Hi thereJS41, great plane, excellent panel, cant wait to see that applied to the upcoming NGX.I've done quite a lot of flying in the JS41 now, and really enjoy the unique features of flying this aircraft over the big jets with their all singing and dancing autopilots.However a quick question about using Speed for descent. I follow the correct procedure of dialing in altitude, selecting alt cap and then Speed. then pulling back on the power levers to commence a descent. So say im going down at 200kts, have set my power to give me a 1500FPM rate. All is good. However, say I get some wind changes, or that I then change the target speed to a lower figure 180kts. Obvioulsy you expect the planes nose to pitch back up to a lower rate of descent to bleed the speed off, I've even reduced power further sometimes to help it achieve this without a drastic nose pitch up, but is it normall or would it occur in real life that the aircraft ends up climbing, and sometimes climbing at a very high rate until the speed falls, where often it then falls below the desired speed, which then puts the nose into a steep down attitude again to get the speed back.Any ideas, if I should be doing it different, or if this is a bug, or if its what would occur for real in the aircraft?RegardsJames

James,That's pretty much how it is. When you're climbing or descending in IAS mode, you can't change the speed setting very quickly or you'll force the aircraft into rapid pitch changes to comply with the command. It's not such a big deal in an aircraft with an autothrottle, but with manual throttles, you've got to be very careful. The solution is to move the thumbwheel more slowly -- 1-2 knots per second -- and pay attention to the vertical speed while you're doing it.

Is the KIAS descent reccommended over the VS descent? I've never tried the KIAS approach yet because I found it easier to follow the FMC VS to descend to the altitude of choice. Since the FMC tells you what the verticle speed required is, you can follow it to make sure you get to the target altitude by the right time. Is it possible to do this in KIAS mode or will you find yourself making several changes on the fly to get where you need to be?Chad

James,That's pretty much how it is. When you're climbing or descending in IAS mode, you can't change the speed setting very quickly or you'll force the aircraft into rapid pitch changes to comply with the command. It's not such a big deal in an aircraft with an autothrottle, but with manual throttles, you've got to be very careful. The solution is to move the thumbwheel more slowly -- 1-2 knots per second -- and pay attention to the vertical speed while you're doing it.

Hi yes accept that, but would it be normal in real life that the aircraft would pitch up to a rapid climb(or descent if the going the other way) to achieve this? Wouldnt or shouldnt it at a worse case just level the aircraft off? It seems it ends up chasing its tail excessively, sometimes even though a large change in speed may have been made quickly going from a 800FPM descent to a 3500 FPM climb doesnt seem appropiate just to lose say 25kts, only for it then to have lost more than the 25kts, you desired so can end up in a 2000fpm descent again to catch the speed back up.RegardsJames

Chad,Neither one is recommended. Two techniques for doing the same thing.IAS mode is a pretty good technique for getting down quickly without overspeeding the aircraft -- Preselect your altitude, pull the power back to 32% or so, and as the airplane slows to 200 KIAS, hit the IAS button, then ALT SEL. You'll maintain a 200 KIAS descent at about 1300 - 1500 fpm with the flaps up.VS mode offers you more precise control over your rate of descent, but you have to watch your airspeed.

James,The airplane is going to do what you tell it to do. If you change the commanded IAS too quickly, it will try to comply, and yes, it will climb or descend as needed to do so. Think of it this way: You're telling the airplane that you want to get to your selected altitude, but that maintaining the commanded airspeed is the priority. So, when you make a change to that airspeed command, it will prioritize your commands and achieve the airspeed first before trying to achieve the selected altitude. On the other hand, if you set a 1500 fpm descent but don't pull the power, the airplane will overspeed -- this is the other side of the same coin.The proper technique for using IAS mode is to achieve the desire airspeed FIRST, then select IAS, which is more properly called "IAS HOLD" mode.

James,The airplane is going to do what you tell it to do. If you change the commanded IAS too quickly, it will try to comply, and yes, it will climb or descend as needed to do so. Think of it this way: You're telling the airplane that you want to get to your selected altitude, but that maintaining the commanded airspeed is the priority. So, when you make a change to that airspeed command, it will prioritize your commands and achieve the airspeed first before trying to achieve the selected altitude. On the other hand, if you set a 1500 fpm descent but don't pull the power, the airplane will overspeed -- this is the other side of the same coin.The proper technique for using IAS mode is to achieve the desire airspeed FIRST, then select IAS, which is more properly called "IAS HOLD" mode.

Thanks for that, I understand the procedure, and generally get it to achieve what I want, just suppose getting used to the lack of Autopilot/Autothrottle control that we get in the big stuff, and expected it to operate in some similar ways to lvl change function on the larger stuff, and not actually put you into a climb, but just level you off. To add to this then, in the real world, say you had set up correctly for a descent at 220kts, had a nice 1200fpm rate etc...then ATC asked you to slow to 180kts, how in the real world would this be managed? Would you change to a VS mode, reduce power futher, and select a lower FPM mode until you have your 180kts and then go back to IAS Hold Mode?RegardsJames

James,That would work...or, you could change the commanded airspeed with the thumbwheel at a rate that's slow enough for the airplane to respond without pitching radically. In the sim, that's 1 - 2 KIAS per second.

I am old school, when ATC throws something like that at me I usually hit the otto off button and fly the airplane.

Or you could do that! :(