mCPx: Known issues, fixes, information rollup

[Gadflyii]

I am hoping that this can be a good roll up of all the known issues with the mCPx, and have it be a good source of information. I will update the thread daily for the next few weeks, and then as required. If you have one of these issues, or have a new issue to report please post it here.

There were several attempts to make a thread like this in the past, so I am going to ask for all of your help in keeping the thread clean, and free of arguments and off topic discussion.


Current known issues:

1.) Feathering shaft screw backs out or is loose from factory.

Symptoms:
- Lateral play in the blade grips
- Main blade and blade grip ejection if the screw backs all the way out in flight

Fix:

- Check the feathering shaft screw and secure with a small amount of thread locker

HH Response:

- This issue has been confirmed by HH and has released an addendum to the manual which can be found here: BLH3500_Bulletin.pdf

2.) Main Blade Grip Bearing Failure

Symptoms:

- Notchy or "loose" bearings after crashes or in some cases new out of the box.
- Main blade and blade grip ejection, however the screw remains in the feathering shaft on the helicopter and "pulls through" the bearings on the blade grip.

Fix:

- Inspect blade grip bearings before first flight, and after any form of blade strike or crash.
- Replace main blade grips (HERE on HH's website)
- Replace with Align Trex 250 bearings, Align PN # H25060 681x mixer arm bearings (confirmed to be a direct drop in to the stock blade grip by myself) Here on Helidirect

HH Response:

- None at this time

3.) Uncontrollable rolls to the right.

Note: Their has been some reports of same behavior but to the front or back or a combination of the two.

Symptoms:

- The helicopter will yaw or pitch violently and unexpectedly without warning, and become unresponsive to any TX inputs.

Fix:

- *Unconfirmed* Rebind the helicopter with the proceedure found in the manual. This is believed to be caused by an incorrect binding of the helicopter to the TX. When binding the helicopter you must complete the binding process with the trainer switch.

Per the mCPx manual for computer TX's:

1.) Connect the flight battery to the helicopter, wait for the LED to flash
2.) Power on the TX while holding the bind switch
3.) Release bind button after 2-3 seconds, the helicopter blue LED will light up solid
4.) move the trainer switch, the swash plate will move up and down to confirm the helicopter is in computer mode.
5.) Disconnect the flight battery and power the transmitter off.


- * Unconfirmed* It has been suggested that a replacement of the all in one board may be required: HERE on HH's website

HH Response:

- None at this time

4.) Loose main motor screws

Symptoms:

- The screws that attach the main motor to the frame are loose from the factory

Fix:

- Remove the screws one at a time and apply a small amount of thread lock to each of the motor mount screws.

HH Response: None at this time

5.) Free play on the main shaft

Symptoms:

- The main shaft will have 1-1.5mm of vertical play
- Causes erratic pitch changes during flight, helicopter will "Jump" up and then "dive" down

Fix:

* First ensure that the main gear is fully "pushed up" on the main shaft as far as it will go*

- Use a few small shims to remove the free play, either on top of the main gear, or under the main shaft collar (it is best to shim under the main shaft collar).

- Remove the main gear & main shaft; use an exacto knife to increase the length of the notch on the bottom of the main shaft to allow the main gear to be pushed up higher on the main shaft to remove the excess play

HH response: None at this time

[Mojappa]

Also, many reports of loose motor mounting screws, me having them myself. Not really an issue as much as a step that should be in your preflight checks.

[RoyArms]

"move the trainer switch, the swash plate will move up and down to confirm the helicopter is in computer mode"

This should really say throttle hold switch, and only works if your normal and throttle hold pitch curves are different at low stick. I was confused by this at first till I read on and found out the transmitter in the RTF kit uses the trainer button as throttle hold. Most real transmitters the trainer switch just activates a timer.

[Jeff_Barrett]

Great info guys. I'll be picking up a BNF this afternoon and hopefully be able to contribute.

Between Gad & JS, I've finally be convinced to look closer at this bird.

[freeze]

Which way should the trex 250 bearings be installed when using them as replacements? Ball race in or out for inside and outside bearing in each grip?

Also should they be greased prior to installation?


Thanks

[mediclavina]

I also want to know the answer to this question. I'm going to use bearings from my GAUI 200. Here's a picture:

[lenrev]

ISSUE
Can probably add that the main gear and shaft are a press fit and the gear will shift until there is about 1/16-inch gap between top of gear and the frame.

SYMPTOMS
Heli won't lift and vibration occurs at high RPM (blades appear out of track).

FIX

Remove landing skids and hold opposite end of main shaft while pressing the main gear until there is approximately 1/16" of the main shaft end protruding out of the main gear.

[Finskeeper]

Several BNF helis seemed to have been shipped with a significant amount of negative pitch at mid stick. Use pitch sub-trim on your TX to achieve 0 pitch at mid-stick.

[Silverexpress01]

Surprised to see no mention of lubricating the feathering shaft. It should freely slide side to side.

[more_klump]

RTF M2 also shipped with significant negative pitch at mid stick. The only recourse with the noncomputerized radio in the RTF is to increase the length of the three servo arms (arms already hooked at the top hole). Maxing out the trim did not bring the pitch to zero at mid stick.

