Aug
26
Filed Under (Chile, gliders, Iquique, MOOMZ, OSU, seagliders, sg158) by shearmar on 26-08-2009
Track line for glider sg158 lauched at the beginning of August

Track line for glider sg158 lauched at the beginning of August

After performing a very nice “butterfly” pattern during the MOOMZ cruise, we sent sg158 offshore to start cross-shelf transects. Shortly after that, we started getting loads of roll retries and even a few roll errors – this means the internal motors were trying to shift the batteries and execute a roll to turn the glider and the motors either did not respond enough or did not respond at all. We panicked a bit a called Fritz at UW. He gently chided us for not digging a little deeper into the log files, and then suggested some glider magic:

Create a pdoscmds.bat file with these 3 lines and let the glider execute it during next phone call:

menu hw/pitch/read
menu hw/roll/read
menu hw/roll/rolls

This ran the glider through a series of tests on the roll mechanism. Things seemed ok, but the problem continued to worsen as we made more and more dives. Eventually, the glider was stuck rolled partially to the starboard side, meaning all dives now executed as a slow clockwise spiral on the way down and counterclockwise spiral on the way up with no real control of heading.

Last 1000 m dive from sg158 stuck rolled to starboard

Last 1000 m dive from sg158 stuck rolled to starboard

Now, this meant sg158 had to be recovered. It wasn’t in imminent danger, but it was way (30+ nautical miles) offshore. Once again, Gadiel Alarcon sprang into action (on a Saturday and Sunday no less), and late on Sunday August 23 sg158 was safely recovered and brought back to Iquique.
On Monday, Laura emailed with Ruben Moraga at UNAP and they got sg158 turned off and stowed away. Now we’ll need to get the gliders shipped back to the US to replace sg157’s batteries and figure out what went wrong with sg158.