Stupid NAT/MNPS Question

[unclematty]

Hi everyone,

I've recently started crossing the North Atlantic in a aircraft equipped with a multi-sensor FMS (NZ-2000). Which sensors are to be used/are you using to accomplish the 10 minute/GNE check?

Logic would dictate FMS position should be used....although if GPS should fail, it does make sense to transpose the IRS positions to the plotting chart.

Also, is anyone documenting winds/TAS/GS on the plotting chart as part of the 10 minute/GNE check.

Thanks for the insight!!

UM

 

[G100driver]

Use the FMS.

I would not worry about it (you are overthinking this ). People cross the NAT all the time IRS only. Your FMS will update your position when it VOR/DME updates when it get a signal.

 

[G100driver]

Here is another question.

What is your airplane navigating off of? Your FMS that takes the most accurate of the following

GPS
VOR/DME
IRS

Your IRS could be up to 2.9 (I think in the NAT). By plotting your IRS you not actually plotting your aircraft position.

 

[banned username 2]

Hi everyone,

I've recently started crossing the North Atlantic in a aircraft equipped with a multi-sensor FMS (NZ-2000). Which sensors are to be used/are you using to accomplish the 10 minute/GNE check?

Logic would dictate FMS position should be used....although if GPS should fail, it does make sense to transpose the IRS positions to the plotting chart.

Also, is anyone documenting winds/TAS/GS on the plotting chart as part of the 10 minute/GNE check.

Thanks for the insight!!

UM

Use the FMS Position, even if you loose GPS, the FMS will use the calculated position difference from the IRS and give you a more accurate position than any single IRS...

 

[unclematty]

ok, next question...

Is there a legal requirment to log IRS positions at the end of a oceanic flight, when using a multi-sensor FMS (Dual GPS, Triple IRS, and DME or VOR/DME) update capibility?

P.S. Legal requirement outside of company procedures/FOM/SOP. Yes we are an air carrier.

 

[604av8r]

Hi everyone,

I've recently started crossing the North Atlantic in a aircraft equipped with a multi-sensor FMS (NZ-2000). Which sensors are to be used/are you using to accomplish the 10 minute/GNE check?

Logic would dictate FMS position should be used....although if GPS should fail, it does make sense to transpose the IRS positions to the plotting chart.

Also, is anyone documenting winds/TAS/GS on the plotting chart as part of the 10 minute/GNE check.

Thanks for the insight!!

UM

UM,

No such thing as a stupid question, right?

The FMS position is used by the navigation system. The FMS position is a blended solution using Kalman filter algorithms. Without getting too out-of-control, it is a weighted solution that uses all navigation updates to formulate its position. However, since GPS is most accurate, it is heavily weighted over the other inputs and effectively is THE position solution. I've heard the Flightsafety instructors teach that it is GPS position only and will only start using other inputs (DME/DME, VOR/DME, etc) if GPS fails. That is incorrect... technically. Keep in mind, if the GPS fails (all 2 or 3 if them!), the Kalman filter starts updating position using everything available to it. If your oceanic, that "pretty much" leaves just IRS accelerometer measurements, which will "pretty much" guarantee DR mode.

So to answer your question, use the FMS position... that is what the aircraft is navigating by.

Responding to your last question, I thought recording the IRS position after landing had to do with maintaining RVSM certification, but can't swear by it.

Hope this helps a little, and made some sense!

 

[unclematty]

604av8r,

Best explination, I've heard so far. As far as IRS position recording at the end of a flight, who knows. I've done some research on this and the AFM says (for this specific nav system) there is no time limit for Class II navigation, with GPS installed and operational. If GPS fails...IRS are to be used (as sole source) for no more than 6.2 hours from the time of GPS failure. Of course this agrees with the advisory circular that deals with RNP/MNPS navigation..

What type of info are you recording on the plotting chart and/or master document?

 

[G100driver]

UM,
Responding to your last question, I thought recording the IRS position after landing had to do with maintaining RVSM certification, but can't swear by it.

Wouldn't that have more to do with MSPS as opposed to RVSM? I really do not know the answer.

 

[AA717driver]

The RSVM requires that you record the altimetery info on the master plan. The FMS positions are probably required for MNPS certification.

I'll ask during our Int'l recurrent tomorrow.TC

 

[unclematty]

AA17...To specify..I'm asking about IRS positions, not FMS positions. PM me with the local of international procedures...


UM

 

[G100driver]

Just looked up our international procedures manual ... could not find any reference to logging IRS in post flight (we do have altimetry logging requriements, however.)

 

[unclematty]

anyone else have procedures loging IRS positions post flight (using multi-sensor FMS)??

 

[unclematty]

ok, another Class II/Oceanic Question....does anyone know the requirements for an FDE check using multi-sensor fms (gps and irs)?