[CocoSantango]

Originally Posted by Finskeeper

Several BNF helis seemed to have been shipped with a significant amount of negative pitch at mid stick. Use pitch sub-trim on your TX to achieve 0 pitch at mid-stick.

It took 36 clicks here...

[dbennettya]

The correct way with 3 axis gyros is to not use trim or subtrim and level the swash with the cyclic servo rods and get 0* pitch.

I have been running my stock blade grip bearings with the bronze side pointing out. This puts max load on the solid side of the bearing and forces the cage into the bearing. So far about 20 flights and 12 or so crashes trying to do flips and inverted. Bearings are still in great shape even after having to replace the feathering shaft. Many crashes into concrete, rocks, fences and grass.

Still trying to get the settings right so it doesn't spin out of control on flips. You gotta fly this thing with finese It don't like brute force.

Gotta love it though, I would have gone through $50 in parts on my Walkeras with these crashes. Toll is messed up canopy nose (fixed with tape), bent feathering shaft, deformed tail blades (straightened), main gear pops down and twists on shaft (remove and press back on), blades tore up and cracked (glued cause on trailing edge and rebalanced with tape) priceless

YMMV, Don

Originally Posted by Finskeeper

Several BNF helis seemed to have been shipped with a significant amount of negative pitch at mid stick. Use pitch sub-trim on your TX to achieve 0 pitch at mid-stick.

Originally Posted by Silverexpress01

Surprised to see no mention of lubricating the feathering shaft. It should freely slide side to side.

The covered side of the bearing should face outwards for the trex 250 bearings.

Maybe this is the true cause of the issue? On the stock bearings, the copper colored plating should be on the inside facing each other. Could it be that someone at the assembly plant was not paying attention? If put the wrong way, the races will slip off since the lips are not high enough on one side. A low lipped side is needed to assemble new bearings.

There's also a possibility that the feathering shaft is too short. This might explain why some people felt notchy grips on a brand new MCP x. This would also cause premature bearing failure since the feathering shaft screw would act as a press - partially pressing out the inner bearing race during assembly at the factory.

Originally Posted by more_klump

RTF M2 also shipped with significant negative pitch at mid stick. The only recourse with the noncomputerized radio in the RTF is to increase the length of the three servo arms (arms already hooked at the top hole). Maxing out the trim did not bring the pitch to zero at mid stick.

Originally Posted by CocoSantango

It took 36 clicks here...

[Mojappa]

Originally Posted by lenrev

ISSUE
Can probably add that the main gear and shaft are a press fit and the gear will shift until there is about 1/16-inch gap between top of gear and the frame.

SYMPTOMS
Heli won't lift and vibration occurs at high RPM (blades appear out of track).

FIX

Remove landing skids and hold opposite end of main shaft while pressing the main gear until there is approximately 1/16" of the main shaft end protruding out of the main gear.

Would add that the gear can spin on the main shaft, make sure the flat spot on the shaft is lined up with the flat spot in the hole of the main gear.

Also, this is by design that it slips, it helps absorb energy in a crash and should be one of the first things to check after a crash.

[Cullen Colapietro]

My unit had considerable play between the main shaft collar and the main gear, leading to inconsistent upright and inverted climb rates. This couldn't be easily fixed using ATVs as the pitch would change from what I was seeing on the bench.

Fix: I removed the main gear, main shaft and used an exacto knife to increase the length of the notch on the bottom of the main shaft. Once reinstalled, I was able to push the main gear up higher to take the play out of the main shaft.

[Skyroo]

Originally Posted by lenrev

ISSUE
Can probably add that the main gear and shaft are a press fit and the gear will shift until there is about 1/16-inch gap between top of gear and the frame.

SYMPTOMS
Heli won't lift and vibration occurs at high RPM (blades appear out of track).

FIX

Remove landing skids and hold opposite end of main shaft while pressing the main gear until there is approximately 1/16" of the main shaft end protruding out of the main gear.

Thanks for the tip on the 1/16" protrusion. Holding the opposite end of the main shaft and main gear using two hands make me nervous in case I bent the shaft. A better way to do it is to place the heli upside down on a bench and press the main gear with the thumb.

[Silverexpress01]

Removed. My statements have no conclusive evidence for support, and I really would not like to see anyone hurt because of it - I was pushing for the Bronze side of the bearing to be on the outside, and I could be totally wrong about this.

[CRITEX]

My RTF MCPX running on a JR9303 radio and set-up as shown for the DX7 radio. The heli seemed like it had almost no pop so I went from 80 on the pitch ATV to 120. I realized this was because the Main gear had slid down on the mainshaft. After fixing the gear 80 was good an the pitch ATV.

[davidpe]

Originally Posted by CocoSantango

It took 36 clicks here...

Me too. 35 clicks.

[superjet112x]

put the align 250 bearings in mine this morning , flew all day, didnt have one bearing issue, yesterday when I got it, in 6 hrs I lost two bearings, GOOD CALL ON THE TREX 250 BEARINGS. THANX!!!!!

[Cullen Colapietro]

Originally Posted by davidpe

Me too. 35 clicks.

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