The aviators scouting the island see only parts of the plane they presume to have come from the SS NC. AE and FN are already too debilitated if not one or both already deceased, and no ground signal profound enough to be visible is made to the planes.
A photo taken during the search confirms that the tide was high with significant surf along the reef edge. An aircraft hung up on the reef edge would obscured by the surf. AE and FN need not be debilitated or dead to not be seen. If they were any distance inland in the shade they could easily have not had time to get out into the open in time to be seen. I can tell you from personal experience that, due to the ambient noise of wind and surf, you don't hear a low flying plane on Niku until it is almost directly overhead. Even if the were able to get to the beach in time there is a good chance they wouldn't be seen. Again from direct personal experience from a helicopter in 2001, it's very difficult to pick out people on the ground at Niku. The vegetation is deceptively bigger than it looks so people are smaller than you expect them to be. Even if they wave, the vegetation along the beach is also waving in the wind so there is no relative motion to catch your eye.
Do historical tide charts for that part of the world support a low tide necessary for landing late on the morning of July 2nd?
There are no historical tide charts for Nikumaroro. We've had to reconstruct the tides by taking the modern tables for nearby Orona (formerly Hull Island), correcting them based on tidal observations we've made during our expeditions to Niku, and "hindcasting" the tides to 1937. We've then verified the calculations by comparing them to historical aerial photos of the island taken at known times. During the window of time on the morning of July 2nd when the aircraft could have arrived over the island, the reef was dry enough to permit a safe landing.
Is there any significant breakup of the ship upon landing?
All we can say is that the plane was apparently intact enough to be able to run the right-hand, generator-equipped engine to recharge the batteries for radio transmissions.
Upon final approach why is landing location chosen that could put the plane dangerously close the the existing wrecked ship?
There is no indication that the landing was made dangerously close to the shipwreck. The "Nessie" feature is over 400 meters north of the wreck.
In that part of the world what was the approximate tidal shift for the first few days after July 2nd? Six feet? Eight feet?
At low tide the reef was dry. At high tide on July 2nd the water level on the reef at the hypothetical landing location was less than half a meter. The water level at high tide increased over the next few days until, by July 8th (the day before the search planes arrived), the water was nearly a full meter deep at high tide. Those calculations are for still water, but the water there is almost never still. Surf running across the reef would raise the water level by as much as another half meter.
Is there any way to know how strong the surf was running in the first few days after July 2nd?
Not that I know of.
How high would the the electrical circuitry of the Electra stand with wheels blown? High enough to still be out of the surf at high tide?
Yes. That shouldn't have been a problem.
How much of the ship is coming apart due to daily tidal and surf action alone?
I would say not much. As long as the plane can "weathervane" freely it should be okay. Maybe some damage to the vertical tail surfaces due to surf impact.
Sometime after the last radio reception but before July 9th the ship goes into deeper water. How large a time window is that?
Probably two days.
Does the ship just slip over the edge or does it float some distance out into deeper water?
I wish I knew.
Was there particularly high surf shortly before July 9th? Was there a storm? What event exclusive of ordinary surf and tide puts the plane into deeper water?
No indication of a storm or high surf, but high tide does get steadily higher. All it would take is for one of the wheels to drop into a hole or groove in the reef surface and get stuck there. The plane would then be prevented from "weathervaning" as the waves hit. At that point something has to give, most likely the landing gear attach points on the side with the stuck wheel.
Does FN possibly go down having been still inside the craft when it slips into deeper water?
Possible? Yes.
Could rising tide and surf ever acted quickly enough to trap the fliers on the disabled craft when they would have preferred to return to the beach?
I suppose, but if they both went down with plane who is the castaway at the Seven Site?
The 1937 expedition does not see evidence of the wreck, but noteworthy is that they aren't looking for it. Yet, how do islanders three years later report a visible, well known airplane wreck on the reef?
Nobody reports a visible well-known wreck. Circa 1940 or '41, Emily's father reportedly pointed out some wreckage that was only visible at low tide. By 1944, there was only a story that there was a wrecked plane somewhere when the first settlers arrived in late 1938.
How much of the plane washes back up onto the reef over time?
No way to tell.
Does a large section wash back up intact? How would the islanders identify it as an airplane wreck if only bits and pieces wash back up?
One islander told of seeing part of a wing on the reef flat in the 1950s.