First, I don't claim to be an expert, but here are some of my ideas on bombing with a DO-217. This is a little ironic, because a few months ago I put up a post where I mentioned that DO's were the planes I most loved to hate... times have changed..
A few important points first about DO bombers (German):
1) When fully spaded, you can take out an enemy base with one bomb load
2) DO's can do "level" bombing" and also "dive" bombing. I've dropped bombs while in an almost vertical dive
3) DO's have a front gunner, but you do NOT control him (AI)
4) DO gunners seem to suck. Don't count on them to save your butt
5) There is a key stroke that changes your view from "pilot view" to "bomber view" (bomb aiming reticle). My keys are set up so my "V" key cycles between views.
Here's my tips for Base/Airstrip Base Bombing, in no particular order of importance... feel free to expound upon my comments or refute them. I'll add tips on bombing ground targets in a later post or an edit to this post.
A) Take note of which side of the map has the most enemy fighters and climb high when you spawn and go left or right to avoid those enemy fighters. Keep climbing if possible.
B) When playing at about BR 5.3 or less, you can usually get off at least one bomb load before a fighter gets to your altitude and (maybe) shoots you down.
C) When playing above BR=5.3, the enemy fighters are generally more capable of climbing to your altitude, so be prepared to take evasive maneuvers (see point "D").
D) If you are at a high altitude and not at your bomb drop point and you have active threats from enemy fighters climbing to you or at your altitude, be prepared to DIVE on your target so you can get to the target more quickly and drop your bomb load BEFORE getting shot down! Remember: DO's can drop bombs in a dive! Some people don't believe in diving with a bomber, but what is the point of flying at 5,000 meters surrounded by fighters that WILL shoot your down if you never drop a bomb?
E) If possible, have a squad mate cover you when you are flying your bomber. A friendly fighter that can knock down enemy fighters will allow your bomber to stay at altitude and drop bombs all day! Thank your fighter escorts, as they make your success possible!
F) "Timing" is everything with bombers. Upgrade your bombers so your bombs respawn as quickly as possible.
G) "Timing" is everything with bombers. After dropping your bombs on the first base, fly a path to the next base that will: 1) fly you away from enemy fighters, 2) Allow for you bombs to respawn just before you get your bomb aiming reticle over the second base, 3) Allow you to climb as high as possible (to avoid fighters).
H) Realize that sometimes you will find yourself having flown past the target before your bombs respawn... Your choices are to loop back around (which takes too much time in my opinion), or my favorite move... dive with no engine power until you can drop your bombs, when apply power and re-climb to altitude. My bomb respawn is fast enough that I find myself doing these short dives multiple times with great success. Make sure your engine power is at zero when you are diving, as you don't want to get any lower than you absolutely have to.
I) You can win matches by killing bases and the enemy airstrip/base, but usually also killing some number of ground targets is more efficient than trying to kill the enemy airstrip base, as the airstrip kill requires many more bombs than it takes to kill the regular bases. If the enemy bases are destroyed and the enemy airstrip base is damaged, you can usually finish off the enemy by just bombing a few tanks or ground targets. This can be the deciding factor in a close match as it can take way too long to fly a respawned bomber all the way back to the enemy airstrip base.
Enjoy your bombing!