« So far we flew 300 hrs with the first aircraft says Dennis O’Donoghue, senior experimental test pilot. Each flight lasts from 4 to 10 hours on average. On the same flight we test the take-off at different weights, we do some tests during the cruise and we also monitor the datas on landing. Most of the test flights will be flown from Boeing Field in Seattle, but we will do the crosswind testing all over the world to find suitable atmospheric conditions. The one-engine take off were flown from Edwards AFB where the lakebed gave us good safety margin. »

The crew consists in two test pilots and a flight test director in the cockpit, who leads all the flight test engineers seated in the main cabin and calls for the tests. The number of engineers varies from 9 up to 22 people depending on the scope of the intended test. The maximum crew is reached when the the aircraft is flying a combination of tests: measurements on take off, landing performances, cruise, stability, flight control testing with different gross weight and center of gravity combinations.

Water ballast fitted in the cabin are used to move the center of gravity aft and forward and check the aircraft response. « We have 12.000 pds of water available and I can make them move aft and forward in less than 2 and half minutes », says engineer Jeri Haggard.

Another important part of the testing concerns the one-engine take off, which are flown at Edwards AFB. « The aircraft is equipped with a thrust asymetry compensator (TAC) says Dennis O’Donoghue. In case we lose one engine on take off, the aircraft will automatically put more rudder to counter the yaw. It is very comfortable and safe for the pilot: you don’t have to put rudder yourself. You just carry on and rotate. The remaining engine is so powerful that you climb away easily ». In case the aircraft loses an engine at the maximum take-off weight, with unfavourable atmospheric conditions, the remaining engine can be used in an overboost mode, delivering more than the nominal 115.000 pds. On the other hand the engines (GE90-115) are so powerful that in normal conditions, with both engines working, pilots can choose to take off with a derate setting of 10 to 20%.

A former fighter pilot with the US Marines Corps, Dennis O’Donoghue has never had so much power availbale under his feet…