I'd suggest just attempting to call and set up an arrangement. They are not going to want to hear from you ever time after that.
As I recall, the regulation says that you “must contact the operator of the airport(s).” However in practice, that isn’t always possible for any number of reasons that are beyond the control of the sUAS PIC. Therefore, it is a weak law that doesn’t address the issue it is trying to address, which is coordination and separation of manned and unmanned aircraft in the vicinity of airports. In fact, notifying the operator of a seldom-used, non-control towered airport does little to address this since the fact that sUASs may be operating in the area may not get conveyed to the pilot(s) of manned aircraft using the airport since no one may be at the airport to tell them when they are approaching or using the airport,
In any case, I think if a sUAS PIC’s aircraft collided with a manned aircraft operating to or from an airport that the PIC couldn’t contact, the sUAS PIC would still be liable because...
1) It could be said that the sUAS PIC should not have flown without contacting the opporator of the airport, and
2) Other regs say sUASs must stay clear of manned aircraft.
So, unless the manned aircraft is violating minimum safe altitude rules, the sUAS would be at fault.
When I find myself in this situation, I document that I contacted or attempted to contact the airport(s), follow all the other rules, and monitor an aviation band hand-held radio for local manned aircraft operations on applicable frequencies as indicated on a VFR aeronautical chart for the area. In an emergency, after doing everything I could to get out of the way, and if necessary to avoid a collision, I would transmit on the radio in an attempt to protect the manned aircraft. Note: Currently, you need a license to transmit on an aviation band radio while outside of an aircraft and on the ground, but, as is true for any licensed radio services, an unlicensed operator can transmit on licensed frequencies to mitigate a life-threatening situation.
I also fly with insurance.
I established a flying field near my company’s office, with the permission of the property owner, to train our sUAS pilots. This field is just inside the 5-mile limit of an non-towered, seldom-used private airport. I found the airport operator’s contact info (he lives in another city), called the listed phone number several times and left messages, and then sent him a letter explaining our operations indicating that unless I heard from him, we would be operating at our training field on occasion for the foreseeable future while following procedures that are similar to those I outlined in the previous two paragraphs (in this post). I have had no complaints from the airport operator and I assume the FAA would consider him properly notified.