Hi all.I've had this problem for quite a while now and I'd really appreciate some explanation. This problem doesnt happen in any of the stock planes, just some downloads, and especially with planes with a certain panel.Im a fairly advanced pilot, so im able to master all parts of flight and start a succesful approach. The problem comes when im intercepting the glidepath.Everything fine at 2 notches of flap, but when i extend the flaps further, the aircraft becomes incapable of maintaining the correct rate of descent, and raises hideously above the glidepath; from that point on the aircraft cant get back on the glidepath and ill end up about 500 foot above the correct altitudes, therefore im unable to land properly. (all this is done with APP hold on, and an IAS hold of 140 ish) (in a MD90)obviously you would question my decision to not just leave flaps as they are, but the answer to that is that the aircraft will not be able to slow down quickly enough to land properly.what ive also noticed is the trim is set to about +12 or so, which seems quite high, so when the plane needs to do descend there are obviously problems.please help me with this as its really annoying my enjoyment of flight.thanks in advance, willg

Donny AKA ShalomarFly 2 ROCKS!!!Up trim shouldn't present too much of a problem. In fact, not having enough is a much bigger problem on landing. Jets normally approach nose high, and if you are holding back stick on a manuual landing you will find it more difficult to flare. You might "run out of stick" for a "take that, La Guardia" slamdown. Just because up trim is applied does NOT mean the plane cannot descend. It is normal for planes to balloon when transitioning to certain flaps settings. I do not know what notches for flaps setting on your aircraft correspond to what degrees. Planes balloon most up to about 15-20 degrees of flaps. At bigger angles, flaps produce a greater amount of drag compared to lift, so the ballooning is less. It seems to me from your descriptions that the planes you have this "problem" on are planes with more accurate flight models/avionics. My advice is to transition to 15 degrees when you decelerate to 140 knots. Two notches- if that is five degrees for you that is the setting for most heavies at 185 knots. Usually you mantain that speed on initial aproach. At two thousand feet above ground level you will intercept a 3 degree glideslope six miles out. When the glideslope indicator unpegs, or before, slow to 140 knots 15 degrees flaps or your closest higher equivelant. When it is a few degrees above the middle, drop the gear. The plane will want to descend which will help out the autopilot establish on the glideslope. Then transition to your final flaps setting apropriate for weight/length of runway etc... With the gear down, and going through 30 degrees, balloning is less or none and much easier to compensate for. Real world autopilots are limited in how much force they can apply, so if nessesary they can be overriden if they can't be shut off quickly. Your plane is "ballooning" due to flaps increase resulting in more lift than drag while attempting to mantain the glideslope. Try hand flying an aproach and seeing how much harder that makes it. In the long run, you might get more enjoyment from your hobby by practicing for a while in a lower performance plane in which you will not be so dependant on the autopilot. To quickly determine what your descent rate should be on the glideslope, take your groundspeed in knots from the GPS or true airspeed minus wind, drop the last digit (acceptable) or move the decimal one place to the left (not really necessary, but more precise.). Divide by half, and that is your target descent rate in hundreds of feet per minute. 140 knots= 14= 7= 700 FPM. Unpressurised planes sometimes follow a six to one to minimise passenger ear discomfort. That would be your three to one target descent rate divided by half. Large deviations are always caused by wind, if you are correcly flying a three to one target descent rate and getting HIGHER on the slope, think seriously about a runway change cuz you have a tailwind. Ditto if the autopilot is on and the descent rate is higher but the glideslope is being mantained. To stay in practice, try following a 3 to one descent path down from cruise. 3 to one means three nautical miles traveled for each 1,000 feet of altitude loss. Thus, you can establish very precise goal altitudes. As a "personal challenge", sometimes I try to nail 10,000 feet 30 miles out, 15,000 at 45 etc... Practicing this math makes monitoring the autopilot or manually following the glideslope a LOT easier.Best Regards, Donny:-wave