You don't mention what you're flying, with what fuel load, at what speed, and at what height?
About fuel, FS is designed to be as realistic as possible, and the designers largely succeeded. An aeroplane with a full fuel load will usually adopt a more noseup attitude than one which is lightly loaded.
Similarly, if you trying to hold too high a speed, the engines may only be able to do that at the expense of the rate of climb. If you are asking the aeroplane to hold both too high a speed AND too high a rate of climb, the engines COULD well be operating at 100% power and still not be able to maintain both.
Generally, with the default jets, and assuming that you're flying on autopilot, I find that the following procedures are best:-
1. Up to 10,000 feet, set the speed to 250 knots, set the desired altitude, and let the autopilot select the rate of climb (usually 1,800 feet per minute).
2. Above 10,000 feet, jack the airspeed up to 275 knots.
3 . Above 20,000 feet, switch from IAS (Indicated Air Speed) to 'Mach. Hold' - I recommend Mach. 0.70 or thereabouts. From then on watch the N1 gauge on the engine instruments - if it goes above say 90%, I suggest reducing the rate of climb to bring it back to that level or below. I usually undertake long trips (currently trying to achieve Qantas' 'Holy Grail,' Perth-Heathrow non-stop in a 787
) so I tend to keep N1 well down, at say 80%, so as to save fuel on the climbout above 20,000.4. On reaching cruising height (not usually higher than say 35,000 feet with the default aeroplanes) set the speed to a sensible level - I would recommend Mach 0.75 for most of them, Mach 0.80 for newer types - and then check fuel consumption etc. With a full load you will probably find that the aircraft settles at about 4 degrees nose-high pitch at first, reducing to around 2 degrees as the fuel load lightens nearer the end of the trip.
For recommended settings on the default aeroplanes, check the entries on them in the Learning Centre (look up 'Boeing' etc.) - you'll find all the recommended speeds, power settings, etc. in there. Most good-quality downloads have similar information in the 'Readme's' etc.
Sorry if all that's 'old hat' and you know it already - but the commonest cause of extreme nosehigh pitch with the default aeroplanes is us 'pilots' asking more of the aeroplane (particularly the engines) than they are able to give. Hope some of it helps, anyway.
