PHold Problems on 450 FB trex

Hi there…
I have build my trad heli 450 He looks fine…have a very good fly on STAB…very stable and very balanced…little stick inputs on hover to correct…

But when i change it to PHOLD it starts to climb hard…then if I bring it down it looks have mutch pitch and low rotor speed and starts to make a pendule effect…

and became hard to control…if I switch to STAB then rotor speed up and heli became stable again

I have no governor and find no parameter to config rotor speed for GPS fligth modes!

I would set ACCEL_Z_P to probably 0.25 for that size helicopter. Set the IM_STAB_COL values to adjust your Stabilize pitch curve so it hovers at about mid-stick in Stabilize. When you switch to the altitude controlled flight modes you will have less variance on hover pitch with the proper Stabilize curve set.

H_RSC_MODE 3 works well with no governor. I fly one helicopter with no governor with mode 3. It provides the capability to set a three-point throttle curve with these three parameters


You will have to experiment a bit with it. But the basic procedure is to set the Power Low to what you would like for rpm with zero collective pitch on the ground. As you increase collective to take off the power requirement increases. Power High is what the rpm will be at full collective pitch. So adjust it to get no change in rpm from zero collective to hover collective. ArduPilot will then increase power as necessary if collective increases or decreases in flight, and properly set it works pretty good.

The procedure is the same for the negative collective pitch (Power NEGC). However, the values will be usually be a bit less for negative than it is for postive pitch for the typical “V” throttle curve, unless you are doing inverted flight.

interesting, i never tried Mode 3. That is why I use Castle Heli ESC,s only with their impressive Governor.

Change subject:
I would like to know what you think of that Jet Ranger pilot. I am blown away by his accurate landing each time,
link: Bell Jet Ranger in Action

Hi Fred,
Yes, the mode 3 works really well with no governor ESC’s. Mode 1 can be used too with a mix in your radio to operate the throttle on channel 8 in conjunction with the collective stick. But I prefer Mode 3 as I think it is much simpler.

That is pretty normal stuff for an ag pilot, refilling with dry fertilizer, or landing on truck beds to refill spray tanks. It’s like anything else, do it long enough and pretty soon you get good at it :grinning:

1 Like

Hi Chris

I do the setup in mode 3… It became another bird, very stable and now it works well…
When I change modes now it keep the altitude and RPM on PHold and ALTHold

Realy nice tip I dont think to put it on mode 3 whith no governor.

I still trying the values to get the best of it…but really thank you for the tip

when I finish it I publish the video and the param files for other users…

Patrik blauth