From a non pilot standpoint I ask this. If you can't use that 200' of soft and sandy ground then you also can't use the 300 foot extension so why have 500' of unusable runway?
The engineers and pilots on the scene apparently saw a different between the forces acting on run way in landing, when the mass of the plane weighs more heavily on the ground because of G forces caused by the rate of descent as compared to the 1 G load (or less) as the plane begins its runout and approaches takeoff speed.
On this treeless and obstruction free island it seems a waste of that manpower and resources. Is this unusable space just to satisfy AE that she has had her request for making the runways as long as possible satisfied? Or something else?
So far as I know, we don't have documentation about the thought process that went into marking landing zones and distinguishing landing length from takeoff length in the final telegram from Cooper on 24 June. All we can do is to make guesses about what kind of thinking might have been behind the decisions they made at that time.
In short takeoffs, it is not unusual for pilots to hold the plane still with the brakes and run the engines to full takeoff power. Every inch helps. 500' of acceleration before reaching the firmest part of the runway may have looked like a good deal to those who decided to add the 300' x 50' strip at the last minute.
Yes, I'm sure that they were reacting to AE's (or Miller's?) repeated requests to create the longest possible runway on the island. So, for example, note Campbell's rather acid remark from 10 March, in the middle of the 312-hour marathon: "The north-south runway will never be used because of too much cross wind, however will be ready since they seem to place a great deal of importance on length regardless of wind direction." He was all alone on the island at that time; when the rest of the ground crew arrived on the 15th and returned in June, they seem to me to have confirmed his preference for the E/W runway and agreed with his assessment that the long N/S runway was not good for takeoff.
It sounds to me--and I admit that I am reading between the lines--that the guys on the island knew that the E/W runway was best for takeoff directly into the prevailing winds. That was probably the easiest runway to keep clear of birds. I imagine (without proof) that the reason for flagging off 1000' of the 5200' N/S runway was because the highest concentration of birds was at the north end of the island. Given limited resources to chase birds, working on the 2750' E/W takeoff strip would have to be easier than clearing 4000' or 5200' on the N/S runway.
It's fairly common to have displaced thresholds at airports. The following is from the official FAA publication known by everybody as the "AIM." (Prior to these days of political correctness it's title was "
Airmen's Information Manual." Hmmm... what ever became of that perfectly good word "aviatrix" as in "Amelia Earhart, world famous aviatrix.")
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Federal Aviation Administration
Aeronautical Information Manual
Official Guide to
Basic Flight Information and ATC
Procedures
Section 2-3-22. Displaced Threshold. A
displaced threshold is a threshold located at a point on the runway other than the designated beginning of the runway. Displacement of a threshold
reduces the length of runway available for landings. The portion of runway behind a displaced threshold is available for takeoffs in either direction and landings from the opposite direction. A ten feet wide white threshold bar is located across the width of the runway at the displaced threshold. White arrows are located along the centerline in the area between the beginning of the runway and displaced threshold. White arrow heads are located across the width of the runway just prior to the threshold bar, as shown in FIG 2-3-4.
NOTE-
Airport operator. When reporting the relocation or displacement of a threshold, the airport operator should avoid language which confuses the two.
i. Demarcation Bar. A demarcation bar delineates a runway with a displaced threshold from a blast pad, stopway or taxiway that precedes the runway. A demarcation bar is 3 feet (1m) wide and yellow, since it is not located on the runway as shown in FIG 2-3-6.
1. Chevrons. These markings are used to show pavement areas aligned with the runway that are unusable for landing, takeoff, and taxiing. Chevrons are yellow. (See FIG 2-3-7.)
j. Runway Threshold Bar. A threshold bar delineates the beginning of the runway that is available for landing when the threshold has been relocated or displaced. A threshold bar is 10 feet (3m) in width and extends across the width of the runway, as shown in FIG 2-3-4.
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You wouldn't want to land on soft sand because plunking your wheels into the sand might cause the plane to nose over (especially with a tail wheel aircraft like the Electra) due to the momentum of the center of gravity of the plane being high above the point where the wheels are stopped by the soft sand. But this is not a problem on takeoff where the only thing the soft sand can do is to slow the initial acceleration due to it's higher "mu" (co-efficient of rolling resistance.)
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