A cold dusk is setting in in Moscow as we pre-flight the aircraft for our non-stop flight to Los Angeles. Slowly thawing our frosty aircraft back life on the ramp, we have more than just the usual transatlantic flight preparations to go over. Our objective today is a little different… The shortest path, and our planned routing, between sub-zero Moscow and mild LA is (as the picture above illustrates) to fly ‘over the top’. I.e. fly at or near to the north pole.

Whilst these routes are profitable and becoming more widely used, flying near to the poles or within areas of ‘magnetic unreliability’ is not without its hazards. Perhaps most obvious to the layman, are the deadly freezing temperatures on the ground below. If you have to divert and land in an emergency, how will people be able to stay warm? Perhaps most obvious to the pilot is how they will navigate reliably when so close to the magnetic pole. Both are two of many very valid operational concerns that are discussed in the article.

Sections covered below:

What is considered North Polar
Communications
For the layman – Why is navigation different in the Polar Latitudes?
Navigating in Polar Airspace
Space Weather and Cosmic Radiation
Cruising Altitudes
Flight Plan
Contingencies

What is considered North ‘Polar’?

Operations North of 78 00º N. The operator must be authorised by their designated authority (i.e. FAA) to fly within this airspace.

Accompanying authorisations may also be required, such as;

• Approval to fly within the Area of Magnetic Unreliability (AMU) (the FAA considers this anything above 67 00 º N).
• Canadian MNPS approval
• ETOPs approval if your flight are that remote that there are no airports within 180 minutes.

Communications

• VHF and HF (HF serviceability depends on solar activity)
• CPDLC Magadan
• Datalink south of 82 00º N

For the layman – Why is navigation different in the Polar Latitudes?

If you’re a pilot then you know that any compass will point to magnetic north (based on the earths magnetic field), not true north (where all lines of longitude run to and intersect – north on your map). The difference between these two values is called declination, or variation. It stands to reason that variation is, therefore, a very important factor in our navigation calculations. If we didn’t apply variation to our navigation calculations, we’d be flying in reference to magnetic north, not the actual geographical true north. The problem is the amount of variation changes in an un-linerar fashion, so we must always refer to our maps and make sure we are applying the correct amount of variation for where we are geographically. Luckily, in air transport aircraft our Flight Management Systems (FMS’s) do the job of factoring in the changing variation during flight to ensure we’re always navigating correctly.

But look at the picture below. The red and blue lines (Isogonic Lines) are lines of equal variation. There is a tighter concentration of isogonic lines close to the poles, and fewer lines toward the equator. So in the northerly polar region, the changes in variation are so large and so frequent over relatively small distances, that compasses become unreliable and computing an accurate course becomes difficult, even for our onboard flight computers.

This could send many compasses haywire.

The green stars represent the North and South Magnetic Poles. The blue and red lines are isogonic lines (lines of equal variation). The black lines represent areas where true north is equal to magnetic north. The isogonic lines have a lobe-like characteristic, with less density near the equator, or more strength and density closer to the magnetic poles.

Navigating in Polar Airspace

In a nutshell, operating by means of magnetic references is not authorised in areas of magnetic unreliability and polar latitudes.

Entering Polar

Some aircraft will automatically switch to true before reaching 78N (the Global would with to true at 7235N). But in some aircraft the pilot must now manually switch the system to true as well. In the Global Express, for example, leaving the system in auto mode without manually setting true, would eventually cause a loss of heading and pitch indications. The red X’s on your PFD’s would not be a fun thing to witness as you’re flying over some of the most inhospitable terrain on the planet. Manual selection could be made via the Maintenance page of the Honeywell FMS. In the Global 5000/6000 Collins flight deck, it can be reached with the Control Tuning Panel Menu > PFD > Mag/True.

Exiting Polar

When leaving Polar airspace, the Global Express FMS would switch automatically back to magnetic passing 72 00º N. But depending on your routing you may still be operating within the Polar Keyhole, or AMU (which your FMS will not be able to detect). In this case, you’ll need to continue flying manually in true. How long for? A sign that you should be in true is if the airways your on or near are in true (see below).

Space Weather and Cosmic Radiation

Atmospheric shielding and the magnetic field of the earth protect us from getting the full force of cosmic radiation from outer space. So on the ground we’re fairly safe. But flights of long duration, high latitude and high altitude are occasions where crew and passengers are exposed to much higher levels of cosmic radiation (and polar flights hit all those criteria!). Flights over the poles experience twice the radiation as flights at the equator.

In FAA AC120-61B,  flight crew are ranked 4th in the world when it comes to radiation exposure in the work place, experiencing an average of 3mSv (milli-sieverts) per year. There is yet no collective worldwide resolution on managing aircrew radiation exposure: whilst some countries have official mandates limiting it (i.e. the EU) others don’t have any (i.e. USA).  For simplicity, the International Commission on Radiological Protection (ICRP) recommend that flight crew should limit themselves to no more than 20 mSv (wow!) of radiation per year (no more than 100 mSv over 5 years). For pregnant crew members, the limit goes down to 1 mSv (thats about 15 flights between LA and Tokyo).

Whether you’re a pilot or passenger, check out how many mSv of cosmic radiation you were exposed to on past flights via this website. It is very basic (since it doesn’t factor in altitude), but the FAA’s ‘Galactic Radiation Calculator’ is currently inop. Before flying it is possible to check the NOAA website for information on current cosmic radiation levels and solar flares that might indicate if you’re at risk of a high(er) dose.

More information on cosmic radiation, dangers, mitigation and health will feature in an upcoming post.

Cruising Altitudes 

The tropopause is lower at the poles (20,000ft), so temperatures are typically warmer at cruise altitude. (Tropopause is an indication of when the temperature becomes constant). Warmer temperatures at altitude might mean your optimum cruising altitudes are lower that usual.

Flight Plan

Ensure that your flight plan is water-tight, specifically the Russia or Asia portion. Check the preferred airways and FIR entry/exit points. A successfully filed flight plan is not always indicative that it is the routing that ATC want you to fly. If you are operating a polar flight than you’re likely already stretched on fuel, so may not to be able to afford any re-routes.

Contingencies

Diverting to airports in artic climes is far from routine, and threats still exist even after the aircraft has landed safely. To obtain the Polar op-spec in the USA here are a few (but not all) of the items that the operator must demonstrate;

• An approved list of suitable en route contingency airportsA minimum of two cold weather exposure suits (for crew) on board
  • Some alternate airports may have approaches in True (not magnetic)
  • Check the weather of en-route diversions before entering Polar airspace
• A recovery plan of the passengers

The information contained within this article is not intended for education or training, and is merely an explanation of my own experiences.