RC Airplanes

Many RC model airplanes lack a conventional landing gear and need to be hand launched. This article will show you how to properly hand launch an RC model airplane.

When you’re learning to fly try to find a hill to launch your RC model airplanes from. This will give you a bit of altitude right after takeoff, which provides more room to maneuver during the initial climb. Follow this procedure to successfully hand launch an RC model airplane:

1. Turn both the transmitter and the receiver on.
2. Hold the RC model airplane at it’s center of gravity (balance point) with your throwing hand and hold the transmitter in your other hand.
3. Make sure that the RC model airplane’s nose points downward slightly and that the wings are level.
4. Increase throttle to full.
5. Toss the RC model airplane forwards like you would throw an overhand baseball.
6. As soon as the RC model airplane leaves your hand, quickly move your hand to the transmitter and begin flying.
7. The initial climb should be straight and gradual, using only small control inputs.

Some RC pilots prefer to launch their aircraft by taking a running start. There is nothing wrong with this method, just make sure that there is nothing in your path that you can trip on. Take a look at this sequence of pictures, which shows what a good hand launch looks like.

Now that you know how to properly hand launch an RC model airplane, get one on RCtoys.com and go flying!

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Phone: 1-800-979-9794 / 306-955-9907
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Introduction

RC jet engines represent some of the most impressive technology that the RC industry has ever created. RC jets are always an amazing sight at the flying field, because they look and sound just like the real jets you find at airports and military airfields. In this article, we will take a look at how model jet engines work, and show you the differences from full scale jet engines.

Before you go out an buy a jet, be warned that RC jets are some of the most complicated, expensive, and difficult RC model airplanes available. You will need both many hours of flying experience and a huge budget to successfully own and fly an RC jet.

This article is about real jet engines which burn kerosene (or jet A1), not the electric ducted fan models frequently found in hobby stores. EDF jets are great models to fly, and some are capable of advanced aerobatics, but they are not to be confused with real RC jets using real jet engines.

How Full Scale Jet Engines Work

In order to understand how model jet engines work, it is helpful to examine the full scale engines used by airliners and other jet aircraft. A jet engine is a device which operates inside a fluid (in most cases air), and expels it at high speed achieving a propulsive effect. The mechanics of jet engines are best represented by Newton’s laws of motion, specifically: “For every action, there is an equal and opposite reaction.” This means that the reason jets go forward is because they expel air backwards, faster than it came in. This basic principle applies for all types of jet engines.

But how do we achieve the movement of air needed to propel an aircraft? We know from high school chemistry that the volume and the temperature of any gas are proportional. Because of this, when air is heated, the volume increases. If the air is held in a container (the combustion chamber of a jet engine), then the pressure will also increase. Releasing the heated gas will result in an exit speed greater than the speed at which the air entered, creating the backwards flow of air needed to travel forward.

Interestingly enough, rockets are considered to be a type of jet engine. The only difference between a rocket and a conventional jet engine is that the rocket operates in a vacuum, and thus needs to take both fuel and an oxidizing chemical with it. The discussion of rockets and other exotic jet engines is beyond the scope of this article, so we will limit our investigation to three of the most common designs. These jet engines are listed in order of complexity, and all were used in full scale aircraft at some point in time.

The Pulse Jet

The pulse jet is one of the simplest jet engines, consisting of little more than a pipe and a fuel source. Pulse jets were used by Germany during World War II to propel primitive cruise missiles (V1 flying bombs). A pulse jet works by igniting a fuel air mixture in high frequency bursts. A typical pulse jet cycle operates as follows:

1. Air is allowed to enter the combustion chamber, and fuel is simultaneously added.
2. The intake valve is closed.
3. Ignition is triggered, resulting in an outward flow of air and low pressure inside the combustion chamber.
4. The valve is opened, and new air rushes in due to the low pressure in the combustion chamber.

This cycle repeats during the entire operation of the engine.

