Wednesday, July 9, 2014

Modern updates to an Historic Aircraft - Pt. 2

We have been following the team at Certified Aeronautical Products, LLC who is busy incorporating an electrical system to an Historic Curtiss Robin aircraft which previously was non-electrical.  For the most part, this particular airplane retains the mystique of its original instrument panel configuration.  Their challenge is to implement modern  electrical components and avionics without significant changes to the look of the airplane. We previously looked at the battery installation in Part 1.  So now, we will watch as this airplane is permanently altered with a master switch, master relay, starter relay, power buss, ammeter/voltmeter, and some important indicator lights.

CAP Technician making a permanent change to this Robin's sub-panel.
 The following standards were the rule in this job.
1) Safety and regulatory compliance are the first priorities (in that order).
2) Whenever possible, avoid alterations that change the panel and interior furnishings. (i.e. Don't drill a hole unless there is no other alternative!)
3) If altering anything, try to do so with minimal changes and try to do so in a way that retains the original "look" and feel of the airplane.

The next image shows the original instrument panel prior to alterations.  The following images show the added components.

Notice that there is a toggle switch visible on the lower sub panel in the "before" modification photo.  As it turns out, this switch (labeled "Navigation Lights") was not connected at all.  The aircraft has no navigation lights.  Aparently, this switch was added sometime in the airplane's history.  So, we decided to utilize this location for our "master" switch. This will be discussed in further detail later on.

The airplane will utilize an alternator to charge the battery during operations. The customer also requested two power receptacles (cigarrette lighter sockets).  These will be used for portable electronic devices such as a GPS or to charge cellular phones, tablets, or laptops.  Therefore, it was necessary to install a "power buss" with circuit breakers for the alternator, "power socket A" and "power socket B".

New power buss with room for expansion.
Power buss under the sub panel.
Mounting for the power buss was accomplished flush screws hidden behind the aircraft data plate.  The assembly is positioned with room for labeling just under the data plate.  The circuit breakers are easily seen if "popped" and convenient to the pilot for re-set. Also visible in the above photo is the combination ammeter/voltmeter instrument.  The location was chosen as the instrument may be hidden during static display by reinstalling the plastic pouch which holds the original registration certificate.  Behind the ammeter and the left rudder bar is the electrical "shunt" which is a necessary part of the ammeter/voltmeter installation.

Normal view of the instrument panel (after mods). 
Note in the "after" photo there are two indicator lights added.  One is just to the left of the hand crank for magneto booster.  This light indicates when the master switch is "on".  The other is above the starter tee-handle control to indicate when the starter is engaged.  The power circuit breakers are barely visible below the data plate.  And the new ammeter/voltmeter has been added to the lower "sub-panel".

  The last photo shows the forward side of the firewall where the electrical equipment and wiring are neatly installed.  Note the master solenoid is mounted at the right and the starter solenoid at the left.  Most of this will be hidden behind the oil tank which was removed at the time of this photo.  One more change will be necessary.  That is to change up the orientation and routing of the fuel primer and primer lines (at mid left)  for better separation from the electrical wiring. Look for further discussion of the starter switch installation (mid right in photo) in the next installment of this series.

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