Jets Column: Fall 2016
Written by Don Slusarczyk
Successful EDF Flights
As seen in the Fall 2016 issue of Park Pilot.
Flying your first EDF (electric ducted fan) can be slightly intimidating because they fly a little different and faster than your average park flyer—you need to be prepared for these differences. I fly a lot of jets at my local club and I have seen others become interested in jets after watching me fly. Their first EDF experiences often end up as piles of foam pieces. I have a few tips to help make your first EDF experience a successful one.
Rob Dedrick gets ready to launch Marc’s F-104 Starfighter.
Launching an EDF model is a little more complicated than launching a typical park flyer. A park flyer has a large propeller up front; the propeller blast blows air over the flying surface. Once launched, the airplane has instant control effectiveness because of the propeller blast, and a gentle toss is all that is needed to get a park flyer going.
EDFs are different because there is no propeller blast. EDF models must be firmly thrown with the throttle running (I launch at full throttle), so the airplane can accelerate quickly to a flying speed where the flight controls have enough air over them for full control.
What I have seen in person or in online videos are light or gentle tosses and the airplane rolling over or nosing in a few feet away. Slightly nose-up and a firm, straight-ahead throw are recipes for success.
When launching an EDF, the nose should be slightly up. A firm throw straight ahead will help quickly build airspeed.
One caveat to be aware of is rolling your hand or wrist over when launching. I have seen in videos a good, straight throw until the last moment before release and the throwing hand rotates and rolls the model over into a crash. This wrist roll is a natural action when extending your hand, but a little conscious thought will prevent it from happening.
I am right handed, so when I launch my models, my right thumb is pointed up on the left side of the fuselage, and my fingers are pointed up on the right side of the fuselage. During the throw, my thumb and fingers stay upright until the model is released.
The natural body movement is for the thumb and fingers to rotate left from vertical to horizontal. This is the roll/flip I frequently see during launches, often leading to a crash. Before you make the actual launch, do a few practice motions to get a feel for keeping your hand from rolling over.
Rotating your wrist over during a launch will roll the model and can lead to an immediate crash. This is often incorrectly called an EDF torque roll.
Once in the air, you need to be prepared for the faster flying speed. When airplanes move faster, your reaction time needs to be faster as well. It is easy to get behind the airplane and that can lead to a crash because you are defensively reacting to the airplane’s movements instead of the airplane following your commands. If things start to get out of hand, throttle back to slow the airplane down.
Another problem I often see is overcontrolling the model after it is airborne, with the aircraft pitching up and down or rolling left and right. This can be a piloting issue, but more often it is because of excessive control surface movements. A 3-D model will have much more throw on the controls compared with an EDF aircraft, and setting up the control for large movements will make the model hard to control.
For my maiden flights, I set up dual rates, so if the factory-recommended throws seem to be too much, I can switch to a lower rate. I also program approximately 30% to 40% exponential on the ailerons and elevator to soften the controls.
Factory-installed controls typically have the control rods in the outermost servo horn hole. Moving the rods in closer will give greater control resolution.
After you get a few flights in, you can fine-tune your control throws to fit your flying style. Sometimes on factory-assembled airplanes, the control rods on the ailerons or elevator are connected in such a way to provide maximum surface deflection. You then have to reduce the end-point adjustment or rates in your radio to reduce the control throw.
I use the radio to control the throws, but when I find the rate getting below 60%, I adjust the mechanical linkage on the control horns to reduce the throw. Many factory-installed servos do not have the best resolution. To get the smoothest control movement, it is best to have the servo move as much as possible. I recall a time at the flying field when I had to reduce a rate to 35%, after the linkages were rearranged, when the rate on the radio was 70% for the same surface deflection.
When you are making a maiden flight, have someone else launch the model for you. It is much easier to have another person launch the airplane so that you can concentrate on flying from the moment it is released. When I launch airplanes for people, I use two hands: one on the nose to help hold the airplane steady, while the other hand pushes forward.
I hope these tips on flying an EDF will make using your first EDF a successful experience!