Exoskid - Flight One

tl;dr:

• So we built it.
• And then we flew it.
• And it worked!
• And then we crashed it...

On one of the first sunny days of 2024 after a long period of rain, we, co-founders Peter and Leon along with Martin (another student engineer on the project) are ready to test our first sub-scale prototype named Exoskid. I, Leon, have high expectations for our first test flight and the tension is palpable as we had invested a significant amount of our free time into this project over the past months. Some of our friends are also present to document the test flight with drones and cameras.

After assembling the model, our test pilot Peter puts on the exoskeleton and we performed a quick integration test. The signal transmission from the exoskeleton to the flyer works flawlessly. The tension continues to rise as everyone gets ready for our first launch ever. I hold the airplane with both hands, feeling my hands become a little sweaty despite the cold wind on this rolling hill near Dresden. I nod to Martin, signaling I'm ready to launch.

“Okay, let's do it,” Martin answers, followed by a loud “Three…” beginning the countdown. I lean back to gain momentum. Martin pushes the joystick halfway, and I'm surprised at how decent the thrust is already. Will this contraption actually fly or just hit the ground like a rock? “…Two…” A flashback from my last bungee jump comes to mind, making me want to retreat. “...One...” And just like back then, I empower myself with a “#$*@ it, what could go wrong?!” “…Liftoff!” I flex and, as hard as I can, throw the nearly 2 kg flyer into the sky like a spear. Martin gives full throttle. And it actually flies..! a beautiful display of the dihedral as it rushes upwards. Relief spreads through me seeing all our hard work paying off. The first bank turn follows and the relief turns into pure excitement and joy! The fear that I might not hit the correct launch angle or somehow mess up our first flight drops off me like a stone.

After a few laps, during which Martin gets a feel for the flight characteristics, it's time for the exoskeleton test: handing over control from Martin on the transmitter to Peter in the exoskeleton. Peter can adjust the dihedral angle of each wing with his arms, the ailerons with his hands, and the elevator and rudder with his feet.

The flyer is about 100 meters east over a field at an altitude of about 30 meters when Peter says, "Okay Martin, switch me in." Martin responded, "Well, let's goooo!" We watch anxiously from a distance and are shocked to see the Skid doing a nosedive! The entire flyer is diving towards the ground like a falcon! Less than two seconds later, the flyer disappears behind a small hill from our view. It's immediately clear to everyone that this is a "Rapid Unscheduled Disassembly" and that the aircraft won't be available for another test soon...

Special thanks to Andy for the follower drone piloting and footage!

Results and Insights

After retrieving the remnants of the Skid from the field, we reviewed the drone footage. Everyone agrees that, up until the crash, the test flight was a complete success. It demonstrates that the flyer could be launched successfully and could gain altitude quickly and safely with the help of the built-in propeller. The flight stability for this design was relatively high, and banking up to a load factor of 3g was possible.

The cause of the crash was quickly identified: although we had conducted an integration test before the flight, where Peter in the exoskeleton assumed a body posture leading to stable elevator and dihedral angle positions, Peter's posture had changed slightly after the first few laps. This caused the elevators to force the aircraft into a nose-dive immediately after switching control to the exoskeleton. We had initially agreed that Martin would retain control of the elevator, allowing Peter to focus on steering the flyer with the ailerons first. However, we had forgotten to re-enable this mode after the pre-flight integration test. In summary, our pre-flight excitement led to an oversight, laying the groundwork for this subsequent dual pilot error. So, better write a checklist, next time!

Additionally, we concluded that future test flights should conduct riskier tests at a higher altitude, giving the main pilot enough time to correct any mistakes made by the test pilot wearing the exoskeleton before the flyer hits the ground.

Next Steps

We will repair the Exoskid in the coming weeks and create a checklist for the next test flight. This should prevent similar errors in the future.

The second test flight attempt will be in the next month. If you want to be there live and in color, you can sign up as a spectator for the second test flight by emailing us. Stick around and watch us make a dent in the Universe!