TO/Climb performance change

>However an operator might certainly, still be able to use the runway. >There may be no need to abandon the operation or close the airport.>Cheers,I think your understanding of airport operations is clouding your speculation. The reality is that the operators who use the airport have no choice but to use the reduced length due to the obstruction and cannot use the entire length for their calculations. No if's, ands, or buts. The airport has the final say and will reduce the runway length to provide an adequate approach clearance by temporarily displacing the threshold. This reduces the overall allowable runway length regardless of whether you're taking off or landing so you need to know how much runway you're working with.Recently at the airport I work at, they were doing some resurfacing work at one end and closed 2200' of a 12000' runway. All takoff calculations had to be based on a 9800' surface. In essence this is what would happen with an obstruction at the end of a runway like you speculate although the closed portion would be more than 2200'. You have to use what the airport lets you use in these situations. In the end your hypothetical situation still requires variables that are not known to get what you're looking for.JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.sstsim.com/images/team/JR.jpg