Some advice for "The Black Heart":
Finish the "The Black Heart" level on pilot first to get the 4th P51 Mustang. It seemed to make things a little easier.
First Objective: Defend the Lancasters
Fly in front and turn around, go a little low and with a bit of practice you can be behind some FW-190's when they appear. Don't shoot, or you'll scatter them. Ace Kill Chain them from left to right for a ridiculously long amount of ace killing. Just fly around spanning LB after that.
Flak Tower: Cannons are pretty effective.
Armoured Car: Quick passes with rockets and cannons. Try and see which way the road runs and follow that line.
Flak Towers: At this stage, you can strafe the two flak towers as normal. ALSO, you can destroy some of the planes on the ground for the next objective. After being destroyed, they will still cause your sight to go red as if they were valid targets, but are still destroyed. You cannot destroy the hangars in advance though, it seems. DO NOT destroy the flak towers when you're supposed to be attacking the armoured car as it seems to glitch the flak towers objective.
Johan Sturm: Yeah... If I ever met this guy... he appears on the runway of the airport, so before the checkpoint (destroying the last guy from the previous objective) try and get yourself in position behind it so you can have a clear run at him for the Ace Kill. If you fail, just restart from checkpoint.
Good Luck!