Understanding collective helicopter setup
09-20-2006, 03:17 PM
#1
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Aug 2004
Location: Warner Robins,
GA
Posts: 3,360
Likes: 0
Received 0 Likes
on
0 Posts
Understanding collective helicopter setup
Hey guys, its me again.
This time Im going to do a thread on what exactly is going on in collective pitch helis. This threads purpose is to help the newb understand how to set up a Collective Pitch helicopter.
First lets look at what happens with a collective pitch helicopter. Collective pitch helicopters allow the pilot to control the pitch of the blades independantly of the throttle.
The normal pitch settings for a helicopter consist of 3 things.
A. Negative Pitch for inverted flying
B. Zero pitch - the point of transition from negative to positive, and positive to negative pitch
C. Positive Pitch for upright flying.
As we know, servos have limited travel. Picture a servo laying down horizontally with its servo arm pointing horizontally.
In this position it would be at position B as listed above....Zero pitch.
From position B as the servo arm moves downward, it would be at position A....Negative Pitch
From position B as the servo arm moves upward, it would be at position C....Positive Pitch
Most modern radios allow us to set pitch curves based upon a 3-5 point "pitch curve".
For the sake of this thread, we are going to base everything on a 5 point pitch curve.
Radio's think of a total servos travel as 0,25,50,75,100
Think back to the horizontal servo. The radio sees 0 as having the servo arm all the way down, 50 as dead level, and 100 as all the way up.
So if we wanted a servo to move from position B to position C. We would have to tell the radio that we want the servo to move from 50 to 100...not 0 to 100.
Get the idea? Remember the radio sees 50 as centered...not 0.
Ok so where does this lead us.
Well on a collective pitch helicopter. Servo movement directly translates into blade pitch.
So when we set up a collective pitch helicopter we want to use what the radio sees to program and set it up.
Now there are two different ways to fly a collective pitch helicopter.
1. Normal mode. - For upright flying only, consisting of positive pitch only
2. Idle up (3D mode) - For inverted flying, consisting of positive and negative pitch
Lets look at Normal mode first. BUT...you want to keep thinking in terms of full collective...that is Negative to Positive pitch.
Lets assume that pitch is controlled by a single servo. Since servo travel is directly translated into blade pitch, we want the radio to understand that we only want the servo to move the blades into positive pitch, and never negative. Which means that we want the servo to be limited to moving from 50 to 100...never below 50.
So with the servo centered, and the servo arm centered. This would be the first point on our pitch curve.
Point 1 would be 50.
The next point...Point 2 would be 62.5
The next point...Point 3 would be 75
The next point...Point 4 would be 82.5
The next point...Point 5 would be 100
The throttle curve would be set as
0,25,50,75,100
This means that when the throttle stick as at dead bottom. There is 0 throttle, and zero pitch.
As you move the stick up, it increases throttle to 25%, and increases pitch to 62.5 (roughly +2degrees pitch based on a max of +8)
When you get to mid-stick, throttle will be at 50%, and the pitch will be at 75 (roughly +4 degrees pitch)
...and so forth.
In this manner, when you have the heli sitting on the ground, the blades arent spinning, and there is zero pitch.
As you increase the throttle stick, the blades start spinning, and the heli lifts off around mid-throttle.
This time Im going to do a thread on what exactly is going on in collective pitch helis. This threads purpose is to help the newb understand how to set up a Collective Pitch helicopter.
First lets look at what happens with a collective pitch helicopter. Collective pitch helicopters allow the pilot to control the pitch of the blades independantly of the throttle.
The normal pitch settings for a helicopter consist of 3 things.
A. Negative Pitch for inverted flying
B. Zero pitch - the point of transition from negative to positive, and positive to negative pitch
C. Positive Pitch for upright flying.
As we know, servos have limited travel. Picture a servo laying down horizontally with its servo arm pointing horizontally.
In this position it would be at position B as listed above....Zero pitch.
From position B as the servo arm moves downward, it would be at position A....Negative Pitch
From position B as the servo arm moves upward, it would be at position C....Positive Pitch
Most modern radios allow us to set pitch curves based upon a 3-5 point "pitch curve".
