Maintenance: Access to Instrument Panel and Aft of Firewall

2011/02/03 Updated 2012/04/07

After having to work behind the panel and aft of the firewall on most of the nine S7 aircraft I’ve flown, I’ve just had enough of this:

and this:

Why torture your body when you can have this:

and work in a comfortable stand up position as we were meant to.

You can get this access by making some minor changes during the build process (a little more major on the S-7S model). If yours is a finished project, by drilling out the rivets and making a couple of backing plates, then using nut plates and screws instead of rivets, the whole top panel mount/boot cowl is removable. With this mod, servicing instruments, bolting new stuff to the firewall and even working on the brake lines is way easier.

This type of mod was almost essential in order to do the work needed on this plane in a more civilized way; things like major wiring changes and installation of a cabin heat rad. You can see some of the results of this work in the picture below. The regulator, filter (blue), fuses and bus bars are all on that plate in front of the panel. For more details on these wiring changes see: Assembly Topics Electrical . The lower mounting tabs have nut plates added.

Below is a view of the panel mount/boot cowl upside down with the firewall flange at the top. The strip with 5 nut plates is riveted to the back of the firewall so that screws instead of rivets attach the fiberglass to the firewall.

The strip at the bottom is positioned underneath the rivet holes for the windshield trim strip and is riveted to the fiberglass. This one eliminates the rivets on the lower windshield hold down strip allowing removable screws instead.

Here it is with the cabin heat air inlet installed:

To facilitate removal, some of the panel mount flange that sits just above fuselage longeron has been removed.

A better way:

A futher improvement of this design would be to make a wider trim strip (maybe 1” forward of the current line of holes) with attachment holes just back of the current ones but spaced in between them and another line of holes ¾” forward of the current ones. Then cut the cowl along the original line of holes. Thus the aft portion with the panel attachment flange maybe left fastened to the windshield by those aft fasteners while the forward section of cowl is removed.

Here it is going back together:

It doesn’t quite fall into place but with a bit of poking and prodding, it is doable.

And here is the finished mod:

The S-7S model with its full boot cowl will take more work to get these results but I feel it is worth the effort.