Thread Tools
Nov 04, 2017, 11:18 AM

EDF Fan "Hunting" on full power

I have a Blackhorse albatross L39 powered by a Fanjet 90mm fan and a Het 1400kv motor running on 10s. The ESC is a Yep 120A.
When I go to full power I get a surging ( hunting) in the fan......this stops when I come down to about 60% throttle.
I have tried various different batteries but all produce the same pulsating surges at full probably not the batteries ?
Has anyone else experienced this?...I am thinking it is either an ESC problem or that the fan is cavitating and not getting enough air ( ?) ..the plane is fully ducted by the way.
The fan is secured firmly and is not slipping on the shaft.
Any advice would be appreciated.
Sign up now
to remove ads between posts
Nov 04, 2017, 11:37 AM
Registered User
Kevin Cox's Avatar
Sounds like it could be low voltage cut-off. That would point to the batteries or the low voltage cut-off setting on the YEP.

You need take amp and voltage reading to be sure. Is it a Fanjet of a JetFan 90?
Nov 04, 2017, 01:44 PM
Official Boat Bum
Eddie P's Avatar
"Hunting" can mean different things. Depends on what you mean.

If you mean a rapid, quick but seemingly rythmic pulsing of the RPM at full power, you probably have packs that are not up to the amp draw.
If you have relatively slower onset RPM changes or cutouts, you might be hitting LVC.
If you have very rough running motor and heat issues you might have a ESC to motor setting issue where the motor needs different settings for smooth operation.
There could be other reasons as well... But I do not suspect you have a loose impeller or stalled airflow causing this based on what you say.

I have seen rapid and rhythmic RPM variability at full throttle before and in my case it has been the result of a cell or pack not able to keep up. You might have tried multiple packs but all your packs may be less up to the amp draw than required.
Nov 04, 2017, 02:11 PM
Registered User
4stripes's Avatar
Put a lipo voltage checker on while you run or a wattmeter to verify if there is any significant voltage sag. This little checker goes on every run in any of my electrics. It will expose any weak cell within seconds of WOT.
Nov 04, 2017, 02:47 PM
deltas are cool
AIR SALLY's Avatar
Could be low voltage cut off needs to be set lower as your batts could be sagging,also a cold solder joint might cause it.
Nov 05, 2017, 01:49 AM
Thanks for all your responses.....I do suspect that my batteries are a little "tired" so I will do as suggested and reset the low voltage cut off on the ESC in the first instance and see if that helps.....sounds like it about time for some new batteries too !
( its a Jetfan 90 by the way not a Fanjet as stated first off ) .
I have lots of batteries - is there an easy and quick way to check which ones are degraded and need discarding and which ones are still ok?
Many thanks .
Nov 05, 2017, 03:14 AM
Registered User
4stripes's Avatar
Charge them up and use the voltage monitor as posted above while operating at full power. Any low cells will be obvious.
A wattmeter can also be used but it will only show total voltage under load which isn't as helpful since you will have packs in series.

Having lots of batteries doesn't mean any of them are any good.
Nov 05, 2017, 07:56 PM
Registered User
tom bacsanyi's Avatar
If you were flying a 747 full of people would you want a low fuel warning that shut the engines off? The YEP controllers allow you to disable the lvc . I have a bunch of YEP controllers all disabled. I try to not run out of power but it happens. Example: I failed to plug in one of two parallel packs. I have telemetering of mah total but hadn't started to look at it it and was low over trees on a down wind leg. Power loss was fairly rapid but I just made the runway landing right angles to the runway. If lvc was on I would have been in the trees. Oh, and the mah would not have been any help because it was reading 3000 mah that was supposed to be half the capacity.
Last edited by tom bacsanyi; Nov 05, 2017 at 08:00 PM. Reason: second thought!
Nov 05, 2017, 08:14 PM
Registered User
tom bacsanyi's Avatar
This is the video of the flight and I noticed the power reduction at about the 3 minute mark.

REC_0009 (10 min 1 sec)
Nov 06, 2017, 06:01 AM
Registered User
4stripes's Avatar
That is why I fly with the lipo monitor all the time. It starts beeping and thanks to my quiet fans I know of a sagging or weak cell in time to land under power.

Quick Reply

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Airbus E-Fan Full Scale EDF Jet Chophop Electric Plane Talk 15 Sep 13, 2016 07:19 PM
Discussion Motors loose power on full throttle JeyO Beginner Multirotor Drones 3 Feb 14, 2016 07:28 AM
Discussion Effects of nicks on EDF fan Performance splais Foamy EDFs 1 Feb 04, 2016 01:14 PM
Discussion "EDF-51" Ducted fan power on P-51 Mustang Smokescreen38 Foamy EDFs 4 Jul 14, 2008 11:23 PM
anywhere to find info on cdrom powered edf fans jeff262 Power Systems 24 Apr 01, 2005 06:20 PM