What the...Nose Drops if FFF???

WREX450 · 12-30-2009, 07:11 PM

Maidened my 450 pro and ran into a problem I've never seen before? I used a swash plate leveler and corrected for CCPM interactions during the build (I thought). Due to my ESC and AR9000 being mounted outside and towards the back, it was tail heavy. I figured this would be the case, so no problem, I'll correct the setup to get the correct CG.

The surprising issue to me was that during FFF the heli progressively drops its nose and I have to give significant elevator to correct as the speed increases. I figured being tail heavy this would be the opposite? The only tendencies during hover are for the heli to creep straight backwards. Any chance the shape of the canopy has an effect at high speed? I had a 450v2 and 500esp before and never had the issue. Tonight I'll recheck pitch, swashplate, interactions and correct the CG. By the way, what a great flying heli, although my 25c flightmax batteries seem way underpowered now.

Any help diagnosing this is appreciated!

bmlasater · 12-30-2009, 07:23 PM

fwiw..
Be sure the paddles are correctly aligned...Yes, the horzontal fin/canopy definitely have an aerodynamic effect....
forward flight in a heli involves a lot of changing dynamics with speed...If you can, get a more experienced pilot to fly it..what you are seing may be normal for the fins/canopy/paddles you have on your heli...One possible fix would be heavier paddles/flybar weights, but that will come as a loss of cyclic snap.
Let us know how you do...

John.

WREX450 · 12-30-2009, 10:05 PM

Thanks for the help, I checked and the swash was slightly out of spec, but nothing extreme. Paddles are good too. Stupid question, but your setting the CG right on the flybar right? I just pick it up by the flybar and watch the skids as I rest it on the table. I check front to back and side to side. If its hitting the rear part of the skid, I would be tail heavy right? Just double checking Im not missing something obvious here.

jondbennett · 12-30-2009, 10:11 PM

I will be interested to hear how this turns out. The little bit I know about helicopter aerodynamics tells me that this is impossible.

I'm not doubting what you report, I am just very interested to hear what the cause turns out to be.

Slyster · 12-31-2009, 12:55 AM

I always watch newly setup helis for rise or drop in FFF and trim it out.. only takes a click or two.

HeliKopter noob · 12-31-2009, 08:12 AM

could it be the swashplate not travelling level throughout the travel. I've had similar happen on my King2 once upon a time.

--N

airjawed · 12-31-2009, 08:14 AM

I'd take a closer look to make sure the paddles are level. This is what comes to my mind as well. If the paddles are not level then during fast forward the wind coming accross might be pushing on it and inducing cyclic input when you don't want it. Paddles are the usual culprit in pitchy flight.

Also remember to check CG with canopy on.

Jermo · 12-31-2009, 09:13 AM

my SE does that if I go fast enough.

WREX450 · 12-31-2009, 01:48 PM

Ok when it rains it pours... Went to spool it up and the motor won't spin at all???!! I have it set on slow start, all stock set up with the 450m. I pulled the motor and it is very difficult to turn with the power on or off. I can manually get it to turn, but with moderate resistance. The motor tries to start but will make a 1/4 revolution before hitting resistance and stopping. I fiddled with it for a while and once it gets a few rpms, it appears to lose the resistance and run just fine. It does this in or out of the heli. Only problem as soon as i stop it, the resistance re-appears??? Nothing has fallen it, nor have any of my DX7 settings changed. Anyone know how to open the motor, I can't find any screws. Ran fine all day yesterday, came down cool to the touch and never been wrecked. I need a beer..

finfan882002 · 12-31-2009, 02:45 PM

make sure u dont have a screw stuck in one of the motor vents

finfan882002 · 12-31-2009, 02:46 PM

redo ur esc settings

markb · 01-01-2010, 06:25 PM

pitch up or down in FF can definitely be caused by "collective" pitch built into the paddles. What I mean is, with the flybar level and the swash level, the paddles both have a bit of up/down pitch. You can see it by looking end on and comparing the paddles to the flybar cage.

