The last month has been an extraordinarily busy time as we gathered up the pieces from a major crash and prepared for our next flight test. On March 15th Atlas climbed to a height of roughly 3 metres coming within inches of achieving the altitude requirement for the AHS Sikorsky Prize. Within seconds, however, one of the rotors plummeted quickly, collapsing the truss in mid air. Much of the helicopter was still intact, but 4 breaks in the rotors spars, dozens of broken ribs and over 100 failure points in the truss would take and entire month to repair. Incredibly, we were able to complete the repairs with no more than 900 grams of carbon fibre and epoxy.
Atlas and Todd coming down gently from their 3 metre ascent.
We suspected that the loss of lift on the front rotor was due to either an improperly spooled hub, a slipping spool, or a drive line that somehow jumped off the spool, but it was difficult to isolate the exact cause. We took measures to ensure that, whatever the actual cause was, none these three things could possibly happen again. At the same time we made some adjustments to the rigging of the truss that would ensure the bracing lines stay in tension at high power so that the torsional stiffness is not lost on the climb. On April 19th we were ready to try again.
After 7 flights, the aircraft was trimmed so that all the rotors were balanced and the drift was absolutely minimal. We proceeded with controlled flights to 1 metre and to 2 metres with Atlas looking better than it ever had before. Unfortunately, on our first prize attempt, upon glancing the 3 metre mark once more, the helicopter broke up mid-flight. The cause is yet unknown, but we have loads of video footage to go through (a Baker’s Dozen worth of camera angles) and we will be able to figure out what went wrong.
The last month has obviously been heart-breaking, but at the same time the results are incredibly encouraging. We know that Atlas can complete the climb and that the pilot has the required power to complete the one minute flight. We have a much better understanding of the dynamics of the structure, and have figured out how to rig all of the lines to minimize the stress while maintaining structural stiffness throughout the high-powered climb.
Todd at the peak of the climb, just as the alpha rotor begins to collapse.