View Full Version : IFR Protocol Query

29th Aug 2012, 23:08
As a helicopter driver I don't get into real airport procedural IFR very often so maybe one of my expert fixed wing colleagues can advise me on this question.

You arrive at an airport in EASALAND with everything set for an FMS based VOR approach. When you get there you find out that the VOR in question is not transmitting. Can I still do my planned FMS-based VOR approach?

Would the answer be different in FAALAND or any other jurisdiction?


G. :ok:

Pugilistic Animus
29th Aug 2012, 23:38
If there is an approved IFR RNAV overlay then most probably...but if there are any charted requirements [or Ops-Specs requirements] they supercede all of the above---some charts will have annotation to the effect of VOR or ADF or RADAR requiredif this is the case then you may not do such a substitution...

And in some areas of the world the procedure may not be permitted because the beacon does not meet WGS84 standards to allow compliance with an RNAV procedure--- the honest answer, as always, in aviation is that it depends...:)

Pub User
29th Aug 2012, 23:59
The basic answer is no. If you're flying a VOR approach, no matter how you get the machine to track the VOR, you still have to have its indications visible to you. If, as PA above says, there is an alternative or overlayed RNAV approach, then you can carry on with that.

ATC would not clear you to fly an approach that was not available.

Check Airman
30th Aug 2012, 05:40
The FAA is gradually updating its procedures to accommodate such a scenario. More and more plates are being renamed as "VOR or GPS RWXX". If that's the case, you don't need to have the VOR.

In any event, even if the approach title didn't have "or GPS", the approach will still be in the database, and you'll get approach sensitivity on the CDI (on Garmin products at least). In an emergency, this is a very useful solution.

30th Aug 2012, 06:54
In my part of the world, flying the VOR approach using a FMC data base stored procedure is legit provided that the VOR is out for any reason other than it has been decommissioned.

Naturally I am assuming that your aircraft and you personally are certified for FMC based approaches.

30th Aug 2012, 07:01
Many thanks you guys, not a decisive answer but the gist is clear. Ten years ago I was operating in Douala, Cameroon where the VOR had been U/S for years yet this did not stop the airlines (BA, SWissair, Air France etc etc) flying into that airport despite the only approach published being one that required the VOR.

How could this be?


30th Aug 2012, 08:52
Ten years ago I was operating in Douala, Cameroon

I think you just answered your own question. My guess is that there isn't that much oversight on actual operations in that corner of the world?



30th Aug 2012, 15:39
Since the VOR is simply a waypoint in the procedure, many GPS procedures are simply overlays. You actually dont need the VOR to be operational.

Pugilistic Animus
30th Aug 2012, 16:11
Technically possible but is it legal without the official wording on the plate?


30th Aug 2012, 16:27
Correct me if I'm wrong but in order to fly IT as an RNAV procedure, you would actually have to be approved for that. I.e. Aircraft RNP APP approved and THE operator must be approved as well for those operations?

Flying a B747 at the moment, our company is approved, however the 74 is limited to RNP 5 and 1 as per FCOM limitations section. So only LNAV/VNAV approaches of regular approaches. Monitoring navaids is not required as long as 2 FMC's are operational etc, etc according to FCTM.

When an approach is published as RNAV(GNSS) whe are not allowed to fly that approach!

Am I wrong in thinking that if for example the ILS in AMS is out, I can't legally fly a localiser approach to that runway, eventhough it is published in the FMS?

I know, from the component inop table, I can skip navaids required for intermidiate fixes if I have a GPS to determine that fix for example, but to fly a loc only approach when the entire ILS is U/S, I was under the impression that that was not allowed.

Thanks for possible enlightenment.

30th Aug 2012, 17:18
PA, I was thinking that of the procedure is in the box, it must have been approved somewhere along the way....the operator would know if their OpSpec and training allow them to use it.

I have noted there is confusion with these types of overlays, that many people feel that the VOR or other navaid must be operational, as it is shown on the plate, but that can be mistake.

