...so I was flying a Kittyhawk 737-700 to Greensboro, NC, about 20 miles from the airport near final approach. I had the autopilot on with the ALT, HDG, and IAS activated. I was flying level at 2800 ft, and I wanted to slow from 250 to 180 knots. When I changed the speed using the autopilot IAS, the plane started to slightly oscillate up and down, and eventually descended toward the ground. Shouldn't it stay level? I still had the ALT hold turned on.I read other posts on AVSIM about similar problems with the glideslope, but I hadn't reached the localizer yet. In fact, I didn't have the autopilot "approach" (APP) switched on yet. So I'm not sure why it descended erratically as soon as I changed the speed.Just curious if this is a known bug.thanks,

Were you using any flaps?Alex M.

I hadn't extended the flaps yet, because I needed to get my airspeed down first.

I assume this only happens when using the autopilot?

Yes - that's the strange part. It should stay level when I have the autopilot (altitude hold) on.

I would say then that the flight dynamics need adjusting. You might have some success by opening the aircraft.cfg file for that plane and find the flight_tuning section. There you will find a line similar to this: pitch_stability=1.000 Try increasing the amount to 1.500 and see if it helps. Also try varying back and forth from that new value until it seems to behave. This can also be (and really should be) accomplished in the airfile but you need a good airfile editor to make the changes, and of course a good idea of what you are doing.

Thanks very much for the suggestion! I'll give it a try this evening.-Jason

Jason,Did you ever find a workable solution to this problem? I had the same situation with a kittyhawk 737-800. I was nearing approach to Tuscon using an ILS approach with autopilot on, alt hold on, approach mode on, when after slowing below 200 KIAS the plane started descending rapidly below the selected altitude. I noticed that the elevator pitch trim tab indicator showed FULL up elevator and the autopilot simply had no further elevator deflection available to hold altitude. This of course caused the plane to descend and crash. The plane ran out of available pitch trim. I tried the same approach four times with the same results. I then tried a different kittyhawk 737 with the same results. I feel that the calibrations for the pitch trim are not perfected on this model. Also when I hit "S" and go to the outside view you can see the elevator in the full up position which really looked wrong for maintaining level flight. Is there any way to correct this situation? Thanks for any advise as I do like the kittyhawk model and would like to be able to use it without this pitch trim defect.Gary

If your at 250 with alt hold and want to slow to 180 you will need to put the flaps out a bit. Start with one notch (5?) then as you slow below 210 or so go to about 10 or 15 flaps. I have no problems doing this with the model.Hornit

ive done tons of approaches with the plane and have never had that happen yet..The biggest thing I noticed is the flght characteristics are kind of weird with the flaps out.

The RW 800 NG will take Abt. 5 miles to slow from 250 to 210 knots at level idle flight. 10 miles from the start of the approach @ 210 knots is where you want to be. I would not use FLAPS to slow although flaps 5 MAX speed is 250 knots. Why not use the speedbrakes since that is what they ARE for? If your descent is not going as smoothly as planned I see no problem in putting out the boards here. If you find yourself in a speed pickle, you can certainly drop the gear to help slow. A 737 or NG will indeed hold altitude and slow at the same time. Engines will be at idle and AOA will increase. One dot on G/S gear down flaps 15. Wait as long as possible for final landing flaps otherwise the folks in simulated houses will wonder if the world is comming to an end and it is not very fuel efficient ;-)Best Wishes,[h4]Randy J. Smith[/h4][h3]P M D G's 747-400[/h3][h4]coming to a runway near you[/h4][/font color]Caution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |

You need to be aware of your fule load as well. Some flaps are requied at 180 knts, infact I believe that is the speed that you can safely extend full flaps. With full tanks you're going to have trouble staying in the air with no flaps at 180 knts.Stephen,http://www.hifisim.com/images/as2004proudsupporter.jpg

When you takeoff and are passing 180 knots what flaps do you suppose one has extended? The 700 in the RW uses flaps one for most takeoffs where the runway is long enough and is not contaminated etc and is most certainly heavier on TO than landing! Flaps are retracted/extended by SPEED/ALTITUDE and SOP regulation, not weight. And I know a RW 700 captain that starts flap retraction on a flaps 5 TO at V2 + 15 retracting to flaps 1. This is done without regards to altitude whatsoever but SPEED. Full flaps up is done at his SOP flap retraction altitude.. Flaps 15 @ 180 knots is a SOP (Standard Operating Procedure) which are often based upon the Boeing OM - FCTM. As for flaps prior to flaps 15 @ geard down, I suggest you follow a airline procedure and stick to that. I personally would not be at 210 knots without flaps 1 but each airline has their own procedures..Best Wishes,[h4]Randy J. Smith[/h4][h3]P M D G's 747-400[/h3][h4]coming to a runway near you[/h4][/font color]Caution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |