Too much subtrim amount in DX7? - HeliFreak
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Old 08-23-2007, 01:39 PM   #1 (permalink)
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Join Date: Dec 2006
Location: Westfield, IN
Default Too much subtrim amount in DX7?

Iím using the AR6100 in one of my modified Esky Honey Bee FPís. I recently noticed that when I hooked up the battery to the 3-in-1, the elevator servo arm moved downwards quite a bit; therefore, imparting forward elevator. I check all trim and subtrim settings in my DX7 and all were at neutralÖthe endpoint settings were all at 100%, as well. I determined that the servo arm needed to be removed and manually centered on the servo. Well, rather than manually centering the servo arm, I got lazy and decided to use the subtrim function of my DX7 to center the servo. I ended up giving the servo a setting of 52 (out of a possible 150) of backward elevator in order to center the servo arm.

So, off I go to the flying field on Saturday morning. I bring the heli up into a hoverÖthe wind is from my right at 5-7 mph. I begin to fly some basic circuits and figure 8s at about 15 ft. above the ground and things seem to be going well. I bring the heli up to about 40 ft. above the ground and start flying some circuits. At one moment, the heli is to my left and traveling downwind, and then I turned the heli 180 degrees into the wind and maintained a hover for a few seconds. Then it happened, I gave the heli some forward elevator, but the heli never moved forward. I gave the heli even more forward elevator and increased the throttleÖstill the heli never moved forward and was starting to be carried backwards by the wind! I then gave the heli full forward elevator and still the heli never transitioned into forward flight and continued to move backward even more. I ended up losing orientation because the heli got so far away from me and I crashed. Of course, the durability of the HBFP came through once again with only a broken flybar. I should have just tried to turn the heli perpendicular to the wind and I may have been able to land safely. Instead, I chose to continue to force the heli to fly into the wind.

Anyway, do you all think that the backward elevator subtrim setting had anything to do with this incident? Could have the subtrim setting of 52 out of 150 been excessive? I have flown the HBFP in the past in winds greater than 5-7 mph with no problems; therefore, the wind itself didnít cause this incident. However, if the subtrim setting was excessive, maybe the wind compounded the problem.

I did end up removing and centering the servo arm manually and Iím going to fly this HBFP tomorrow morning. I certainly would appreciate your comments on this incident. Thanks.
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Old 08-23-2007, 02:23 PM   #2 (permalink)
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Join Date: Mar 2007
Location: Petersburg, VA
Default sub trim

You have changed where the servo thinks it's centered-now you have less travel in the forward swash servo(elevator)
Always center everything mechanically first-that way the heli starts at the known datum point-effectively"Zero".....then adjust the radio...
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