For the sake of this thread, we are going to base everything on a 5 point pitch curve.
Radio's think of a total servos travel as 0,25,50,75,100
Think back to the horizontal servo. The radio sees 0 as having the servo arm all the way down, 50 as dead level, and 100 as all the way up.
So if we wanted a servo to move from position B to position C. We would have to tell the radio that we want the servo to move from 50 to 100...not 0 to 100.
Get the idea? Remember the radio sees 50 as centered...not 0.
Ok so where does this lead us.
Well on a collective pitch helicopter. Servo movement directly translates into blade pitch.
So when we set up a collective pitch helicopter we want to use what the radio sees to program and set it up.
Now there are two different ways to fly a collective pitch helicopter.
1. Normal mode. - For upright flying only, consisting of positive pitch only
2. Idle up (3D mode) - For inverted flying, consisting of positive and negative pitch
Lets look at Normal mode first. BUT...you want to keep thinking in terms of full collective...that is Negative to Positive pitch.
Lets assume that pitch is controlled by a single servo. Since servo travel is directly translated into blade pitch, we want the radio to understand that we only want the servo to move the blades into positive pitch, and never negative. Which means that we want the servo to be limited to moving from 50 to 100...never below 50.
So with the servo centered, and the servo arm centered. This would be the first point on our pitch curve.
Point 1 would be 50.
The next point...Point 2 would be 62.5
The next point...Point 3 would be 75
The next point...Point 4 would be 82.5
The next point...Point 5 would be 100
The throttle curve would be set as
0,25,50,75,100
This means that when the throttle stick as at dead bottom. There is 0 throttle, and zero pitch.
As you move the stick up, it increases throttle to 25%, and increases pitch to 62.5 (roughly +2degrees pitch based on a max of +8)
When you get to mid-stick, throttle will be at 50%, and the pitch will be at 75 (roughly +4 degrees pitch)
...and so forth.
In this manner, when you have the heli sitting on the ground, the blades arent spinning, and there is zero pitch.
As you increase the throttle stick, the blades start spinning, and the heli lifts off around mid-throttle.
09-20-2006, 03:39 PM
#2
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Aug 2004
Location: Warner Robins,
GA
Posts: 3,360
Likes: 0
Received 0 Likes
on
0 Posts
RE: Understanding collective helicopter setup
Now...on to Idle up or 3D mode.
Now we want to take things to the next level. In order for us to do this we have to tell the radio that we want to make use of the servos travel below 50.
So how do we do that.
Well via a switch on the radio. The Idle Up switch.
When we flip this switch we are telling the radio that we now want to discontinue use of the normal mode, and that we want the throttle stick to now control the entire range of the servos travel
Remember the 5 point pitch curve. This is what really confuses beginners.
Now the 5 point pitch curve contains points for the entire servo travel instead of only half of it.
View the attached graphic.
Now the 5 points have to represent the entire servos travel instead of half.
So the first point would be 0...full down on the servo, full negative pitch
Point 2 would be 25....mid-way down on the servo, half negative pitch
Point 3 would be 50...centered servo...zero pitch
Point 4 would be 75...mid-way up on the servo, half positive pitch
Point 5 would be 100...full up on the servo , full positive pitch
See how it works?
Notice also that the throttle curve changes. In idle up mode we never want the throttle below 50% or else the blade RPM will get too slow.
This is where the collective pitch independant of throttle comes into play. In idle up, the blade pitch is no longer dependant on throttle.
Please bear in mind that the included pitch and throttle curves are examples only. You will have to adjust yours to get your heli to fly right. These are just to show how the system works, and the communication between Blades, Servos and Radio.
Enjoy, hope this helps everyone out.
Now we want to take things to the next level. In order for us to do this we have to tell the radio that we want to make use of the servos travel below 50.
So how do we do that.
Well via a switch on the radio. The Idle Up switch.
When we flip this switch we are telling the radio that we now want to discontinue use of the normal mode, and that we want the throttle stick to now control the entire range of the servos travel
Remember the 5 point pitch curve. This is what really confuses beginners.
Now the 5 point pitch curve contains points for the entire servo travel instead of only half of it.
View the attached graphic.
