Autopilot not trasnitioning to descent in Vnav Mode

[Skybet]

HI there, tryed really really hard to make it work, but we are facing some issues in our Tecnam P2002 with Skyview Classic with last updated software.
Two strange behaviours, not present last year when I first tried the function:

1) The blue line when VNAV becomes armed is not visible
2) When the VNAV mode kicks in (turning Magenta on the annunciators line) the autopilot is not commanding a descent

All other nav functions are ok, as well as the Lnav behavoiur of the autopilot and Vertical Speed transitions.

I read in a few posts that maybe the bluie line has been rmoved, and it would not be a problem, as long as the plane is then following the gliding path when intervepted, which does not happen..... Any suggestion?

PS: The glide path indicator at the right of the HSI does appear and behaves as expected, as well as the magenta Caret on the Vertical Speed tape, on manual it is easy to follow the indications.....

 

[airguy]

Are you capturing the glideslope from below? It will not capture and follow the glideslope unless you intercept from below.

 

[Skybet]

Sure, the glideslope is above, when I move closer to the airport in gets down. When in the middle the white vnav arm label.is replaced by a magenta vnav mode in the annunciator. And yet the autopilot does not react......

 

[airguy]

Sure, the glideslope is above, when I move closer to the airport in gets down. When in the middle the white vnav arm label.is replaced by a magenta vnav mode in the annunciator. And yet the autopilot does not react......

Check for a broken shear screw on the pitch servo.

 

[Skybet]

MEchanical failure you suggest... however in all other conditions eems to work well. ANy further check I can do?

 

[Marc_J._Zeitlin]

MEchanical failure you suggest... however in all other conditions eems to work well. ANy further check I can do?

Are you talking about using VNAV purely from the Skyview, approaching an airport or runway, or are you talking about using VNAV as driven from an IFR navigator of some type?

 

[Skybet]

Vnav purely from skyview......

 

[Solana]

Are you waiting and letting the glide slope go full deflection? Mine used to overshoot almost half deflection and then would dive for the glide slope. I had to reduce the VDI gain (RNAV approach) from 4 to 3.3. Now I have a great intercept.

 

[Skybet]

We set a 6 degrees angle, therefore we were low and near, no time to wait for a late recovery: we left anyhow the plane by itself and by the time we were over the airport the descend had not yet begun..... By the way, are you getting the blue line as per manual? We are not ......

 

[Solana]

Don’t remember anything other than the magenta line on the glide slope bar next to the HSI.

 

[Rhino]

I think he means the blue tick mark on the VSI.