Does APP on the MCP light up during RNP approach?

[Boeing or not going 578]

My first time flying gps rnp approaches in the ngx and I have a question. When I press APP on the MCP, the light on the APP button does not light up like it would during an ILS approach. I see on the PFD that RNP is activated. Is that by design? - David Lee

[scandinavian13 5,192]

 

 

Is that by design?

 

It's normal for the APP light to extinguish after capture, yes. Have a look at the manuals that came with the product. They'll answer all kinds of questions like this.

[ALF1 15]

Approach arms VORLOC and GS. It actually remains lit until you capture, then it extinguishes. Remember that a button on the MCP, when lit, means that the mode can be deselected by pushing it. As APP cannot be disengaged after capture, the light extinguishes. You have to disconnect the A/P or press the TOGA button to exit APP mode.

 

APP mode relates to LOC and GS only and has no place in RNP approaches. The RNAV waypoints in the FMC fly the approach and on some RNPs and airlines it is required that you leave the autopilot fly the approach down to the DA, with the LNAV and VNAV modes engaged.

 

I just had a closer look at your question, if you are executing an RNP you dont have a valid LOC/GS signal APP will not arm. If you are combining RNAV legs to an ILS approach you can arm APP as long as you have tuned the ILS frequency and are receiving the valid LOC/GS signal.

[downscc 1,327]

This is interesting to me because I just flew the UA1230 KMCO-KIAH B739 flight yesterday and used the GLS27 approach... nice to fly something besides an ILS on every arrival.

[Boeing or not going 578]

It's normal for the APP light to extinguish after capture, yes. Have a look at the manuals that came with the product. They'll answer all kinds of questions like this.

The glideslope on the rnp approach wasn't captured yet though, that is when the APP light turns off for an ILS approach. Is RNP different? David Lee

[downscc 1,327]

The glideslope on the rnp approach wasn't captured yet though, that is when the APP light turns off for an ILS approach. Is RNP different? David Lee

There is a lot of information behind your simple question that has a lot of depends.... good place to start reading is FCTM pg 5.60 that describes how to fly an IAN approach.

[ALF1 15]

Here is some good info on how to conduct these approaches...Boeing specific

 

http://www.smartcockpit.com/docs/B737-Brnav-Rnp_Ops_and_VNAV_Approaches.pdf

 

Pages 41 onwards, a read to the whole document would be great.