Now the 5 points have to represent the entire servos travel instead of half.
So the first point would be 0...full down on the servo, full negative pitch
Point 2 would be 25....mid-way down on the servo, half negative pitch
Point 3 would be 50...centered servo...zero pitch
Point 4 would be 75...mid-way up on the servo, half positive pitch
Point 5 would be 100...full up on the servo , full positive pitch
See how it works?
Notice also that the throttle curve changes. In idle up mode we never want the throttle below 50% or else the blade RPM will get too slow.
This is where the collective pitch independant of throttle comes into play. In idle up, the blade pitch is no longer dependant on throttle.
Please bear in mind that the included pitch and throttle curves are examples only. You will have to adjust yours to get your heli to fly right. These are just to show how the system works, and the communication between Blades, Servos and Radio.
Enjoy, hope this helps everyone out.
09-21-2006, 02:32 PM
#4
Member
My Feedback: (2)
Join Date: Jun 2003
Location: Dallas,
TX
Posts: 32
Likes: 0
Received 0 Likes
on
0 Posts
RE: Understanding collective helicopter setup
Thanks for the explanation! question:
does this mean that in idle up mode the throttle is constant no matter what picth the blades have? in that case, is it better to set the throttle close to 100%?... or there is also a mix like throtle increases as I give more negative pitch and it also increases as I give more positive pitch?
Thanks,
Manuel
"Notice also that the throttle curve changes. In idle up mode we never want the throttle below 50% or else the blade RPM will get too slow. This is where the collective pitch independant of throttle comes into play. In idle up, the blade pitch is no longer dependant on throttle"
does this mean that in idle up mode the throttle is constant no matter what picth the blades have? in that case, is it better to set the throttle close to 100%?... or there is also a mix like throtle increases as I give more negative pitch and it also increases as I give more positive pitch?
Thanks,
Manuel
09-22-2006, 12:10 PM
#6
RE: Understanding collective helicopter setup
Manual, no the throttle curve should be set so that the blades maintain a constant rpm, the mix you are looking for IS the throttle curve.
Also the 50 percent isn't a hard and fast number, it depends on several factors, I've set several helis up so that idle up mid point throttle curve is under 50 percent simply because thats what was required to keep the head from overspeeding during a flat pitch desecent.
Also the 50 percent isn't a hard and fast number, it depends on several factors, I've set several helis up so that idle up mid point throttle curve is under 50 percent simply because thats what was required to keep the head from overspeeding during a flat pitch desecent.
09-22-2006, 01:05 PM
#7
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Aug 2004
Location: Warner Robins,
GA
Posts: 3,360
Likes: 0
Received 0 Likes
on
0 Posts
RE: Understanding collective helicopter setup
Yup, barracuda has it right.
The throttle curve in idle up is supposed to be set to maintain a specific RPM on the head.
As pitch increases, it requires more power(more throttle) to maintain a constant head speed, and as pitch is reduced it requires less.
Ideally in idle up mode we dont want any changes in RPM despite changes in pitch, hence the "independant collective from throttle".
Even though there is a throttle curve set in the radio, that curve is designed to maintain a constant headspeed. If you ran all points to 100%, when you got to zero pitch, the RPM's on the rotor would be overspeeding because there is no resistance from the blades.
That also brings us to "governors". Some ESC's come with a "governor" mode that acts independantly from the throttle curve. What it does when activated is constantly measures motor RPM's while your in idle-up, and trys to maintain a preset headspeed regardless of the throttle curve. Now, you should STILL program a reasonable throttle curve in the radio. This way if for some reason you accidentally turn the governor off, or it malfunctions, you can go back to the radio controlled throttle curve as a backup.
johnnyf, I would not recommend setting it up for just normal mode. While you CAN set it up this way, when (and I do mean when not if) your ready for inverted flight, you will have to start ALL over again re-programming the radio and adjusting control horns to do so. Its best to set it up for norm and idle up to begin with.
Also you will probably find that you get more stable and better performance in general if you fly it in idle-up mode vs normal mode.
You can of course leave it in normal mode until your ready for idle-up if you so desire.
The throttle curve in idle up is supposed to be set to maintain a specific RPM on the head.