In hover, it wont have any effect. But in FF, if the paddles are pitched up, then the advancing paddle will lift more than the retreating paddle. Dissymmetry of lift due to the FF airflow. Precession causes the flybar "disc" to respond by lifting up in the front. which in turn causes pitch up of the main rotor. If the paddles are pitched down... the opposite happens, and the main rotor will pitch down.

WREX450 · 01-05-2010, 11:01 PM

Finally got my replacement motor installed and it must have been the flybar paddle. The swash was only slightly out of spec, but one flybar paddle had definitely moved. Corrected it and all is well, THANK YOU !!!!!!!

12-30-2009, 07:11 PM	#1
WREX450 Registered Users Join Date: Oct 2008 Location: Austin, TX	What the...Nose Drops if FFF??? Maidened my 450 pro and ran into a problem I've never seen before? I used a swash plate leveler and corrected for CCPM interactions during the build (I thought). Due to my ESC and AR9000 being mounted outside and towards the back, it was tail heavy. I figured this would be the case, so no problem, I'll correct the setup to get the correct CG. The surprising issue to me was that during FFF the heli progressively drops its nose and I have to give significant elevator to correct as the speed increases. I figured being tail heavy this would be the opposite? The only tendencies during hover are for the heli to creep straight backwards. Any chance the shape of the canopy has an effect at high speed? I had a 450v2 and 500esp before and never had the issue. Tonight I'll recheck pitch, swashplate, interactions and correct the CG. By the way, what a great flying heli, although my 25c flightmax batteries seem way underpowered now. Any help diagnosing this is appreciated!

12-30-2009, 10:11 PM	#4
jondbennett Team Taco Member My HF Map location Join Date: Feb 2005 Location: Athens, Ohio	Wow. I will be interested to hear how this turns out. The little bit I know about helicopter aerodynamics tells me that this is impossible. I'm not doubting what you report, I am just very interested to hear what the cause turns out to be. __________________ Jon Bennett (AMA #836296) T-Rex 450S CF: HKII 2221-8, BL35G, GY520, HS65MGs, R617FS, Futaba 7CH (2.4) Align Metal Head/Tail, Align 325 woodies, 1191s K&Bs, S9257 Planks: US Aircore Trainer 40, Acromaster, Tiger 2 Kit, RealFlight G5

12-31-2009, 12:55 AM	#5
Slyster Registered Users My HF Map location Join Date: May 2008 Location: Maplewood, MN	I always watch newly setup helis for rise or drop in FFF and trim it out.. only takes a click or two. __________________ It's not just a hobby... it's a lifestyle! Outrage Fusion & 550 / Goblin 700 / SK540 / Kontronik / DX8 / Quantum / RJX / 4010 Duo Pete Team Outrage.

12-31-2009, 08:14 AM	#7
airjawed Registered Users My HF Map location Join Date: Mar 2008 Location: Cliffside Park NJ	I'd take a closer look to make sure the paddles are level. This is what comes to my mind as well. If the paddles are not level then during fast forward the wind coming accross might be pushing on it and inducing cyclic input when you don't want it. Paddles are the usual culprit in pitchy flight. Also remember to check CG with canopy on. __________________ Trex 450 Pro 3xDS410M + MKS8910A+, Align FBL head w/Microbeast, CC 45 Gov@ 3400rpm(max timing, outrunner mode), Scorpion 2221-8 on 14t, Edge FBL main and tail, CF boom, CC BEC @ 6V

12-31-2009, 09:13 AM	#8
Jermo Registered Users Join Date: Nov 2006 Location: SC USA	my SE does that if I go fast enough. __________________ Jerry Moore, AMA #878954, IRCHA #2988 Pantera .61bbc - Takes a licking and keeps on kicking! , Trex 500CF, MCPX V2 Readyheli BL Ok, you can fly...but can you HOVER?? To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. KISS = Keep it simple stupid (to maximize fun and reduce costs!)

