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shazapis
12th Nov 2008, 08:24
Hello,

I need some help guys.

I am involved in developing standard op procedures for a newly upgraded military bird and I need some opinions on this:

The avionics suite has multiple position sensons (two INUs, two GPSs, blended INU/GPS solution etc and the EFIS has the capacity to build a very nice map display - pretty much like the one you get in the B734).

My question is: how do you fly a non precision approach from the standpoint of automation?

Do you build the prodedure up in the FMS prior to TOD and let the AP fly it in LNAV/VNAV?
After the FAF, do you need to have the PF in raw data (HSI mode and VOR/DME)?
Also, during transition to final (IAF-> FAF) do you have one of the pilots on raw data or is it all LNAV/VNAV?

BTW, the database only includes GNSS procedures (regular VOR/DME have to be built-up by the pilot). Also, the FMS does not talk to VOR/DME for the purpose of position sensing (it does interface with the receivers, but only for tuning them).

Please share your views on this with me.

Any reply will be very appreciated!

Thanks

shazapis
Athens, Greece

PS I could not figure out which PPRune forum is appropriate for this post so, if this one is not, sorry.

driftdown
12th Nov 2008, 08:33
Interesting, I expect the Mods will move it to the Tech Log forum as it is probably more relevant there.

Wizofoz
12th Nov 2008, 08:57
I fly B777s and we regularly fly NPAs in LNAV and VNAV, but ONLY when the approaches can be line selected from the data base. This ensures that details of the approach cannot be entered mistakenly due to transcription errors.

I would suggest that, if your avionics suite does not include an approved data base or it's military equivalent for the approach being flown, NPAs should be flown in one of the more basic modes (VORLOC or HDGSEL).

That notwithstanding, I don't see a problem with flying in MAP mode on the ND, as long a source of raw data is available to check correct tracking. Most EFIS systems have the capability of putting VOR, NDB or ILS data on either the ND or PFD even in Map mode. Provided your procedures ensure raw data is available in some form, MAP mode gives a better situational awareness than a full-compass rose type VOR display.

The question as to whether your avionics has sufficient sensor capability to fly certain approaches is covered by RNP/ANP. Do you have an approval as to the Actual Nav Performance of your gear? Generally to fly an NPA without tracking guidance, you require an RNP of .3NM.

Hope that helps.

ItsAjob
12th Nov 2008, 08:57
Our procedure forbids building or modifying the approach past the IAF as this apparently has to be verified by the supplier - Honeywell or such.
If it aint in the database you cant fly it by FMS here!

Denti
12th Nov 2008, 09:11
737 ops we do fly all non-precision approaches either in normal approach mode similar to an ILS (Integrated Approach Navigation) or LNAV/VNAV, only exception is a LOC approach with lateral navigation in VORLOC (IAN just tune the localizer and still fly in approach mode). However approaches have to be selected from the database and we are not allowed to change them or create them ourselves. If there is no database procedure available we have to revert to basic modes (VORLOC, HDG, V/S).

Raw Data check is not a problem as we can display NDB/VOR needles on the navigation display in map mode, ILS/LOC is displayed on the primary flight display.

As mentioned above we have to check Actual Navigation Performance against RNP. In newer airplanes we get visual cues about those on the PFD as well.

kriskross
12th Nov 2008, 10:02
The rules are that, as stated above, the approach must be selected from the database, must be accurate and must NOT be pilot modified.

Plus the obvious one for a NPA, you must be able to monitor raw data as well.
We usually fly it in autopilot but don't think that is specified in the rules,Flight Director is.

shazapis
12th Nov 2008, 10:42
Hello again,

thanks for the replies guys, they are very helpful.

Just a couple of additional questions:

1. Can you point me to any document that includes the requirement for the approach to be selected from the DB (FAA, ICAO, whatever)?

