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jayunited wrote:flee wrote:JNB's longest runway is 14,495ft/4,421m long - that is 2,105ft/645m longer than the longest runway at ATL. Is that enough to overcome the A359's hot/high deficiencies in wing/engine performance?
You are forgetting to take into account max tire speed. The length of the runway is but one factor but the fact remains the aircraft has to be off the ground before reaching max tire speed.
The highest max tire speed that I've seen is 214 MPH or 344 KPH, on some aircraft even some wide-bodies max tire speed is lower than 214 MPH. So the length of the runway is one factor, another factor is how much performance does that engine loose in a ISA+ environment, also how much performance is lost do to density altitude. I'm not 100% sure what max thrust is on the A359s RR engines, the last thing I can remember hearing was around 84,000 pounds of thrust for the A359, but that number is at sea level. However with JNB altitude being over 5,000 feet density altitude is a problem and if your in ISA+ territory that becomes a double negative. The air at altitude is less dense which effects lift and the engines performance is reduced.
Also keep in mind we are talking about a twin engine aircraft therefore engine failure safety after V1 comes into play as well. When a dispatcher sends a captain their performance data the captain can have confidence that engine failure safety after V1 has been accounted for. If a fully loaded (passengers, bags, and cargo) A359 flying JNB-ATL experienced an engine failure after V1 taking off can the one remaining engine take over and get that aircraft safely in the air under those conditions because you may not have enough concrete in front of you to safely stop the aircraft.