12-30-2009, 07:23 PM	#2
bmlasater Registered Users Join Date: Jun 2006 Location: Orange county CA usa	fwiw.. Be sure the paddles are correctly aligned...Yes, the horzontal fin/canopy definitely have an aerodynamic effect.... forward flight in a heli involves a lot of changing dynamics with speed...If you can, get a more experienced pilot to fly it..what you are seing may be normal for the fins/canopy/paddles you have on your heli...One possible fix would be heavier paddles/flybar weights, but that will come as a loss of cyclic snap. Let us know how you do... John.

12-30-2009, 10:05 PM	#3
WREX450 Registered Users Thread Starter Join Date: Oct 2008 Location: Austin, TX	Thanks for the help, I checked and the swash was slightly out of spec, but nothing extreme. Paddles are good too. Stupid question, but your setting the CG right on the flybar right? I just pick it up by the flybar and watch the skids as I rest it on the table. I check front to back and side to side. If its hitting the rear part of the skid, I would be tail heavy right? Just double checking Im not missing something obvious here.

12-31-2009, 08:12 AM	#6
HeliKopter noob Registered Users Join Date: Aug 2008	could it be the swashplate not travelling level throughout the travel. I've had similar happen on my King2 once upon a time. --N

12-31-2009, 01:48 PM	#9
WREX450 Registered Users Thread Starter Join Date: Oct 2008 Location: Austin, TX	Ok when it rains it pours... Went to spool it up and the motor won't spin at all???!! I have it set on slow start, all stock set up with the 450m. I pulled the motor and it is very difficult to turn with the power on or off. I can manually get it to turn, but with moderate resistance. The motor tries to start but will make a 1/4 revolution before hitting resistance and stopping. I fiddled with it for a while and once it gets a few rpms, it appears to lose the resistance and run just fine. It does this in or out of the heli. Only problem as soon as i stop it, the resistance re-appears??? Nothing has fallen it, nor have any of my DX7 settings changed. Anyone know how to open the motor, I can't find any screws. Ran fine all day yesterday, came down cool to the touch and never been wrecked. I need a beer.. Last edited by WREX450; 12-31-2009 at 01:52 PM.. Reason: Add details...

12-31-2009, 02:45 PM	#10
finfan882002 Registered Users Join Date: May 2006 Location: ftr laud fl	make sure u dont have a screw stuck in one of the motor vents

12-31-2009, 02:46 PM	#11
finfan882002 Registered Users Join Date: May 2006 Location: ftr laud fl	redo ur esc settings

01-01-2010, 06:25 PM	#12
markb Registered Users My HF Map location Join Date: Sep 2007 Location: Virginia Beach, VA	pitch up or down in FF can definitely be caused by "collective" pitch built into the paddles. What I mean is, with the flybar level and the swash level, the paddles both have a bit of up/down pitch. You can see it by looking end on and comparing the paddles to the flybar cage. In hover, it wont have any effect. But in FF, if the paddles are pitched up, then the advancing paddle will lift more than the retreating paddle. Dissymmetry of lift due to the FF airflow. Precession causes the flybar "disc" to respond by lifting up in the front. which in turn causes pitch up of the main rotor. If the paddles are pitched down... the opposite happens, and the main rotor will pitch down. __________________ Mark Logo 600se, Scorpion 5020-450, mini-V, Jive 80HV Trex 600 ESP FBL, Scorpion 4025-740, cgy750, CC85HV Trex 450 Vx FBL, Scorpion 2221-10, RJX head, mini-V, Ice 50

01-05-2010, 11:01 PM	#13
WREX450 Registered Users Thread Starter Join Date: Oct 2008 Location: Austin, TX	Finally got my replacement motor installed and it must have been the flybar paddle. The swash was only slightly out of spec, but one flybar paddle had definitely moved. Corrected it and all is well, THANK YOU !!!!!!!

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