Pulse jets are not very efficient, and are extremely loud. Because of this they are not often used in full scale aircraft, but hobbiests often build them due to their design simplicity and lack of moving parts. In some cases, pulse jets are built to small dimensions and used on RC model airplanes.

Turbojet Engines

More sophisticated jet engines use turbines to compress the air fuel mixture before igniting it. A turbine is a device which consists of sets of moving blades attached to an axle. If the turbine blades are spinning, they will move air through themselves and towards the back of the vehicle. This figure shows a moving turbine, spinning on an axle.

The operation of a turbojet is represented in this figure.

Unlike pulse jets, turbojets lack a repeating cycle (the engine operates continuously). There is a sequence of events that occurs during the engines operation though, so we list them here in chronological order.

1. Air enters the turbine and becomes compressed.
2. The compressed air is routed to the combustion chamber, where is is mixed with fuel.
3. Ignition occurs, and the resulting hot air is allowed to exit the jet engine.
4. Before leaving the engine, the hot air is forced through a gas turbine, which drives the compressor used in step 1.

Turbojets are far more efficient than pulse jets, because some of the energy produced by the combustion process is reused

Turbofan Engines

Even though turbojet engines are more efficient than pulse jets, they are not often used in subsonic aircraft because of the noise they produce. Turbojet engines are well suited to high speed operations, exceeding the speed of sound. They become less efficient at the subsonic speeds which airliners and other commercial jet aircraft operate at.

The turbofan design operates on exactly the same principle as the turbojet engine, but instead of routing all of the intake air through the combustion chamber a small amount is allowed to exit unburned. Instead of being mixed with fuel and burned, some of the cool air is mixed with the exhaust, reducing the exhaust speed and increasing fuel efficiency. This figure illustrates the operation of a turbofan jet engine:

How Model Jet Engines Work

RC Model airplane jet engines work in exactly the same way as the full scale ones discussed above, with the exception of the air compression. Instead of using an axial turbine compressor, RC jet engines use a centrifugal compressor. A centrifugal compressor propels air outwards after it enters the engine, causing it to hit the engine case and be compressed. Centrifugal compressors need fewer moving parts than axial turbine compressors, and are more efficient for small applications. Many small full scale jets use centrifugal compressors for the same reasons.

Here is a picture of a typical RC model airplane jet engine, mounted on top of an RC model airplane.

RC jet engines operate on kerosene, exactly the same fuel that full scale jet engines use. Ignition is achieved with a small glow plug, like those found on two and four stroke RC model airplane engines.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
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Every RC model airplane has a center of gravity, or balance point, and it must be in the correct location for the RC model airplane to fly well. This article will show you how to correctly balance your model. Here is a general procedure that you can follow when balancing a new RC model airplane:

RC Model Airplane Fore and Aft Balance

1. Look at the plans or instructions that came with your RC model airplane. They will tell you where the correct balance point is. In most cases, the correct balance point lies on or near the main spar of the wing.
2. Depending on the size of the RC model airplane, you may need a friend to help you with this step. Install the RC model airplanes wing, and balance it on two finger tips, placed several inches away from the fuselage.
3. Move your fingertips so that they both lie on the recommended balance point.
4. Check to see if the RC model airplane balances. If it is correctly balanced, then neither the nose nor the tail will tip forward or backward.
5. Assuming that it is not correctly balanced, take off the wing and shift equipment inside the RC model airplane forwards or backwards. Correct a tail heavy balance by shifting equipment to the nose, and correct a nose heavy balance by shifting equipment to the tail. If you cannot get the RC model airplane to balance correctly by shifting the internal parts, then you will need to add ballast to the nose or the tail.
6. Find a suitable ballast material (like lead) and secure a small amount to the fuselage.
7. After making these adjustments, do step 4 again and see if the RC model airplane balances correctly. If it does not, add more weight to the nose or tail and try again.

Please note that it is far better for the RC model airplane to be slightly nose heavy than tail heavy. A tail heavy RC model airplane will fly in a chaotic, unpredictable manner, almost guaranteeing a crash.

