steve m
Member
Been trying practice a lot of IFR approaches over past few months. I have the AP settings dialed in as much as I think possible until new version is released.
On about 25% of the time, when established inbound on LPV approach, I have intercepted the glideslope and proceeding\tracking down the glide path nicely when after about a minute or two, VNAV goes away.....
This happened again today, on my 2nd LPV approach. 1st approach (KSPA RNAV 05 in actual IMC) all worked fine, 2nd approach (KAVL RNAV 17) was at another airport about two hours later when I lost VNAV on AP.
When this happens, roll guidance via flight director remains valid but pitch guidance goes away and "VNAV" disappears.
When this happens, I still have valid glide slope indication on HSI but flight director is probably trying to maintain altitude hold. (not sure about this but I think the Pitch AP goes from VNAV to Alt hold mode and the Pitch servo disconnects while roll servo remains engaged.)
Couple of questions\advice.
1) Anybody else experienced this? I have a Garmin 175 for the GPS IFR navigation.
2) Once it loses\drops VNAV, I think the vertical portion of flight director becomes useless. I try and get back some vertical guidance from flight director by enabling VS mode and dialing in 600 fpm descent rate and this seems close to following the glide path and gives me the flight director back and I cross check with the Glide Slope indicator.
3) This problems seems to appear more prevalent on Vectors to Final (VTF) vs flying full approaches. Not sure this makes sense but nonetheless, this is my inclination at this time.
Any help, comments appreciated.
On about 25% of the time, when established inbound on LPV approach, I have intercepted the glideslope and proceeding\tracking down the glide path nicely when after about a minute or two, VNAV goes away.....
This happened again today, on my 2nd LPV approach. 1st approach (KSPA RNAV 05 in actual IMC) all worked fine, 2nd approach (KAVL RNAV 17) was at another airport about two hours later when I lost VNAV on AP.
When this happens, roll guidance via flight director remains valid but pitch guidance goes away and "VNAV" disappears.
When this happens, I still have valid glide slope indication on HSI but flight director is probably trying to maintain altitude hold. (not sure about this but I think the Pitch AP goes from VNAV to Alt hold mode and the Pitch servo disconnects while roll servo remains engaged.)
Couple of questions\advice.
1) Anybody else experienced this? I have a Garmin 175 for the GPS IFR navigation.
2) Once it loses\drops VNAV, I think the vertical portion of flight director becomes useless. I try and get back some vertical guidance from flight director by enabling VS mode and dialing in 600 fpm descent rate and this seems close to following the glide path and gives me the flight director back and I cross check with the Glide Slope indicator.
3) This problems seems to appear more prevalent on Vectors to Final (VTF) vs flying full approaches. Not sure this makes sense but nonetheless, this is my inclination at this time.
Any help, comments appreciated.
