It depends on the situation eg weather related, a/c servicability, time available such as from lack of fuel, encroaching darkness etc
With lots of time a prec. search could take as many circuits around the field as needed to determine if it is, or is not, a reasonable choice.
With limited time or worsening circumstances then some of that 'leisure' is lost. Time might only allow a precursory inspection..
The basic procedure is a guide & gets modified to suit circumstances.
I base my teaching on a nominal 3 circuits, each one with a progressively lower & closer final ---> upwind. The idea is that each subsequent lower flight path is only over terrain that has been observed from the previous and higher circuit. It may involve a a few orbits of the chosen paddock first to decide if it really is worth the time & fuel to observe further, general circuit direction etc. Generally pax. would be briefed, radio calls done etc prior to commencing this procedure. Establish a 15 or 20 min radio call time with someone so that if you don't call by then they'll come start the SAR process.
Each circuit is flown at approx. 500' apart from the final ---> upwind. Fly the approach on base/final as if you are trying to land on the selected aim point. The only difference is that sufficient power is added to stop the descent at each of the minimum descent heights.
The first circuit is one at approx 500' to establish generalities such as obvious items that prevent the use of the field, major obstacles, line features (power lines, fences) & colour changes on the paddock's surface etc to be examined during subsequent & lower circuits, time to ensure a/c configuration is acceptable eg 1st stage of flap.
Make sure final ---> upwind is offset far enough to the right so that the ground path of the subsequent lower approaches can be observed. Fly upwind far enough along to allow the climb out ground path of the lower circuits to be seen too. Pick an easily seen feature to be a go around marker on the subsequent circuits.
Next one descends to approx 200-250' on final, flying level until the go around marker then a full power Vx climb back to 500'. This time assessing the viability of the approach & climb out paths, any obstacles that would modify these or are too close for comfort for a further lower approach. Look at any line features or colour changes as well. Evaluate how the approach, offset flyover & climb out went. Were there things that would adversely affect a lower approach? Should the go around marker be changed to start the go around earlier?
If that was OK then next circuit will involve an approx 50-100' descent on final, againflying it towards the landing aim point as if a landing is intended. Add power at the nominal height to maintain this while flying directly over the landing surface. Look again at any doubful features and for smaller things eg electric fences, that weren't spotted from the previous circuits.
At the marker (adjusted back if necessary) climb at Vx to 500'.
Now is the important part. These have all be purely information gathering exercises and it is now time to review & assess all that was seen. Should it be used or not?
If not what are the options? What are the constraints?
Make a decision to land or to check a different paddock and use the radio to keep someone informed.
Brief the passengers about what's happening. If a landing review the exits, seatbelts tight, possibly a rougher than usual landing.
Sorry, didn't intend to make it so long winded. It's easier to describe with a white board & in practice.
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