I know of wuite a few RNP AR procedures where one of the waypoints on final is a VOR or NDB, but that is simply using the waypoint in the database, not an operational navaid.

Some RNP AR procedures use the navaid as one of the entry points, but again, it doesnt need to be operational.

Would really have to see specifics...


Pugilistic Animus
30th Aug 2012, 18:00

Oh yes everything is contingent on OpsSpecs approval but that doesn't mean that the FMC depending on the set-up can't fly the procedure without an approved RNAV most can and will many many procedure are still stand alone ...under Part 91 it's not permitted to make that substitution

Though I can not imagine the POI would grant the approval without the the codesignation VOR or RNAV (RNP) I would imagine that the opens up a can of worms that no one wants to deal with...

Pugilistic Animus
30th Aug 2012, 18:12
Oh you posted the plate after my last response but that's under a differnt administrator...one poster mentioned above that CASA allows that to be done...but the FAA doesn't...definitely not under part 91...but I couldn't imagine getting FAA approval under 135 and 121 OpsSpecs either

30th Aug 2012, 18:59

For a fact I can say that for one large European carrier, the T7 and 330 can fly the procedure above, the B74 can't!

Pugilistic Animus
30th Aug 2012, 19:03
Maybe a database issue T7 is more modern also...:)

30th Aug 2012, 19:33

Simply because in the FCOM 1 section limitations it does not say RNP APP ( or something to that effect) approved. The procedure are in the database and RNP alerting is provided, guess it's a payment deal to Boeing!!!

The plane is capable, but still not allowed.

Doesn't answer my earlier question though?

Pugilistic Animus
30th Aug 2012, 19:53
Flyburg in the US the carrier's POI or principle operations inspector is the one who approves everything for operations specifications i think you all call Opsspecs 'AOC'...but as you know everything even a change on paper in this business always requires bribery to the OEMs and the Authorities

All $$$ under the table...they're into the rackets I tell you!!!


31st Aug 2012, 03:32

no worries...I know there are procedures out there, just could not remember other than the AUS plates. There are many of those type of procedures in Alaska, GPS overlays to replace the navaids...

I dont even bother with the frustration of anything under FAA jurisdiction, they still believe that you can design an approach queue with RNP procedures with all of the ac on idle descent...and that somehow increses capacity while reducing fuel...

Pugilistic Animus
31st Aug 2012, 18:05
FPOBN why would a procedures designer not like CDAs just curious?


31st Aug 2012, 18:28
Nothing wrong with CDA, but the queue cannot be managed with ac on idle descent to threshold, which is the FAA mantra to 'save fuel"

I have plenty of RNP AR procedures that are CDA. What you have to do is idle descent from the STAR down to FL10, then manage the descent below FL10. You will actually save much more fuel, and ATC will be able to manage the queue.

Some countries in Europe do not allow idle descent below 3000 feet, as the engines are not at clean burn, and actually emit more pollution at idle...

Pugilistic Animus
31st Aug 2012, 19:03
Thank you for the explanation---makes sense...Generally,it's the airlines that are the ones obsessed with the fuel.. some times a bit too obsessed for safety...:\


31st Aug 2012, 20:14
No worries...I cant understand why they are so stuck with the RNP idle descent...

when you look at it, at a 3 degree GPA, its not a whole lot of throttle to go 180 or 160 on final...especially with CDA...

Look at FL400 to FL50 CDA idle descent fuel savings compared


Pugilistic Animus
31st Aug 2012, 20:58
Sir the FAA and the airlines are in the same racket together...;)

Just saw your last post...interesting figures...it does all add up after a while though...in fact I think that's why AA had the Silver Birds at one point, cuz the weight of the paint about 200-300lbs increased fuel burn, ironically this increased maintenance costs...but if they don't have the capacity to implement the scheme appropriately, I can imagine that they may actaully waste fuel with holds and such...engineers can never win!...:)