shaping the future of flight, check out the DarkAero Careers page and apply today! Interested candidates can also inquire at careers@darkaero.com.

Looking Ahead
Drop testing in a nose high attitude will be conducted in October, as well as side loading on the landing gear.