Saturday, June 16, 2007
Saturday, June 9, 2007
• Roll test steering in a driveway or car park. If it doesn't roll straight at home, it won't roll straight on a runway. Set steering control to the least sensitive position.
• Put small marks at the CoG. (Centre of gravity) on the wing to indicate balance location. Makes it easy to check at the field
• Balancing laterally (side to side) will help aircraft track better in manoeuvres. Hold at spinner and tail with glow plug removed. Add wing tip weight as necessary.
• Check receiver battery every 2-3 flights. Make a chart of how long you have flown vs. Voltage drop. Do not operate below recommended voltage level.
• Always turn on transmitter 1st, receiver 2nd. Always turn off receiver 1st, transmitter 2nd.
• Range check your system before 1st flight every time out. This should be performed with engine running at both idle and full throttle.
• When using the buddy box system, make sure both boxes are set identical. Never turn buddy box power "on"!
• Remove transmitter neck straps when starting engines.
• If you don't have a starter, at least use a "chicken stick". Do not hit it against the propeller; start your flick with the stick touching the propeller.
• Never jam a running starter onto the spinner. Back up the propeller, and place the starter cone against spinner before turning on.
• When you start your engine, look at your watch and keep track of time. After flight, check fuel level to assess maximum available flight time.
• Do not reach over propeller to adjust needle valve do it from the rear of the propeller. Do not position yourself (or others) to the side of a rotating blade. It could fail on run-up or kick up debris.
• Taxi while holding "up elevator".
• Always fly with a co-pilot/spotter.
• Never practice manoeuvres at low altitude. Fly 2-3 mistakes above the ground.
• When trimming an aircraft in flight, trim only until it stops the incorrect movement.
• Most trainer aircraft will recover from unusual attitudes (mistakes) by killing the power and pulling up elevator (depending on altitude). Be ready to level out and apply power.
• Remember, unless you are "dead stick", you do not have to land. If it's not right, go around. It's much easier, and safer, to try again rather than try to salvage a bad approach.
• If you get nervous for any reason, climb out and do some simple circuits over the field. When you calm down, try again. Don't' push yourself to try again too soon. Take your time.
• Do not fly too far away as it is easy to get disorientated. This is especially true when the sun is low on the horizon and the aircraft becomes a silhouette.
• Installing larger wheels on your trainer will :
1) Make taxiing in grass easier.
2) Improve your visual orientation in the air.
3) Improve your landings as gear won't bend as easily.
• Maintain your flight path. Do not make any erratic manoeuvres to avoid faster, more manoeuvreable overtaking aircraft (experienced pilots etc.). It is their responsibility to avoid you. However, make a conscientious effort to not be a hazard either.
• If it is obvious that you are going to crash, kill the power to minimize damage.
• If for any reason your aircraft is in trouble and headed for the pit area or spectators: Do your best to kill the power and ditch it. Don't try to save it. Planes are cheaper than people. It's a small sacrifice to make.
• If your aircraft does go down in the field or trees-Don't move! Note where you are standing, and pick a far distance reference point or object. Follow a straight line in your search and rescue effort.
• If you are searching in the trees, listen to glow powered aircraft overhead to orient yourself to the flight line and runway.
• When you do recover a crashed aircraft, be sure to pick up every last part, piece and splinter. You'll be glad you did when you decide to rebuild it after the shock wears off. All those little pieces can be glued together to make templates to create replacement parts.
• If you have adjusted the elevator trim to compensate for lower fuel weight during the later part of the flight, immediately reset the elevator trim to the "full fuel tank" position when you have landed. You probably won't remember until you are about 10 feet off the ground on the next take-off and struggling to maintain climb out.
This should be the first step in the assembly of any ARTF model that uses heat-shrink covering. Use an iron or heat gun to remove wrinkles that may have appeared during shipping, and then turn the heat up and go over all the surfaces where the covering overlaps or ends on bare wood. Be sure you don’t melt or shrink the covering too much, and pay particular attention to the engine compartment and wing seating areas. After you’ve sealed the covering where it ends on bare wood, apply Superglue (Cyano) along the edges to ensure that it stays that way.
Fuel proof the engine compartment
After a few flights, the firewall or engine compartment of diesel and glow powered planes can incur damage if left unprotected. Check these areas, and if needed, paint, epoxy and even cyano can provide the necessary protection. (Heat-shrink covering material will not sufficiently protect these areas from repeated exposures to fuel and oil residue.) The paint can be sprayed or brushed on. Epoxy should be thinned with a little rubbing alcohol and applied with a brush. Thin Cyano can be dripped on the surface and allowed to soak in, but thick Cyano should be rubbed in with your finger. It’s a good idea to wrap your finger in thin kitchen film.
Check high-stress glue joints
All visible glue joints should be checked for cracks or stress breaks when you unpack a new kit. Damage can easily occur during shipping; changes in humidity levels from one part of the country, or even the world, to another can warp parts and cause cracks or other damage tojoints. When checking the joints, pay particular attention to high-stress areas such as the wings, stabilizer, rudder, firewall, landing-gear attachments and servo trays. Repair the damage with Cyano or epoxy, and reinforce the area with balsa triangle stock, plywood, or fiberglass cloth.
Protect your antenna
If you have a high wing trainer, run your receiver aerial through a small hole behind the wing. Take a small screw and carefully screw it into the top of the vertical fin. Next take an old servo arm with three holes and weave your aerial through two holes and adjust it up to the little hole behind your wing inside the fuselage. Take a small rubber band and a small piece of fuel tubing and feed the rubber band through the fuel tubing. Push the end of the aerial through the loop of the rubber band protruding from the fuel tubing then slide your tubing up the rubber band till the loop holding your antenna is in the middle of the tubing also hook the other end of the band to the screw on the vertical fin. Your aerial is now held firm and should your model crash, the rubber band will pop off the screw and your aerial will be safe.
