First I would like to give a few definitions of helicopter terms

AUTOROTATION - This is the term for when the engine is either not running or is put into a idle position with the "HOLD" switch.

ATS or Revolution Mixing, or Anti Torque Compensation - This is " Automatic Tail System". This refers to the radio mixing in a certain amount of tail rotor when the throttle / pitch is increased or decreased.

ATV or ENDPOINTS - This is "Adjustable Travel Volume". This refers to the amount of movement the servo has when the stick is moved from one extreme to another.

COLLECTIVE PITCH - This is the ability to vary the main blade pitch when the throttle is increased or decreased.

CONSTANT DRIVE TAIL - This is a special autorotation clutch that will always drive the tail rotor even when the engine is off or in "HOLD".

CURVES - This is the end shape of the different functions, like the "PITCH CURVE", or "THROTTLE CURVE". On the computer radio's you might have a 5 point curve. You will be able to set the low point, 1/4 point, 1/2 point or hover point, 3/4 point, and high point. Some radio's will have more and some less. At those particular points you can vary where the servo's output will be. On non computer radio's you should be able to at least control the low and high points.

HOLD or ENGINE HOLD - This is a switch that will take the engine to a preset idle position and will disengage the engine clutch. While in "HOLD" though you will have full control of the "COLLECTIVE PITCH". This allows you to practice "AUTOROTATION" providing you have a autorotation clutch in your helicopter. This clutch will let the main blades free spin with out driving the tail rotor. There are certain conditions where you might want to drive the tail rotor. You can drive the tail rotor with special items called a " SLIPPER CLUTCH" or a "CONSTANT DRIVE TAIL".

HOVERING PITCH - This is the amount of pitch you will need to hover the helicopter. On average this is about 5 degrees. Most helicopter radio's will have a knob on the transmitter to vary the amount of pitch at the present hovering stick position.

HOVERING THROTTLE - This is the amount of throttle you will need to hover the helicopter. On average this is about 50% throttle. Most helicopter radio's will have a knob on the transmitter to vary the amount of throttle at the present hovering stick position.

IDLE - UP - This function is controlled by a switch and what it does is keep the engine speed at a present position when the throttle stick is lowered past that point. This way you can get into the negative range of pitch and will keep the blades spinning with out taking the engine to an idle. Some helicopter radio's will have either one or two "IDLE - UP's".

INVERTED - This is when the helicopter is inverted and the functions of the Pitch, Elevator, Rudder can be reversed by the use of the "INVERT" switch or the pilot can do it him or her self at the sticks. This is referred to as "SWITCH LESS" inverted.

SLIPPER CLUTCH - This is another special unit that is attached to the autorotation clutch will let the main blades turn the tail rotor when the engine is off or in "HOLD". The difference between this and a "Constant Drive Clutch" is that this one will "SLIP" a little so the tail rotor while spinning will not load the main rotors as much while in the "HOLD" function doing a "AUTOROTATION".

BASIC HELICOPTER RADIO FUNCTIONS

1 - More Throttle / Collective Pitch: Makes the helicopter go up by increasing throttle and the amount of collective pitch in the main blades.

2 - Less Throttle / Collective Pitch: Makes the helicopter go down by decreasing throttle and the amount of collective pitch in the main blades.

3 - (SEE PHOTO #2)Left Tail Rotor Yaw: Makes the NOSE of the helicopter left by increasing or decreasing tail rotor pitch.

4 - (SEE PHOTO #3)Right Tail Rotor Yaw: Makes the NOSE of the helicopter go right by increasing or decreasing tail rotor pitch.

5 - (SEE PHOTO #4) Forward Cyclic: Pushes the NOSE of the helicopter down and makes the helicopter go in the forward direction. NOTE: If there is not enough collective pitch added, the helicopter will also go downwards. To maintain level forward flight, you must add collective pitch / throttle.

6 - (SEE PHOTO #5)AFT Cyclic: Pulls the NOSE of the helicopter up and makes the helicopter go in the aft direction. NOTE: If the helicopter has any amount of forward movement in it, this can and will make the helicopter pitch up as in doing loops. If there is not any forward movement or enough forward movement, the helicopter will travel in the aft direction by dropping its tail boom.

7 - (SEE PHOTO #6)Left Cyclic: This will make the helicopter roll to the left.

