Carburetor Icing



When you apply carburetor heat to melt ice that has formed in the throat, or venturi, of the carburetor, you may notice that the engine begins to run even rougher. This happens because the fuel mixture, already enriched because the ice is choking off some of the induction air flow, is suddenly made even richer by the addition of hot air.

This triple whammy can make the mixture so fuel-rich it will not ignite in the cylinders. The solution is to lean the mixture (and sometimes it takes some pretty radical leaning) and get a burnable mixture going to the cylinders.

Let’s review some carburetor basics. Airflow through the carburetor venturi results in a pressure drop that draws fuel from the float chamber. The mixture control can vary the amount of fuel supplied for a given amount of air. Opening or closing the throttle actually changes the amount of air flow, and the carburetor automatically supplies (more or less) the correct amount of fuel to mix with that amount of air.

Carb ice forms because the pressure drop in the venturi causes the air to “cool,” and draw heat away from the surrounding metal of the carburetor venturi. Ice then can begin collecting on the cooled carburetor throat. This is the same principle that makes your refrigerator or air conditioner work. 

Meanwhile, fuel being drawn through the fuel discharge nozzle into the airflow atomizes into very fine droplets that evaporate easily. When the fuel changes from a finely atomized liquid to a vapor it, too, cools—stripping more heat from the surrounding metal.

The result is that the carburetor’s internal temperature may drop below freezing, even on a warm day. If the ambient air contains sufficient moisture (which can be the case even in seemingly dry air), frost (carburetor ice) can form on the inside of the carburetor.

It’s important to understand that carburetor ice results not from a decrease in airflow through the carburetor, but the change in pressure caused by the restriction in the venturi.

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Secunda Fly In

Secunda Fly In
Secunda Fly In

Our monthly Sunday Fly Away weekend was not dampened by the threatening weather that we had planned to Zebula Lodge. as all was clear we decided to head South and had an amazing flight to Secunda where all 5 aircraft landed safely. The recent rains meant that the scenery on route was great with rolling green hills and full dams.

Disappointment again at Secunda as for unknown reason the usually vibrant airport with its excellent breakfast was closed. No problem as we returned to Rand and all lined up in front of the Harvard cafe and had a great brunch.

In January we are again planning a visit to a Ranch in the North and will post details on our website soon.

Join us and it will be great fun.
Safe Flying

Safety Letter – Take-off Emergency

Take-off Emergency
Take-off Emergency

As a South African flying school it is our responsibility to instill safety conscious habits in all our students.

Let’s take a particular scenario: You’re a flight academy student lined up on the runway, the pre-departure checklists is complete, you’re ready to do some hour building towards your commercial pilot license. You’ve confirmed the runway is long enough, that you’ve sufficient fuel, the weather is within your personal limits and all NOTAM’s have been checked.

Is there anything you missed? What about the engine failure you’re about to have on take-off?

That’s right. As a pilot, you always need to be thinking “Engine Failure” on every take off. You can hope it will never happen, but luck is no substitute for preparation.

And remember your training from flight school, climbing at the best rate of climb airspeed might not always be the best idea. Climbing slowly at best angle airspeed will put you higher, closer to the runway. Our flight instructors taught us all about the “impossible turn”. But depending on when the engine decides to quit, you might be high enough and close enough to make it back to the runway safety area, if not onto the runway itself.

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Mongena Lodge Monthly Fly Away

Central Flying Academy Monthly Breakfast Fly Away

Located just 50km North of Pretoria this is an amazing destination for a Sunday Breakfast or weekend break away. The tarred runway is in excellent condition and our groups of 7 aircraft were easily accommodated. We were greeted by the owners and offered a game drive vehicle ride to the resort, which is a mere 300 meters away, but we chose to stretch our legs.

A massive outside lapa and tables under umbrellas greeted us in these beautiful surroundings.

Tame Nyala, Zebra and other antelope wander around the lawns close to the tables totally unperturbed by the people “grazing” adjacent to them.

Breakfast is a full buffet service of superb standard and we were all well satisfied when it became time to leave. Our compliments to the Chef and service staff.

There are a number of facilities available which we regretfully were unable to see in the short time available. We had planned a game drive but due to a late start with misty weather and the threat of afternoon thunderstorms we were unable to take advantage of the opportunity.

I would highly recommend this venue and our thanks to Marina at Mongena for making the arrangements and making our visit so enjoyable.

If your future involves becoming a commercial pilot or private pilot, and you are planning on joining a flying school in Johannesburg Gauteng, or even South Africa, then come to Central Flying Academy for your introductory flight and take a tour of our facilities. We focus on pilot safety, both in ground school and flight training. Contact us for more information

Sun City Fly Away

Central Flying Academy Monthly Breakfast Fly Away

On Sunday the 31st May 2015, CFA undertook yet another successful Fly-Away. The destination was the much loved Pilansberg Airport, a mere 11km from Sun City. With 5 aircrat packed and ready, including golf clubs stowed in the back, the trip from Rand Airport was made to Pilansberg Airport in just over one hour flight time. On landing, the group was collected by bus and transported to Sun City.

Our morning started with a scrumptious breakfast at the well renowned Wimpy, and discussions naturally gravitated toward aviation, of course. Once everyone’s had satisfied their hunger and thirst, it was indeed time to hit the Golf Course and Gaming section. For the next few hours the team were faced with the challenge of keeping track of lost balls in the rough and attempting to win in multiple games of air hockey.

If your future involves becoming a commercial pilot or private pilot, and you are planning on joining a flying school in Johannesburg Gauteng, or even South Africa, then come to Central Flying Academy for your introductory flight and take a tour of our facilities. We focus on pilot safety, both in ground school and flight training. 

Once the day was done a relaxed late afternoon flight took everyone back home to Rand Airport. A fantastic time was had by all and we look forward to having more exciting experiences at Klerksdorp this coming month.

We invite everyone to join in the fun and share these amazing experiences. Contact us now and reserve your place. Family and friends are always welcome to accompany suitably qualified pilots.