LNAV NDB approach
 

Hello everybody

My question is: Is it legal to fly NDB or NDB/DME approach in LNAV FD/AP mode while non-flying pilot is monitoring raw NDB data ?

Thank you.

Yes,

Though why not fly in LNAV with the raw data an the PFs ND? Is it not possible to have the ADF needle displayed along with the LNAV track on your aircraft?

Sure, I can see the NDB needles on my aircraft, that's not a problem.
But some my colleagues state that it's not legal to fly in LNAV mode, so I should use HDG/TRK mode.

Wouldn't you always back up LNAV with raw data when flying a STAR, Approach or SID?

Aflora,

Ask them to back that up by reference to the Regulations!

There is no regulation about HOW you fly the approach, only that you fly it with reference to the appropriate aid.

Mike hotel, htese days most SIDS and Stars are RNAV and do not reference am aid.

Wizofoz
 

Thank you, but I still have some doubts

As they said, one of the main causes of Tu-134 crash in Petrozavodsk, Russia, is using of GPS on NDB approach, while some waypoints coordinates on final approach mismatch the actual WGS-84 coordinates. It's typical for Russia region where the SK-42 were used instead WGS-84 for long time.

AC120-29A states: 4.4.2. FMS Use for Procedures Other Than xLS or RNAV. FMS may be used to conduct VOR, VOR/DME, NDB, NDB/DME, LOC, and LOC Back Course approaches when suitable navigation position updating which
provides required accuracy and integrity is used by the FMS (e.g., DME-DME-IRS, or scanning DME, or VOR/DME, or GNSS position updating, or Localizer (LOC) updating, etc.).

So, I can use LNAV on any NDB approach while FMS in GNSS or D/D or V/D position updating? Or only charts with "NDB (GNSS)" statement?

Thank you

Two different things. That's what you need to conduct an NDB( or other NPA) WITHOUT the raw data.

If you are using the aid to navigate, you can fly in any mode you like.

we fly Lnav /vs with adf needle overlay. also vor can be lnav with other guy on green needles. can also stick pre view under FD

Ok.
Let's see into two LSZH (Zurich) VOR approach charts with two different headers:
- VOR Rwy 28
- (GPS) VOR Rwy 34
As I understand, I can fly in LNAV mode both approaches, but on VOR Rwy 34 it's allowed to use FMS (and LNAV mode) ONLY if FMS is in GPS updating mode.
Is that right?

The way I see it the approach to rwy 34 can either be done with GPS or VOR reference.

On my current job we fly NDBs with the PF displaying FMS data with both needles overlaying ADF data and the PM displaying green needles and the RMI needles selected to ADF and FMS (that one for cross checking the FMS data).

Approach can be flown either using NAV or HDG.

I wouldn't say 'most'. In fact, in western Europe I would say 'a minority' do not reference a nav aid. The majority of RNAV approaches around here are overlay approaches and while strictly speaking unnecessary, raw data backup is worth doing. That's just my opinion (and company SOP).

As for an approach based on an NDB, I imagine tuning the beacon is standard practice for most people, no?

in the company i fly for, the SOP standart for an NDB app is actually LNAV with the PM side in raw data for monitoring.

so yes, its legal, and in some cases like mine its what the company wants.

I'm with Mikehotel152. When flying an NDB approach there is absolutely no excuse not to tune the relevant beacon. Likewise, when cleared direct to an NDB, we all know that we can select direct to that beacon in the FMC and engage LNAV, but good airmanship dictates that the beacon is also tuned and that basic tracking is monitored. Same goes for NDB holding patterns.

We fly it managed / managed... Infact not allowed to fly it selected by our own company rules.

Flying in none WGS84 airspace is another issue however... As I dont currently do it... I would need to look it up... But from what I remember our ops manual does not let us fly the approach in managed unless it is in a list of procedures in our ops manual that have been "verified"

But in short for us we are not allowed to fly an NDB in heading select... It has to be done via the FM.

The Douglas/Boeing FCOM required raw data to be set on at leastone of the ND for a VOR/NDB approach. Said approach can only be flown in NAV if it is loaded into the FMS from the FMS data base. In other words, one can't build the approach with PBD and then fly it in NAV and/or PROF.

one can't build the approach

Very naughty to do that. The box accuracies are different as I understand between what the pilot and the database OEM can do. More than a few mishaps have had pilot built approaches implicated in the swiss cheese sequencing of events.

Hopefully one of our procedures experts will jump in to comment.

Raw data monitoring is recommended but not required anymore. All non precision approaches are flown as IAN which means the same presentation and basic procedure as an ILS, however the final approach course and glide path are FMC generated. That means of course that the approach has to be in the database, self generated procedures are not available and not allowed. During winter one has to be careful about temperature correction and in case of FMC procedures about the temperature limit for that particular procedure.

Generally we have tuned the NDB and have the needle on our ND, same for VOR approaches. LOC approaches have to be flown with reference to the localizer anyway which is then shown on the PFD. That is for the 737 fleet, dunno how they do it on our busses (A320/A330).

Interestingly, for reasons unknown, several NDB approaches are not in the database. Eg, YAYE NDB only has the final section of the approach coded, not the reversal turn.

For now I'm convinced in the next statements:
- I can fly any NPA in LNAV mode if procedure has generated by FMS from database;
- It's strongly recomended to monitor the raw data from relevant beacon for cross-check, because of probable mistakes in the database, FMS faults or manual entries;
- It's restricted to use FMS in non-GPS (DME/DME etc. ) updating mode if NPA requires GPS (DME/DME etc)

Hi John,
I agree.
Some crews seem to believe that the published Jeppesen / Aerad Non Precision Approach, (based on radio aids) can be replaced by the RNAV display for the overlay.

Building one's own approach in the FMC / FMGC with an undetected error will only mislead the crew. The overlay method was supposed to enhance situational awareness but some to seem to believe it can now be used in stead of the published approach.

If the Jep plate says RNAV GNSS / DME/DME then "fill your boots" - else you must display and monitor the published aids.