SonexBuilders.net

Hi everyone, tried to do a full static run up to check rpms but my brakes would not hold. Just curios if anyone has had this problem and what did you do. I could tie the plane to the back of my truck. Am not going to do it in my tie down area while tied down in case something happened and I launched forward. Just wondering!!

John

This is normal. My Sonex standard brakes hold to 2500 rpm. You will need to tie down for full static ground run.

nwawingman wrote:This is normal. My Sonex standard brakes hold to 2500 rpm. You will need to tie down for full static ground run.

Pretty much the same for me. With the hydraulic brakes I get up to about 2,700rpm before is starts to scootch forward. For static tests you really need to tie it down. Much safer that way, too.

All my static runs have been with the tail wheel tied to a tie down anchor (set in the tarmac)brakes set and 2 x 4 wheel chocks. A friend used only wheel chocks and the gear walked over them.

My Great Plains hydraulic disk brakes will hold back my Sonex TD with CAMit 3300, -- BUT -- Couple of years ago running the Jabiru 3300, after conversion to solid lifters, was at end of runway that is on top of hill, and stray gust picked up the tail, despite holding full aft stick, and was looking down at runway. With a tail dragger, strong engine is trying to pull fuselage up over its gear, but with a runway light in front of me, could not just release the brakes and still not sure what kept it from going all the way over, but did bend tail spring when came back down. Now the only time I do full power runups is with tail tied.

David A.

I am surprised that peoples brakes aren't holding then back for full static RPM. I have the standard Sonex brake pads with the machined drums and they have always held to full static RPM.

I'm a Onex owner and I added a single foot brake pedal in front of and between the rudder pedals that is attached to the hand brake lever with a simple rod. I can hold a WOT run up with out a problem. The Onex has a busy left hand during that time and you don't want to have to hold a brake lever. It works great, I would do it again. I only use it during a run up.
If you want pictures you must email me at flyvfr@comcast.net.

Thanks for the response guys. I have a lever for disc brakes on the control stick so the foot brake thingy wouldn't work for me . Thanks anyway. I'm going to tie my rear to an empty tie down area and go at it.

John

*

n982sx wrote:I am surprised that peoples brakes aren't holding then back for full static RPM. I have the standard Sonex brake pads with the machined drums and they have always held to full static RPM.

I have the same machined drum breaks and do run up's at full static RPM and have no problems holding. I must say before the breaks where run in a bit the breaks could not hold fully at full static RPM but I could run up to at least 2500 RPM.
Peter,
Sonex 19-8464, Aerovee 2.1
Tri-gear. 138hrs.