RC Model Airplane Lateral Balance

After completing the above procedure, your RC model airplanes fore and aft balance should be correct. This procedure will show you how to balance the RC model airplanes roll, so that it doesn’t need much trim to fly straight.

1. Loop some string around both the motor shaft and the tail.
2. Suspend the RC model airplane by holding these string loops.
3. Does the RC model airplane rotate? If it does, add some ballast to either wingtip until it stays still while suspended.

Congratulations! You now have a correctly balanced RC model airplane!

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
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Now that you know how to perform basic and intermediate level RC model airplane aerobatics, you can progress to the most advanced maneuvers. This article lists some of the most interesting advanced aerobatic maneuvers in order of difficulty.

Immelmann Turn

The Immelmann turn is a type of aerobatic maneuver named for World War I fighter pilot Max Immelmann. When done precisely, the Immelmann turn is a very crowd pleasing maneuver, and can be used in combination with a wide variety of other aerobatics. Perform an Immelmann turn by using full throttle, turning the aircraft into the wind, and then pulling up into a vertical climb. When climbing, use the rudder and elevator controls to keep the aircraft climbing in a straight line. After gaining a significant amount of altitude pull back on the elevator to enter inverted flight. Keep the wings level, and execute a sharp 180 degree roll, bringing the aircraft back to straight and level flight. The net effect of this maneuver is that the RC model airplane is higher, and facing the opposite direction then it was during the start of the maneuver. Take a look at this picture, which shows the different parts of an Immelmann turn:

Split S

The Split S is basically the same as an Immelmann turn, but performed in the opposite direction. As always, begin by turning the aircraft into the wind. Then enter a vertical dive. Pull out of the dive by applying more down elevator, so that the aircraft levels off and enters inverted flight. As with the Immelmann turn, exit inverted flight by rolling 180 degrees in a left or right direction. This figure illustrates the different parts of a Split S:

Cuban Eight

A Cuban eight is one of the most challenging, and interesting, aerobatic maneuvers to perform. Performing a Cuban Eight involves making the airplane follow a vertical path resembling a horizontal eight in the sky. Make sure that you perform this maneuver at a high altitude, this is not to be attempted at twenty feet off the deck.

Start by facing into the wind, and applying full throttle, then pull up and perform a graceful half loop (1). Don’t level off after reaching the top of the loop (2). Instead, continue to use up elevator until the RC model airplane enters an inverted 45 degree descent (3). Wait until the RC model airplane reaches the midpoint of the eight – or about halfway up the first loop, and then perform a crisp 180 degree roll (4). Keep in mind that the RC model airplane will be inverted before you perform the roll.

After performing a roll, level off from the 45 degree descent and pull up again (5). Perform another half loop (6), and then begin another 45 degree descent (7). Wait until the midpoint of the eight (8), and perform a 180 degree roll like in step 3. After that, gradually level out and enter straight and level flight (8).

Ideally, the Cuban eight should be completely symmetrical along both the horizontal and vertical axis.

Congratulations! You can now perform advanced RC aerobatics!

——
© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
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Introduction

After learning about the basic aerobatic maneuvers, you are probably looking forward to trying something more advanced. Before we explain these new and exciting maneuvers though you will need an aerobatics capable aircraft.

Most of the aerobatic maneuvers described in the first part of this series are relatively gentle, and almost any 4 channel RC plane is sufficient to perform them. The intermediate aerobatics described in this article need a moderately capable RC model airplane, preferably with a large engine or motor and relatively little dihedral (upward bend) in the wings.

The process of choosing a second RC model airplane is daunting, and beyond the scope of this article, but here are some general points to consider when choosing a second RC model airplane:

Try to choose a model that uses the same radio hardware and engine as your trainer. That way, you can use the radio and engine from your old trainer in your new airplane – instead of buying them new.
Look for a RC model airplane with a mid to low wing. Most trainers have high
wings mounted on top of the fuselage while the more aerobatic aircraft have low wings, mounted at the bottom of the fuselage.
The RC model airplanes advertised as good second models generally are. Consider this when buying.

