I have tried both ways and from replies when I called, I know I was not seen most of the time. And not being seen caused repeated calls when I had pipeline right of way to look at and they had traffic that could affect them to look at. I was creating a dangerous situation by calling.
On the other hand, there was only one time, that I know of, when someone else saw me. Oxford, Mississippi. My Mississippi Natural Gas line ran right by the airport. I watched for traffic as I approached the airport from the South. One airplane in the pattern. I continued on my pipeline until I was southwest of the airport and he had landed on runway 09. I then turned and landed 09 and turned off at the first taxiway. At that time I noticed he was just turning off at the last taxiway.
I was out of my 172 when he pulled in with his nice airplane, I forget what model but fast single I think. He asked if I had just landed to which I replied yes. He accosted me with great vigor for some time. At each pause to catch his breath, I answered, "You're probably right." After some time and several. "You're probably rights." he shook his head and left.
Of course he was right. But my radio call from southwest of the airport at 200' AGL on a pipeline would only have disrupted his approach and might have caused a dangerous go around. In the interest of safety, I did not make that radio call. In the interest of safety I also did not climb up to 1,000' only to return to 200' to land. DOT requires that every foot of the pipeline be observed by air or driven or walked by the pipeline folks. This scenario happens a lot and no, other pilots don't necessarily know about it. Nor would it improve safety to involve them. Nor does ATC, when a tower is available, take the pipeline pilot up through his traffic to 1,000' only to come back down through his traffic to land. It just doesn't make sense. Nor are any FARs violated by how it is being handled stealth at uncontrolled fields.
A very, very important consideration must be made for those in the normal pattern by crop dusters and pipeline pilots using stealth to avoid confusion at the uncontrolled airport. We must give way to all. We can see them easily above our horizon. They cannot see us easily below their horizon. It would be very stupid and unsafe to insist on spacing in normal traffic unless we climbed up there. It would also be unsafe, in my opinion, for us to climb up there.
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