Flight Plan

My flight plan....to encourage, mentor, guide those pining for the sky. I'm also here to virtually open the flight deck door for those who want to take a peek at the many aspects of aviation.....enjoy!

...and welcome aboard!...

Yes, we get that close!

Wednesday, May 11, 2011

Aviate, Navigate, Communicate and Radiate?

The cardinal rule for any pilot is to aviate, navigate, communicate.... but radiate????

Recently, a blog follower (Mike) asked about pilots and radiation. In my book, I alluded to “space weather” when flying over the North pole. Cosmic radiation is predicated on four factors and it’s part of doing business. But before you think you will be glowing in the dark it turns out we are at less risk than thought! Sigh of relieve….

So the four factors are: latitude, altitude, flight duration and solar activity. And before I go any further, it’s true I am a meteorologist, but this topic is out of my field of expertise and much of it is derived from a recent pilot union survey. And I learned a lot!

The term 'cosmic rays' refers to elementary particles (such as electrons and protons), nuclei (such as helium nuclei, or alpha particles), and electromagnetic radiation (x-rays and gamma rays), of extra-terrestrial origin. These cosmic ray particles are produced by high-energy events very distant from the Solar System, such as supernova explosions. They come from all directions in space.

1. Aircraft at higher altitudes receive greater amounts of cosmic rays than at lower altitudes. But guess what….jet engines like higher altitudes? In fact, the rule is generally the higher the better. When I'm at FL 350 and I look up and see bizjets scooting along at FL 470..I think...hmmmmmmm....

2. Geomagnetic latitude. The North  and South polar regions are less shielded by the Earth's magnetic field than regions near the equator. The earth's magnetic field shields us from cosmic radiation.

Remember we are talking magnetic North pole and not the “true” North pole. Presently it’s parked over Northern Canada at 85 degrees north and is slowly moving to Siberia. It's why runway numbers change now again. So we in Canada have to contend with the "hole" more than Ivan in Siberia..for now.

3. Solar activity level. The Sun's activity varies over an 11-year cycle. When the Sun is active, it shields the inner Solar System. When the Sun is inactive, the Earth receives more cosmic radiation! The Sun's activity level is described by the 'heliocentric potential'.
Like most....I thought the entire opposite. Bizarre...I know. It’s because of the “Forbush Decrease.”

Why? When sunspots explode, they hurl massive clouds of hot gas away from the sun. These clouds contain not only gas but also magnetic force fields, knots of magnetism ripped away from the sun by the explosion. Magnetic fields deflect charged particles, so when these clouds sweep past Earth, it also sweeps away many of the electrically-charged cosmic rays that would otherwise strike our planet.

The 2009 study I alluded to transpired during the highest level of the 11 year cycle so in years to come the exposure rate should be less. 

The dose from radiation that a person receives is measured in units of sieverts (Sv). The average Canadian receives about 2.6 millisieverts (or 0.0026 Sv) per year from normal natural, industrial, and medical sources. A typical medical x-ray, for example, generates a dose of about 0.01 to 0.1 millisieverts. To see more medical dosages, see the FAQ section to PCaire's website.

A typical trans-Canadian flight (e.g. YUL to YVR) will generate a dose of about 35 microsieverts, or 0.000035 Sv. (A microsievert is one thousand times smaller than a milliservert). Thus, it would take over 75 such flights per year to generate a received dose that is roughly equivalent to the normal annual background dose.

Recently a company (PCaire) conducted a radiation exposure analysis on myself and my colleagues in 2009. After compiling all the facts….

GOOD NEWS!!!!….We remained below the recommended intervention level of 6mvs which is one third the limit of 20msv used for occupational workers.

Many would assume the B777 doing transpolar flights would see the higher doses. Not so, because they usually fly at lower altitudes where the exposure is less. When they get light enough to fly higher there are heading south over Siberia so the exposure gets less and less.

This is what Health Canada said on their website. Health Canada
It would take about 100 one-way flights between Toronto and Vancouver to obtain the same exposure as we get in one year from other sources of natural background radiation.

Twenty msv (milliserverts) is the benchmark for regulated occupationally exposed workers. I am less than one third the suggested intervention level. The highest during the survey was 6 milliserverts and remember this survey was when cosmic radiation was at it's highest 11 year cycle. When I retire, it will peak again. 

Frequent flyers and you curious sorts can enter the website.   PCaire
It can tell you how much radiation you can expect on any given flight. For fun, I went on and found out on Christmas day in 2009 I radiated with less dosage than my transcon Vancouver flight a few weeks prior. So heading south is better, but then again UV rays will get ya while you capitalize on Vitamin D. Either that, the "all you can eat" all inclusives may give you a cardiac surprise from the 15 pounds you gained. :)))

Here are some dose rates per hour for each aircraft:

B777 Highest YYZ-YVR  7.5 microSV/hour
B777 Lowest  SYD-YVR  3.9

B767 Highest  YYZ-YVR 7.0
B767 Lowest   YYZ-LIM  3.4

A330 Highest YYZ-YVR 8.2
A330 Lowest  YVR-NRT 5.7

A320 Highest YWG-YVR 6.0
A320 Lowest YHZ-YUL  4.3

E-175 Highest SEA-YYZ 7.1
E-175 Lowest PHL-YYZ  2.4


carlton said...

Thanks for an interesting post.

To offer further reassurance, for my university dissertation I was planning on covering airline crews and radition exposure (it was rejected, but I still did some background reading) and a study carried out several years ago found that on average British Airways pilots live longer than the national average, with no more excessive reports of radiation induced cancers than the national average.

There was one report of skin cancers being prevalent among cabin crew of a certain airline, but you could put that down to lay-overs in sunny destinations.

Radiation is all around, in some places more than others. In 'granit-rock' areas such as Cornwall UK the yearly dose could be 8mSv/year, and flying ten hours /week shouldnt add more than 4mSv to the annual exposure - so there is no more risk than living in certain areas.

carlton said...

I guess Concorde had a higher cosmic exposure due to the 60,000 + ft cruising altitude?

Craig Ritchie said...

Hiya Captain Doug

That really was an interesting post and link, particularly the comparisons between similar aircraft types on a common route. I'll continue to favour 767s over 777s when I travel YYZ - YVR!

Thanks for the most interesting read.


Daniel Asuncion said...

Beautiful first photo. Didn't know what I was looking at, at first. Reminds me of a few lines...
"For all its sham, drudgery and broken dreams, it's still a beautiful world."

Maybe magnetic fields will be used, in the future, to help clean up radioactive messes like we see in Japan.

From the Flight Deck said...

Daniel Asuncion

Maybe you are onto something regarding magnetism and radiation?

I have a physics degree, but I will be the first to admit it's out of my realm. :)

And yes, it's still a beautiful world!