Tomorrow we’ll be making another attempt at the AHS Sikorsky Prize. This last week we installed small aluminum inserts to fix the stripping problem we had last week, and we’ve adjusted all structural lines to their final positions. We’re confident, collected and ready. Wish us luck!
Below is a plan for the progression of flights tomorrow. You can follow along on Twitter or Facebook. If we can keep to the schedule we should be attempting flights in the early afternoon, with a few extra hours to spare before we have to back up at 4pm.
- 6AM Assembly: team arrives and begins assembly
- 8AM Initial Balance Check (Calvin): first test run, only a few second flight to ensure rotor balance is reasonable and it’s safe to proceed to longer flights
- 9AM Low-Altitude Balance and Height Trimming (Calvin): Several runs, progressively improving the balance of the rotors and making sure everything lifts to the same height
- 10:30AM Mid-Altitude Drift Trimming (Trefor): Several flights from 4 – 6 feet up, trimming the rotors and the controls based on the amount of drift.
- 12PM AHS Sikorsky Prize Simulations (Todd): 2 Flights, first to 1m, then 2m, practicing power ramp, control, and final trimming for drift.
- 1:30PM AHS Sikorsky Prize Attempt (Todd): Give’r.
This week there were only a few final adjustments to be made. First we installed inserts into the bottom of the rotor axle where a single screw holds the axle/bearings assembly together. This screw had stripped last time, which costs us a fair bit of time. The inserts added 15 grams, but in total we were able to remove over 100 grams this week by continuing to strip other parts of the helicopter.
Wednesday we assembled the truss and adjust all the lines. Now that we fully understand the influence of the all the lines in flight we were able to set them in their final position. The lines that connect hang the bike were adjusted so that the pilot’s load is distributed evenly over all four rotors. Then the bottom lines were taken in so that they remain under tension all the way up to a 1000 Watt load from the pilot. If they go slack the torsional stiffness of the truss is severely reduced, but if they are too tight they deflect the structure too much, which could cause structural failure or cause a rotor to clip a line. After many tests, we feel we’ve finally got it right! I guess tomorrow we’ll find out!!