If you used a nitro fuel powered trainer with a .40 or .46 sized engine, a Sig 4 Star 40 is a great second RC model airplane. It features a low wing design, very forgiving flying characteristics, and will work with almost any .40 sized engine and 4 channel radio system.

Now that you have a suitable RC model airplane, we will show you how to do some very fun and crowd pleasing maneuvers.

Stall Turn / Hammer Head

A Hammer Head, or more accurately, a stall turn, involves stalling the RC model airplane, and then using the rudder to pivot and descend. Begin by turning the RC model airplane so that it faces into the wind. Increase throttle to full and use the elevator to climb in a vertical path. Continue this vertical climb, until the RC model airplane stalls. The instant the stall occurs, apply full right or left rudder. This will cause the RC model airplane to tip over on one wingtip. Allow the RC model airplanes nose to point downwards, and recover from the stall as normal. This sketch shows what a stall turn looks like.

Spin

The spin is an aerobatic maneuver which induces an asymmetric stall. This means that one of the RC model airplanes wings is stalled more than the other. The result is a graceful downwards spiral, rotating either clockwise or counterclockwise depending on the direction of rudder input.

You can perform a spin by entering a stall as normal, and then using full up elevator and left or right rudder. The spin will continue as long as you hold the elevator and rudder in their maximum positions.
Exit the spin by applying full rudder in the opposite direction of the spin, and dropping the nose to exit the stall. Be sure to stop the spin at a safe altitude – high enough that you have room for at least one mistake. Take a look at this sketch showing the different parts of a spin.

Snap Roll

The snap roll is a type of “aerial somersault”: a quick, rapid flip around the horizontal axis. When done correctly, it is a very crisp and accurate maneuver. Get ready by flying straight into the wind, with the wings straight and level. After that, apply the following control inputs simultaneously.

• Full up elevator
• Full left or right aileron
• Full left or right rudder

These control inputs should result in a sudden, and rapid roll and upward “snap”, which ends as soon as you neutralize the controls. Be careful though, because snap rolls can sometimes induce spins.

Outside Loop

The outside loop is exactly like the inside loop, but it is performed “inside out”, with the bottom of the RC model airplanes fuselage facing inwards. Perform an outside loop the same way as you would perform an inside loop, but enter the loop inverted. Because the RC model airplane is inverted, you will have to use down elevator to climb. After you exit the inverted loop, the RC model airplane will still be upside down, so perform a half roll on to the side to right it. This sketch depicts an outside loop.

The next article in this series will cover advanced maneuvers, including Cuban eights, Immelmans, and Avalanches.

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Phone: 1-800-979-9794 / 306-955-9907
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After you finish learning the basics of model airplane flight, you will probably want to progress to more advanced flying. Aerobatics are maneuvers which are performed outside the normal performance envelope of an aircraft. This means that the aircraft is subject to stress, speeds, and attitudes not encountered in straight and level flight. There are several relatively easy to perform maneuvers for a beginner to try. This article will show you the basic maneuvers such as loops and rolls, and later articles will detail more advanced maneuvers.

The Stall

Although the stall isn’t exactly an aerobatic maneuver, you will need to know how to avoid and survive them before you try the basic aerobatic maneuvers which can sometimes cause stalls.

In order to produce lift and keep the RC model airplane flying, air must constantly move over the wings. If the angle of attack (how high the nose is pointed) is increased, then the aircraft will climb and slow down. A stall is a condition of flight where little to no lift is produced by the wings, causing the aircraft to free fall. All aircraft wings have a critical angle of attack, beyond which they cannot effectively generate lift. If this limit is exceeded, then the RC model aircraft will enter a stall.

