Thursday, August 17, 2006

P47 -P 56 Idle-up and pitch curves

Packs 47 through 56 were spent hovering high and practicing side in hovering at various heights.  I'm flying in the church parking lot almost exclusively now as I really need the space to "fly out" of trouble.  I had a couple of really close calls (back and forth pendulum swings close to the ground) and had to punch out full throttle to get out of trouble.

I also played with flicking to idle-up mode today.  I've been wanting to try it ever since I tached the headspeed.  However, I just didn't feel confident to do so. 

So, I spooled up slowly and got a nice stable however at 1/2 stick, reached up and flicked into Idle-up mode.... Nothing...... no change.... which is what I expected as I matched my pitch and throttle curves between normal and Idle-up.

Flew around fine, it was nice having more "downward authority" to get the heli down (today was about 10 mph gusting winds).  I then tried to do a full-collective climb out.  Pushed the throttle stickup up hard, the Trex shot up but I could hear the motor really bog, and the tail swung all the way around and headed for the nearest tree.   Fortunately, I was able to recover and get the Trex under control.

After another pack, I called it quits and set upon examining the swash movement and actual blade pitch.  As you know, this heli was built for me by someone else as I did not feel comfortable building the SE from kit.  Now, after countless hours of reading forum postings and watching Finless's videos, I'm pretty confident I can manage any Trex build/tuning issue.

OK, put the Trex on the bench and unplugged two motor wires (to prevent accidental spoolup) and set to measure the actual blade pitch in idle-up.   Using the Align pitch gauge, my full up-stick pitch was +15!   Way too high (in-fact off the gauge)  No wonder my motor bogged on the climb-out.    I set about adjusting the pitch using the swash menu, reducing Ch6 (pitch) from 70 to 35.  That brought the pitch down from 15 to around 9 (positive and negative).   Changing the pitch swash also gave the swash clearance at full negative pitch.  Before, the swash actually hit the top of the frame.  I also adjusted the EPA of the CH1 (aileron) to prevent the servo from over-driving the swash left and right.

So the take-home lesson for today... if you get a RTF helicopter, don't assume that it was built correctly.  Educate yourself and check it.


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