As pitch increases, it requires more power(more throttle) to maintain a constant head speed, and as pitch is reduced it requires less.
Ideally in idle up mode we dont want any changes in RPM despite changes in pitch, hence the "independant collective from throttle".
Even though there is a throttle curve set in the radio, that curve is designed to maintain a constant headspeed. If you ran all points to 100%, when you got to zero pitch, the RPM's on the rotor would be overspeeding because there is no resistance from the blades.
That also brings us to "governors". Some ESC's come with a "governor" mode that acts independantly from the throttle curve. What it does when activated is constantly measures motor RPM's while your in idle-up, and trys to maintain a preset headspeed regardless of the throttle curve. Now, you should STILL program a reasonable throttle curve in the radio. This way if for some reason you accidentally turn the governor off, or it malfunctions, you can go back to the radio controlled throttle curve as a backup.
johnnyf, I would not recommend setting it up for just normal mode. While you CAN set it up this way, when (and I do mean when not if) your ready for inverted flight, you will have to start ALL over again re-programming the radio and adjusting control horns to do so. Its best to set it up for norm and idle up to begin with.
Also you will probably find that you get more stable and better performance in general if you fly it in idle-up mode vs normal mode.
You can of course leave it in normal mode until your ready for idle-up if you so desire.
09-24-2006, 11:37 AM
#9
Member
Join Date: Oct 2005
Location: Seaford,
DE
Posts: 56
Likes: 0
Received 0 Likes
on
0 Posts
RE: Understanding collective helicopter setup
While your on the subject of curves , wouldn't you set your throttle curve something like this
0-15-80-80-80 ? this would give you a slow start and a even head speed . That is if you spool up at 0 degrees and find that at 85% on your radio that your motor doesn't climb any more past that . Then take like 5 % of that for head room and set your curve at that ? I'm not sure about the calculations , maybe you can put it right for me . Thanks !
0-15-80-80-80 ? this would give you a slow start and a even head speed . That is if you spool up at 0 degrees and find that at 85% on your radio that your motor doesn't climb any more past that . Then take like 5 % of that for head room and set your curve at that ? I'm not sure about the calculations , maybe you can put it right for me . Thanks !
06-26-2007, 09:30 AM
#11
Member
Join Date: Jun 2007
Location: carrick on shannon, IRELAND
Posts: 53
Likes: 0
Received 0 Likes
on
0 Posts
RE: Understanding collective helicopter setup
AAAAAGGGGHHHHH!!!!!!!! jeez my head is gona blow, all this pitch curve talk is too much to take in... i only want to hover my new 22e!!!!!!! the bugger just sits there cause it knows i ai'nt got a clue how to set up the pitch.... surely there is a way of doing it without needing to "understand" it? it's ballanced perfect,swashplate is so level, blades track fine, i think i have bitten off more than i can fly!! well i did go from a picco z to a 22E! yes i am mad....
06-27-2007, 01:49 PM
#12
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Aug 2004
Location: Warner Robins,
GA
Posts: 3,360
Likes: 0
Received 0 Likes
on
0 Posts
RE: Understanding collective helicopter setup
Ok, the above is based on what is commonly referred to as a "linear" pitch and throttle curves. In reality though, linear curves will get you started in the general direction. As you progress, you will want to start experimenting with actual real curves for true performance.
Once you've got the basics down, its time to make the heli a little more dialed in.
Here's how to finely tune the pitch and throttle curves.
In normal mode, the ideal set-up is to have a slow gradual spooling up, with plenty of RPM's once you lift off. You'll also want very little pitch until it spools up, and even a touch of negative to hold it down until liftoff time.
So the pitch curves would look something like this
48,48,50,70,100
Which means you would have just a touch of negative pitch until mid stick, then it would begin its transition into positive pitch. What that does is holds the heli on the ground until the rotors spool up, and then it starts to lift off. You dont want more than 2 degrees of negative pitch. Just enough to keep it on the ground until its ready to lift off.
The throttle curve should also be similar.
0,25,60,80,100
So that from low to quarter stick the rotor begins and continues to spool up as normal, from quarter to mid stick, its getting up to flight RPM's, then from mid stick to full stick, its in flight.