8 - (SEE PHOTO #7)Right Cyclic: This will make the helicopter roll to the right.

9 - Idle-Up Switch: On most helicopter radios, this is the usual position for the idle-up switch. This will keep the engine at a preset throttle position so you can use negative collective pitch.

10 - Hold Switch: On most helicopter radios, this is the usual position for the engine hold switch. This will take the engine to a idle so you can vary the collective pitch of the main blades.

11 - Throttle Hover Trimmer: This will let you vary the amount of throttle at 1/2 throttle stick for hovering. NOTE: If you are setting up for 3-D style flying and will hover at 3/4 throttle stick position (not 3/4 throttle) this function will not help.

12 - Collective Pitch Hover Position: This will let you vary the amount of collective pitch at 1/2 throttle stick position for hovering. NOTE: If you are setting up for 3-D style flying and will hover at 3/4 throttle stick position (not 3/4 throttle) this function will not help.

PHOTO #1 STICK MOVEMENTS

PHOTO #2 AND #3 ( Shows left and right tail rotor yaw )

PHOTO #4 ( swash plate is lower at the front of the helicopter )

PHOTO #5 ( swash plate is lower at the aft of the helicopter )

PHOTO #6 ( swash plate is lower on the left side of the helicopter. Photo from front of helicopter. )

PHOTO #7 ( swash plate lower on right side of helicopter. Photo from front of helicopter. )

Brief over view of what the helicopter radio does and how it affects the helicopter
Some of the following applies to fixed pitch helicopters also, that is the ones that have the main blades set to one constant pitch and that the altitude is varied by speeding up the head speed to get more lift, which makes the helicopter go up. This type is in lieu of the collective pitch types or the ones that when the engine throttle is increased the main blade pitch also increases, thus keeping the main blade or head speed at one constant speed.

THE RADIO:

The radio will be similar to the aircraft version. The biggest difference will be that the throttle and collective pitch will be mixed together. These two will also mix in yaw or rudder when the throttle is varied. This is know as anti-torque compensation. What happens is at a hover which is usually 1/2 throttle stick, there is a certain amount of pitch, usually 5 degrees. At this setting there will be needed a certain amount of tail rotor to correct for the amount of drag induced by the main blades, and the amount of opposite torque that the engine produces. So at this setting the tail rotor will be set to keep the nose straight. When there is more pitch added to the main blades by increasing the throttle, you get more drag and torque, so you will also need more tail rotor compensation to keep the nose straight. By taking away the pitch, there will be less drag and torque, so there will be less need for the added tail rotor input. If you have a helicopter with clockwise rotating blades, looking down on the helicopter, you will need right tail rotor from 1/2 throttle to full throttle, and left tail rotor from 1/2 down. This can be a little confusing because at 1/2 throttle you added to start a certain amount of right throttle and when you decrease the throttle you are really taking out that right tail rotor or going in the left direction.

Next you have extra switches on most helicopter radios for what is know as IDLE - UP 1, maybe IDLE -UP 2 and engine HOLD. The idle up switches keep the engine at a certain level about 1/2 throttle to full throttle. This is for doing aerobatics. When you come down on the throttle stick, you will get a certain amount of negative pitch for loops, rolls, or even inverted flying. So since you don’t want the engine to quite from being over loaded, the throttle will stay at a percentage to keep the main blades at that set rpm. For example, lets say that your pitch range was from a minus 5 degrees to a positive 8 degrees, and you hover at a positive 5 degrees. At this positive 5 degrees the throttle is at a 50% setting. When you come all the way down on the throttle stick you will a minus 5 degrees. This will in essence let you hover inverted so when you hover you will need that 50% throttle again. At 0 degrees pitch you will have the least amount of drag induced by the blades and you will need less throttle. So the final throttle curve will look like a “J”. The low end will be at 50%, about 1/4 stick will have about 40% throttle, and 1/2 stick will have 50% throttle and full stick will have 100% throttle. The only difference between IDLE - UP 1 and 2 will most of the time be the amount of pitch you will have or want at the low throttle stick position, this in turn will also need a different amount of throttle at the low stick position.

The HOLD switch will take the engine to an idle position on the throttle and hold it there. By doing this the engine will still stay running but will let you have control of the collective pitch so you can practice your autorotation with the helicopter. The typical pitch settings will be about a minus 4 degrees to a positive 10 degrees. Both the top end pitch and low end pitch will very during test and set up of the helicopter.

