Sorry for replying so much later, but I believe that many people still have this doubt, I bought the TOPER B777. is very good and low cost, there are Sorry for replying so much later, but I believe that many people still have this doubt, I bought the TOPER B777. is very good and low cost, there are other app too LANDING CALCULATOR

https://secure.simmarket.com/toper-calculator-tool-b777-v3.0-(takeoff-performance-calculator).phtml