I am having trouble with VS [Answered]

[sharpless281]

Hi, before take off with fmc setup, I set my max altitude, click on VS and set that to 1500, press nav. No AP yet. When I take off I engaged AP. FMS enables and the KA does climb but higher than 1500, varies. I adjust throttle to about 180kts. I do set it back to 1500 but not sure why it does this.

[norcali.pilot]

Could you explain "FMS enables and the KA does climb but higher than 1500, varies." more?
Is the airplane leveling off at 1,500' indicated altitude? If you mean 1,500FPM it is because you set the autopilot to climb right at 1,500FPM vertical speed. You may have so much power on takeoff that the plane wants to climb at a higher rate during the initial climb.

Try this: Before takeoff, set the heading bug to runway heading (or arm the NAV mode), and set PITCH to +10°. During takeoff and initial climb, maintain 10° pitch up until the airplane reaches 170kts indicated airspeed (you may have to lower pitch gradually). Then, when the airspeed indicator reaches 170knots, engage the FLC mode to continue the climb.

[sharpless281]

Could you explain "FMS enables and the KA does climb but higher than 1500, varies." more?

Usually in the past I would set the altitude say 12000, then set the VS at +1500 then throttle back to 180KTS. (I have a Thrustmaster Throttle, not a auto Throttle Not sure if that a matters. I am started to use the FLC more so I will try your suggestion I am flying a SID so I use the heading bug as a reference only. Thanks

[Taguilo]

Hi, before take off with fmc setup, I set my max altitude, click on VS and set that to 1500, press nav. No AP yet. When I take off I engaged AP. FMS enables and the KA does climb but higher than 1500, varies. I adjust throttle to about 180kts. I do set it back to 1500 but not sure why it does this.

Hi,

FGS pitch modes (PTCH/VS/FLC) take the current pitch value at the moment the AP is engaged. For example, if aircraft is climbing with FD only and the VS was set to 1500 fpm, but the current VS is, say, 1800, engaging the AP will command a VS of 1800 fpm.
Same logic applies for the other modes (FLC and PTCH).


Tomas

[Victory103]

FLC set to the climb schedule is the normal way to climb in the KA, climbing in VS can end badly if you are not paying attention. Depending on load, you may not see the 1500'FPM up to cruise (I've seen <500 FPM in the high 20's on hot days).