Very strange indeed. In the history are more odd flights, one says 19 hours, a few round-robin flights with extremely long durations but not too much distance.
That strange track reminds me of an idea I had. I’m going to rent a 172, file IFR for “practice approaches” somewhere I can have a bunch of miles of open space…and I’m going to fly my name in cursive. Like virtual skywriting for my FlightAware friends. A man can dream can’t he!?
The Twin Otter in question is a geophysical equipped aircraft.
Where did you find that out? Or are you familiar with the aircraft? The N-number registration information isn’t indicative of a geophysical contractor.
Probably just supposition on Dave’s part Toby.
There’s not much you could accomplish with a geo-survey aircraft over the ocean.
Actually, a flight can do aerogravity and/or aeromag offshore, but either would have a gridlike flight pattern, very unlike a hold oval pattern or a flight to check the plane. Thus, geophysical aircraft are not likely to fly IFR. They wouldn’t get clearance for the back-and-forth flight paths they need.
My second degree is in physical oceanography, I know what they can do.
Fishspotter?
I think he was out there looking for WhaleJets. 
I saw the aircraft at LVK a couple of years ago. I looked it up in the JP Airline Fleets and that’s what it said it was.
The latest flight (Aug 1) is even weirder. Up until the aircraft arrived at Portland Hillsboro, it had normal flight paths.
Somebody must have dropped something really valuable out there.
Go to the Twin Otter International web page for information on their activities. They not only do airborne research but also make the Vistaliner conversion of the DHC-6.
Vistaliner
http://www.vistaliner.com/P3110004.JPG
Grand Canyon Airlines uses the Vistaliner. They are pretty perfect for that application, the huge windows make for easy photography. (saw them at GCN when I proposed to my wife)
Grand Canyon Airlines Vistliner
Also used in Hawaii if memory serves. (saw them on my honeymoon!)
Princeville (now Island Air), Royal Hawaiian Air Service, and Maui Airlines operated Twin Otters. I lived in Hawaii for over 10 years and did not see a Vistaliner in operation with any of those airlines.
Maybe it was a regular twotter and not a vistaliner. (I was busy not ID-ing airplanes…)
We stayed at the princeville when we were on Kauai, it was beautiful.
Let me add that these flights are IFR. The flight plan is filed from HIO out to a point that the air work will begin, and the “D3+30” is actually recongized by the Center computer as an airborne Delay. This basically pauses the flight plan at that point for the time specified. In this case, 3 hours and 30 minutes. In that location, and often late at night, controllers have no problem issuing block altitudes or blocks of airspace for air work.
dm
Could all these flights possibly be somebody that desperately needs to rack up multi-engine hours? If so, why not fly someplace interesting?
No. They wouldn’t use a research-equipped aircraft to do it.