Contrails Over Perth

Spotting a contrail over Perth is a hit and miss affair. Spontaneous sightings are so uncommon, they rank behind wayward meteorites, and alien spacecraft. You stand a better chance of glimpsing Elvis Presley in your local lunch bar, than spotting a vapour trail over Perth.

Being the world’s most sunniest capital city, and enjoying vivid blue skies, you would logically think spotting a vapour trail would be a simple matter of looking skywards. Unfortunately if you are a contrail enthusiast, and who isn’t, it is much more problematic.

To understand why Perth is so contrail challenged, it is necessary to examine the conditions favourable for their formation.

A typical blue sky over the Perth CBD.

Blue Skies.......smiling at me......nothing but blue skies......do I see.

Air Austral - UU 772: 11km above Perth en-route to Reunion Island.

Contrail Formation Over Perth

In Perth we require an aircraft to be flying overhead, preferably at an altitude greater than eight kilometres. Now, that’s high! Only at these lofty heights is the temperature below -40C, and conducive to vapour trails forming behind the heated exhaust of aircraft engines. The exhaust from the engines release hot water vapour, which pushes the existing water content of the colder air beyond the saturation point. It is at this point that the vapour condenses into tiny water droplets, which form the contrails we see from the ground. In the cold temperatures of the high altitudes, these water droplets freeze instantly into ice crystals, which reflect sunlight and become very visible.

Contrails can also form around plane wing tips, when a drop in air pressure reduces the surrounding air temperature. This forces the water content of the air to condense into vapour trails. These trails generally occur during humid days, and at lower altitudes. They are usually observed when planes take-off and land. Onboard, they are typically viewed from the economy window seats behind the wing, and are sometimes referred to as Econotrails. They are formally known as Wingtip Vortices. First Class passengers can still enjoy the occasional Cointreau, which only appear forward of the economy section on long flights.

Why are contrails so rare over Perth?

Isolation means very few long haul flights pass over Perth.

Perth is the most isolated continental capital city in the world, meaning 99.99% of our air traffic is at a low altitude. Everybody is generally just taking off, or landing. Very few flights cross over Perth at the high altitudes necessary to form contrails. With the Indian Ocean to our west, Antarctica down south, and the vast Australian outback to the north-east, flying non-stop over Perth to another destination is a very long haul. Some carriers do make these flights, though they are relatively rare. After travelling great distances, it is unusual for the flight path to be directly over Perth, and then coincide with our daylight hours.

The best way to observe a contrail over Perth is to study the international flight schedules of those planes most likely to fly over the city. After taking into account the curvature of the Earth, prevailing winds, and flying hours, we had some success with the following routes. The aircraft generally connect with Sydney (SYD), or Melbourne (MEL), and fly between the following international destinations.

Look for flights that connect with Abu Dhabi (AUH) and Dubai (DXB). Emirates and Etihad Airlines fly regularly from these two cities, and present some great opportunities to spot contrails over Perth.

Etihad - EY 460

Air Austral is a French Airline which operates out of St Denis on Reunion Island (RUN). They cross the Indian Ocean and connect with Sydney (SYD).

Air Austral - UU 772

The Flight Stuff
Working out the Perth fly-over time is not an exact science. The easiest solution is to first estimate the flying hours between Perth, and the Australian connection. The following flying hours are a good guide.

	Perth to Melbourne		3hr 15min
	Melbourne to Perth		4hr 15min

	Perth to Sydney		4hr 00min
	Sydney to Perth		4hr 30min

The prevailing winds blow from west to east, and form a solid headwind against all flights crossing the desert to Perth. This is why the flying hours are slightly longer when travelling to Perth.

Once you know the arrival or departure time at the Australian connection, you can then estimate the Perth fly-over time.

Example: An Emirates flight departs Dubai (DXB) at 2:40am, and arrives in Melbourne (MEL) at 10:00pm that same day. Melbourne is 2 hours ahead of Perth, meaning it lands at 8:00pm Perth time. It takes about 3 hours 15 minutes to arrive in Melbourne after it passes over Perth. The Perth flyover time should be around 4:45pm. Allow a 20 minute window around your estimation, as there are many factors which can effect the fly-over time.

NOTE: During summer daylight saving, both Melbourne and Sydney are an annoying 3 hours ahead of Perth!

Air Mauritius operate a service from Port Louis, in Mauritius (MRU). It is during their direct flights between Mauritius, and the eastern states of Australia, that their planes could leave a contrail over Perth. We are yet to actually spot an Air Mauritius contrail, but like many great scientific theories we are sure they exist. They change their flight schedules frequently, and possibly sneak over during the night.
	Night Cruiser
Australia’s own international airline, Qantas, operates a regular route between Johannesburg (JNB) and Sydney. You can occasionally spot a “Qantrail” over Perth, though we believe they don’t fly overhead that often. They possibly cross the coastline south of Perth when nobody is looking.
	A Genuine Qantrail
At least you can rely on this guy. He might make only one flight a year, but he will never let you down. No flight schedules are necessary, though having a 5 year old nearby is a sure bet for success. Expect him to cross over sometime on Christmas Eve, .........only if you've been good.
	Flight XMAS 25

Western Australia has a booming iron ore mining industry in the northern Pilbara region. Some of the bigger mining companies have established fly-in, fly-out (FIFO) services for their mining workers. While the majority of these flights transfer between Perth and the North-West, a few now fly directly to Busselton, which is further south. They occasionally produce a contrail over Perth. These flights are difficult to predict, as they are operate on a private charter basis. They travel in both directions, and will usually return on the same day.

