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hank01 -> >UPDATE< Severe Hitec HS-81 servo chatter (3/30/2008 2:29:39 PM)
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Problem:
Severe Hitec HS-81 servo chatter combined with slow return to the neutral position or failure to return to the neutral position.
The plan is to have crow mixing in ACRO mode using the Eclipse 7 radio. With the programming described below the flaps are controlled by CH5 and operated with the landing gear switch. The landing mode is programmed to raise both ailerons when flight condition ST2 is activated by flipping the Flt. Cond. switch forward. So, to turn on the crow mix, the Gear switch is flipped forward to lower the flaps and the Flt. Cond. switch is flipped forward to raise both ailerons. It works but the servos have this nasty chatter as the video demonstrates. At first I wasn''t sure if it''s a servo problem or if it''s a programming problem or a servo lead problem or a problem with the BEC or Rx. Through the process of elimination, the problem is reduced to either the Eclipse 7 radio or the Hitec QPCM receiver or both.
In the investigation I first brutally worked the strip CA control surface hinges until they went totally limp. I next checked the hinge lines and they are spot on without binding in any position. Everything was hooked back up and the chatter is still there. To take this exercise one step further, I disconnected the push rods from the control horns on all four surfaces and taped the surfaces up out of the way. Even with no load on them, the servos still chatter and hesitate to return to neutral. I pulled the servos from the wing and hooked them up to another Rx that uses a different Tx. Guess what? The servos worked perfectly. The servo lead question was answered by pulling the Hitec Rx, ESC, external BEC and battery harness from the model and plugging the servos directly into the Rx. On the bench, the servos act just as they do in the wing- chatter city. The external BEC question was answered by unplugging it and re-enabling the Atlas internal BEC. Lots of chatter, even more so than with the external BEC. The radio, along with the servos, receiver and spectra module was bought brand new about a month ago.
About the video:
0-15 seconds illustrates the servo chatter with the flaperon function operating. 16-29 seconds shows the flap operating with the chatter and 30-39 seconds shows the flap servo chatter with a jerky, slow return to the neutral position after turning the flaps off.
Video link: http://www.rcuvideos.com/item/8K3JWSYYTDWN0B1H
Hardware:
Servos: Hitec HS-81 2 aileron, 2 flap
Two 24" aileron servo extensions
Two 12" flap servo extensions
BEC: Atlas switch mode 8-42V
ESC: Atlas Black 45A w/internal BEC disabled
Battery: RC Battteries lipo 3s 1800 mAh 20c/30c
Motor: Atlas AM2921/11 outrunner (.40 sport)
Tx: Hitec Eclipse 7
Rx: Hitec HPD-07RH Q-PCM
Rx channel assignment:
1- Right aileron
2- Elevator
3- Throttle
4- Rudder
5- Left flap
6- Left aileron
7- Right flap
Programmed mixes:
PMX1- RT ail/RT flap mix (L/U 60%, R/D 60%) Master CH1, Slave CH7
PMX2- RT ail/Left flap mix (L/U 60%, R/D 60% Master CH1, Slave CH5
PMX3- Left/RT flap mix (L/U 100%, R/D 100%) Master CH7, Slave CH5
PMX5- Elev/ail mix (L/U 100%, R/D 100%) Master CH2, Slave CH6
Preprogrammed functions enabled:
Flaperon mix (FLAPN) using the default settings
Flight condition (FLT.C) ST2
Landing mode (LAND) where elevator (CH2) is set to 5% & aileron (CH6) to 80%
Sub trim (S.TRIM) and endpoint adjustment (EPA) set to align and synchronize the control surfaces
Other info:
The wing servos chatter regardless of the mode of operation or mix selected and frequently fail to immediately return to the neutral position. It doesn''t matter if the motor is running as the servos still chatter if it is. Battery charge also has no effect as the servos chatter the same with a fully charged or a partially drained (motor has cut out) battery. Tx proximity also has no effect as the servos chatter when the radio is as close as 2 feet or as far as 20 or more feet away from the Rx. All programming setup so far has been with the Tx antenna fully extended and no less than 8 feet away from the Rx.
This is my first computer radio and believe me, it has been one frustrating experience. What could possibly be wrong here? Any insight is greatly appreciated.
Hank
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