We were finally able to schedule a radio-tracking flight for Friday afternoon, but the weather didn’t cooperate and we were rained out. We were able to reschedule to Sunday morning at the crack of dawn – and three of us braved the early hour and lifted off the ground at about 6:30AM.
The clouds were low – a solid deck at 1,400’, right at the legal allowable minimum. We figured we’d make it at least to the narrowing of the McKenzieValley at HendricksBridge. We took off, and headed towards the Willamette. I was sitting shotgun, with the window up, arm out the window with the handheld antenna. It wasn’t pretty, but it was effective and didn’t require any special rigging or FAA approvals. Two volunteers, let’s call them ‘volunteer man familiar with telemetry’ and ‘volunteer woman familiar with telemetry’, were in the rear seats. VManFWT had the datasheet and GPS; VWomanFWT had the receiver. We planned that the receiver-holder would call out the tag number and power, and the recorder would scribble down the data.
We set the receiver at a high gain of +90 and flew up the McKenzie. We started hearing tags clearly around HaydenBridge, but the receiver did not code any of them. We received many error codes (I1, I999, etc). We continued upriver to Hendricks, where the clouds had socked in the upper valley. We turned around and went downstream, figuring there was no use continuing upstream unless we were able to code fish. We played with the gain, dropping it to +70, and began coding fish on the way downstream near Bellinger. We turned around again at Armitage, and flew back upriver, with the gain at a lower setting. We coded several known fish in a row (I6, I5, I19, I13, I10, I3, I22) and voted to continue the flight upriver, even though it seemed as if we were only coding about every other ping.
The clouds had lifted just enough that we could get past Hendricks. We flew up the valley / canyon (and when you’re at only a couple hundred feet above the river, turning to follow the river course, it feels very much like a canyon!) from Hendricks. We coded many tags upstream of Hendricks; however, only one was ours (I11). The low cloud layer prevented us from going much past Marten Creek, about 5 mi above LeaburgLake. Our pilot executed a slick 180 in the narrow valley and brought us back downstream. On the last pass, we turned the gain down to +55, and were able to code in rapid succession 11, 22,3,10,19,13,16,5,6, and 17. Powers were relatively low (50-150 range) but worked well enough.
The good news was that we were able to effectively code fish from the air once we got the settings figured out. We coded most of our fish twice. We covered 50+ miles of river in less than two hours at a cost of about $400. We covered all of the back channels that we haven’t surveyed by boat or car.
The bad news is that we already knew the locations of fish 11, 22, 3, 10, 13, 19, 16, 5, 6, 8, and 17. We didn’t find any of the missing fish!
A few observations on this method:
- Our pilot did a fantastic job of slowing the Cessna 182RG to near its minimum speed and maneuvering skillfully along the river course. I was very pleased with Cedric Hayden (owner) and Paul Bruington (pilot) from Oregon Air Charter.
- We flew most of the route at 65 knots – about 75mph.
- Each tag/fish would appear and disappear very quickly. We would typically get two pings per fish/tag.
- It was not possible to record data (tag/power/gain) and GPS coordinates in the limited time per tag. We referenced outside landmarks for location.
- With the ‘hold it out the window’ setup, a crew of 3 was almost mandatory. The front seater was holding the antenna and directing the pilot. It would have been difficult for a single rear-seater to record information while concurrently maintaining outside visual reference for landmarks. It might be possible to run a crew of two if the antenna was fixed in position.
- That said, I wonder whether a small two-seater which could be flown in the 40-45 knot range (say, a light sport type aircraft or a Piper Cub) would do a better job – fix the antenna to a strut, and have the passenger operate the receiver while recording data – at the slower speed, it would be easier to maintain references. Or you could just rely on the receiver to record GPS coordinates.
- The tags were surprisingly strong and easy to detect once we got our settings right. Probably due to the signal traveling through less water and more air (versus boat tracking).
- We were limited in altitude today by the clouds and were usually right at 500’ above the river. I wonder if it would have been more effective from a slightly higher altitude. We would have had more time to record each tag as we flew over it, at least, and there should be little signal loss from an additional 500’ – 1000’ of air.
- The aircraft engine/systems put out much more interference than a car engine. If there were a way to reduce this, we could run a higher gain and acquire at a greater distance.
- We got an incredibly smooth morning in terms of the lack of turbulence. The combination of low altitude and maneuvering could have created a very trying experience if it had been combined with turbulence. As it was, it was a very pleasant flight.
Overall, I feel like this was money very well spent, even though we did not locate the fish we were after. The method was effective in thoroughly surveying the area and we can now start looking at other culprits for our lost tags.