RNAV Approach with 737 NGX

[wanabflyer 53]

I have pretty well got the hang of flying the NGX using the various navaids, using SIDS, STARS and Localizers and hand flying approaches and landings, but do not know how to set up and fly an RNAV approach from TOD to touchdown at a runway with no LOC freq as it should be done.

 

Is there any tutorial on this procedure, specific to the 737NG and its FMC?

 

Thanks,

[Simba 34]

Did you read the FCTM document that came with the software? I think it's probably your best resource on learning how to fly an rnp approach.

 

Sorry I meant rnav approach

[Vagabondo 23]

Start by selecting the RNAV approach in DEP/ARR page of the FMC. Your choice of of approach method is either LNAV/VNAV or IAN. As Simba says, these are described in the FCTM Apprach Chapter, under Non-ILS Approaches. But also look at FCOM1 Normal Amplified Procedures for IAN and VNAV Instrument Approached. Also FCOM1 Supplementary Procedures, RNAV AR instrument approaches.

[megs8888 20]

Thanks.

[wanabflyer 53]

Thanks for the replies guys. Busy reading.

 

Regards,

[hopskip 253]

RNAV approach from TOD to touchdown at a runway with no LOC freq as it should be done.

 

Is there any tutorial on this procedure, specific to the 737NG and its FMC?

 

Being that an RNAV approach is still a non precision approach (a very precise non precision approach to be sure), I believe that the procedure includes not running the autopilot to touchdown, and instead disconnecting the autopilot, and using the yoke at or prior to minimum decent altitude. If you don't have both Autopilots coupled, and flare/retard mode armed, the aircraft won't autoland with autopilot engaged through to touchdown.

 

You can't get both Autopilots coupled and flare/retard mode armed if you have no localizer/glideslope tuned on both nav radios.

[Fabo 213]

Indeed. It might even call out "Autopilot" at 100ft to remind you, not sure if that is a feature of the NGX.

[Vagabondo 23]

Being that an RNAV approach is still a non precision approach (a very precise non precision approach to be sure), I believe that the procedure includes not running the autopilot to touchdown, and instead disconnecting the autopilot.

 

You are quite correct. Just to add some detail, an RNAV approach is a non-precision approach. The requirement for disconnecting the autopilot is an operating limitation, not a technical one. If you look at FCOM1, Limitations, Autopilot you will see there are FAA rules and JAA rules. JAA rules define a minimum use height for a non-precision approach of 158' AGL (curiously above ground level, not threshold/airport level!) and that the A/P must also be disconnected by 50' below the MDA. FAA rules simply state the AP must be disconnected by 50' AGL.

 

Which rules to use depends on your aircraft registration. Most of the world operate to JAA rules. Apart from obviously the US, I know China is FAA. I expect all the Americas to be FAA and perhaps some parts of Africa?

[hopskip 253]

You are quite correct. Just to add some detail, an RNAV approach is a non-precision approach. The requirement for disconnecting the autopilot is an operating limitation, not a technical one. If you look at FCOM1, Limitations, Autopilot you will see there are FAA rules and JAA rules. JAA rules define a minimum use height for a non-precision approach of 158' AGL (curiously above ground level, not threshold/airport level!) and that the A/P must also be disconnected by 50' below the MDA. FAA rules simply state the AP must be disconnected by 50' AGL.

 

Which rules to use depends on your aircraft registration. Most of the world operate to JAA rules. Apart from obviously the US, I know China is FAA. I expect all the Americas to be FAA and perhaps some parts of Africa?

 

Good detail. The exact Autopilot disconnection altitude would usually be part of the Airline's SOP (and by definition would never be "lower" than the FAA/JAA/CAA rules.)

 

Regardless, whatever that altitude is, it will be before touchdown. There's no Auto Landing for a Non-Precision approach, and "Precision Approaches" basically include the following types of approach.

• ILS approach.
  

 

and that's pretty much it.

[wanabflyer 53]

 

 

Being that an RNAV approach is still a non precision approach (a very precise non precision approach to be sure), I believe that the procedure includes not running the autopilot to touchdown, and instead disconnecting the autopilot, and using the yoke at or prior to minimum decent altitude. If you don't have both Autopilots coupled, and flare/retard mode armed, the aircraft won't autoland with autopilot engaged through to touchdown.

 

You can't get both Autopilots coupled and flare/retard mode armed if you have no localizer/glideslope tuned on both nav radios.

 

I understand that I do not use autopilot to the runway, I don't even on an ILS approach, I merely use it down to runway visible, then disengage AP & AT and manually land. I am more concerned with the instrument procedures used from TOD to runway being visible on a RNAV approach. I don't have a problem finding my way to the runway and landing, I just would like to do it as it should be done.

 

Regards,

[hopskip 253]

I understand that I do not use autopilot to the runway, I don't even on an ILS approach, I merely use it down to runway visible, then disengage AP & AT and manually land. I am more concerned with the instrument procedures used from TOD to runway being visible on a RNAV approach. I don't have a problem finding my way to the runway and landing, I just would like to do it as it should be done.

 

Regards,

 

NAV display screen on MAP mode, VNAV and LNAV engaged. Chart out and setting MCP Altitude to either ATC assigned, or the next step-down where flying class G or OCTA. FMS in LEGS page so you can cross-check vertical profile against the chart by waypoint name and expected crossing altitude. Disconnect autopilot when visual and transition to visual approach. Never decend below minimums without being visual. Keep an eye out on ANP Navigation performance.

[Fabo 213]

Or you may just press the APP button and watch the magic, if your airline coughed up for IAN option

[Vagabondo 23]

Or you may just press the APP button and watch the magic, if your airline coughed up for IAN option

I use IAN regularly and I am not a fan. It is like an ILS, but not quite. For example, there are gottchas in the setup, the phraseology is different, the procedure is slightly different, it doesn't work with some RNAV approaches, there are (not demonstrated type) limitations on the slope and now we have to re-cycle the FDs at minimums. LNAV/VNAV is easy enough and works for every kind of non-precision approach where the FMC contains the approach or something close enough. Also it is a different procedure than ILS for a different type of approach to an ILS, this makes ergonomic sense to me.

 

However, despite all that ranting, I haven't used IAN much in NGX to know if some of these foibles exist in the sim.

[wanabflyer 53]

One should not forget that many runways that require an RNAV approach, are not Localizer equipped, so LNAV/VNAV to visual is your only option. example: RWY 19L KLAS.

 

Regards,

[Vagabondo 23]

One should not forget that many runways that require an RNAV approach, are not Localizer equipped, so LNAV/VNAV to visual is your only option. example: RWY 19L KLAS.

 

Regards,

IAN can be an option then too, not just LNAV/VNAV.