Throttle Hold - Pitch Curve

[asomaro]

I'm assuming that one day (hopefully soon) I will have a bash at a real auto rather than just on the sim.

Nothing like asking questions, so here are two......

a) I know that I will need to apply negative pitch to maintain head speed during the auto, however, does this mean that the pitch curve for throttle hold should be linear (just like idle up)?

b) It's almost certain that I will bottle out, so I will flick the power back on to get me out of the doo doo - but what if I am using soft start on my ESC, does this have to be changed to normal start - or is there some kind of time lapse on the ESC that assumes normal re-start within a ceratin time span?

Cheers,

[trillian]

There may be different opinions and approaches on this but what I have at the moment is my TH curve is almost identical to my normal mode curve and both are at 50% (zero pitch) at mid-stick as is the idle-1. The only difference is I might have some TH curves set where the position 1 is at 0 or very near for full negative vs the normal mode curve maybe having a bit less negative pitch at the bottom, maybe a value that gives - 4 or 5 degrees instead of -10 etc (using Spektrum DX7).

'Not sure about the soft start as I am only doing autos on my nitro and gasser helis (my only electric is a 450 and it autos only slightly better than a boat anchor).

[scallybert]

[...] b) It's almost certain that I will bottle out, so I will flick the power back on to get me out of the doo doo - but what if I am using soft start on my ESC, does this have to be changed to normal start - or is there some kind of time lapse on the ESC that assumes normal re-start within a ceratin time span?

What ESC are you using ?

[alex]

Depends what ESC as some need a 0 stick input to reset the soft start. You should be able to reprogram the ESC- check in the instructions, but I am not sure if you will be able to program different start up settings for the various modes- the other problem is the sudden hit on the main gear if the head speed has dropped too much and you are on instant start up which involves most motor torque

[asomaro]

What ESC are you using ?

If (and its a very big if) I do this it will be on my Trex 500 which uses the standard RCE-BL60G esc.

I could try on my 450's (both of which use hobbywing 40a Pentium esc's) but I think that the 500 offers a more stable platform and of course its heavier which ought to help maintain blade speed (?)


Cheers,

[tourerjim]

Best to forget about reprogramming esc first learn to flick thottle hold as you are about to land so to begin with you only giving plus pitch then add in some forward flight landing & as you gain more hight start giving say 2% neg pitch.

[scallybert]

[...]Trex 500 which uses the standard RCE-BL60G esc.

I could try on my 450's (both of which use hobbywing 40a Pentium esc's) [...]

I've seen articles on this kidn of thing for CC ESCs, where there are some clever things you can set up, but I'm not sure you acn do much on teh ESCs you have. (Mind you, the Pentium 40A doesn't really have a soft-start anyway, IIRC...)

One thing I did wonder about (shoot me down if this is a bad idea), is having a flight mode with a low, but non-zero, throttle. ie so the motor is still running, but much slower than the blades should be spinning. This may make more sense if the headspeed is governed. Maybe..?

[GravityKills]

one philosophy for beginners is "set -5 degrees negative pitch". When power is lost suddenly, pull the stick all the way down for the descent.
This is a very bad auto, but it guarantees that you won't accidentally kill headspeed and drop like a rock. If you remember to flick the switch...

I would use the same curve as in idle up, so that the feel of the heli does not change.

With one modification: Try to maximize positive pitch. It gives more hang time and allows to intentionally kill the headspeed, when you're heading for the forest.

For example:
Idle-up 10-30-50-70-90
Throttle-hold: 0-30-50-70-100

With this strategy, I have autoed my 700N into a tree with zero damage (not sure about the tree). It's especially important on the negative side, if circumstances force you to land on the head.

[Steve]

I agree with gravitykills. An extra 2 degrees pitch on the top end helps loads to really kill off the head speed just before touch down.

Be careful of bottling out too late. If you let the head speed drop off too much and then hit the power button, the heli may will do a couple of unexpected pirouettes - because the tail has also lost all its authority due to a lack of speed and no matter how hard the gyro tries to keep the heli straight, it simply can't do it until the tail blades pick up enough speed to lock in again.

Once you go for an auto, you should make that 'bail-out' decision at at least 20 feet up I rekon, to give yourself a good chance of a successful recovery. Anything less than that then commit yourself to the landing and stick it on the ground. The extra 2 degrees top end will help no end to settle it down gently.

I remember bailing out of an auto a few months ago with my 700, took off the hold switch far too late and the heli did two complete (and unexpected) pirouettes as the engine fired up before the tail managed to gain hold again. It scared the life out of me for a split second at the time but all turned out ok in the end. Don't bother bailing out any more - just commit to making the landing from the onset.