RNP airbus driver

[michelda]

Hi guys,

somebody can explain me the RNP procedure reported in fcom 2.4.46 for brnav, rnp4 or rnp10?
I understood that I can insert my required accuracy (4-5-10) on prog page, but what is the redial equivalent?

thanks for your help
Michelda

[engfireleft]

I think you meant "radial", in which case there is no equivalent. The accuracy requirements for RNP and RNAV are completely different than anything for ground based navaids.

If you can get your hands on Airbus's "Getting to grips with modern navigation, version 5", it is an excellent primer. www.smartcockpit.com has version 4 dating from 2002 but it's still good information.

[michelda]

Thanks engfireleft

I meant radial........I have that getting to grip, but.......
I write for you the procedure for rnp10 (is the same for 4 or 5 but with different number).....

if a manual entry of accuracy is desired, the flight crew must manually enter: for rnp 10, enter 10 NM or use the radial equivalent to 10 NM XTK accuracy that is 12.2 NM.

ciao
Michelda

[engfireleft]

Oh I see. I've never considered using crosstrack on the CDI as the RNP integrity alerting is triggered off the RNP value entered in the PROG page. The crosstrack on the map display is an indication of where the airplane thinks it is in relation to the calculated track. The EPE of the airplane is a calculation of how accurate that track is. Two separate things.

I'm not sure about 4 and 5, but RNP 10 oceanic airspace does not require RNP alerting. Non-GPS equipment is certified for various periods of time from their last alignment or DME update. Airbus FMGC use a more or less linear formula in non-gps airplanes to increase the EPE once IRS only navigation begins, but the values have no connection to how the kit is actually performing. As long as you don't exceed the time you're good to go.

Sorry I couldn't be more help.

[michelda]

sorry engfireleft, but I think that my right engine gets fire.........

I didn't understand a lot...... But can you explain me how I have to use the radial equivalent?

thanks
Michelda

[engfireleft]

No I'm sorry I can't, except to say you don't have to. Just input the required RNP into the PROG page so that the FMGC will alert you if you exceed it.

[michelda]

thanks engfireleft

michelda

[guiones]

The RNP requirement that you refer to is an Oceanic requirement that you will likely never exceed unless you fly an ACJ. It use to apply more often when the A320 family was not equipped with GPS Primary.
In short, RNP-10 it limits the Navigation without ground based NAV's to 6.2 hrs from ground alignment and to 5.7 hrs from inflight update with a ground based NAV. This limits go to RNP-4 with GPS Primary.
With the range of the A320 family, except the ACJ, it is very hard to exceed this limitations. We took them into account during North Atlantic ferrys, but never came close.
As far as the paragraph on the mode of entry in the MCDU PROG page, it is a technicality; it mentions the Radial Equivalent as per certain regulations, but the common way of entering it would be 10NM or 4 NM.
The "normal" radials we refer to a VOR do not apply here, it is just RNP.

Hope it helps!

G

[michelda]

Hy guiones

Thank you for your help.
I fly A321 and A330 in etops operations and the procedure is the same...I guess that also on A340.

I think that procedure on fcom 2.04.46 is a little bit misleading....

Michelda

[Microburst2002]

Hi guys

I don't have that chapter in my FCOM: 2.04.46

I only have the 2.04.51, RNP is the title

What is the title of 2.04.46?

[guiones]

Same thing, just depends on the FCOM revision.

[Microburst2002]

I see

It is not very clear.

So you can choose between inserting 5 or 6.2 when in BRNAV airspace?

or between 10 and 12.6 when in RNP 10 airspace?

Obviously everybody would select the higher one, since it is less restrictive.