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HelicopterMain Discussion › Trex 700N DFC
12-20-2015 03:47 PM  20 months agoPost 1
Davej 700

Heliman

Bastrop Texas

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Hey Guys I have a Trex 700n DFC I have a Crazy flight problem. No I am not a beginner. Around a 1/4 Tank left of fuel while Flying my heli Start to change elevation almost like jumping up and down or very short and quick pitch pumps My heli is in Great working Order. I thought it was my fly barlesl system I upgraded from Beastx to BeastX HD and still have the Same problem. FLight 2 is even worse as it starts doing this Much Quicker. Any Ideas? Thanks Dave

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12-20-2015 04:45 PM  20 months agoPost 2
wc_wickedclown (passed)

rrProfessor

long beach calif

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sounds like too much cyclic gain

Insha Allah made in america

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12-21-2015 12:17 AM  20 months agoPost 3
dkshema

rrMaster

Cedar Rapids, IA

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How is the motor running during this time? Still running strong, or starting to behave oddly?

Does your 700N have a header tank installed, and which engine are you using?

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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12-21-2015 03:41 AM  20 months agoPost 4
Davej 700

Heliman

Bastrop Texas

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Gain is Set to Low Setting and Will Fly Full Collective in forward flight and is Normal. Engine is in Great Shape ton of Power 11 Minutes Strong. Main Drive Gear 1 way bearing is new along with Clutch and Clutch Bell. I can Fly hard Core for 8to 9 minutes before its starts to act up. Sorry still have not figured this one out

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12-21-2015 03:41 AM  20 months agoPost 5
ssmith512

Key Veteran

Indianapolis, IN USA

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I would start by replacing your RX pack to a known good battery pack of sufficient capacity. Less than adequate RX pack power can cause all kinds of weird behavior.

Steve

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12-21-2015 03:43 AM  20 months agoPost 6
Davej 700

Heliman

Bastrop Texas

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Flight pack is A New Pulse 2S 5000 Mah Feeding a Castle Pro set to 6.0 Volts.

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12-21-2015 04:42 AM  20 months agoPost 7
grim.the.grim

Veteran

Houston, Texas

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Possibly running lean. If the rev-limiter is having problems maybe creating a problem.

Is your fuel clunk in good shape and getting fuel at all angels?

Maybe installing a header tank or re-doing the clunk and line inside your primary tank?

*** Real Pilots BEAT the air into submission! ***

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12-21-2015 04:54 AM  20 months agoPost 8
Aaron29

rrProfessor

USA

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Sounds like it's leaning out. Lean motors get pitch sensitive.

Or perhaps a leak in fuel clunk line, etc.

If it's OK and then gets bad at a certain fuel level, you can BET it's a mixture or fuel delivery issue.

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12-21-2015 10:39 AM  20 months agoPost 9
banshee rider

Senior Heliman

n.e. illinois

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Probably a hole in fuel line just above the clunk
or where line goes on clunk

ageing is manditory maturity is optional

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12-21-2015 02:14 PM  20 months agoPost 10
Tyler

Elite Veteran

Chicagoland area

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The 1/4 tank aspect does lend itself towards a fuel line leak. Similarly, I have seen a stripped muffler bolt cause a sudden lean condition part way through the tank after the engine has warmed everything up, causing expansion. The engine made inconsistent power, sometimes a surge in power. On the ground the muffler seemed secure. A helical in the muffler mounting flange resolved the issue.

If you place your feet on the skids to hold down the helicopter while pulling up on the headlock, how tight is the fit? Any movement? What about if you push down on the head? I would look for a cracked lower jesus bolt or other shimming issues.

Enjoy things that money can buy IF you don't lose the things money can't buy.

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12-22-2015 12:58 AM  20 months agoPost 11
Davej 700

Heliman

Bastrop Texas

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I have replaced clunk line all Fuel lines filter etc I did all the Small Normal things First Pipe and Muffler are Tight. OS91HZ With Hatori Pipe all in Great Condition. Yet Problems Remains. Going to Buy a Go Pro this week with Head Gear so I can wear it on my head when I fly and get a Video of this. I have also got Todd Bennett Involved Attended his School 5 Years Ago Now. Thanks for all the Input What Ever this is it Still Eludes Me.

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12-22-2015 01:01 AM  20 months agoPost 12
Aaron29

rrProfessor

USA

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First off, if you haven't already, deactivate the governor and run on the throttle curves. The governor is going to mask what you need to know.