A good cleaner
In an empty spray bottle, add a tablespoon of dish washing detergent, then fill the bottle half way with surgical or rubbing alcohol, and top up with hot water. This recipe works really well for cleaning the oil off of the wings and fuselage after a flying session. It is a strong cleaner but will not hurt the covering or remove colours.
Simple propeller blade balancing
Here is a simple way to balance props. You will need to obtain or borrow a decent prop balancer. Once you have determined which blade is heavier, apply clear nail polish or clear dope to the LIGHT blade. Add thin coats until they are balanced. It should stand up to fuel and cleaners as long as the prop is cleaned thoroughly before applying the fluid. If not simply remove it and rebalance it.
Receiver battery pack precautions
Most radio control systems come with a 600 - 1100mAh battery pack. The latter is fine for a few good flights but if you are using digital servos, there are times when the current drain from the airborne system can reach several amps. An 1800mAH pack should give up to two hours of continuous flying for just a little extra weight penalty. So if you want more safe flight time, get a bigger battery pack..... JUST A SUGGESTION!
New life for old landing gear legs
It is not uncommon for your wire landing gear legs to get gradually weaker and weaker. A possible solution is to remove the gear from the airframe and remove all the hardware from the legs (i.e. - the wheels, collars, spats, etc). Preheat your kitchen oven to 235ºC (450ºF). Place the wire on a baking tray in the oven for one hour. Turn off the oven and toss the wire into cold water to cool it off quickly. What you have just done is to re-temper the piano wire and you should have put new life into that old gear. Note that soldered joints should not be harmed as solder doesn't melt until about 700ºF.
Clear Canopy polish
Toothpaste makes an excellent polish for the canopy. Smear a liberal amount of toothpaste on the canopy and use toilet tissue to buff it to a glossy finish. The process will not scratch the clear plastic at all. Then use an alcohol cleaner to remove any residue left by the toothpaste.
Have you ever had trouble peeling the backing from polyester covering materials when you have cut away all the edging paper? The easiest way to peel the backing off is to use two pieces of masking tape. At a corner of the sheet, stick a piece of masking tape on the front and back of the covering, with about half hanging over the edge so that the pieces of tape stick together past the edge of the covering material. Then peel the two pieces of tape apart. As the two pieces of tape come apart, the backing sheet will come away also.
A flying tip for new pilots
Control reversal is when the inputs on the transmitter sticks must be reversed when your plane is flying toward you. When flying away from you, there is no problem, just move the stick in the direction you want to turn. Many new pilots become disoriented when their plane is approaching them. To help with this, remember to always move the stick towards the low wingtip. This will level the wing when your plane is coming toward you, avoiding a sharp bank, and possibly a crash.
If you want to make a turn when flying toward yourself, then you must push the aileron control stick in the opposite direction to which you want the plane to turn. E.g. If you want the plane to turn to your right, you must push the stick to your left.
2. Follow the line up to where it intersects with the shaded area.
3. Each point within the shaded area corresponds to the appropriate prop size range on the left axis.
Note: Four Stroke engines are typically higher torque engines and should use the larger props indicated in the range. Recommended prop ranges will vary depending on your particular engine and airplane. This chart represents average prop usage and should be used only as a general guideline. Always refer to the manufacturer's instructions included with your engine.
Temperature sensitive items
In warm summer months, bear in mind several RC items that deserve a temperaturecontrolled environment. Batteries left in airplanes that are hung in the garage can get too hot. Fuel can evaporate quicker. Some covering films can separate from their backing. Cyano glues can age quicker. Try to keep these things cool so they’ll be ready to use in good condition when you need them.
Rubber band storage
Put your rubber bands in a Ziploc bag and cover them with Talcum Powder or Corn Starch. This will soak up the any fuel or oil residue, condition the rubber and help them last longer.
Cyano or Superglue storage
One popular method is to store the Cyano in the refrigerator. Another possible answer may be to simply keep moisture away from the opened container. This can be done by storing the opened Cyano bottles in a polythene bag with a silica gel desiccant bag. The silica gel keeps the moisture out and the CA flowing. The silica gel can be revitalized by baking in your oven.
The best way to remove bearings from your motor is to heat up the case. This can be accomplished by using a propane torch, a small butane pencil torch, or in an oven @ 235 - 260ºC (450-500º F) for only a few minutes. Be sure to remove EVERYTHING that can come off the motor. i.e. Carburetor, cylinder head, back plate, everything up front and all paper gaskets. Just give no more than 7 minutes at these settings or it may warp the case. Be sure to use an oven mitt to remove it from the oven. Once out, have a piece of wood handy and while the engine is still hot, just firmly tap the back of the motor on the wood and the bearing should fall out. The bearings will be hot also so take care.
Tip for cleaning bolts
Place the bolts in a fine strainer (stainless) and immerse it in a pot of boiling water with a strong liquid detergent for about 10 minutes. Rinse thoroughly and dry when complete. The parts are VERY, VERY clean when done. No further prep work is needed. This leaves the bolts clean enough for the application of Loctite.
Cleaning fuel soaked balsa
Remove the fuel tank and try to dry as much as possible from the affected area. Take some corn starch and fill the compartment. Also coat external affected areas and leave for 24 to 48 hrs. After that, tip out the excess or use the vacuum cleaner. You will probably have corn starch stuck to the balsa where the fuel was. Push the tank in and then remove it again and use the vacuum to get the rest out. If it is still damp reapply fresh corn starch for another 24 hrs. Repeat as you feel necessary.
