We know we’re close, and we know the helicopter/pilot is capable, but to clinch this prize absolutely everything has to go right. Unfortunately, yesterday we saw some very strange behaviour in one of the rotors and spent several flights trying to chase down the problem. We ended up figuring out that it was a stripped screw that was allowing play in the rotor, but our time constraints on the field are very tight and by that time it was too late.
On the plus side, our weight/drag savings from the week before proved highly effective, with even lower power numbers than we’ve seen in the past. Calvin flew for an epic 9 flights, finishing off with a 47 second flight that was only stopped because of access drift. On the last flight we were able to put in 730 Watts without any danger to the structure, which popped us up nicely to 6 feet, again stopped due to access drift. With more time to trim for drift, we are very excited about our next time out!!
Keep reading below for a more complete summary.
Calvin warming up for one of his 9 flights on Friday.
We start with short balancing flights to make sure that the rotors are balanced enough to do longer flights and flights up to altitude. After two flights, the second one lasting 20 seconds, we attached the controls and prepared to do more accurate balancing and trimming for drift. Unfortunately at that point we started seeing some very strange behaviour from Beta (the rotor that had been repaired last week). We would decrease the angle of attack of one of the blades, only to discover that the balance would be even worse on the next flight. After several flights we decided to disconnect the controls, since they may be introducing an additional unknown variable. At the same time Trefor noticed slop in the attachment of the Beta hub. We realized that the screw that holds the hub/axle assembly had been stripped and each flight it was allowing more and more play. We fixed the problem within the hour and proceed with trim flights, still without controls.
Within a few more flights the helicopter was balanced (all the rotors spun relatively flat), but not well trimmed (it was still drifting). Wanting gain more information about the control system and how the helicopter reacts to higher power inputs we attached the controls and did one last flight. Todd held a low altitude for 10 seconds to make sure that the controls had not causes any severe balance issues, then slowly ramped up to 730 Watts at which point he was at 6 feet of altitude. Laying off power Cameron arrested the drift and we slowly set her down.
This week we’ll be evaluating the controls a bit further and figuring out an effective strategy for trimming with the controls attached right from the get go. This should same time and give us the extra couple of hours that we need. Great work on the part of the team, including the photographers and the large support crew!!
Todd and Cameron analyzing video footage. Hey Apple, are you interested in sponsoring us? ;)
Nick and Dan spooling up for the next flight. This is the dynamic duo that put together the music for the Snowbird Human-Powered Onithopter’s feature video and will be back again with a new composition for Atlas!