TREX500 Helicopter Project

My quest to build and fly an Align TREX 500 Remote Controlled Helicopter

I was struggling with flying nose-in. Every time I tried, my brain would freak out and I had to abort and rotate the tail back to tail-in.

After reading a suggestion from someone on an RC forum, I tried out their trick on the simulator and it worked. After 1 hour on RealFlight, I thought I’d try with my TREX 500.

This video shows my first attempt. I was able to fly nose-in, what a great feeling. This is not an instructional video, but it does show you how I did. I kept the heli up high in the air in case things went wrong.

The trick is when you’re nose-in, you have to “flip the circuitry in your brain” to view the blades as a plate that you have to keep level. If the “plate” tips to the left, then you need to “push-up” the left side of the plate by giving some left collective. Same goes for right, front and back.

Just remember to flip your brain back to normal once you’re no longer nose-in.

Good luck,
Gary

P.S. – Recommend that you click on the video and play it in full screen mode.

I have always been flying with the NORMAL pitch & throttle curves. However, when flying on windy days, the wind pushes the helicopter up and down. If the TREX 500 goes to high, then I lower the left stick to bring the helicopter lower. The problem is, this also reduces the motor (head) speed and tail rotor speed, so I don’t have good control at this point. I then have to spool the motor back up as the helicopter gets to the correct altitude. So, now is the time to start using the IDLE-1 pitch & throttle curve. I”ll keep the IDLE-2 for 3D flight.

I’m using the IDLE-1 pitch and throttle curves recommended from the Align TREX500 manual. Today I took off in NORMAL mode, then flipped the switch to IDLE-1. The first thing I noticed was a drop in head speed, so I have to modify my throttle curve higher for IDLE-1. Then I noticed the there is negative pitch at the lower range. I’m not a big fan of negative pitch, maybe when I able to fly 3D, but for now, I don’t want negative pitch. So I have to modify my IDLE-1 pitch curve as well.

Throttle Curves:

Pos |  Norm  | Idle-1 | Idle-2

P5  |  100 %  | 100 % |  100 %

P4  |   85 %   |  85 %  |    93 %

P3  |   70 %   |  70 %  |    85 %

P2  |   40 %   |  70 %  |    93 %

P1  |      0 %   |  70 %  |  100 %

My values for the pitch curves are custom to my helicopter so I won’t publish them here.  The key point is that for NORMAL and IDLE-1, I don’t have any negative pitch.

The third thing I noticed was that my THROTTLE-CUT switch (A) is right beside the NORMAL/IDLE-1/IDLE-2 switch. When I went to land, I flipped SW-E from IDLE-1 to NORMAL….and hit the THROTTLE-CUT (SW-A) at the same time. I had to quickly un-flip SW-A. This happened twice!! So I need to move my THROTTLE CUT switch to the other side of the Futaba T7C radio.

My 11th flight day. I’m gaining confidence and improving my skills. I’m okay to fly. Take-offs and landings are good. BUT it’s easy for the heli to fly a little too far or a little too high. This happens quickly and can be nerve racking. I have to bring the bird back into my “comfort zone”. So yes, I’m still nervous.
I talked to a another heli pilot at the field. He said it took him till the 2nd year to feel comfortable.

 

 

I solved my problem with the Turnigy 8150 only seeing 5 of 6 cells.  There was nothing wrong with the battery or connectors.  The issue is with the charger.  To solve this problem, I gave a ~2 minute LIPO CHARGE to the battery (not a LIPO BALANCE).  Here are the steps with photos:

  • Connect the balancing plug and the main battery plug to the charger.  (Just like you would normally).
  • Using your normal charge setup, set the Turnigy to LIPO CHARGE.
  • Start the charge.  Ignore any warnings about only seeing the 5 cells.

  • While its is charging, press the INC key to monitor the individual cell voltage.
  • Stop the charge after 85 seconds.  I saw the cell voltage increase rapidly from 3.5 volts to 3.62 volts in 85 seconds.

  • Now the cells are at ~3.62 volts (21.72 volts) which is larger than a fully charged 5 cell LiPo (5 x 4.2v = 21 volts), so the charger now sees it as a 6 cell battery.
  • Next step is to do your regular LIPO CHARGE.  Again, press INC to check the individual cell voltages to verify that there is no cell damage.  Monitor the charging.