2. When PF is on raw data (EHSI - HSI mode and steering source is VOR) is it OK for the PNF to be on FMS (EHSI in MAP and steering source FMS - the only config that allows for the map to be displayed. If steering source is VOR then MAP display only draws a line from the aircraft position to the VOR - not very helpful). Also, EHSI has the capacity to draw bearing pointers on the display...

I suppose this is getting a little too type-specific... sorry

Again, your replies are very appreciated!

Best regards

Spiros

eckhard
12th Nov 2008, 15:27
Hi Spiros,

As long as you can display the relevant raw data, for example NDB or VOR needles, I would suggest that if the approach is not in the database, you construct a simple FMS final approach course. That way you can fly the final approach in LNAV, while monitoring the raw data via the needles. This will provide a much lower workload and a stable lateral profile, enabling you to devote more attention to the vertical profile.

How you construct this final approach course depends on the situation. For example; if the final approach course is aligned with the runway, you might be able to construct a 'Runway Extension' at a certain distance from the threshold. Some FMSs have this feature and it provides a relatively easy way to construct an extension to the runway centreline. If you can't do this you could define the final approach course towards or away from the beacon by using the 'Place bearing/distance' method of constructing waypoints. This does amount to 'map building' and may be frowned upon by some authorities.

Another simple method is to wait until you are approaching the final course and then to go 'Direct to' the relevant beacon, making sure that you type in the correct DTK (Desired Track) or course (CRS) before you execute. Some FMSs refer to this as 'PVOR' (Pseudo VOR) or 'OBS' (Omni Bearing Selector) mode.

There will be some who say, "What if you enter the wrong inbound course?"
My answer is that the same cross-checking skills are used and the same potential errors could occur when you are setting the raw data on a VOR approach using an HSI or an FMS course Line-Select Key. Both pilots must cross-check the inputs and the results must be checked against charts, common sense, etc.

Remember, in all this you are still displaying and monitoring the raw data, so it could be described as a 'raw data' approach with LNAV stabilisation.

As far as the vertical profile is concerned, I would use VS if the autopilot is capable of displaying the selected rate.

As to the missed approach, if the approach is not in the database you will have to fly this using HDG, but even here a simple depiction on the EFIS MAP of some relevant points may improve situational awareness.

With reference to 'the rules' about databases, etc., my understanding is that you must indeed fly an RNAV (GNSS/GPS) approach from a database-selected procedure, without modification. I don't believe there are any rules about using the FMS as described above to support conventional non-precision approaches. I did exactly this whilst being observed by a UK CAA Flight Operations Inspector and he had no comment to make. As always, it's a matter of knowing what you're doing with the equipment and keeping in mind any limitations thereof.

Hope this helps.

Capt Claret
12th Nov 2008, 17:34
G'day shazapis,

I fly 717-200. Dual IRS/GPS. Our FMS database contains many NDB and VOR NPAs but not all.

The FCOM requires that for a Database non-precision approach one of the two Nav Displays must be selected to VOR to display raw data, but it doesn't specify whether it's the PF or the PNF.

Our Company SOP requires that if the pilot builds the approach, it will be flown in TRK/HDG and V/S or FPA from the MSA.

flying for fun
12th Nov 2008, 17:41
Spiros

Why don't you do both? - automation is great when you have time to set up an approach & then have the a/c fly it - but when you are in a hurry - say because ATC have changed the goal post - then the old fashion needles can get you out of trouble.

Last year I heard an A320 crew get themselves very very messed up when they found out that the ILS approach was actually an ndb/dme approach at the last minute....

Giggey
12th Nov 2008, 17:47
Hi all.
My company allows full manged NPA just in case you have been trained in the sim, the DB is authorized and the authorities allows the company to do so.

The mai rule about doing such a procedure is absolutely not to make any change on the procedure, and even a DIR TO the final approach fix is not allowed so unless you'll fly the full procedure it is all useless.

So much better a selected on the needles.

