Throttle Hold

[vinljp]

I am having a Futaba 6EXHP and I just wondering is there a set of pitch curves for the throttle hold function?

Is it important to have a separate pitch curves for throttle hold and what function does it serves as I could still perform auto-ratotation with either my idle-up or normal pitch curves right?

[kgfly]

No there is not. It is one of the several weaknesses of that radio. IIRC the radio will apply whichever pitch curve is in effect at the time. So if you are in Normal mode then you get the Normal curve, which is usually not good for doing autos. You should be able to check on the ground which curve you get when you throw the switch in each flight mode by simply observing your main blade pitch (disconnect the motor first!).

[DavidH]

My Normal pitch curve and throttle hold pitch curve are set up the same. I don't have a 6EX. But I have always had the curves on throttle hold and normal mode set the same.
Really throttle hold is just a condition that allows the motor to stop ( electric) or idle (nitro) and still have control of the collective without throttle input.
If my engine quits, I don't worry about throttle hold. The heli can still be autoed with any pitch curve that has positive and negative pitch in the range.

David

[BarracudaHockey]

It uses the normal pitch curve.

[vinljp]

Thanks guys for the reply...

But I am just wondering whatis the purpose of a Throttle Hold Pitch curve then?
Do you really need a separate pitch curve when on throttle hold?

I have heard that if you hit throttle hold for T-rex, it will go into a piro due to the high rpm.
Is this true?

[kgfly]

It's all about choices. Many folk perfer their Normal pitch curve to have restricted negative pitch, say -2 to +10. Then they need Stunt/IdleUp for acrobatic flying and want the full range, say -10 to +10. In ThrottleHold you want enough negative to be able to hold the headspeed and enough positive to be able to flare. Some folk just leave it at full range, some limit the range so if they panic they want stop the rotor dead. It's a preference. What is fairly common though is to want more pitch range in TH than in Nrml and hence why it is a pain to have TH tied to the Nrml pitch curve.

Dunno, never did it in anger. I would guess you would get a blip on the tail since the tail rotor would still be pushing against a torque that was no longer there. The HH gyro should correct for it. I would not expect it to piro.

[ave_eme]

I was thinking too about this tail drive in auto on the TRex.

When you hit the throttle hold you have no tourque so the tail rotor could stop and still the heli shouldn't piro because there is no torque.

But! If you have no rpm in the tail rotor you can;t control the heli on that axis. So to gain control of tail while in autos align have put this spinning against no torque rotor. And as kgfly also said. The gyro should cope with that and put the tail on 0 pitch. And when you go right or left you would still have a control.

[BarracudaHockey]

For whatever reason, the Trex 450 has a driven tail, much like the 50 and up size nitros. A heading hold gyro will ensure you dont start spinning once you remove the torque but still give you rudder control on the way down.

The down side is that it saps energy from the rotor system and the trex doesn't have enough to spare. Ray's E series DVD's outlines a mod to make the tail undriven and in his flight sequences the damn thing autos like a 30.

Without a driven tail the tail will weather vane and the nose will end up pointed into the wind, in that case you would set your gyro up in rate mode with enough offset to drive it to zero pitch.

As for pitch curves, if you do advanced autos like inverted autos, or if you just dont want to worry about switch flipping in an engine out emergency if you run a full symetrical pitch curve in all modes it makes for less stress. Otherwise the normal mode pitch curve should be set up with 4 or 5 degrees negative pitch if throttle hold defaults to normal like many low end radios.