Marc Halcomb's Posts (6)

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Ranger EX 757-3 Auto Mode Test

3689714324?profile=originalCompleted a successful "Auto Mode" test today using a simple rectangular circuit.  From the "CTUN" graph you can see the roll and pitch response matches the demand.  The aircraft flew stable and as expected, I also repeated this test using 2 different altitudes verifying throttle, airspeed, and rate of climb in "Auto Mode" as well.  Finally, everything is coming together for auto takeoff and landing, which is next.  Followed by FPV installation and some longer range tests.

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Ranger EX 757-3 (Auto Tune & Auto Trim)

I finally completed "AUTOTUNE" and "AUTOTRIM" activities on my Ranger, after fixing a self-induced configuration mistake.  Once "AUTOTUNE" was completed, FBWA mode flights were stable and responsive, ready to test an "AUTO" mode mission next.  Once "AUTOTRIM" was complete I ended up with a nice "MANUAL" mode trim and stable flying characteristics.   

Final PID's from "AUTOTUNE"


Note:  The initial problems with the Ranger being underpowered were most likely caused by my selection of a 3S battery pack.  I then replaced the motor, followed by changing the battery pack to 4S.  I have not switched back to the original motor, but I think the 4S pack and the original motor would also provide good flight characteristics.  (and saved me $$'s)

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3rd Flight of Ranger EX 757-3

Finally had the time for the next flight.  I increased the Roll and Pitch gain settings as the first two flights were quite sluggish to control inputs.  I was hoping to complete the "Manual" mode trim setup this flight but I continue to have too much starboard roll for the trim setting on the controller.  

  • The gain setting increases helped (some) with the sluggish control responses.
    • In addition, I found the control surface hinge lines to be far too stiff. (I cut relief sections to reduce stiffness) 
    • During the build, I laminated the wing, tail, and control surfaces to stiffen the airframe
  • Manual mode trim was also affected by the laminating material, which caused a slight twist in the starboard alerion.
    • Reheated starboard control surface to improve the shape, next flight will tell

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Maiden Flight of Ranger EX 757-3


I completed the maiden flight of my Ranger EX 757-3 today, with mixed results.  The flying weight today was 6lbs, using a standard rule of thumb, the power requirements would be 450 - 600W.  The supplied 3715/1000KV outrunner brushless motor only provides 300W.


  • Initial parameter selection flew the aircraft safely and successfully in Manual and FBWA! 
  • The build was good (no bits flew off)!
  • All the systems checked out
    • Pixhawk
    • GPS/Compass
    • Power monitor
    • LIDARlite V3
    • Airspeed sensor
  • Modes checked
    • FBWA
    • Manual - now have a good trim

The Mediocre:

  • Under powered, with the current motor and 6lbs flying weight takeoff and climb out were sluggish
    • Batteries 2 x 5100mah 3S 8C batteries in parallel - which should deliver 40A each 
    • 40A ESC
    • 25A motor (~300W)
    • Looking to upgraded the motor to 450W plus and may need 60A ESC for 600W motor
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Ranger EX 757-3


Update:  The local weather is improving and looks like tomorrow will be the maiden flight, really looking forward to its first flight.  The field I have selected is grass, and I have increased the main gear size to 4.5", which I hope will help with takeoff and landing.  With any luck, I'll have some video to post tomorrow.

  • Build complete
  • Weight and Balance Complete
  • Ground checks complete
  • Manual and FBWA ground checks complete


  • Motor: 3715 1000KV Outrunner Brushless Motor
  • Volantex 40A switch mode BEC Brushless ESC
  • Volantex Ranger EX 757-3 kit
  • Battery 11.1V 10200mAh LiPo 
  • 3DR Telemetry Transceiver
  • FRSky RC Receiver & FS-TH9X RC Transmitter
  • Aileron, Rudder, Throttle, Elevator, Flaps and mode control
  • Digital Airspeed Sensor
  • LIDARlite V3
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Initial Parameter Settings


For my maiden flight, takeoff and initial tests will be in the FBWA mode.  Followed by switching between FBWA and Manual to get the trim correct. 

Initial Parameter Settings:

Some basic gain/dampening factors for the first flight, except for power monitoring, compass/AHRS zero's and calibration the remaining parameters are left at the default value. 

  • RLL2SRV_P 0.80
  • RLL2SRV_I 0.00
  • RLL2SRV_D 0.02

  • PTCH2SRV_P 0.60
  • PTCH2SRV_I 0.00
  • PTCH2SRV_D 0.02


I'll update these, and post some plots of the roll/pitch control loops and power usage once

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