I would be very carefull in flying a managed NPA just building it on the mcdu. Don't even know if it's generally allowed on another aircraft (i fly 320)

cheers

Denti
12th Nov 2008, 17:49
Checking raw data is of course good airmanship, but it is not required by EU OPS, at least not in all cases. We do not have to check and monitor raw data on NDB and VOR approaches if we have 2 FMC and database selected approaches. It is however still recommended (and most just display the RMI-needles on the ND). It is required to check and monitor raw data on LOC approaches and non database selected ones.

Putting relevant points for the procedure and missed approach onto the ND is of course allways a good idea, easy to do with the fix pages on the 737 and if you do not have any procedure you can select a runway and a runway extension which helps. But dont go too much heads down in the last minute, if you have to switch in the last moment just switch off everything and fly it manually raw data, basic flying is sometimes still required and actually quite a lot of fun.

safetypee
12th Nov 2008, 18:10
Slightly off thread, but if you have EGPWS fitted, check to see if it uses a direct GPS input, (or its own internal GPS receiver), opposed to a NAV blend. The latter could suffer map slip (drift), especially in areas without accurate raw-data nav aids, you may experience problems.

Port Strobe
12th Nov 2008, 22:22
To those quoting requirements to leave alone the approach in the FMC or whatever type specific term applies, does this originate from a national aviation authority or a company limitation? For GNSS approaches I can understand this because there are no raw data backups required for the approach hence any alteration to the procedure in the database is DIY approach design which is bound to end in a smoking hole somewhere, absolutely no questions asked about GNSS then. However when it comes to VOR or NDB approaches, these are overlay approaches flown in LNAV and VNAV (or fully managed or whatever it may be called). Why would it be illegal, or frowned upon at least, to either select an equivalent procedure or modify an existing procedure as circumstances require as long as raw data is monitored and adhered to in the event there is a disagreement from the map? An example that comes to mind is an NDB procedure is not in the database, however the NDB FAF coincides with the ILS FAP and follows the same descent path as the ILS procedure, so why not fly the ILS overlay in LNAV and VNAV whilst monitoring the NDB and appropriate DME and adhering to the NDB minima? Its not in the database but it puts you in the same point in space. With the same setup in the FMC, the pitch and roll modes could be changed to V/S and HDG SEL respectively whilst you monitor the raw data - great if there's a discrepancy whilst executing the approach but why increase the workload when there are perhaps more appropriate modes of automation available? It doesn't make sense to me why it needs to have the right label if it puts the jet in the same place at the same speed with sensible monitoring, but then again I'm eager to stand corrected if I've missed something?

Tee Emm
12th Nov 2008, 23:43
if you have to switch in the last moment just switch off everything and fly it manually raw data, basic flying is sometimes still required and actually quite a lot of fun.

Agree. The problem is that surprisingly few pilots are competent to do this because in all their FMS lives, full use of all available automation has been drilled into them and they lack both the self confidence and the situational awareness to keep their hand in during sunny weather.

As for quickly switching from automatics and all its pretty colours on the MAP mode to basic raw data hand flying all in the space of a few seconds, well there are some who argue for an immediate go-around and go into a nearby holding pattern in order to perform an extensive brief on how to set up the raw data. I kid you not..

shazapis
13th Nov 2008, 06:44
Tee Emm

>>Agree. The problem is that surprisingly few pilots are competent to do this because in all their FMS lives, full use of all available automation has been drilled into them and they lack both the self confidence and the situational awareness to keep their hand in during sunny weather<<

Actually it is the other way around for us. Most of us are rather experienced in the non-upgraded airplane (and its steam-gauge suite) and therefore a bit skeptical about the reliability of all this glass-cockpit magic. The fact that we had some pretty bad cases of failures doesn't help either. I personally had a case a month ago that I lost both GPSs and both INUs in flight. The blended solution (Kalman-filter aided INU) held on for a while but eventually died as well. Left me with an extreme case of map shift and DR as the best available navigational solution. Not pretty. Fortunatelly this was in rather nice wx and in familiar airspace.

Regards,

Spiros