Now on to idle ups.
The idle up should look more like "S" shapes.
The pitch curve would look like
0,31.5,50,69.0,100
So there is a rapid pitch change from low stick to quarter stick, then it flattens out near mid stick, and then begins its rapid change from 3/4 stick to full stick. This gives you a softer pitch curve around neutral so a stable hover is easier to obtain, also in transition maneuvers like tic tocs, and such, the stop at each point of the tic toc doesnt violently go from positive to negative pitch. Picture a tic toc. As the heli comes over it should gradually and smoothly come to a stop, change directions and travel back. With a linear pitch curve, the heli tends to come to an abrupt stop, and violently "snap" towards the other direction.
The throttle curve should also be less linear.
100,85,60,85,100
Now if youve got multiple Idle-ups. Program normal mode as above, then Idle1 as above, then Idle2 is your "extreme" mode.
This mode should only be used when you are making RAPID 3D maneuvers, dont do gentle hovering/forward flight in this mode, as the high rotor RPM's around neutral will probably overspeed the rotor head.
Pitch curve...same as Idle1
Throttle curve 100,90,90,90,100
These are just basic guidelines, you will have to adjust your pitch/throttle curves for your specific helicopter. Try to keep the point at which it hovers around the same pitch and throttle throughout all three curves. If you dont, when you flip the switch you may notice a rapid change in altitude if the RPM's suddenly change, or the pitch changes. If you get it dialed in just right, the heli will stay put even with switch changes.
Also...next Ill go into the dreaded "Throttle Hold"....dont be scared...its fantastic!!!!
Once you've got the basics down, its time to make the heli a little more dialed in.
Here's how to finely tune the pitch and throttle curves.
In normal mode, the ideal set-up is to have a slow gradual spooling up, with plenty of RPM's once you lift off. You'll also want very little pitch until it spools up, and even a touch of negative to hold it down until liftoff time.
So the pitch curves would look something like this
48,48,50,70,100
Which means you would have just a touch of negative pitch until mid stick, then it would begin its transition into positive pitch. What that does is holds the heli on the ground until the rotors spool up, and then it starts to lift off. You dont want more than 2 degrees of negative pitch. Just enough to keep it on the ground until its ready to lift off.
The throttle curve should also be similar.
0,25,60,80,100
So that from low to quarter stick the rotor begins and continues to spool up as normal, from quarter to mid stick, its getting up to flight RPM's, then from mid stick to full stick, its in flight.
Now on to idle ups.
The idle up should look more like "S" shapes.
The pitch curve would look like
0,31.5,50,69.0,100
So there is a rapid pitch change from low stick to quarter stick, then it flattens out near mid stick, and then begins its rapid change from 3/4 stick to full stick. This gives you a softer pitch curve around neutral so a stable hover is easier to obtain, also in transition maneuvers like tic tocs, and such, the stop at each point of the tic toc doesnt violently go from positive to negative pitch. Picture a tic toc. As the heli comes over it should gradually and smoothly come to a stop, change directions and travel back. With a linear pitch curve, the heli tends to come to an abrupt stop, and violently "snap" towards the other direction.
The throttle curve should also be less linear.
100,85,60,85,100
Now if youve got multiple Idle-ups. Program normal mode as above, then Idle1 as above, then Idle2 is your "extreme" mode.
This mode should only be used when you are making RAPID 3D maneuvers, dont do gentle hovering/forward flight in this mode, as the high rotor RPM's around neutral will probably overspeed the rotor head.
Pitch curve...same as Idle1
Throttle curve 100,90,90,90,100
These are just basic guidelines, you will have to adjust your pitch/throttle curves for your specific helicopter. Try to keep the point at which it hovers around the same pitch and throttle throughout all three curves. If you dont, when you flip the switch you may notice a rapid change in altitude if the RPM's suddenly change, or the pitch changes. If you get it dialed in just right, the heli will stay put even with switch changes.
Also...next Ill go into the dreaded "Throttle Hold"....dont be scared...its fantastic!!!!
