Posted on

What is VFR?

IFR Flying Conditions. Image Courtesy of Langley Flying School.

It’s springtime, and out here in Alberta the weather is all over the place. From clear, sunny, calm days arrive strong wings, snow, sleet, rain, low ceilings and all sorts of weather, signifying change of seasons. Yesterday for example we did not have VFR weather here.  In fact, with a visibility of 1/2 SM, vertical visibility of 500 feet and snow at CYBW we have LIFR, or low instrument flight rules conditions – this means ceilings and visibility conditions below IFR minimums. Ceiling is below 500 feet and visibility is less than 1 SM.

There are two kinds of flight rules, visual flight rules and instrument flight rules.  VFR stands for visual flight rules and means the pilot flies the aircraft with visual reference to the ground, using landmarks, roads, avoid aircraft in the vicinity, avoiding terrain and obstacles.  The pilot must know where they are at all times and maintain visual contact with the ground at all times.

Weather minimums have been established to allow the pilot to fly VFR.  These are listed in the table below:

VFR Weather minimum. Image from the AIM and Langley Flying School.
VFR Weather minimum. Image from the AIM and Langley Flying School.

As long as these minimums are observed, the pilot can fly VFR.  Remember that some types of airspace do not allow VFR traffic, or VFR traffic must seek permission in order to enter certain kinds of airspace.

Also applying to VFR traffic are altitude rules. VFR traffic flying at 3000 feet AGL or higher must follow specified rules about altitude depending on direction flown. Cruise altitude is based on magnetic track. The altitudes are:

For headings: 000 degrees – 179 degrees = ODD thousand + 500 feet

For headings: 180 degrees – 359 degrees = EVEN thousand + 500 feet

VFR traffic is not allowed to fly over cities (built up areas) lower than 1000 AGL, and should not descend below 500 feet AGL during flight – of course this does not apply to special flights (police, ambulance) nor during take off or landing phases of flight. This explains why the traffic helicopter always seems to buzz my house!

VFR traffic can use instruments to operate, but are not allowed to rely on them unless they have an IFR rating, and are flying IFR.

Pilots flying VFR are allowed to start a flight that is initially VFR but changing to instrument meteorological conditions (IMC), and where visual flying will not be encountered anymore.  The best thing to do in this situation as a VFR pilot is to either fly straight and level until the conditions improve, or complete a 180 degree turn where you came from to return to visual conditions. Also, if you are near a control zone, you can request SVFR – special VFR.  The aerodrome must have at least 1 mile visibilty and you must remain clear of cloud.

If you are not near a control zone and encounter these conditions, you are forced to fly IFR.  The best solution is to avoid IMC if possible unless you are IFR rated.

Another solution is to fly VFR “over the top” or OTT.   This is a special rating that private pilot license holders can get to fly over cloud cover, maintain visual contact with other airplanes flying IFR while giving VFR pilots greater flexibility. This rating can be added to your PPL with 15 hours of  flight training.

Posted on 1 Comment

Aviation and climate change

C-141 Starlifter contrail. Image Courtesy of

We live in a world where there are growing concerns regarding human induced climate change. It is very high on the policy agenda of most governments, issues I have experienced first hand working as an environmental economist.   Not surprisingly, in the community it is generally accepted that we are without question experiencing climate change, and there is a consensus that a lot of it is human-induced due to increased carbon emissions.  It is not a debate, but a generally accepted consensus in the scientific community.

Global GHG Emissions By Source (2004). Image from US EPA website.
Global GHG Emissions By Source (2004). Image from US EPA website.

So like you, I love to fly and also love to travel by commercial air service.  How does commercial aviation contribute to climate change?  How do airplanes contribute negatively when it comes to greenhouse gas (GHG) emissions?

Let’s examine what the main contributors are to GHG emissions. Globally, the sources of GHG are primarily from energy supply (26%) and industry (19%). Transportation is close at 13%,  where fossil fuels are burned to power transportation activities such as rail, road, air and marine transport (IPCC 2007) and aviation represents about 12% of the transport figure.  The contribution of civil global aviation is about 2%  of total GHG emissions (CleanSky website). Flights produce about 628 million tonnes of Co2 annually.  A typical car emits about 5 tonnes per year and there are about a billion cars (Huffington Post 2013)  out there in the world (of course, this is a very rough figure) meaning about 5 billion tonnes are produced by cars, making it a greater net contributor. In Europe, road vehicles contribute about 1/5th of carbon dioxide emissions (European Commission 2012b).   In Canada, transportation accounts for over 28% of total GHG emissions (Conference Board of Canada 2010).  But what about per passenger kilometer?

The current rating for car is about 140 g / kilometer (European Commission 2012a). For air travel, this figure is higher, (2000 data) at about 170 g / kilometer (BBC news).   But the figures from aircraft vary extensively, depending on the type of flight, type of airplane used and distance flown.  Domestic short distance are as high as 260 g/km, domestic long distance 178 g/ km and long distance the lowest at 114 g / km ( British Airways has estimated their per passenger rate at 100 g / km.  Flying trips cover far longer distances than could be undertaken by car, so total emissions would be higher because of the ability to travel longer distances.

