tail wag fixed, new problem>suddenly falling out of the sky - RC Groups
Thread Tools
Apr 18, 2005, 04:27 PM
Registered User

tail wag fixed, new problem>suddenly falling out of the sky

So I switched out the GY240 for the 401 and that did not help the wag...received the 9254 mount Saturday, installed it Sunday and the wag is gone- great...took it outside this am and it was fantastic- AVCS held in crosswind, no wag, Normal mode weathervaned and then held- great... 3-4 minutes of gentle side to side and hover the heli suddenly dropped 10' straight to the ground...checked the pinion setscrew etc, put in a fresh battery and hovered 1' off the ground in AVCS and it cut out again and dropped to the ground... 2 flights with the 9254 = 2 ESC cutouts...the motor and PH45 were both pretty warm...
Castle Tech said the 9254 was pushing the BEC over the edge and it was shutting down, he had me set the 'Current limiting' to 'Disabled' from 'Normal' and said that should fix the problem, and suggested adding a UBEC/SBEC and disabling the PH45 BEC...
I hovered inside about a foot off the floor for 2 batteries and it did not cut out but the motor and PH45 were very hot...throttle curve at 0-30-60-80-100, hovers at 65%...60 flights to date, fighting tail wag all the way until yesterday anyway...
Heli setup- ( flying at 5000'), stock aluminum crutch and tail boom, GY401, Phoenix 45, Berg 5, Mega 16/15/3, HS 85mg on cyclics, 9254 on tail, 1/8" CF tail pushrod with ball links, Hyper Drive with 13T, 6-6 grips, tail belt drive, 8 cell GP3300... I have tried reducing grips but lost too much lift- same with going to 12T...
So what do I do now?
It was only 65'F this am so I am really nervous about pushing things not only now, but when it gets to 90'+ outside...
Switching to the 9254 brought the flying weight to 48oz from 46 oz and lift was a bit less so I don't think i can add any more weight (UBEC/SBEC)without going to LiPO's. A Crooked Crutch is on the way which should bring the weight down a little.
A different brand ESC?
Anything else?
Sign up now
to remove ads between posts
Apr 18, 2005, 04:40 PM
Registered User
Were you using governor mode? If so, the throttle curve should not go below 80% of max headspeed. Less than 80% of max headspeed, some may say 85%, will decrease the efficiency of the ESC and heat it up. It then may have a heat cut-off.

Please note that 80% of max headspeed may not be 80% on throttle curve. In gov. mode, you may reach the max heaspeed with, say 74% on the throttle curve and 80% of that would be 56% on your throttle curve.

You need to find out at what % on your throttle curve you are getting the max headspeed first. You can start with 100% on your throttle curve and gradually dial down the % until you hear the headspeed begin to decrease -- the % on the throttle curve at the point is the % that would give you the max headspeed.

In my Log0 10 with its power system, 80% on my throttle curve gives me the max headspeed. I then set the throttle curve to 90% of the max -- -meaning 90% or the 80% = 72% on the throttle curve.

Never mind all these if you are not in governor mode.

Apr 18, 2005, 04:49 PM
Registered User
SBK- 'Throttle Type' is 'Fixed'... I did not change any TX settings or PH45 settings (except after the 2 cutouts I switched the 'Current Limiting' to 'Disabled', but I have not flown outside with this change- a bit apprehensive about getting it more than 2 feet off the ground now- unless no one things it will be a problem)
Apr 18, 2005, 04:57 PM
Your attitude is your alt
Gary Morris's Avatar
As Castle said, the BEC can't support the additional power of the digital servo. I'd just go ahead and get a UBEC from Hobby Lobby or direct from Koolflight. It should be able to handle the added load with no problem. As far as weight goes, the light weight of the UBEC shouldn't even be noticed by the Corona, even at 5000 ft alt. I've weighed mine down with cameras and video links which added nearly 12 oz to it's stock weight and it flew just fine on 8 cell 3300GP packs. The UBEC costs around $30.00 dollars vs a new ESC like a JAZZ 40 amp controller which costs $169.00. I think the ubec would be the winner there!

Apr 18, 2005, 05:09 PM
Registered User
Originally Posted by SBK Formosa
Never mind all these if you are not in governor mode.

i think it would be tough for alpine to run governor mode on a corona...with it being fixed-pitch and all. good info for the rest of us though.
Apr 18, 2005, 05:30 PM
Registered User
Gary- Castle said just switching 'Current Limiting' to 'Disabled' should fix problem, but, if not to go with UBEC/SBEC...my post didn't come across quite right... but you would just go ahead with the UBEC anyway?...am I taking a big chance if I fly it until the UBEC shows up?
Apr 18, 2005, 05:38 PM
Registered User
I see where there 3 versions of the UBEC at Hobby Lobby- standard, with High Voltages, and with High 6V Output... which do I need?
Thanks again
Apr 18, 2005, 05:55 PM
I broke my kerpellor.
Artemetra's Avatar
Originally Posted by alpine
I see where there 3 versions of the UBEC at Hobby Lobby- standard, with High Voltages, and with High 6V Output... which do I need?
Thanks again
I just went through the same thing. The UBEC seems to have fixed the problem perfectly. (I also had the digi tail servo, and Castle told me too much current draw.)

I got the regular version, KFS001. The high voltage unit is if you use lots of cells on you battery, like 14 or 16 cells. With your 8-cell, get the regular one. I use mine on 10 cells and 11.1 lipos. I

I wouldn't fly until I got mine installed, but I didn't have a Corona, either.

There is a thread "to UBEC or Not to UBEC" - loads of info there. https://www.rcgroups.com/forums/showthread.php?t=348938
Apr 18, 2005, 06:52 PM
The speed control just needs alittle more air flow. The BEC can handle the load but it runs a bit hotter. Make sure there is good airflow to the speedo and you will be good.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Why does my XE2 keep falling out of the sky? Lost_Dawg Flying Wings 11 Nov 26, 2006 11:23 AM
Discussion planes falling out of the sky Ralph Walton Crash Discussion 16 Mar 11, 2006 02:29 AM
CAn you help stop my Zoom falling out the sky? Calling you electronics masters wildstallion Mini Helis 16 Jun 22, 2005 07:48 PM
T-rex tail wag. location cause problem ? rcmarty Mini Helis 0 Mar 19, 2005 11:27 PM
Birds of time Falling out of the sky Lite2bolt Sailplane Talk 37 Jul 10, 2004 11:57 AM