06-27-2007, 02:30 PM
#13
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Aug 2004
Location: Warner Robins,
GA
Posts: 3,360
Likes: 0
Received 0 Likes
on
0 Posts
RE: Understanding collective helicopter setup
Ahhh...the throttle hold.. Secret weapon of the pro's....LOL
Throttle hold serves MANY purposes. The main purposes are uses in Autorotation landings, and what I refer to as "mini-autos" or spool downs. Now obviously, beginners want to stay FAR FAR away from autorotation landings, but....Ill take flak for this.....beginners should program throttle hold.
Now before you fire off that pyro filled PM....here's why!!
Throttle hold, can also keep your heli from spooling up to 100% throttle in your bedroom when you least expect it sending it crashing through your ceiling.
Throttle hold quite simply is a switch on your radio programmed to maintain a constant throttle setting. This setting should be 0%, or motor completely OFF.
Say your in your bedroom, and you want to plug in your heli, but dont want any risk of bumping the throttle stick and sending it crashing through the house. If your throttle hold switch is programmed, you can flip throttle hold on, turn on radio, plug in heli, without fear of it doing the funky chicken on your workbench. How it works is simple. You are basically programming a switch on the radio to tell the heli, to keep the throttle at 0% regardless of where the throttle stick is.
Now, say you go to the field, and are ready to fly. I dont know about you guys, but Im always nervous when I plug that battery in, that the heli might suddenly spool up. With the throttle hold activated, I dont have to worry about it. I plug in the heli, after Im a safe distance away, I flip the throttle hold off, and take off as normal. Since Im not exactly proficient with auto-rotations yet, I like to do "mini-autos". Ill come in for a landing, and when it gets about 3ft off the deck, Ill activate the throttle hold. In the Trex, it shuts off the motor, but due to the Trex's auto-rotation gear, the rotors keep spinning long enough for me to flair and set it down.
Its great, because it lands spools down right after it touches down, theres less risk of a tip-over, If it does tip over, there's no power applied to the rotor head, so it results in less damage, and I dont have to worry about bumping the throttle stick. I also dont have to rush over to unplug the battery, I can walk to it, pick it up and carry it back to the pits, and .....then unplug it. Without being in the middle of the runway trying to unplug a battery.
Some radios dont have throttle hold....so sorry for you folks, but if your lucky enough to have a radio capable of programming throttle hold....DO IT.
Here's how.
If you are using the Futaba 9C, go into the advanced menu, and look for "THR-HOLD". Open that menu, and change MIX from INH to ON or OFF. Set POSI to 0%. Exit that menu and go to SW-SELECT and put the T-HOLD onto a switch of your choice.
Now here's how to test it. Rev up your heli a little bit, and flip whatever switch you programmed it on. The motor should stop immediatly. Test it in all your modes. DONT test it while flying. Do it on the ground!!!
Once youve ensured that all is working properly. Your good to go.
For advanced pilots ONLY!!!
Now once you get gutsy, and are ready to attempt a crash....er....autorotation. Get rediculas amounts of altitude. Make sure your in IDLE UP mode. Flip the throttle hold switch, and go into negative pitch. The blades should keep spinning. It will come down faster than a meteor. When you get to 20ft in altitude, Flip the switch quickly, and go back to positive pitch to level out, and try to go to a stable hover as the RPM's come back up. Keep practicing this.
When you are ready for your first true auto-rotation. Do same as above, only dont flip the motor back on. As it comes down, at about 5ft off the deck, start your flair gently. Get it down QUICK, but not so quick you slam it into the ground.
I will tell you that auto-rotations in the Trex are insanely, rediculasly, stupid fast. It comes down at about 45-50mph, and you have to have lightning fast reflexes and awesome depth perception to time the flair at the right time. Two slow a reaction, and it will slam into the deck. Too fast a reaction, and you will bleed off too much rotor RPM's and it will once again slam it into the deck. Do it at your own risk.
Throttle hold serves MANY purposes. The main purposes are uses in Autorotation landings, and what I refer to as "mini-autos" or spool downs. Now obviously, beginners want to stay FAR FAR away from autorotation landings, but....Ill take flak for this.....beginners should program throttle hold.
Now before you fire off that pyro filled PM....here's why!!