 

I am seeing a problem with my Turnigy Accucell 8150 charger where it only reads 5 cells during the battery check of my 6 cell LiPo.

Turnigy 8150 showing 5 of 6 cells

I have three 6 cell LiPo batteries, labeled battery “A”, “B” and “C”.  All three are the same make/model and purchased at the same time.  They are 20C FlightMax 2650mA made by Zippy battery (click HERE for more info).

They have been used about 7 times each, so they are still very new.  I used all three batteries last weekend, no problems.  I was able to charge batteries A and B.  But when I connected battery C, the Turnigy charger only read 5 cells, instead of 6.    I canceled the balance-charge operation and did the following to verify the battery:

  1. Using my 6 cell battery meter (see earlier post), I measured the voltage of each cell + the total voltage.
  2. Using my very expensive voltmeter (multi-meter), I measured each pin on the battery’s balance plug to verify the cell voltage as well.  I wanted a very accurate cell-by-cell voltage.  Here are the measurements:
    • Battery “C” voltage readings:
      • cell #1 = 3.48 volts – BLK-WHT
      • cell #2 = 3.48 volts – YLW-WHT
      • cell #3 = 3.47 volts – BLK-YLW
      • cell #4 = 3.50 volts – WHT-BLK
      • cell #5 = 3.49 volts – BLU-WHT
      • cell #6 = 3.44 volts – RED-BLU
      • TOTAL = 20.9 volts

Based on the above, I can conclude the following:

  • Each cell has a voltage that a reasonable voltage, meaning it’s > 3.0 volts and they are all in the same voltage range: 3.44 – 3.50 v.  So I don’t think its a “low cell voltage” condition.
  • The white balancing tap connector on the battery is good.  I was able to read voltages using the 6 cell battery meter AND by touching the metal pins with my multi-meter probes.
  • The Turnigy 8150 battery charger is also okay since I was able to charge battery A and B both before and after the false cell reading with battery C.  So the connector on the charger is okay.
  • I suspected that the pins on the charger were pushing the wiring in the battery connector.  So when inserting Battery “C” into the charger, I try pushing the wires in a little more and also moving the battery to different positions.  I was trying to see if there was a flaky wire or solder connection.
  • I thought that the Turnigy charger may have fallen-out-of-calibration.  My thinking was that the charger thought that cell#6 at 3.44 volts was off and reading < 3.0 volts.  By if it was, it should have given a low voltage error.  So its not a calibration issue.

Next Steps:

  • Not really sure what to do next.  I will try giving it a little charge, say 100 mA to see if I can bring cell #6 up a bit.  Maybe cell #6 is below some threshold that is preventing the charger from seeing it.

Any ideas?

 

My latest purchase, a 6 cell battery meter for my Lithium Polymer batteries.  Only $10 CDN from the local hobby shop.  It measures the individual cell voltage as well as the total battery voltage.  Very handy at the field to see which batteries still have some juice left.

Great Hobbies - TGH6CDBM Battery Meter

2011-04-22: First flight of 2011. I went to the Stetson Flyer’s club field. I’m still a hit nervous since I did not fly over the winter. So I took it easy in this flight.

After my flights, someone from the club came over. He noticed that my blade tracking was off. That is, when hovering, one blade was slightly higher than the other. We fixed it immediately at the field by adjusting one of the short linkage rods. It made a big difference when flying afterwards.

 

 

There was a article in the March 2011 issue of www.rchelimag.com reviewing the G5 Pro carbon fiber blades from Mavrikk (www.heliwholesaler.com).  They were rated a 10 out of 10.

I was looking for iPhone apps that might be useful for remote control helicopters. I found the following on the iTunes store:

App Name & Link Author Screen Capture (Click to zoom in)
HeliTach

(a.k.a- Heli-Headspeed)

Jacob Niehus Heli Tach
RCpitch_express and RCpitch Gerhard Klauser RC Pitch
rcFlightbook Claus Bonnhoff

I’ve downloaded them and will do a review.  If you have tried these apps, leave a comment below with your opinion.

Gary

I solved the issue with the rotor head wobbling.  It was to replace the main rotor head unit. See the video below: