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Old 04-02-2014, 12:17 AM   #1
Brewerpaul
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Default Help! Hawk Sky motor won't run.

It did but now it doesn't
I have a new RTF Hawk Sky which I assembled and had everything working just fine. The receiver and Tx bound, all servos worked as they should and the motor responded well to the throttle. Today I finally got a chance to maiden so I went through my binding routine and checked everything out again. Perfect. Before launching I decided to give it a little glide test to see if the CG seemed right. It nosed down from shoulder height, but not very hard, onto grass.
Now I can't get the motor to run at all. It just twitches back and forth. I've tried re-binding it many times with varying results. The motor never actually runs, but sometimes one of the aileron servos ends up in the down position and won't respond to the stick. Sometimes all control surfaces work fine. Sometimes the rudder doesn't respond.
For a plane that's supposed to take a licking and keep on ticking, it's hard to believe this tiny crash caused so much chaos. Any and all advice would be welcome!
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Old 04-02-2014, 01:25 AM   #2
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Hi Brewer. First, what tx/rx are you using? Also might help if you list the motor, esc, prop. Did the motor get real hot when testing? Second, once you get the initial bind done, except in some very rare circumstances, would you have to bind again.

A twitching motor usually means a bad connection in the wires between the motor and esc, or even in the motor itself. Or it could mean a bad esc.

With all your re binding, I assume you made sure the throttle is at idle and throttle trim at neutral? Also, make sure the battery is fully charged. Maybe you're already on top of those but just throwing out ideas.
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Old 04-02-2014, 02:17 AM   #3
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Originally Posted by Brewerpaul View Post
It did but now it doesn't
I have a new RTF Hawk Sky which I assembled and had everything working just fine. The receiver and Tx bound, all servos worked as they should and the motor responded well to the throttle. Today I finally got a chance to maiden so I went through my binding routine and checked everything out again. Perfect. Before launching I decided to give it a little glide test to see if the CG seemed right. It nosed down from shoulder height, but not very hard, onto grass.
Now I can't get the motor to run at all. It just twitches back and forth. I've tried re-binding it many times with varying results. The motor never actually runs, but sometimes one of the aileron servos ends up in the down position and won't respond to the stick. Sometimes all control surfaces work fine. Sometimes the rudder doesn't respond.
For a plane that's supposed to take a licking and keep on ticking, it's hard to believe this tiny crash caused so much chaos. Any and all advice would be welcome!
It sounds like the receive got hurt, check all of your wire connections, and if its not that, then its the receiver

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Old 04-02-2014, 02:48 AM   #4
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Originally Posted by xmech2k View Post
Hi Brewer. First, what tx/rx are you using? Also might help if you list the motor, esc, prop. Did the motor get real hot when testing? Second, once you get the initial bind done, except in some very rare circumstances, would you have to bind again.

A twitching motor usually means a bad connection in the wires between the motor and esc, or even in the motor itself. Or it could mean a bad esc.

With all your re binding, I assume you made sure the throttle is at idle and throttle trim at neutral? Also, make sure the battery is fully charged. Maybe you're already on top of those but just throwing out ideas.
The Tx and Rx are the Dynam ones that came with the RTF plane. Ditto the prop and esc. (Speaking of the ESC, how the heck do you get to that? I can't even see it!).
The motor never got warm at all.
Before the "crash" (bump?) I never had to bind again. Mind you, this was just during testing, before trying to fly. The few times I didn't have throttle at idle, it wouldn't bind at all, which makes sense. I tried both with the throttle trim at neutral and also at minimum. And, as soon as I got home I topped off the battery which didn't make a difference.
I did check the Rx connections-- took 'em all off and put them back.
If I can figure out a good way to get to the ESC (maybe cut a hatch in the belly of the fuse?) I'll look at those connections plus the motor connections which are stuffed down in there. I'd sure hate to replace the Tx after so minimal a rough landing. It's pretty flimsy if that's all it takes to ruin it!
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Old 04-02-2014, 09:08 AM   #5
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I'm a bit confused by your first post. After the test flight 'bump' did all the control surfaces work ok, was it just the motor that didn't run?

Or were all the controls malfunctioning after the bump?

If you can get it bound so that all the surfaces are responding then the motor problem is most likely just the bullet connector on one of the three wires that runs between motor and ESC that has come loose.

If on the other hand all the controls went 'wonky' after the bump then a bad receiver is a possibility.

Steve

PS.. to get the ESC out you probably have to pull it out by it's wires.
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Old 04-05-2014, 02:19 PM   #6
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Thanks for the advice. Following some hints I gathered on another RC forum, I found that the two black motor leads were loose. They're really flimsy and it doesn't take much to dislodge them. To get at them, and to allow future repairs/upgrades I cut a hatch in the belly of the fuselage. Once I had the wires hooked up correctly I secured the connections with black electrical tape and now everything runs fine.
My current problem is launching the darned thing. All control surfaces are neutral, but when I try to launch the plane it almost instantly does a power nose dive as if I'd given it maximum down elevator. I know that pylon mounted motors do tend to make a plane nose down under power, so I've experimented with 3/4 and 1/2 power launches with the same result. I've double and triple checked CG and experimented with battery location.
My current best guess is my launch technique-- maybe too wimpy a toss, too high a launch angle producing low airspeed, or a combo of the two. Any other suggestions would be appreciated.
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Old 04-05-2014, 02:43 PM   #7
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Originally Posted by Brewerpaul View Post
Thanks for the advice. Following some hints I gathered on another RC forum, I found that the two black motor leads were loose. They're really flimsy and it doesn't take much to dislodge them. To get at them, and to allow future repairs/upgrades I cut a hatch in the belly of the fuselage. Once I had the wires hooked up correctly I secured the connections with black electrical tape and now everything runs fine.
My current problem is launching the darned thing. All control surfaces are neutral, but when I try to launch the plane it almost instantly does a power nose dive as if I'd given it maximum down elevator. I know that pylon mounted motors do tend to make a plane nose down under power, so I've experimented with 3/4 and 1/2 power launches with the same result. I've double and triple checked CG and experimented with battery location.
My current best guess is my launch technique-- maybe too wimpy a toss, too high a launch angle producing low airspeed, or a combo of the two. Any other suggestions would be appreciated.
Give the plane some up trim when launching, give the plane a hard toss on a slight up angle, launch Full Throttle into the wind, that plane tends to be low on power, Heads Up Rc has a nice powerful motor combo, that will allow the plane will take off from the ground with no wheels

http://www.headsuphobby.com/Firepowe...00kv-C-424.htm

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Old 04-05-2014, 02:47 PM   #8
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with a more powerful motor

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Old 04-05-2014, 02:49 PM   #9
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Old 04-05-2014, 03:49 PM   #10
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Originally Posted by Brewerpaul View Post
My current best guess is my launch technique-- maybe too wimpy a toss, too high a launch angle producing low airspeed, or a combo of the two. Any other suggestions would be appreciated.
You probably have hit it on the head, assuming the CG is about right and the elevator is set neutral AND you have the elevator moving in the correct direction (check all these things) Then your launch technique is most likely to blame.

On a pylon mounted motor I'd launch at half throttle then roll the throttle smoothly to full power once you have control. Launch must be into the wind and firm, no wimpy half hearted stuff. Launch the model straight at the horizon, not steeply up or down.
Its not like throwing a ball, it's more of a firm push than a throw. If you throw it like a ball you will impart a twist into it as you release which causes the plane to roll.

If possible fly in a place with soft grass so that if you screw up the damage is less. Personally I'd not advise 'souping-up' the motor until you are confident at flying it as it is. Making it whiz around at high speed doesn't make it easier to fly, it makes it harder, and it makes the crashes harder too. The stock Hawk Sky has plenty of power for a beginner.
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Old 04-05-2014, 04:28 PM   #11
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A little tip for the future. When you post a question about a plane, include a link to the plane so people can be sure what plane you are talking about. People will know the context and you will get better advice. We won't have to ask what radio, what servos, what receiver, etc. It will all be there.

Also, there is often a manual at the link which can be helpful in diagnosing problems.

Is this your plane?
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Old 04-05-2014, 04:58 PM   #12
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The problem you are having when hand tossing is simple to solve. You are simply giving the plane too much power on launching. Pusher planes of this type have a tendency to dive momentarily when given full throttle and no elevator; this is because of the thrust angle of the motor and prop combo. All of these types of planes exhibit this tendency. Launch the model into the wind at just a hair over half throttle and straight ahead, do not pitch it up. It may be better to have a friend or experienced pilot launch it for you.
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Old 04-08-2014, 02:57 AM   #13
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Yes, AEAJR-- that's the plane.
Thanks to all for the helpful hints. I'll try again as soon as the weather permits.
To top things off, my elevator servo may be buggy. In testing, every so often it stops responding. I'll cycle up and down for 20 cycles or so and then it stops working. All other servos are fine as is the throttle. If I manually move the servo arm even a tiny bit it starts working again. Bad gear tooth?
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