EXPO on throttle?
01-19-2008, 01:42 AM
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EXPO on throttle?
Not sure how to explain this... I seemed to have gotten the tail wagging to stop on my B400 during hovering, which is good. However, I was testing the gyro and was doing some piros. One time as I gave full rudder input, I must have moved the throttle down because the heli began losing lift (didn't really notice/hear any change in headspeed). In a panic, I stopped the rudder input and slowly brought the throttle up to is began hovering again.
Assuming for the moment that there's not something going on mechanically/electrically, is there a way to prevent this? I've started reading about adding expo, but that seems to be something that only affects how the sticks react from a neutral/centered position on the TX. What I'm experiencing is me potentially moving the throttle up/down while moving the stick side to side. I'll never know where the throttle is at any given time when I decide to move the rudder, so I'm not sure expo is going to help in this situation.
Is this just something I'm going to have to work hard to control, or is there some setting in the controller to make things a little easier on myself as a newbie pilot?
Assuming for the moment that there's not something going on mechanically/electrically, is there a way to prevent this? I've started reading about adding expo, but that seems to be something that only affects how the sticks react from a neutral/centered position on the TX. What I'm experiencing is me potentially moving the throttle up/down while moving the stick side to side. I'll never know where the throttle is at any given time when I decide to move the rudder, so I'm not sure expo is going to help in this situation.
Is this just something I'm going to have to work hard to control, or is there some setting in the controller to make things a little easier on myself as a newbie pilot?
01-19-2008, 02:31 AM
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RE: EXPO on throttle?
If you use EXPO it will seem like there is very little throttle at low stick then it will jump up rapidly to full throttle. I think it would be harder to fly like that. That is what I understand about it. I could be wrong. I have never heard of using EXPO on throttle just the other channels.
01-19-2008, 04:49 AM
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RE: EXPO on throttle?
A way to prevent you from accidentally moving the stick the wrong way? Sorry, there's no setting that can do that. 
There is no expo on the throttle, you have a throttle curve instead.
You just have to learn to control it. If the problem is that the throttle stick is too sensitive, you can adjust the pitch curve (move the right most point down a little bit) or the pitch mix ratio (lower the pitch value in the swash mix menu) to make the collective more tame. I would make pitch adjustments first, then adjust the throttle curve to lower the head speed if it's starts getting to high as a result of the pitch adjustments.
If you haven't done so already, it's a good idea to copy the factory settings in the TX to another model as a backup before you start tweaking things.
There is no expo on the throttle, you have a throttle curve instead.
You just have to learn to control it. If the problem is that the throttle stick is too sensitive, you can adjust the pitch curve (move the right most point down a little bit) or the pitch mix ratio (lower the pitch value in the swash mix menu) to make the collective more tame. I would make pitch adjustments first, then adjust the throttle curve to lower the head speed if it's starts getting to high as a result of the pitch adjustments.
If you haven't done so already, it's a good idea to copy the factory settings in the TX to another model as a backup before you start tweaking things.
01-19-2008, 07:14 AM
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RE: EXPO on throttle?
I have no reason to think that I can resolve this but here's a take from the sideline. If it makes you feel any better, I did stay at a Holiday Inn Express last night. 
First, about hearing a change in headspeed. On a collective pitch, the head speed doesn't change. Once it's at the governed RPM, you are changing pitch, not rpm. And for the helicopter to go from stable to slowly sinking would be / could be so little change in pitch that you wouldn't hear it.
On Tx units intended for use with airplanes the throttle has a ratchet. Most of us who fly RTF helicopters using the stock Tx remove the ratchet bar from the throttle so the throttle is completely smoooooth. The ratchet would be OK except it seems that the hover we want is always between clicks of the ratchet so the bird is alway drifting up and down as we work between the notches.
Soooo, it's my guess that you are doing exactly what you suspect. When you move the rudder control, you also move the throttle / collective. I know for a fact that I have the same problem. I get better vertical stability by pinching the throttle stick between my index finger and thumb. The natural movement of your thumb is not a side to side movement. Using a normal grip, your thumb works in a down and left / up and right arc. If you hook your finger over the throttle stick, you finger will sense the vertical movement and help to correct it. You may also find a dramatic improvement if you use a neck strap so you are using your fingers to control the helicopter, not hold the radio.
When I first suspected that I have that problem (flying the Falcon 40 Fixed Pitch) I was all over the garage vertically. My F40 has no real gyro so it takes a lot of stick work to keep the tail in line. And if every move of the tail brings a vertical input from my dumb thumb, well you know the rest. I proved what I suspected using my sim. There is a calibration feature that shows arrows aligned at neutral when both sticks are centered. I tried to move just the rudder arrow while leaving the throttle arrow stationary. With a lot of practice watching the arrows I am getting better at controlling just one arrow at a time.
I hope there is something in here that's worth something.
Good day!
Soloboss
First, about hearing a change in headspeed. On a collective pitch, the head speed doesn't change. Once it's at the governed RPM, you are changing pitch, not rpm. And for the helicopter to go from stable to slowly sinking would be / could be so little change in pitch that you wouldn't hear it.
On Tx units intended for use with airplanes the throttle has a ratchet. Most of us who fly RTF helicopters using the stock Tx remove the ratchet bar from the throttle so the throttle is completely smoooooth. The ratchet would be OK except it seems that the hover we want is always between clicks of the ratchet so the bird is alway drifting up and down as we work between the notches.
Soooo, it's my guess that you are doing exactly what you suspect. When you move the rudder control, you also move the throttle / collective. I know for a fact that I have the same problem. I get better vertical stability by pinching the throttle stick between my index finger and thumb. The natural movement of your thumb is not a side to side movement. Using a normal grip, your thumb works in a down and left / up and right arc. If you hook your finger over the throttle stick, you finger will sense the vertical movement and help to correct it. You may also find a dramatic improvement if you use a neck strap so you are using your fingers to control the helicopter, not hold the radio.
When I first suspected that I have that problem (flying the Falcon 40 Fixed Pitch) I was all over the garage vertically. My F40 has no real gyro so it takes a lot of stick work to keep the tail in line. And if every move of the tail brings a vertical input from my dumb thumb, well you know the rest. I proved what I suspected using my sim. There is a calibration feature that shows arrows aligned at neutral when both sticks are centered. I tried to move just the rudder arrow while leaving the throttle arrow stationary. With a lot of practice watching the arrows I am getting better at controlling just one arrow at a time.
I hope there is something in here that's worth something.
Good day!
Soloboss