After entering the stall, the RC model airplanes nose will drop. Most beginning pilot’s first instinct is to pull back on the elevator and attempt to slow the descent. This is actually the opposite of what should be done to recover from a stall. Remember, the lift produced by the wings is proportional to the amount of air moving over them. The only way to increase this airflow over the wings and thus end the stall is to increase the RC model airplanes speed through the air. This is accomplished by letting the nose drop, and then gently pulling back after sufficient airspeed has been gained.

You can safely practice stall recovery by letting the RC model airplane climb to a safe altitude, reducing throttle, and pulling back on the elevator. After inducing a stall, just let the nose drop, increase throttle, and then gradually pull back on the elevator. Once you are comfortable with stall recovery, you can start learning about the fun stuff – aerobatics!

The Loop

The loop is one of the easiest (and most fun) aerobatic maneuvers to perform. Begin by flying the RC model airplane to a safe altitude (about 50 feet should be enough) and into the wind. Increase throttle to full, and gently pull back on the elevator to start climbing. Continue to use the elevator, and let the aircraft enter inverted flight. After the RC model aircraft’s nose starts to point downwards, gradually decrease the amount of up elevator until the RC model aircraft is level again. Take a look at this sketch, which shows what a loop looks like.

The loop described here is an inside loop, performed with the RC model airplanes bottom facing outwards. An inside loop is a much more challenging maneuver, and will be discussed in a later part of this article.

The Roll

The roll is another easy to perform maneuver, consisting of rolling the airplane on its side 360 degrees. We recommend having a RC aircraft with ailerons to perform this maneuver, but some three channel aircraft are able to roll without problems. This sketch shows what a roll looks like. We have colored in one wingtip of the aircraft in the picture, so that you can see the

Start the roll with the RC model airplane facing into the wind. Then apply a small amount of up elevator (to compensate for the loss of lift from the wing) and apply full aileron in the direction that you want to roll. Don’t center the ailerons until the RC model airplane is level again.

Inverted Flight

Flying the RC model aircraft inverted is a fun and impressive aerobatic maneuver. You already have some experience with inverted flight after performing loops and rolls, the two major ways to enter inverted flight.

The loop is the simplest way to enter inverted flight. Enter the loop like before, but at the top, don’t use up elevator. Instead apply a slight amount of down elevator. Because the RC model airplane is inverted, every control input will be opposite to what it is when the plane is flying normally. For example: when flying inverted, use left aileron to turn right, and right aileron to turn left. Likewise: use up elevator to fly downwards, and down elevator to fly upwards. You can exit inverted flight by completing the loop, using up elevator, or rolling 180 degrees. This sketch illustrates the two main ways to enter inverted flight.

Part II of this article will discuss more advanced aerobatics, including snap rolls, stall turns, and
hammerheads.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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The 12 inch DF-1245CR, 10 inch DF-1045CR, and 8 inch DF-8045 CR are pairs of counter rotating propellers. Counter rotating propellers are useful for experimental and twin engine aircraft, because they cancel out torque and p factor.

When an aircraft’s propeller or rotor spins, it generates torque. Torque can be described as the tendency for the aircraft to move its nose in one direction, due to the motion of the propeller.

Torque can be eliminated by using a pair of propellers, each spinning in opposite directions. Each propeller is curved in opposite directions, so that they both provide forward thrust while spinning in opposite directions.

The Lockheed P-38 lightning is one of the most famous applications of the counter rotating technology. During world war II, engineers needed a way to ensure that their fighters remained on target while using their weapons. They eventually settled on the counter rotating design, because the torque caused by each engine spinning in the same direction made it difficult for the plane to remain on target.

Because they eliminate torque, counter rotating propellers are an ideal choice for quad rotor and twin engine RC aircraft. A great example is the Draganflyer RC helicopters, which use the counter rotating design to prevent torque. Counter rotating propellers are difficult to find, so get some for your RC aircraft today.

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© Draganfly Innovations Inc.
Phone: 1-800-979-9794 / 306-955-9907
Email: info@rctoys.com
Web: www.rctoys.com
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