navigation to us
 

Okey dokey.

Second stage interview fast approaching - as in Friday week - and i was wondering if someone could offer me some advice.

Last week i went to Swanwick and was amazed at the set-up and also how generous people there were with advice and their time. Thanks to you all. It was hugely appreciated.

One of the most common questions which seem to be asked is "How an aircraft navigates over the Atlantic?" What exactly do they expect you to answer.

The document which they send out for us potentials to learn revolves largely round VOR's whereas it seems to be via waypoints and GPS. Could someone give me an idea what they are and also what the interviewer will expect you to know.

I would be incredibly grateful

To my admittedly limited knowledge, aircraft for the majority fly on pre-determined tracks (NAT - North Atlantic Tracks). These are set by ATC each day and positions of said tracks are determined by the jetstream. which moves west-east over the atlantic. The pilots speak to Oceanic controllers at Shanwick (shannon and prestwick) when over the eastern n-atlantic and to Gander when in the west n-atlantic.
Due to the expanse of water there is no radar coverage and communications are done on a HF radio rather than the normal radio's. Pilots fly the track by entering waypoints into their fmc/mcdu like they do normal flight. The NAT waypoints consist of an entry and exit point, eg LIMRI and then lat/long points eg 56N020W. Crossing the atlantic pilots make position reports at every waypoint, or every 45mins (whichever is sooner). Should the controllers wish to contact the pilots they send an audible alert to the a/c using the a/c's SELCAL id. Each plane travelling over the atlantic must have a SELCAL, this means the pilots don't have to stay tuned in on the HF radio as this contains a lot of static noise.

I hope this is of some help to you, someone else maybe able to correct any errors I have made and/or give you more detail.

Start off by saying NAT tracks and INS (using the lat/long MARKED ON THE RAMP) as a start point...
Then say it uses a Gyro and an accelerometer for knowing where it is and how fast its going!
If you mention GPS make sure your ready for him to ask the problems with it...
1. sattelite coverage.
2. in civil terms its accurate to 100m in mil. terms 2m.
3. the U.S can take it away at anytime for mil. use in a war.

Say these and believe me, he won't ask anymore simply because he wont know anymore!!

This is straight out of the Intro course Nav and Navaids lessons.

God bless you all. Unbelievably grateful.

Anyother advice on what to swot up on. On trip to Swanwick it was implied that there is pretty much a set questionnaire for the interview. Firstly would you say this is true and secondly are there any other incredibly likely questions?

What i am really struggling with is the depth in which i am meant to learn things. ANy advice?

Thanks again!!

Info
 

http://www.gps.gov/faq/gpsfaq.htm

This might help. Taught me as much as I need to know about GPS and I've been doing the job 20 years.

Back when I applied to NATS (10 years ago...) there was pretty good description of the north Atlantic track system in the literature sent out to applicants, and many of the questions were a test of whether you'd done the reading - there was a reading list given too and it wasn't long!

INS uses gyroscopes which measure accelerations in all directions to constinuously update the position of the aircraft. It is so accurate that it is set up using the lat and long of the individual stand at the departure airport.

You might want to mention RVSM (reduced vertical separation minima) which allows suitably equiped aircraft to use 1000 ft vertical separation above FL290 rather than the 2000 ft used between non-RVSM certified aircraft and in non-RVSM airspace. The Shanwick FIR is RVSM airspace. If you get that in, they'll probably assume you've read enough to show willing. Ultimately, that's what the interview is all about. If you knew it all already, you wouldn't need training! They want to know that you're dedicated enough to the job to do some research. Good luck.

On the personnel interview you are asked 60 set questions and are expected to give honest answers with examples, like do you have good common sense??? answer: yes....please give and example...

that sort of thing...I didn't enjoy that part one bit and must have used the same example about 10 times! lol

All previous posts correct.

Just to add a little more info, some aircraft, indeed the more modern ones have IRSs in lieu of INS. That stands for Inertial reference sytem - lasers and smoking mirrors! INS applies mainly to the older DC-10s, L1011s, DC-8s, 747 classics.

Not all aircraft fly the standard NAT tracks depending on their final destination and the allocated Flight Plan route. These are called "random" tracks and usually cross the standard ones diagonally. For example LGW to TAB or GND. Some but not all operators have 180 minutes ETOPs capability. Should there be an aircraft defect which cannot be deferred because of the strict requirements, then you may find you can only do 138 or 120 minutes from the nearest suitable airfield on your route. This means a more circuitous route and hence more time!

All the stuff about RVSM, HF radio links, position reporting and SELCAL is spot on. The North Atlantic (NAT) is actually divided up into 4 sectors: Shanwick, Gander, Santa Maria and New York. Which you use depends on your route. Since most modern aircraft are 2-pilot operations, operators will require one of the pilots to keep a running plot on a trans-oceanic chart. This way you will find out soon enough if you are on track without any VORs/NDBs to rely on!

Still amazes me that after coasting out over Lands End and getting your oceanic clearance and ETOPs entry point, after 8 hours or more of nothing but ocean, you can still accurately find the correct Caribbean island and runway:cool: !!

Good luck!

767 Driver

Question for the Atlantic Oceanic controllers.

In Oz over water we have CPDLC (Controller Pilot Data Link communication) and ADS (Automatic Dependent Surveillance) which both use satelite or VHF (when in range) links to give us on our display a position of the aircraft (actually more accurate than radar) and the capability to communicate to the pilot by text message.

Do you have this capability at Shannon, Gander, Santa Maria, or New York? I know we had the New York oceanic controllers looking at our gear 2 years ago but went with an american version of our eurocat 2000.

By the way, I understand that modern aircraft use GPS nav rather than INS or IRS these days. I thought it was the older models that still had INS or IRS.

They use both - most of the time the crew will not even Know what is being used at any particular point in time.
Interesting to see the anti-GPS slant in the questions - it's more accurate than 100m, even in the raw form. Why not ask what can go wrong, does go "wrong" with an INS or IRS....

reynoldsno1, I'm not sure if you're referring to me, but if you are, GPS is a godsend in Australia with our large expanses of f#ckall and few navaids in between, with only 15% radar coverage of our airspace. Certainly no anti-GPS bias here.

DP

I think the inaccuracies of GPS quoted may refer to before the "degradation" was switched off a couple of years ago. Even with my cheapo handheld GPS I can resolve my position to 20ft so suspect properly mounted all singing and dancing airliner ones are probably more accurate still.

DP - most certainly not. I am involved with GPS on a daily basis, and I totally agree with you!! I was referring to the bias in Europe/UK - at least in aviation applications, anyway.

Alexb757

That amazes you??

Think about the old boys in WW1/2 in their paper aircraft DR navving hundreds of miles over the sea at night to bomb Taranto etc... thats what amazes me!!

Dirty Pierre,

Yes, CPDLC and ADS are used on the North Atlantic. Shanwick, Gander and Santa Maria have full capability whilst NY operates the system slightly differently. Iceland is also ADS capable. At the moment, only certain companies have approval in certain areas.

For example, BA 777s (my lot) can use CPDLC in Santa Maria, Shanwick and Gander and ADS for NY. Tremendous system. At the moment there are certain CPDLC functions which can't be used, such as 'reasons for a request', but the basics are more than sufficient.

For those not in the know, ADS is a satcom datalink of position reports at each waypoint. CPDLC allows controllers and pilots to exchange clearances and instructions without using the radio.