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THERE’S A QUICK FIX FOR THIS UNEXPECTED VISITOR

BY JERRY L. ROBINSON

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.

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.

WHY DO YOUR WINGS HAVE DIHEDRAL?

If you look closely at the wings on most aircraft, they’re tilted up slightly. Why would they ever do that? It’s not because you pulled too many Gs on your last flight. It’s because of a design feature called dihedral.

FIRST OFF, WHAT’S DIHEDRAL?

Dihedral sounds like one of those words you cringed at in math class, but it’s actually pretty simple. Dihedral is the upward angle your aircraft’s wings.

See how the 777’s wings angle upward? That dihedral makes the jet more laterally stable, or in other words, more stable when it rolls left or right. And it’s not just large jets that have dihedral like this. It’s found on almost every aircraft out there.

HOW TO HANDLE A POWER-OFF LANDING FOLLOWING AN ENGINE FAILURE

When you think about power off landings, there are probably a lot of things that go through your head, like finding an airport within gliding distance, finding an off-field landing site if there aren’t any airports, and last-ditch efforts to get your engine running again before you’re out of altitude.

In 2013 alone, there were thirteen fatal accidents related to power off landings, according to the NTSB. You’re faced with some very serious decisions during a power off landing. But after you’ve run your checklists and determined your engine isn’t coming back to life, handling a power-off landing really comes down to three simple things: aviate, navigate, and communicate.

MAXIMIZING GLIDE RANGE, OR TIME ALOFT?

The first question you need to answer in a power-off landing scenario is this: do you want to maximize the distance you can glide, or do you want to maximize the amount of time you can stay aloft?

HOW TO MAKE A GREAT SHORT FIELD TAKEOFF
Taking off from a short runway? Does your runway have trees or buildings at the end of it? Then it’s time for you to dust your short-field takeoff skills. Here’s how you’ll do it.

HOW SHORT FIELD TAKEOFFS ARE DIFFERENT

How does a short field takeoff differ from a normal one? It starts by creating a short ground roll, and then climbing at the best angle you can to clear obstacles (vx).

Why? By keeping your ground roll short, you don’t use as much runway. And by climbing at vx, you more easily clear obstacles beyond the runway.

So what are the steps of a good (or great) short field takeoff? We’ll break it down into three phases: takeoff roll, liftoff, and initial climb.