Did you richen? If you are running a normal setup, it's normal for the mixture to lean out as tank level goes down. You may start your flight with good mixture and go lean as that level drops.

Did you try disassembling and cleaning that carb and inspecting
O-rings? Doosh that thing and replace questionable O-rings. It's possible you have an air leak or obstruction. Filters aren't perfect. Air leaks and obstrcutions can cause irregular fuel flows and change with temperature. Could be engine gets up to an op temp and it begins.

Are you pressure regulated? These deliver same fuel flow for different tank levels. If you're running one and getting that lean-out at 1/4 tank as you say, it could be a regulator issue. Unfortunately not much to do other than change regulators.

I liked Tyler's idea. I had a Raptor misbehave due to vertical play in the main gear. Check for that.

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12-22-2015 02:57 AM  20 months agoPost 13
RappyTappy

rrProfessor

North Denver, Colorado

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Not knowing how exactly it's jumping around if its truly linear collective action or a mixture of cyclic/collective, could be a worn cyclic servo that as it heats up from the flight it is starting to fail. I had a 8900g that did this, would work fine on the bench but after a while in the flight it would start glitching. Just a thought.

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12-22-2015 03:21 AM  20 months agoPost 14
Tyler

Elite Veteran

Chicagoland area

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Also, check for stripped splines on servo output shaft or servo horns/wheels. Align plastic wheels can do this, and many of us prefer the plastic wheels because they act as a disposable fuse to protect the servos from stress.

Enjoy things that money can buy IF you don't lose the things money can't buy.

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12-22-2015 04:08 PM  20 months agoPost 15
RappyTappy

rrProfessor

North Denver, Colorado

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Never hurts to check, but a stripped servo horn spline would show itself randomly even at the beginning of the flight, but the OP says it only happens near the end of the flight but works fine otherwise. Making me think something is wrong electronically in the system, unless the engine is simply going lean and he is over controlling the collective being more sensitive due to increased headspeed. A video of what is happening will probably be best to see what is going on. Love them gremlins.

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12-22-2015 05:55 PM  20 months agoPost 16
Davej 700

Heliman

Bastrop Texas

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Well its not the Governor I deactivated it and still the Same. I talked with Todd Bennett Last Night and I have to agree with him. this is the Helicopters 3rd set of DS615 in under a 100 flights. He Feels a servo is failing -getting Hot and backing Feeding an Electrical Signal to my Flybarless controller as he put it Pissing it Off. The Current Cyclic Servos on Board have less than 30 Flights. This also Helped me remember the time I had a DS655 Failing and tail would not cooperate at all. Until I changed out that Servo and all was fine again. Thanks Guys I will post after Servo Swap out and let you know.

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12-22-2015 07:10 PM  20 months agoPost 17
Aaron29

rrProfessor

USA

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Hmm. Maybe try a gentle flight that doesn't stress the servos. If it doesn't happen, then that theory holds water. And if it does, touch the servo case to see if it's hot.

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12-22-2015 08:15 PM  20 months agoPost 18
Tyler

Elite Veteran

Chicagoland area

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Maybe inspect the elevator bell crank shaft that crosses between the two frames. After a crash this shaft can get bent and cause undesired stress to the servos and battery power supply to your electronics. If you are burning up cyclic servos I would find that culprit. You may have to disassemble that whole elevator system and dial indicate the shaft.

Enjoy things that money can buy IF you don't lose the things money can't buy.

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12-22-2015 08:50 PM  20 months agoPost 19
flycatch

Senior Heliman

Barstow, California

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Check upper and lower "Jesus" bolts. I experienced a similar problem on a TT Titan and upon spool down the bottom bolt dropped to the ground. Sounds incredible but it did happen.

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12-25-2015 10:11 PM  20 months agoPost 20
Davej 700

Heliman

Bastrop Texas

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Its Fixed

Merry Christmas Guys. Well I changed out all 3 DS615,s on my Cyclic Re Did My Set up and Flew 3 Heart Pounding Flights Today. It was a Blast. Smooth and Fast. I went with 3 Savox SC 1267SG,s I like them very Much. No more Jumping up and down for that Helicopter. Not Sure Which of the 3 615,s were bad Well doesn't matter now Thanks Dave Jensen Case Closed.

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