Throttle hold, can also keep your heli from spooling up to 100% throttle in your bedroom when you least expect it sending it crashing through your ceiling.
Throttle hold quite simply is a switch on your radio programmed to maintain a constant throttle setting. This setting should be 0%, or motor completely OFF.
Say your in your bedroom, and you want to plug in your heli, but dont want any risk of bumping the throttle stick and sending it crashing through the house. If your throttle hold switch is programmed, you can flip throttle hold on, turn on radio, plug in heli, without fear of it doing the funky chicken on your workbench. How it works is simple. You are basically programming a switch on the radio to tell the heli, to keep the throttle at 0% regardless of where the throttle stick is.
Now, say you go to the field, and are ready to fly. I dont know about you guys, but Im always nervous when I plug that battery in, that the heli might suddenly spool up. With the throttle hold activated, I dont have to worry about it. I plug in the heli, after Im a safe distance away, I flip the throttle hold off, and take off as normal. Since Im not exactly proficient with auto-rotations yet, I like to do "mini-autos". Ill come in for a landing, and when it gets about 3ft off the deck, Ill activate the throttle hold. In the Trex, it shuts off the motor, but due to the Trex's auto-rotation gear, the rotors keep spinning long enough for me to flair and set it down.
Its great, because it lands spools down right after it touches down, theres less risk of a tip-over, If it does tip over, there's no power applied to the rotor head, so it results in less damage, and I dont have to worry about bumping the throttle stick. I also dont have to rush over to unplug the battery, I can walk to it, pick it up and carry it back to the pits, and .....then unplug it. Without being in the middle of the runway trying to unplug a battery.
Some radios dont have throttle hold....so sorry for you folks, but if your lucky enough to have a radio capable of programming throttle hold....DO IT.
Here's how.
If you are using the Futaba 9C, go into the advanced menu, and look for "THR-HOLD". Open that menu, and change MIX from INH to ON or OFF. Set POSI to 0%. Exit that menu and go to SW-SELECT and put the T-HOLD onto a switch of your choice.
Now here's how to test it. Rev up your heli a little bit, and flip whatever switch you programmed it on. The motor should stop immediatly. Test it in all your modes. DONT test it while flying. Do it on the ground!!!
Once youve ensured that all is working properly. Your good to go.
For advanced pilots ONLY!!!
Now once you get gutsy, and are ready to attempt a crash....er....autorotation. Get rediculas amounts of altitude. Make sure your in IDLE UP mode. Flip the throttle hold switch, and go into negative pitch. The blades should keep spinning. It will come down faster than a meteor. When you get to 20ft in altitude, Flip the switch quickly, and go back to positive pitch to level out, and try to go to a stable hover as the RPM's come back up. Keep practicing this.
When you are ready for your first true auto-rotation. Do same as above, only dont flip the motor back on. As it comes down, at about 5ft off the deck, start your flair gently. Get it down QUICK, but not so quick you slam it into the ground.
I will tell you that auto-rotations in the Trex are insanely, rediculasly, stupid fast. It comes down at about 45-50mph, and you have to have lightning fast reflexes and awesome depth perception to time the flair at the right time. Two slow a reaction, and it will slam into the deck. Too fast a reaction, and you will bleed off too much rotor RPM's and it will once again slam it into the deck. Do it at your own risk.
06-27-2007, 02:55 PM
#14
RE: Understanding collective helicopter setup
Why would you get flamed?
Setting up throttle hold is good common sense.
Its also good if you loose the tail, hit throttle hold and there's no torque and the helicopter stops spinning like a top and weather vanes into the wind.
Setting up throttle hold is good common sense.
Its also good if you loose the tail, hit throttle hold and there's no torque and the helicopter stops spinning like a top and weather vanes into the wind.
06-27-2007, 04:09 PM
#15
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Aug 2004
Location: Warner Robins,
GA
Posts: 3,360
Likes: 0
Received 0 Likes
on
0 Posts
RE: Understanding collective helicopter setup
Well, there is the crowd out there that thinks that newbies should learn to fly in normal mode, and that programming a throttle hold is a recipe for disaster if they "accidentally" flip the switch. I give newbies more credit than that. Some dont.....
