Autopilot descent behaviour

[X-wing 0]

I'm using method 1 as described op page 86 in the Pilot's Tutorial.

During the descent the rate of descent and airspeed is changing constantly. It is causing an uncontrollable up and down movement of the aircraft and the only way to stop this, is disconnecting the autopilot and fly the aircraft manually.

 

Cruising level: FL160

Target level: 2000ft

IAS: 240kts

Initial rate of descent approx: 1000ft/min

The problem starts (slowly) below FL100 and is getting severe below FL60

 

Is there a way to avoid this, did I overlook something in the manual?

[scandinavian13 5,192]

 

 

did I overlook something in the manual?

 

My guess is that you didn't let the airspeed or V/S stabilize prior to setting the mode.  It's important to make smooth changes in throttle or IAS / V/S settings or the AP will start to chase the setting, and it can make things worse.

[X-wing 0]

Thanks Kyle,

 

IAS always was steady 240kts but maybe I've been a bit rough on the throttle during the descent. I think I have to read the manual once more.

 

I just practised method 2 as AP descent mode and this one is very smooth.

I don't know why I've never tried it before. :blush:

Problem solved!

[scandinavian13 5,192]

 

 

Problem solved!

 

Glad to hear it.  If you're using IAS, you definitely have to be easy on the throttle.  Smooth, slow, deliberate changes will mean smooth, slow, and deliberate AP reaction.

[SkipperMac 1]

Be careful with that 240 kts in descent! 240KIAS is surely very close to Vne!!!