Another method is to blow a heat gun on the affected area to bring the fuel to the surface. Then you can easily wipe the fuel away. A covering iron works as well.
Avoiding screwdriver damage when installing control horns
There is a simple tool that you can make that will eliminate this damage. Take a small piece of thin plywood and cut a rectangular opening in it just slightly larger than the base of the control horn. Place this opening around the control horn base before tightening the mounting screws. Now when the screwdriver slips there will be no damage to your new model.
Firewall fuel proofing
Firewalls are normally coated with epoxy to help prevent fuel and oil damage to the wood. Apply a coat of epoxy on the firewall after you have covered the plane with film covering. Ensure the film overlaps a little onto the firewall. The epoxy seals the edges of the film covering.
Mixing epoxy resins
If you use an old coffee can lid, when the residue of epoxy hardens, flex the lid and the epoxy will pop off.
Marking hinge positions
Use a marker to draw a black line across the middle of Mylar strip hinges. This will indicate whether the hinge is being pushed into the wing when you push on the control surface. If you can't keep the hinge from being pushed into the wing stick a pin through the middle of the hinge. This will not weaken the hinge in any way.
Correct fin alignment
To get a fin in correct alignment with a fuselage, try using thread. Make sure you have an accurate centre mark near the top-front of the fuselage, and tack-glue a long piece of thread to the top near the nose half the thickness of the fin away from the centre-line. Run the thread back to the tail, and hold it against the side of the fin. The thread should touch the side of the fin evenly overall. If it doesn't, then rotate the fin until it does, then tack glue the fin into place, reinforcing it later. Finally remove the thread you tack-glued in place.
Fiberglass Wing Joints
Give the cloth a light spraying of 3M Spray Adhesive, then apply it to the wing. Now you can apply the epoxy resin without wrinkles appearing. This method works extremely well, and it's safe for foam.
Installing triangular stock
Triangular reinforcements can been difficult to handle due to their shape, especially when they're coated with epoxy.
Try sticking your modeling knife loosely into one end of the triangular stock. Lay it on the bench so that the wide part of the triangle (the hypotenuse) is against the bench surface. Now apply the epoxy or other adhesive to the sides that will glued to the airframe.
Using the knife handle to insert the triangle into position in the airframe, press down with your finger onto the wide side that has no glue, and carefully slide the knife out of the piece. This way you can cleanly install triangular stock, and not get any glue on your fingers.
Cut two ribs from thick litho plate or a similar hard material. Drill two holes along the center line for 1/4-inch bolts to pass through, one near the leading edge and one near the trailing edge. Make sure both ribs are identical.
Use one of these ribs as a template to draw ribs onto balsa sheet leaving a small margin of waste wood around each rib. Cut each rib "block" out of the sheeting, and drill the holes in each.
Assemble all ribs on the correct length bolts, and sandwich all between the template ribs. Using nuts, tighten the assembly down, making sure it's straight.
Using a belt sander (a disk sander will work too) or hand sanding block, remove the extra wood around the ribs down to when the templates begin touching the sander. Cut out the spar notches with a hand saw, and clean them out with a file.
This will make all the ribs for a wing in one go, and they'll all be identical. This results in a straight, uniform wing. This method can also be used for a tapered wing (with all the ribs of different size). Multiple bulkheads and formers can be made using this method too.
Making holes in polyester covering
Holes for wing bolts, switches, hatch screw holes, pushrod openings, etc. can be difficult to finish neatly. You could cut the hole/opening with a modeling knife, or razor blade, but then you have to seal the fresh cut covering to the surrounding wood. Take an old soldering iron tip (pointed preferably) in a 25 watt soldering iron and cut the hole/opening with it.
Be sure to clean the tip after each cut. A wet sponge similar to that used for soldering is fine. Do not use the same sponge that you use for cleaning your soldering tips. If you don't clean the tip regularly the burned covering will cake on. It will not only smell badly but will inhibit the cut, as you will not have maximum heat. Thoroughly clean the tip with a wire wheel or wirewool after each use once it completely cools down.
For laying out sheets of heat shrink covering for cutting intricate shapes or just straight lines, nothing beats glass for a surface to cut on, it will not dull the knife or slow it down when cutting. The covering material will stick to the glass if the backing is removed all by itself for easy cutting. You can also use a little low heat from a hair dryer to make it stick even better for critical cutting. You can use solvent to put together large panels of covering without it sticking to the work surface. An old rectangular glass coffee table top is ideal. Try to get safety glass or plate glass.
Vertical rib supports
Obtain a piece of aluminum 1 or 2 inch right angle that can be found at most hardware stores. Make sure it is really square (90%) then cut off 1/2 inch wide pieces. Drill small holes in each end about the size of a modeling pin. Use the angles to hold ribs perpendicular to the building board by putting one on each side of the rib and then pinning it to the board.
Cutting clean holes in thin balsa & plywood
Do not try to use a common wood drill as it will usually leave a ragged hole that is the wrong size. Purchase a piece of thin wall brass tubing the same outside diameter as the hole you want to drill. Mount the tubing in an electric drill (preferably a drill press) then hold a piece of sand paper or a file against the end at 45º while running the drill to sharpen it. Use this sharpened tube to drill your holes it will cut perfect holes.
After cutting several holes you may have to push out the wood that collects inside the tube with a stiff wire. If you can find a drill that is the same size as the inside of the tube, push it in the top of the tube so that the drill chuck does not crush the tube. Also watch that the tube does not flare out at the bottom and change the size of the hole.
Better Screw Holes
When you have to use screws that will be removed often drill the holes for the screws large enough to allow you to insert a small length of Sullivan Gold-N-Rod and glue the rod in the hole. The screws can then be removed and reinserted with out weakening the wood.
