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onebob

RNAV Approach

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Just completed a flight from Oakland (KOAK) to Red Bluff MUN (KRBL). didn't enter a flight into the GTN750, just used vor to vor on the autopilot NAV until 50 miles out then did a direct-to KRBL, picked the RNAV 33 GPS LPV approach.

decent/target alt 3500, All went well, Alt-Trim on the autopilot changed to ALT-Trim GS and GS indicator appeared on the strip. However when the GS hit the mark it didn't descend. Turned off Autopilot and did a manual landing.

Not sure what I missed, should I have hit the Apr on the autopilot.

 

Interesting to note the waypoint/dist/trk info from the GTN750 was passed onto the G600 ( of course not the flight path). The autopilot hit all the alt's using the vs .

 

bob

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I dont have the aircraft you are flying and I am not a pilot, so forgive me if I am wrong but....if you select a RNAV approach, why would the aircraft follow the glideslope ?  RNAV is an approach to get you to decision altitude without the use of ILS or G/S ?

 

If you want to do an ILS approach you should be selecting that from the FMC/FMS and activate APR on the autopilot.

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I dont have the aircraft you are flying and I am not a pilot, so forgive me if I am wrong but....if you select a RNAV approach, why would the aircraft follow the glideslope ?  RNAV is an approach to get you to decision altitude without the use of ILS or G/S ?

 

If you want to do an ILS approach you should be selecting that from the FMC/FMS and activate APR on the autopilot.

 

You can perform an LPV approach with GNSS in the US which will give vertical guidance and takes you to decision height minima just like an ILS. A "normal" RNAV without vertical guidance takes you to the MDA (Minimum Descent Altitude) from where you proceed visually (either straight in or circling), which is a little different to a Decision Altitude.

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It's probably just a bug in the database or the autopilot not seeing the vertical guidance. Was it showing on the CDI?

Even non-LPV approaches should give vertical guidance if it's available. When I used to fly into Potomac, I always had it even though it wasn't legal to follow.

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What altitude did the OP select on his MCP. As far as I am aware the aircraft will not descend below MCP altitude unless in APP mode ?

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Yes, you need to arm APR for LPV approach just like you would for an ILS

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Same problem here. Aircraft follows vertical guidance at the beginning of the descent but when approaching the runway, it stops descent, i should say it doesn't descent fast enough to follow the vertical guidance. Another thing, oil pressure is always  around 40 psi (yellow arc) . The green arc starts at 60 psi.

 

Regards

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Yes, you need to arm APR for LPV approach just like you would for an ILS

Yes that was it, still had a problem which was it didn't like flying the transition (IAF at 3500' down to the FAF 2000'), when I tried without the Transition it was spot on.

 

bob

Same problem here. Aircraft follows vertical guidance at the beginning of the descent but when approaching the runway, it stops descent, i should say it doesn't descent fast enough to follow the vertical guidance. Another thing, oil pressure is always  around 40 psi (yellow arc) . The green arc starts at 60 psi.

 

Regards

same here, also the cyl head and EGT temp don't appear to go up either.

 

bob

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