It's a big, heavy aeroplane... so expect it to be slow.
Additionally, you can put far more stuff onto it than it will cope with, so you need to make a strategic decision about your mission to determined the correct loadout. For example:
- If you are U-boat hunting, sure, take the Davis gun. But then leave the bombs and some MGs behind.
- Level bombing mission? Forget that Davis gun, and you can probably lose a couple of MGs too.
- High-alt photo-recon? Forget the bombs and Davis gun. Be selective with the MGs.
- Gunship? Lower the fuel, remove the camera, bombs and davis gun and then cram in the MGs.
Also, 100% fuel will give you 6 hours in the air. Chances are you don't need all that fuel.
Tune your response curves
It is good to be able to take your hands off the stick and have it gradually climb or spiral up. Another trick is to temporarily switch to mouse-control to let you carry out the long slow climb. Then switch back to joystick for the operational action in the mission.
Your varying airspeed is probably a mix of being on the brink of stall, and by being heavy-handed on the stick. The latter is likely to be a result of having a poor response curve. This means you need to hang on to the stick the whole time. Apart from being tedious, this adds some movement, causing the aircraft to pitch up (losing speed) and down (losing altitude). When you have a heavy load, this is critical, so tweak the response (or use the mouse) to achieve stability.
If just did a test and used the following (assuming a bombing mission):
- 100% fuel
- nose twin MGs
- top-turret twin MGs
- single rear-fuselage MG
- 2 x 230 lbs bombs
I had no camera, Davis Gun or co-pilot MG.
It took me 10 minutes to get from water-surface to 500m altitude. My climb speed was about 110 km/h. I used manual engine control:
- Full throttle
- Manually tuned mixture for best RPMs (approx. 60%)
- Manually tuned radiators for 85-90 deg C (approx. half open)
I then climbed for another 10 minutes and got to 1000m without any problem. At 1000m, I could then use the auto-leveller for cruising to target, during which time it was doing about 130 km/h.