Easier Plastic Bolting
After cutting a plastic wing bolt to shorten it, use a pencil sharpener to give it a beveled tip. This makes it much easier to insert the bolt and cleans up the start threads.
Covering Iron Cleaner
To remove the residue that accumulates on your covering iron, use a Cyano cleaning fluid. Brush on a thin coat on a cool iron and then wipe off with a clean rag.
The following list of quick tips should help newcomers to our hobby eliminate some of the problems that beset their first attempts.
Based on the Apid 55 from Linköping's Cybaero, Saab took over the rights to the product and development.
Lenght : 4 m
Height : 1,2m
Weight : 150kg
Payload : 25Kg @ 3500 meter altitude @100km range @ 100km/h.
Saab launched at Eurosatory 2006 the Skeldar V-150 lightweight unmanned helicopter, designed for military and commercial applications. The Skeldar is currently in final testing and is expected to be ready for operational use by mid 2007. The maximum takeoff weight of the Skeldar is 150kg, including 55 kg of fuel and payload. It can fly a 4 - 5 hour mission, up to a range of 100 km, dashing at maximum speed of 100 km/h. The basic system includes two unmanned helicopters, EO/IR payloads and a control station. The platform can accommodate an optronic, stabilized payload, or a SAR or various electronic sensors (ELINT, EW etc.) Saab is working with the Swedish Airworthiness Authorities to establish the necessary procedures and regulations to certify Skeldar UAVs to operate in civilian airspace.
The Skeldar is designed to take off and land vertically, and maneuver precisely even in tight airspace. The system uses a water cooled two cylinder, two stroke fuel injected gasoline engine located in the front of the fuselage. The rotor system uses a Bell-Hiller configuration, with stabilizer bar and paddles. Navigation is performed by redundant GPS and IMU system, air data and magnetic heading indicator enabling autonomous operation while maintaining total radio silence.
Friday, May 25, 2007
Lean and rich refer to the mix of fuel and air. To lean out or richen a nitro RC engine means to adjust the mixture of fuel and air going into the engine. Lean is the addition of more air to the fuel/air mixture. Rich is the addition of more fuel to the fuel/air mixture.
When you lean out a nitro engine you are adjusting the mixture so that there is more air going into the nitro engine than there is fuel. This provides a little more horsepower but can result in very high engine temperatures. If you are not careful leaning out a nitro engine you could run it too lean. This will wear out the glow plug prematurely or cause engine failure.
When you richen the nitro engine's mixture you're adding more fuel than air to the nitro engine. This can give you better results for some kinds of races because this method, unlike leaning out, will give you cooler engine temperatures.
But if running too rich you can not only bog the engine down and stall out but also flood it and foul the glow plug.
When to Lean Out or Richen a Nitro RC
You might be running too lean if the engine dies while idling, you don't see a light stream of blue smoke from the exhaust, or the engine gets so hot that a drop of water on the engine immediately starts sizzling and popping.
Too much blue smoke or a lot of unburned fuel from the exhaust and an inability to reach top speed are some some signs that you may be running too rich.
How to Lean Out or Richen a Nitro RC
Engine tuning and adjusting the fuel/air mixture involves adjusting the high-end (high speed / engine temperature) and low-end (low speed / idle speed) needles on the carburetor. This is also called dialing in your engine. There are usually base-line settings for each nitro engine that provide a good starting point for adjusting the needle settings. You'll turn each needle in very small increments to lean out or richen the fuel.
Turn clockwise to lean out or add air and counterclockwise to richen or add fuel. The low-end needle controls idling and low speeds. The high-end needle controls how the engine accelerates and runs at high speed and has a greater effect on engine temperature.
Lean, Rich, and Engine Temperature
You want to adjust the fuel/air mixture so that your engine runs at an optimal temperature which is generally somewhere between 225-250 degrees Fahrenheit for most nitro engines. Much over 250 degrees could cause a lot of damage and also shortens the life of your nitro engine.
Check your nitro engine's temperature often to keep it at optimal temperature for longer runtimes and overall better life for your nitro engine. If the running temperature is less than 200 degrees you need to turn your high-end needle adjustment clockwise to lean out the mixture a bit to get the temperature up a little. If your temperature is above 250 degrees you would bring it down by adjusting the high-end needle to richen the mixture by rotating the high-end needle counter-clockwise. The ambient temperature outside and the elevation according to sea level will adversely effect the nitro engine's temperature so adjust accordingly.
For your nitro engine break-in, choose a clean, flat, paved or smooth surface. You'll be doing the initial break-in with the body off so you don't want to be kicking up dirt or doing flips during break-in. During the first couple of tanks of fuel focus on varying and limiting your speed. Don't run your engine past half-throttle. Don't run at a constant speed.
During break-in deposits build up and can foul out the glow plug so your engine might seem like it's stalling or not running properly. This is normal. Proper break-in alleviates these symptoms. Do have an extra glow plug or two handy in case you need them.
Here are simple safety checks you need to do before starting:
1. Turn on the Controller First
Turn your transmitter/controller on first followed by the receiver on the RC. When finished running your RC, turn the receiver off first, then the controller. This sequence will keep your nitro RC from running amok if someone nearby is running on the same frequency. Do yourself a favor though and check frequency before running your RC.
2. Put The Engine in Neutral
Move the throttle forward and reverse to ensure your nitro engine is in neutral and is in the idle position when the throttle is released.
3. Check Your Steering
Move the steering controls from side to side. If steering seems sluggish or hesitant, replace the receiver's batteries before proceeding.
Prime Your Nitro Engine
Start up your RC. Watch to see if fuel is moving through the lines. If fuel doesn't reach the carburetor after 3-5 seconds place and release your finger over the tip of the exhaust for a couple of seconds to help the engine start. This is known as priming the engine. Be careful when doing so because if too much fuel goes into the engine when priming, it will flood causing the engine to lock up.
