why the rush (second line item) to attain optimum relight speed 300kts?
You may have "roll back" (very low RPM) and flying at the relight speed will help N2 to be at / above self sustaining RPM (provided combustion continues).
See Page 21
https://www.airbus.com/content/dam/c...agazine_07.pdf
"1) During the engine start sequence all fuel pumps were left in the OFF position, leading to the triggering of the following ECAM Cautions: FUEL L TK PUMP 1+2 LO
PR FUEL R TK PUMP 1+2 LO
PR The crew cleared both Cautions but left the fuel pumps in the OFF position. As a consequence, both engines were being gravity fed during the engine start, take-off and climb phases of the flight.
2) The behaviour of the engines was normal until the aircraft reached FL380, some 23 minutes after take-off. At that point, both engines rolled back, leading to: • The Mach Number to decrease from M0.78 to M0.63 • The disconnection of the Electrical Generators 1&2 (Engines 1&2 N2 being below 53%) • The Ram Air Turbine deployment (Emergency Electrical Configuration).
3) The aircraft started to descend and the crew declared an Emergency. At FL 320, the engines were recovered leading to an automatic re-connection of both Electrical Generators. The crew then decided to turn back to the departure airport where an uneventful landing was performed."
WTF?