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How to properly arm autopilot for RNP approach?


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Hi,

 

What is the proper technique to fly RNP approach with the CRJ? On the Working Title CJ4 with Proline avionics I enter the approach to FMS, then wait for TERM mode and finally LPV. Before the FAF I would arm the APPR mode and the plane would fly RNP approach similar to ILS. With the CRJ this seems to be different. Thanks!

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The CRJ is not capable of RNP approaches. When you fly an RNAV approach it will have to be flown in either a dive and drive or CDFA/CANPA method. The aircraft will not fly itself down vertically to the runway. We use V/S with a predetermined rate based off of our groundspeed for these approaches and begin that descent 0.3nm before the FAF. This is not an Airbus, this is not a Boeing. This plane will not hold your hand at anytime, it'll make you work. 

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3 minutes ago, Alexander Pressley said:

The CRJ is not capable of RNP approaches. When you fly an RNAV approach it will have to be flown in either a dive and drive or CDFA/CANPA method. The aircraft will not fly itself down vertically to the runway. We use V/S with a predetermined rate based off of our groundspeed for these approaches and begin that descent 0.3nm before the FAF. This is not an Airbus, this is not a Boeing. This plane will not hold your hand at anytime, it'll make you work. 

Thanks for your reply. That's the thing, I wasn't able to figure out if it's capable for LPV or LNAV/VNAV RNAV approaches or not. I was now able to make it fly vertical guidance itself by pressing VNAV before the FAF point. But then it must not be the proper way to execute it.

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5 minutes ago, speedbird1229 said:

y. That's the thing, I wasn't able to figure out if it's capable for LPV or LNAV/VNAV RNAV approaches or not. I was now able to make it fly vertical guidance itself by pressing VNAV before the FAF point. But then it must not be the proper way to execute

Not really. There aren't many operators that even have that Vnav button. And even then it is only used for enroute descents as far as I know. The Vnav in a crj is advisory only. I would side with the Vnav mode should not be used for Rnav approaches as it's no different then the snowflake on the rest of the CRJ's it just does the V/S adjusting for you. But if there is any Bluestreak guys on here, I know y'all have at least a few birds with that VNAV mode on the MCP, do the Fed's allow y'all to fly your Rnav's in that mode or do they force you to CANPA it?

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There is a (very expensive) real world STC modification available for the Proline 4 avionics system that will give a CRJ the ability fly a WAAS LPV RNAV approach with full vertical guidance. (It can be flown like an ILS using APP mode), but very few (if any) airline operators have installed it. It is more likely to be found on CRJs used for charter or corporate flying. WAAS LPV Is not emulated in the Aerosoft CRJ.


As Alexander noted, the real CRJ is also not approved for any RNAV approach labeled “RNP” or “RNP AR”.
 

In the real CRJ FMS, RNP approaches won’t even appear as selectable options on the DEP/ARR menu at an airport where they exist, but since the Aerosoft nav database shows every available approach at every airport, they do show in the list. You can try flying one in the sim, but it may not display or behave correctly under autopilot control. Sort of a “try this at your own risk” situation.

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