The effects of flights at high altitudes may be greater than those at low altitudes. An important effect appears to be from contrail emissions.

Cirrus clouds caused by jet contrails. Image from CO2 offset
Cirrus clouds caused by jet contrails. Image from CO2 offset

Remember from weather theory that jet engines produce contrails, which are mostly water vapor. One of the effects is that jet contrails cause cirrus clouds to form in the higher atmosphere where commercial jets fly (10-12 km above ground, at temperatures of -40). There still appears to be debate about what this contribution is to global warming, and most calculations are done from contributions of fuel burn.  However, a NASA study has found the warming effect caused by increased cirrus cloud formation from aircraft in the US (NASA 2004). Because of this, aircraft cause more than just CO2 emissions but also contribute to radiative forcing, which has to do with contrail production and nitrous oxide emissions.

These contrails are rare for low altitude aircraft or propeller driven aircraft, meaning the contribution of commercial aviation could potentially be more significant than other types of flights.

Another chief concern is the increasing use of air travel.  Since planes continue to run on fossil fuels, the increase in CO2 emissions from aviation will likely grow. In fact, between 1990-2004, number of airport users in the UK rose 120%. On average, global airline growth amounts to approximately 5% per year (MIT 2006).

Winglets on a Boeing aircraft. Image from
Winglets on a Boeing aircraft. Image from

The industry is making changes to be more efficient. Experimenting with cleaner fuels (biofuels), aircraft made of composite materials that are lighter, and addition of aircraft modifications such as winglets or sharklets which block wing tip vortices (and reduce drag) are all being considered.  Wing tip devices, such as winglets or sharklets have been found to reduce fuel burn by as much as 3.5% (  Westjet’s 737 airplanes configured with winglets record a decrease of 2.7% fuel burn (Westjet website). The use of biofuels has it’s own issues – we see that with vehicles, where mandatory levels of ethanol (grain alcohol) in gasoline for vehicles has stressed grain markets -so these are being researched and considered. There are little things that can be done to reduce the impact.

It is an interesting issue.  A bit of food for thought!I am no expert in this field and your comments are welcome and appreciated.

Further reading and Sources can be found below.

BBC News (2000) “Pollution Warning on Holiday flights.

Clean Sky webpage, “Aviation & Environment”

Conference Board of Canada (2010) “Greenhouse Gas Emissions

European Commission (2012a). “Co2 emissions from new cars down by 3% in 2011.”

European Commission (2012b) Climate Action. “Road Transport. Reducing CO2 emissions from vehicles.”

Huffington (2013) “Number of cars worldwide surpasses 1 Billion. Can the world handle this many wheels?

IPCC (2007) Intergovernmental Panel on Climate Change, Climate Change 2007: Synthesis Report.

NASA (2004) “Clouds Caused by aircraft exhaust may warm US climate.”

MIT (2006) “Global Airline Industry Program: Airline industry overview.”

US Environmental Protection Agency, EPA (2010) “Global Greenhouse Emissions Data.” (2013) “Environmental commitment (2013) “Fuel economy in aircraft.” “Environmental Impact of Aviation

Posted on

Forward Slip

Forward Slip - Transport Canada photo

The other day I was out flying with my instructor reviewing soft field procedures. We were doing circuits on runway 25, and on the turn from the downwind to base leg of the circuit, we were  hit with strong turbulence every time.  The leg goes close to the river so we assumed it was something to do with that.  It was a bit much for me and I lost my concentration, so I kept coming in too high and fast.  After a few we landed and the controller immediately announced a runway change to runway 16.   I decided that I still wanted to try it, given that the circuits we did on 25 weren’t really that great.

After takeoff from runway 16 the turbulence hit us again only a few hundred feet AGL. I decided that it was probably best to ask for a full stop and end the lesson.  The turbulence was too distracting and kept me from being able to concentrate on the maneuver.  Inadvertently on the landing again, I came in too high.  So my instructor told me to use a forward slip – which is something that I’ve done numerous times – but I hesitated and my mind went blank.  I eventually did it, but think this is a procedure I need to practice still, particularly when I go solo.

What is a forward slip?

It is a turn that is prevented by use of rudder.  The airplane moves in straight, drag inducing position that increases rate of descent and doesn’t increase airspeed – because of all the drag that is created by the airplane in that configuration. The aileron holds the bank while the opposite rudder causes the nose to point in the other direction.

To enter a forward slip, power to idle, turn the aircraft into the wind, and use opposite full rudder. The configuration feels somewhat awkward to me since the airplane is steeply banked and pointing in the other direction. Like everything in flying, it is all about practice until it feels natural!

Another thing is I REALLY need to start bringing my camera and maybe my video camera to my flights! I am always too lazy to take photos but it is great to have them particularly so I can share them here.