Here is the quote from Leach''s narrative re the aircraft:
Visibility continued to improve and by 0430 was about 12 miles. Consequently orders were given to refuel the aircraft. Owing to delays, principally on account of water in the fuel, aircraft was not ready until after fire had been opened on the enemy and it was damaged by shell splinters before it could be flown off. As the petrol constituted a danger, the aircraft was jettisoned into the sea.
He does not say that the aircraft was being refueled when fire was opened, but that it was not ready until that time. I really don't think McMullen, faced with Bismarck, would have held Y turrets fire because a plane was on the catapult. But this is all speculation still.
Also Leach's words:
A turn of 2 blue at 0555 opened "A" Arcs at "Prince of Wales" ninth salvo.
One thing I've kept emphasizing is the events do not take place instantaneously. An order is given, it has to be passed to the signalmen on the flag deck who have to select the correct flags, and hoist them. Then when the commander is ready to execute, another order has to be communicated to them and the flags are hauled down. The order is then passed to the helm to execute the turn, then the ships' rudders have to be turned to the requisite angle and the ships have to respond and attain the new course.
Therefore for Hood and PoW to be on course 280 at 0555, the order for the turn would have to have been given at least, IMHO, when they opened fire. If it was given at 0555, then it is perfectly feasible that the a-arcs would open at the time indicated on the plot.
Littorio's aircraft were on the quarter deck right under the guns of C-turret! Blast damage was almost a given!