If the engine does flood use your glow plug wrench to remove the glow plug. Place a rag over the engine head. If equipped, use your electric starter. Start the engine to get the remaining fuel out and wipe off the head with a dry towel to remove any remaining fuel. Reinstall the glow plug and start on the first tank of the break-in process. Your nitro engine shoudn't be primed for more than 1-2 seconds at a time to avoid flooding.
Do Five Tank Nitro Engine Break-in
With each tank of fuel you'll increase the amount and duration of throttle. Use these tank-by-tank guidelines for your nitro engine break-in.
Give the engine one-quarter throttle slowly for 2 seconds. Apply the brakes. If you pull back on the throttle too fast you may cause your engine to stall.
When there is a nice trail of blue smoke coming from the exhaust it means your fuel mixture is properly set and the engine is being lubricated. If no smoke is present, richen the fuel mixture by giving the air/fuel mixture needle a quarter turn until smoke is present.
Continue running the first tank of fuel, repeatedly giving it one-quarter throttle then braking until it is almost empty. Do not run the tank dry because this will result in a burned out glow plug from the fuel mixture being too lean and can also lead to damage from high engine temperatures.
Shut off the engine by pinching the fuel line to the carburetor and let it cool down for about 10-15 minutes before you start on your next tank of fuel.
Advance to half-throttle for 2-3 seconds for the second tank of fuel. Remember to accelerate smoothly through the entire break-in process. Do this repeatedly as long as you have fuel. When the second tank is done repeat the shut-off and cool-down steps as you did in the first tank of fuel.
On the third tank of fuel you will run for a 3-second count at half-throttle then brake. By this time the engine begins to loosen up and the idle may need to be adjusted down.
You will know an idle adjustment is necessary when your nitro RC won't sit still when idling. Use your tuning screwdriver to turn down the idle by turning the idle adjustment counter clockwise to reduce the idle speed. From this point forward you don't have to let your engine cool down between tanks.
For the fourth tank give your nitro RC full throttle for a count of 3 seconds and then brake. If your nitro RC is equipped with a multi-speed transmission and tries to shift into another gear let off the throttle and then brake. When doing a 3 second count on tank 4 remember to accelerate smoothly to avoid doing wheelies or flipping the RC over.
For this final tank of fuel you will repeatedly accelerate to full throttle in 3 seconds and hold for 2 seconds then brake. After this tank is done you will have completed the break-in process.
Maintain Your Nitro Engine After Break-in
After break-in and after each session with your nitro RC you'll need to perform after-run maintenance. For a nitro engine this includes :
* Drain the fuel tank
* Clean and oil the air filter
* Add after-burn oil
Sunday, May 20, 2007
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Saturday, May 19, 2007
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Tuesday, May 15, 2007
Why Do We Need Them?
Most people think it is to compensate for the wind, but that is not the real reason. I myself give examples of a gust of wind hitting the helicopter from the side, this is to keep the explanation simple but the real reason is to compensate for sudden loads on the main rotor. The tail spins at over twice the speed of the main rotor so if you lose 100 rpm from the head then you dropped over 200 rpm from the tail. The tail rotor is a lot smaller then the main and its effectiveness is highly dependent on the speed. So every collective and cyclic change you make effects the tail. Now keep in mind just because we have highly advanced gyros now does not mean you do not have to take this effect into consideration. Any gyro will work its best when you can keep the head speed constant. This means fine tuning both the throttle curve and cyclic mixing is important to achieving the maximum performance from your gyro.
Basically you have two types, mechanical and piezo. I do not think anyone still sells the old mechanical gyros but if you bought a used helicopter it is possible you may have one. The mechanical gyros will have a buzzing sound coming from the sensor unit. They use an electric motor with two flywheels, one on each end of the motor shaft. And this is where the noise comes from. To understand how it works hold a spinning bicycle wheel by the axle and try to turn it, you will feel it resist you moving it. The flywheels in the mechanical gyro are mounted on a pivot and a sensor measures the deflection of the motor/flywheels when the helicopter makes a sudden movement. The piezo type gyros work with no moving parts. It uses a triangular crystal with a piezo element on each side. The piezo element is used in a lot of watches to make the beep sound from the alarm function. The material not only can make sound but also sense it. So it is used in both speakers and microphones. Two of the piezo elements on the crystal are set to sense vibration and the third one is setup to vibrate. When the helicopter is not rotating the vibration travelling through the crystal hits the other two piezo elements at the same time. When the helicopter is rotating one sensor will have a stronger signal then the other. It is a very efficient design and has a lot finer degree of resolution then the mechanical type. In addition power consumption is greatly reduced as there is no spinning motor to power.
What is the Difference between Heading Hold (HH) and Standard Rate (Non-HH)?
In Non-HH mode the gyro just dampens unwanted movements of the tail. To keep things simple let say you are hovering and a constant wind hits the helicopter from the side, the gyro will keep the helicopter from suddenly swinging nose into the wind, but the helicopter will eventually drift nose into the wind. All the gyro does is to prevent any jerk type reaction.
In HH mode the gyro will keep the nose pointed in the same place until you tell it to move. You can fly sideways with the rudder stick in the centre and the nose will remain pointed in the same direction.
If you have not used heading hold before then you will notice in fast forward flight that when you make a turn, the tail will not follow the helicopter, you have to give some rudder in your turns. Another thing is that you'll notice the rudder stick feels different. In heading hold, the amount you move the rudder stick from centre tells the gyro how many degrees per second that you want the helicopter to rotate. The gyro moves the rudder servo however much it needs to obtain the requested rotation rate. With a standard rate gyro if you did a slow pirouette (one rotation) with the wind then to keep the helicopter spinning at the same rate you would have to move the rudder stick more as the tail is going upwind and less as the tail goes downwind. But with a heading hold gyro, it will tell the rudder servo to move more or less to maintain the constant rate; you just keep the rudder stick in one place.
