The reason why I'm confusing is I retracted the LED during go-around with the loss of system B pressure on the simulator. I read the AMM about PTU, it says when alternate flap master switch on ARM AND alternate flap position switch DOWN, it will inhibit PTU working. For single engine(starboard failure) going around, we lost B system EDP pressure, TE flaps in 15 and on air, all conditions satisfy the PTU operation, but the QRH says as long as we extend LED, WE CAN NOT retract it.