Another two features the radio will most likely have is two knobs that will be called “HOVERING PITCH” and “HOVERING THROTTLE”. What the hovering pitch knob will do is very the amount of pitch you have at you set hovering stick position. example would be if you hover at 1/2 stick position and at that position you had a positive 5 degrees pitch. When you vary this knob you might get lets say 4 degrees to 6 degrees of pitch. This will fine tune your helicopter so it will hover at exactly 1/2 stick position. The hovering throttle knob will do the same as the hovering pitch knob but it will do it only to the throttle. It will vary the throttle position or fine tune it at the 1/2 throttle position or where ever you have set that hover position to be. Yes there are some radios that will let you dictate where you want to hover at. Some people will set up for 3-D aerobatics by hovering at 3/4 stick. This will let them also hover inverted at the 1/4 stick position. By doing this the pitch and throttle curves stay more linear.

A few things to consider when buying that first ( hopefully the only ) radio.
No matter what get servo's that are ball bearing supported. these will handle the loads better and last longer. Try to get the strongest ones you can. The smaller helicopters can use mid torque servo's but when you get to the larger helicopters they will push the limits of the servo, so get the strongest ones you can. Most 60 will be ok with the servo's that are about 70 oz. in. torque.

Like computers, try to get the most you can. You might not need a computer radio now but what about when you start doing that switch less inverted flying, will it work for you then? I'm not trying to get you to spend all your money now but I am trying to get you to think about the future. $400 now and another $600 later for a better one well you could have saved money by buying the most once.

Service and Parts for the radio is also something to consider. Will that radio sit in the shop for weeks on end or can it be fixed in a week. Does that particular radio fail more often than others? Can you go and get parts at your local hobby shop? What about the price for a new servo or rx? Just things to think about.

Just a few thoughts about setting up the helicopter.
Try to keep all of the end points equal. example would be for instance the throttle. With the throttle trimmer all the way down to the position it will turn off or kill the engine. The endpoints or the position that the servo will travel in its max range from low stick, trimmer down, to full stick, full throttle, the servo should travel equally in both positions. This will make sure that when your at 1/2 throttle stick the throttle is indeed at a 50% setting. If you don’t have end point adjustments via pots or computer control, you will need to try to get it the closest you can mechanically. By doing this the radio will work better for you because you will be closer to its designed positions.

Balance every thing you can that turns; fan, gears, tail rotors, main rotors, everything that will spin at any kind of speed.

Try to get the main rotor head paddles in line with each other. That is they have the same pitch in each of them. Keep them level or at 0 degrees when the swash plate is level and all the trims are at a neutral position. One way to check that you have the swash plate level is put a pitch gage on one of the paddles and rotate the head around 360 degrees with radio on to hold the swash plate stationary. Check to see if the paddle pitch has changed any. If it does the swash plate is not level.

These will by an average range of pitch setting. Use the ones that are recommended with your helicopter. For all helicopters the max pitch will be the setting or the amount of pitch that the strength of the engine can handle. The low end pitch will set up the amount of collective sensitivity you will have. The following will get you into the ball park, the finial adjustment will be made by flying. You should get a trained pilot to help you set it up at first. (NOTE: I feel that the radio should be set up completely before you start. You might not use them now but you will not have to readjust it later.)

Beginners:
normal idle up 1 idle up 2 hold
-1 to + 8 deg -2 to +8 deg -2 1/2 to +8 deg -4 to +10 deg
Intermediate:
normal idle up 1 idle up 2 hold
-2 1/2 to +8 deg -2 1/2 to +8 deg -4 to +8 deg -4 to +8 deg


For all the above it is what every pitch will hover with not to much or to little rpm in the head. This is typically at +4 1/2 to 5 degrees of main blade pitch. Typically about 1550 - 1600 rpms is about normal. If it gets to slow the helicopter will be sluggish and you can get in trouble with it in the wind. If its to fast it becomes touchy and will be hard to control.

* These are just some typical set ups. They will very between pilots. These will only get you started. If you don’t use any negative pitch to start you end up with a helicopter that is like one with fixed pitch. And if you learn with what you will have later or close than the transition will not be a big thing later.

Helibuf
Copyright © 1999 by [Helibuf's World]. All rights reserved.
Revised: 27 Aug 2003 20:33:32 -0700 .