Due to typical marketing ploys you will see many names for heading hold. They all are just different names for the same thing. The different names are just because each company wants to make it seem like their version is more special then another companies.
AVCS = Tail Lock = Smart Lock = Heading Hold
Rudder ATV (End Point, Travel Adjust) Values?
On a non-heading hold gyro this function in your radio is used to set how far the rudder linkage will travel.
On heading hold gyros this function works completely different. It is used to set the maximum rotation rate. So what do you do about limiting the travel so as not to allow the servo to bind? Some gyros have a limit adjustment on them that you use to set this. The ones that do not require you to move the ball on the servo arm further or closer to the centre of the arm to limit the travel.
Can I Use Rudder Trim?
If you are using a heading hold gyro then the quick answer is no. The reason is that heading hold gyros are looking for a centred command from the radio to keep the helicopter from rotating. If you move the rudder trim a few clicks one way or the other then a gyro in heading hold mode thinks that you wanting it to spin in that direction.
Example: Say you have switched to non-heading hold mode and the helicopter is rotating left so you add a little right trim until the helicopter is still. Now when you flip back to heading hold then you will find the helicopter now constantly rotates to the right.
So how do you make it so the helicopter is trimmed in both heading hold and non? This confuses a lot of people because they often do the setup out of order. The first step is to centre the trim and zero the sub-trim. Next with the gyro in heading hold mode adjust the sub-trim so the helicopter does not rotate. Normally this should be zero but due to small differences in the radios as well as some gyros you may find you have to adjust the sub-trim. The next step is to switch to non-heading hold and if the helicopter drifts, then adjust the rudder linkage. If the helicopter is drifting left then turn the link clockwise, opposite if drifting the other direction.
Helicopter spins out of control as soon as it gets light on the skids
This is another very common question I get. The cause is the reverse setting on the gyro. Do not get this confused with the reverse settings in the radio, that is not the same. To check the gyro move the rudder stick to the right, the control rod for the tail should be pulled toward the front of the helicopter. Next pick up the helicopter by the rotor head. Grab the tail boom and quickly rotate the helicopter so the nose goes to the left. Watch the control rod, it needs to move forward. If it does not then the gyro is backwards. Most gyros have a reverse switch or jumper located on the gyro, this is not done in the radio. A few gyros require you to turn the gyro upside down.
What is Gyro Gain?
This refers to the sensitivity of the gyro. When the gyro senses an unwanted movement it commands the tail servo to move in the opposite direction to compensate. How much it tells the servo to move is the 'gain'. Ideally the amount of gain should match how much the helicopter was rotated so that it stays pointed in the same direction and does not move. If the gain is too high then the helicopter over compensates. The effect you will see is the tail will bounce back and forth (wag). If the gain is not enough then you will notice the tail does not hold very well. When setting the gain, you want to turn it up until you see the tail 'wag' (bounce back and forth) then turn the gain back down until it stops.
How to Set the Gain?
Gyros with Remote Gain :
This depends on the type of radio you have and how you set it up. Some radios do not have a dedicated gyro function such as the Futaba 6X, 8U (not Super), and JR 622/642/652/662. For these you adjust the gain in the travel adjust (End Point, EPA, ATV) menu. In this menu select the gear channel (channel 5) and use the switch assigned to it to toggle between the gain setting for heading hold and non heading hold. For radios with gyro menus leave the ATV set to the default values (usually 100) and then use the gyro menu to set the gain
Gyros without Remote Gain :
This type will have an adjustment on the gyro. It is usually a small pot that you use a screwdriver to turn.
Different radios treat the values differently. On the Futaba 8U(super) the range in the gyro menu is 0 to 100. From 0 to 50 is one mode (such as heading hold) and 50 to 100 is the other. To fully understand this you have to look at it just as the gyro does. That radio sends a pulse from 1ms to 2ms to each of the connectors on the receiver. From 1ms to 1.5ms is one mode, say Non-HH, and 1.5ms to 2ms is the other. The further it is from 1.5ms the higher the gain. On the 8U(super), 0 would correspond to 1ms and 100 would be 2ms. Now on the Futaba 9C it has 0 to 100 for HH and 0 to 100 for Non-HH. So in the Non-HH position 0 would be 1.5ms and 100 would be 1ms. In the HH position it sends pulses from 1.5ms to 2ms.
Now to add a little confusion some radios allow the end points (ATV) you set to effect the setting you made in the gyro menu. So in other words if you have the gyro menu set at 100% but the end point for channel 5 is at 100% (with a range up to 150%) then instead of sending a 2.0ms pulse to the gyro (for maximum gain) you are only sending a 1.83ms signal which is about 65% of the actual gain in the gyro.
So to help unconfused you now, don't worry about the details. Just set your end points to 100% and 100% for the gyro gain too. Then if the tail wags lower the gain from there. If you have to go below 85% then move the ball on the servo arm in one hole toward the centre and try again.
What is the Delay Setting?
This is a setting found on some gyros such as the popular Futaba GY401. It is used to compensate for slower servos. To set it do a quick pirouette and when you stop watch to see if the tail stops still or bounces. If it bounces then increase the delay to stop it. For a fast servo like the Futaba 9253 leave the delay setting at 0.
Saturday, May 5, 2007
The foam is rather brittle and do not sustain a crash well. Then again, spare parts are available.
