Progress continued on the DarkAero 1 prototype in July, with testing occupying the team over the past month. The second static test run of the engine was performed, building enough confidence to proceed into the first taxi test of the airplane. The first round of ground vibration tests were conducted as well.

Second Engine Test Run
The UL520iS engine was tested for the second time in mid July. The main objective of the first test was just to get the engine to start, while the second test was focused more closely on monitoring engine parameters like EGT, CHT, fuel pressure, oil pressure, oil temperature, and battery voltage. Data logging through the Garmin G3X EFIS system was implemented as well. During the second test, the EGT and CHT measurements all trended together, and the oil system temperatures and pressures remained within acceptable limits. The alternator function was confirmed as well as the functionality of all redundant systems. A load cell to measure static thrust was added in series with the straps that secured the airplane. Another objective was to try to uncover anything about the engine installation that should be corrected or updated prior to any future testing. Several fixes and improvements were identified to be addressed while the airplane is disassembled for painting, but otherwise everything performed well, which gave enough confidence to proceed into the first taxi test. 

Taxi Testing
The first taxi test was conducted to confirm the basic function of the Beringer brake system and to begin understanding the ground handling characteristics of the aircraft. In preparation for the test, the brake lines were installed and the brake system was filled with brake fluid. Air was purged from the system using the air bleed process recommended by Beringer. The brakes were first checked by rolling the airplane by hand and applying the brakes in the cockpit. 

The brake system on the DarkAero 1 is different relative to most conventional configuration aircraft, but it is the same as what is found in most canard configuration aircraft. The aircraft is steered on the ground through differential braking, and the castering nose wheel pivots in response. The brakes are applied simply by pushing the rudder pedals to their travel limits. The first portion of rudder pedal travel actuates the independent split rudders, and the brakes come on at the limit of pedal travel. A distinct detent is felt in the rudder pedal force as the brake master cylinders begin to engage. This arrangement provides yaw control on the ground and in the air through a simple, reliable system.

The first taxi test did not extend beyond a walking speed. The low weight of the airplane combined with its powerful engine enabled easy taxiing, even at idle power settings. The tracking and steering were explored through a series of straight runs and basic turns. Gradual turns were conducted first, followed by sharper turns, both to the left and right. Steering was easy and intuitive, and the general feel of the airplane during slow taxi operations was quickly established. 

Performing functional tests on the aircraft has been a fun change after focusing on manufacturing components and assembling the prototype. The FAA’s Amateur-Built Aircraft Flight Test Handbook (AC 90-89B) has been used as a guiding document for ground testing.

Ground Vibration Testing
The first ground vibration test (GVT) was recently performed on the DarkAero 1 prototype. Aeroelasticity Engineer, Sam Jaeger, completed the test preparation and planning, obtained the test hardware, and set up the test fixture. The objective of this first GVT was to test the experimental setup and identify the first few vibration modes of the aircraft. There were four critical components of this test. First, the aircraft was suspended using bungees with the landing gear retracted to simulate an in-flight configuration. Second, accelerometers were attached in strategic locations around the airframe to measure the structural response of the aircraft due to a controlled excitation. Third, a modal hammer, which measures impact force, was used to excite the airframe at 27 measurement locations. Finally, the acceleration and force data were used to compute frequency response functions, the first building block of experimental modal analysis. The results from this test will help refine the flutter analysis and guide future vibration testing of the DarkAero 1.

YouTube
Two new YouTube videos documenting the latest progress on the DarkAero 1 prototype were recently released. These videos can be viewed at the following links:

First Engine Start! - DarkAero 1

How we built the DarkAero 1 "impossibly" light...

AirVenture
The EAA AirVenture airshow was held during the last week of July in Oshkosh, WI. The DarkAero team attended the show for a day to spend time with customers, vendors, and the broader aviation community. UL Power Engines was kind enough to share their booth as a central location for the DarkAero enthusiasts to meet up. Connecting with people who share a passion for aviation is always fun, and attending AirVenture served as a boost of energy in the DarkAero project. Thank you to UL Power, and to everyone who stopped by to say HI!

Now Available Online! - DarkAero Aerospace Composites Course
The DarkAero Aerospace Composites Course has been held routinely every month for almost a year now. Nearly 100 students have attended, while many others have inquired about an online version of the course. The last few course sessions were filmed and edited, and now an early release of the course is available online! The online course can be accessed here:

DarkAero Online Aerospace Composites Course

Sign Up! - DarkAero Mold Making Course
The DarkAero Mold Making Course was born out of interest from students who attended the DarkAero Aerospace Composites Course and expressed interest in developing a deeper understanding of building tooling to create their own composite parts. The goal of the two-day course is to provide a foundation of knowledge and hands-on training so that building molds does not become a barrier in the process of creating composite parts. The first session of the DarkAero Mold Making Course was held in June. Since then, the course material has been refined, and a dedicated sign-up page has been added to the DarkAero website. The next session of the course will be held in September, and there are still a few seats available. Learn more and sign up for the Mold Making Course here:

DarkAero Mold Making Course

Looking Ahead
In August we will continue on remaining projects including the flap controls, main landing gear actuation, and paint. New YouTube videos highlighting exciting recent progress will be released in August.