Admittedly just seeing a contrail over Perth is an unusual event. Sometimes the prevailing conditions conjure up an optical effect, which enhances the contrail. We always keep a bottle of Coke in the fridge for these special moments.

Contrail Shadows
Pictured below is a sequence of photographs showing Etihad EY 460 flying over some lower altitude clouds. The sun cast a shadow of the contrail onto the clouds. The opacity of the clouds allowed the shadow to be visible from the underside.

The contrail shadow is now ahead of the plane.

In the first three images, the shadow can be observed extending directly behind the higher contrail. When the contrail crossed the sun, the plane then appeared to be chasing its own contrail shadow, as seen in the image on the far right. Perspective can be very deceptive. The optical effect is dependent on where you are standing relative to the contrail, and the sun.

An impressive contrail shadow at sunset.

Optical Illusion. The contrail appears to be below its own shadow.

Emirates EK 408 at sunset. The bright contrail disappears above the cloud, and casts a dark shadow well forward of the aircraft. The sun is well behind the contrail.

The shadow almost appears to be above the contrail. The illusion is created by the optical thickness of the cloud, and the sun being positioned behind the contrail.

Persisting Contrails

In this sequence the contrail left by EK 408, persisted for 30 minutes. Light winds promptly spread the contrail, before it dissipated into the evening sky.

Persisting contrails are very rare over Perth. The atmospheric conditions have to be just right. This one made headline news for nearly a week, and forced all our Conspiracy Theorists out of retirement. Explanations ranged from an alien spacecraft, a missile launch, to high altitude chemical spraying. In reality it was simply Emirates flight EK 408 en-route from Dubai to Melbourne. The evening was relatively cool, with a light breeze, and higher than average humidity.

We removed two Coke bottles from the fridge that night. Persisting contrails might be twice as good as shadows, but they can still be bettered by the elusive Dusk Trail.

You can see that the aircraft made a turn after crossing the coast.

The plane made a left turn after crossing the coast.

Dusk Trails

Pictured here is Emirates EK 408 just after sunset. Even though the sun had set behind the horizon, it was still illuminating the sky at the higher altitudes. Fortunately EK 408 was flying through that high altitude zone, and generating a contrail. The contrail was illuminated with a rather nice red hue against the night sky. The plane's nose light is visible fore of the contrail.

The elusive Dusk Trail.

We had three Cokes before going to bed that night. We couldn't sleep.

Comet McNaught 2007. It was also illuminated by the sun, though it was over 25 million km's away!

An out of this world "Comtrail".

It is most unusual for two contrails to be visible over Perth at the same time. Strangely at 5:20pm on Sunday June 7th 2009, it happened. As the sun slowly set behind the Indian Ocean, two high flying jets passed overhead. Emirates EK 408 was on schedule from Dubai to Melbourne, cruising at an altitude of 12 km. Unexpectedly at an altitude of 13 km, a corporate jet en-route from the Maldives to Sydney appeared. For a brief moment both jets left visible contrails in the sky. The Maldives aircraft was an ultra long range Bombardier Global Express, capable of carrying up to 19 passengers in high speed luxury. You can just make out its shorter contrail, above and to the left of the larger vapour trail of the Emirates jet.

So unusual our Airforce went to DEFCON 1.
We had no time to drink the Coke.

Supporters of the Chemtrail Conspiracy Theory contend that contrails are actually biological agents sprayed by Governments around the world to perpetrate evil on human kind. Have you ever woken up in the morning with a dry throat. Believers speculate that chemtrails might be the cause of your annoying unproductive cough.

So why does Perth have no chemtrails? For the same reasons we have very few contrails over Perth. Only a handful of commercial jets fly over Perth at the altitudes necessary to form contrails. If contrails are indeed chemtrails, most Perth residents won’t see any. This is disappointing news if you love a good conspiracy theory, and who doesn’t?

When they start to resemble crop circles it's time to get serious.

Natural Clouds.

It is apparently uneconomical for our Government to charter private jets to deliver these chemical payloads. We have to rely on a few commercial flights, and some nifty calculations to work out the fly-over times. The absence of any chemtrail activity over Perth, is a good indicator that the whole theory is a trail of water vapour. Until the evidence is more substantive, we will have to be satisfied by spotting them in replays of Top Gear.

Good luck with your contrail spotting. We reckon flights connecting with the United Arab Emirates, and Reunion Island present the best opportunities. After a few calculations, and some luck you should be in business. All of our photos were taken with compact cameras, usually set on the highest zoom.

Don’t be at first disappointed by failure.
Things will eventually look up........
....12 kilometres up, that is.

Etihad EY 460: 12km above Perth.

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