Throttle and Trim Change - 13 June 2010

Before any of the syndicate members could fly JQP, we needed to make some changes to the engine and trim control installations. These changes were required because the instructor who will be rating us on JQP raised a defect with the aircraft in that the main controls weren't easily accessable to the instructor from the right hand seat.

As such Paul Blackmore and myself starting making the changes on the weekend of the 30th of May by removing the existing throttle and mixture controls in preparation for fitting a new central mounting bracket for the controls in a couple of weeks time.

Then on the Sunday the 13th of June, Paul and I drove down from Auckland and started working through fitting the new components. First up we disconnected the existing Trim Tab and installed a new Balance Trim mechanism onto the elevator control. This mechanism trims the aircraft by applying forward or back force to the control column to move the elevator itself to trim the aircraft for level flight. It is quite a neat solution and means there is no external trim tab required.

Following on from installing the balance trim we then installed the new central mounting bracket for the throttle, mixture and trim adjustment controls. This proved to be quite difficult because access to the Sonex cockpit is quite tight particularly for someone my size. However we managed to get it installed and then fitted the throttle, mixture and trim controls to it.

The other major change required was to re-route the throttle and mixture controls through the firewall as the original position on the left hand side of the firewall left insufficient cable available to reach the carb. As such Paul drilled a couple of new holes in the firewall, threaded the cables throught and fitted two pre-prepared shrouds around the cables to seal the firewall.

All in all a busy days work. The pictures below are from the day.



A shot in the cockpit after we had removed the throttle and mixture controls from the left hand side of the panel.
The hole in the left hand angle bracket was the throttle while the hole to the left of the switches was the mixture.


This is a photo of the bottom of the cockpit with the seat pan removed and before the balance trim was fitted.


The first component fitted for the balance trim was the eye bolt and rear spring.
This was quite fiddly and took considerably longer than anticipated.


Next up we fitted the small aluminium tab to the control swing arm for the forward spring attachment.
We later had to move this tab to the right about a centemeter as it was not quite in the right place.


We then attached the cable and spring to the tab and adjusted the balance trim.


Next step was to fit the new mounting bracket for the controls.
This is yours truly squeezing into the cockpit to drill and rivet the bracket in place.


Meanwhile at the front Paul was marking the firewall for the cables holes.


And then drilling the holes.


With the cables routed through the holes, Paul fitted and riveted the cable shrouds.
(Sorry not a very good photo, the auto focus keep adjusting to the engine mount.)


A blank was fitted to the firewall where the old cables used to be.


The finished bracket in the cockpit with the controls fitted.


And refitting the engine cowls as it was getting dark. A long but satisfying day.

www.kiwikr.co.nz