To bring your plane in, start by lining it up with the place where you want it to land, either grass or a runway. Then reduce the power, without turning the engine completely off. Use just enough engine power to maintain a gentle rate of descent while keeping the airplane in the landing attitude (that means wheels down - not nose down!), use the rudder to keep the plane in a straight line, allowing it to glide down to the ground gently. Remember that the amount of engine power you need will vary according to the strength of the wind you are flying into - and that can change from day to day.
Some model airplanes have an elevator control. In this case, you can adjust the height, but if your plane doesn't have this feature, don't worry--the engine will do the same thing if you power up brieﬂy to help slow the descent down. Otherwise, it's best to use the elevator to pop the nose up lightly as you touch down, this drains excess speed from the plane.
If you're uncomfortable with landing, turn the engine back on to full power. Then, circle around and try again, lining up again with the runway or grass. Remember that even the experts make mistakes and have missed approaches, and you'll do far better to circle three, four, or ﬁve times than to crash your plane. However, you want to make sure you do not run out of fuel or battery power before landing, or the plane could end up somewhere you do not want it to go
Again, thank you for subscribing to this special 5-part report. Hopefully, you have read each of the previous instalments in this series and are now fully aware of five ways you can increase your enjoyment of this great hobby while protecting the safety of your plane and of those people on the ground.
The small trim tabs located on the transmitter are used to fine-tune the controls. These too can vary from one transmitter model to another. What you are doing is putting in a constant adjustment to the flying controls to balance the defect affecting the airplane.
Once the trim tab has been moved, allow your model plane to fly on its own for about 10 seconds to check that it is flying straight and level, and then, if necessary, you can make further small adjustments until you get it right.
Next, stand directly behind the plane. Turn the engine on to full power, allowing the airplane to accelerate while on the ground. If necessary, use the rudder to keep the plane headed straight down the runway. Just as with a full size plane, the model will gain speed and eventually lift off the ground.
When the plane starts to take off, give it just a little bit of up elevator. Typically you see beginners make the mistake of climbing too steeply, which causes the plane to slow down, stall, and crash. A gradual climb, as stated before, is much better. So go light on the up elevator.
If you plan to hand launch your model plane, be sure you never throw it angled up. Instead, it should be thrown firmly --but not too hard--with the nose pointed straight ahead. You want it in a nice stable flying position while you get your hands back on the transmitter box.
Friday, May 4, 2007
For the pre-ﬂight check, turn the transmitter on ﬁrst, followed by the receiver switch. Then, pull the transmitter antenna out so that it's completely extended. Next, make sure the rudder or elevator is working properly, moving in the correct way then centre it in a neutral position.
Now hold your airplane facing away from you, at head level and into the wind. Very gently launch the plane from your hand, making sure it is level or pointed slightly downwards. If the plane is right and ready to ﬂy, it will gently glide to the ground after a short, smooth ﬂight.
This has a direct impact on the plane's balance. As a general rule, the center of gravity should be about one-third of the way back from the front edge of the wing (and two-thirds of the “wing-chord” forward from the trailing edge). To test, place the tips of your index ﬁngers under the wing tip, about one-third of the way back from the leading edge.
Then, very carefully, lift the model airplane up, balancing it on your ﬁngers. If the balance is good, the plane will be level, with the nose pointing horizontal, or maybe just a bit downward. If the plane's tail is pointing downward, then you have a balance problem and should not ﬂy the plane until it is ﬁxed.
Before adjusting it, think of what might have caused it. If you tested your model before leaving home and it was OK but now it isn't then what might be the cause? A loose screw or piece of material which has moved around during transit can be enough to affect the CG. If you now adjust it back to balance by adding another weight then you may have left a loose item inside your model which will surely come back to haunt you when it moves again during a flying manoeuvre.
If you are sure you have nothing loose and you do need to adjust the CG, add weight to the nose, something like ﬁshing shots, plasticine, or even modelling clay. Add just a little at a time, checking the center of gravity after each addition. (Or, you can move the engine more toward the front.) If you do not want to lose control and maybe crash and ruin your plane, this is a crucial step.
Tuesday, May 1, 2007
For beginners, flight simulators are excellent tools for building spatial orientation, motor skills, and confidence. For more experienced pilots, flight simulators help in building motor skills required in doing the more difficult maneuvers. The amount of benefit that the pilot can gain from the simulator depends entirely on how well the simulator emulates the model. On most simulators, the flight characteristics can be adjusted so that it more closely emulates the "feel" of the model. None of the simulators have progressed to the point that the flight physics are perfect but they are close enough that they can be of significant benefit.
Dne of the most difficult things to master for the beginning pilot is approach orientation. There is a natural tendency for the beginner to move the stick in the direction he wants the model to go. When the model is moving toward the pilot, the aileron and rudder controls are reversed. This means that in order for the model to turn to the pilot's left, the stick must be moved to the right. Using a simulator allows the pilot to practice approaching maneuvers for hours on end so that it becomes second nature to move the stick in the correct direction for the model to take the desired flight path. After approach orientation has been mastered, all other maneuvers start to become easier to accomplish, especially landings.
The primary benefit of flight simulators is that of building motor skills. The pilot, whether a beginner or experienced, can practice specific maneuvers for hours without having to be concerned about weather, time of day, temperature, or number of people at the field. The motor skills that are developed through hours at the simulator are basically the same as "muscle memory" in golf. This means that the skills are related more to the muscles reacting to a simple command than the brain sending a series of commands to the muscle. For instance, the pilot wants to perform a snap roll with a Giles 202 model. He thinks "snap roll" and his fingers simply move the sticks to the appropriate position rather than his having to think in what position the sticks need to be. The end result of the muscle memory is where modelers get the term "feel" for a model. Since there is no positive feedback system built into a transmitter, there is not true feel for a model. The feel of the model comes from the difference in the expected feel based on muscle memory and the actual feel from the movement of the sticks.
Many beginners do not progress as well as others simply because of a lack of confidence. This is especially true if the student is not able to fly very often due to conflicts in scheduling time to devote to learning to fly. With each trip to the field, he must re-learn some of the things that he has forgotten during his absence from the field. He must again reinforce his motor skills and regain his muscle memory or feel for the trainer. Since his progress may be much slower than that of other students at the field, he may become frustrated and much less confident. The simulator allows the beginner to practice what he has learned to maintain or improve his motor skills and not lose his confidence. When he goes to the field, he will subconsciously think, "I can do this."
If pilots get proper instruction and use the flight simulator to practice what is taught, it can be of significant value in learning to fly or to perfect various maneuvers. It can greatly increase the "stick time" that the pilot is able to achieve in given period of time. It is a tool that if properly applied can help a pilot to progress at a much faster rate than normally possible. Above all, it is up to the pilot to make sure that this tool is properly applied by getting the right kind of instruction and not try to learn on his own.
All resistors 1/4w / 5% tolerance, unless otherwise posted.
R1 = 47K
IC1 = MC14013B
R2 = 1K
Q1 = BUZ11, IRFZ42, NTE2395, or ECG2395
R3 = 10K
S1 = on/off switch (optional)
P1 = 100K
C1 = 22nF
This device contains protection circuitry to guard against damage due to high static voltage or electric fields. However, precautions must be taken to avoid applications of any voltage higher than the maximum rated voltages to this high-impedance circuit. For proper operation, Vin and Vout should be constrained to the range Vss [much-smaller-than] (Vin or Vout) [much-smaller-than] Gnd. Unused inputs must always be tied to an appropriate logic voltage level (e.g. either Vcc or Gnd). Unused outputs must be left open.
The circuit, as described above, is a so-called "Radio Controlled Electronic Switch". It can be used to switch on/off anything electrical, whatever it is. Here are a couple of examples : navigation lights, landing gear, sound systems, glow plug driver, bomb release, parachute, search lights, gyros, and so on.
Fig. A shows the regular setup for common accessories such as motors, glow plugs, bomb-doors, relays, etc. If you like to hook it up to a camera, see Fig. B. Note that for the Camera Shutter version the value for R1 and R2 is different (100K). Please note that this system will not work with PCM.
Heart of the circuit is a CMOS Dual 'D' Flip-Flop MC14013B. The input Flip-Flop is designed as a monostable pulse generator by means of R1, P1 and C1 connected between 'Q' and the RESET input, which produces a preset pulse-length set by the adjustable potentiometer and starts at the rising edge of the input pulse. When this monostable times out it's inverted 'Q' signal goes high and clocks the output stage of the Flip-Flop, which is used as a normal type 'D', to sample the input pulse. If the duration of the input pulse is longer than the preset monostable pulse, then a logic high level will be clocked to the output of the 'D' type. A shorter input pulse will cause a logic low to be clocked to the output. In short, both halves of the IC perform two different logic functions.
The output drives the output device which in this circuit is the IRFZ42 TMOS FET. It needs only 2-volt on it's gate to fully turn-on and has an rDS-ON resistance of only 0.028 ohm. To invert the operation of the r/c switch, you can connect R2 either to pin 12 or 13 of the MC14013B. This circuit is easy in design and to built and can easily be done using vector board, vero-board, or whatever. The complete unit measures 5/8" by 1-1/4" but it can be a lot smaller by choosing SMT components, probably 3/8" x 1/2". You can use a case or heat-shrink. This unit is NOT meant as a motor-switch for electric flight.
Adjusting the Switch
To test the unit hookup a light and a battery, making sure the + of the battery goes to the Drain of Q1. Adjust the potentiometer P1 to somewhere in the middle and set the transmitter function of your choice (say the throttle) to the point where you wish to switch the unit. Now adjust the potentiometer P1 to the point the light comes on. If it does, your unit functions properly and you can play with whatever other setup you have in mind. If you intend to use this unit as a on-board glow driver, make sure to use heavy wiring between glow plug, battery and r/s switch. A 'Y'-lead to the throttle servo is required. If you use this unit to switch relays or a small dc-motor, then a 'spark eliminator' diode (1N4001) is required. Cathode of the diode goes to the '+' side of the battery. (See diagram).
The IRFZ42 is a TMOS Power FET and can be costly (approx. S$18). Other substitutes like the IRFZ44 will work too. Watch for static discharge with this one!
IC1, the MC14013B, is a CMOS SSI type Dual Flip-Flop. It features a direct pin-for-pin replacement with the CD4013B, NTE4013B, ECG4013B, and others.
The output signal can be inverted by selecting either pin 12 or 13. To make life easier, you could install a miniature on-on switch.
The middle contact going to R2, and pin-12 & 13 to the other two contacts.
Sunday, April 29, 2007
Raptor 50 with a fully bling aluminium rotor head and tail boom. My first Nitro and biggest flying heli. But it will definitely not be my last. It is used to be fitted with an Electric power plant. Due to the limited flying time with an electric setup, she now sees a brand new setup with a Nitro engine. More economical to run and longer flight duration. With a TT50 sizer, she could do 20 - 30 minutes of flight in one full tank. This is certainly a lot of flight time for me for I'm not an agressive Heli pilot. It is an awesome flying machine!
Hovering at 30cm off the ground.
Closing in shot. Isn't she Gorgeous!
The other option is to buy a ready made cables off the shelf but do bear in mind they do not come cheap.
Tx Signal and Tx GND to be connected to the appropriate Tx connector of your choice. The connection diagram for the different Tx connectors are shown below.