Hi
I recently crashed my Align T Rex 550 E. I replaced all the broken bits and started flying it. At low head speed, around 1850 rpm, I am getting a slow up and down oscillation of the boom. It is fine at higher head speeds. I have checked the vibrations and they appear fine.
I normally use standard head dampers. I also tried the grey soft damper. I couldn’t tune out the oscillation with either.
I have tried tuning by assigning parameters to elevator proportional gain and elevator integral gain. The best results were with elevator proportional gain = 0 and elevator integral gain = 100. This didn’t completely stop the oscillation. These values seem extreme particularly since the heli previously was fine at these head speeds at basically default settings.
Attached are the mtr file, log file and events file.
I would appreciate any tips to eliminate the boom oscillation.
Thanks.
Vertical tail movements can only be caused by mechanical problems:
1) Incorrect blade tracking
2) Twisted spindle that rotates inside the head during flight and changes blade tracking
3) Twisted main shaft
4) Rigid head dampers used when flying at low RPM
5) Broken or damaged head dampers
6) Crooked tail shafts
7) Loose tail belt that tends to swing up and down
Attention: If you set the elevator gain all the way to zero you risk not having elevator control of the model.
Many thanks for the response.
1) Blade tracking is spot on;
2) Feathering shaft is new and true;
3) Main shaft is new and true;
4) Have tried softer head dampers to no avail;
5) See 4;
7) tail is drive by torque tube which is straight.
I did replace the tail shaft, but will look closer at the assembly.
Many thanks for reviewing and providing advice so quickly. No wonder I am such a fan of Brain / Ikon.
Regards
Acrow
With torque tubes, the correct position of the support bearings is crucial to avoid the generation of resonances (which can cause the tail boom to swing up and down).
Hi BrainDev
Due to bad weather I didn't have a chance to fly until this weekend.
The problem is solved. I shifted the torque tube bearing. My 550E FBL was one of the first manufactured. It turns out there was a mechanical problem and they issued an amendment sheet and updated the manual. This moved the torque tube bearing a further 3.3 cm outwards. I was using the original manual for the rebuild.
Thanks again for your advice.
Regards
Acrow