Mike Dawson:
I finally found a original Beech “Aerostart’ Aux Power outlet and want to install on my Sundowner. I looked at the drawings in the Parts Manual and it looks like it mounts directly to the skin of the aircraft. Is this correct or do you have a “doubler” of some sort? The drawings in the Parts Manual is not very clear on this.
Search strings: external power, auxilary power, charger connection, ground start receptacle, power receptacle.
Technical Editor:
The parts manual does not show any bracing or doubler between the socket flange and the skin, in the IPC section for the external power. But it also shows only one style of factory installation, when there are at least two and probably four. The third being in the 2-seat Sports; the fourth is the Skipper. The Duchess is the same as the 23 and 24. There may be pages in the fuselage area somewhere that show the bracing and doubler, but I have not found them yet. The IPC also shows the socket-mounting screw size as an AN525-10R7. That is a structural truss-head size -3 (10-32 threads) Phillips-head screw, with a grip length of only 1/16″ (.0625″ long). That implies that there is no doubler, or else the grip portion of the screw would not pass through the flange area of the socket and skin as it should. The screw threads would ride within the flange and skin holes, potentially causing chafing and the formation of abrasion corrosion. This may be normal for the lower ‘bathtub-side’ installation used after 1978. But I know for a fact that a doubler is used on the earlier installations, along with longer screws. Its edges are riveted into the vertical and horizontal bracing members. Just another example of the many errors and omissions in the IPC.
I don’t usually have any external power receptacle parts. They are sometimes available from a salvage yard, along with all of the other needed parts (bracing, doubler, cable). There are at least two design locations for the external power.
The location used on the latest planes in essentially underfloor, in the ‘bathtub’ area just aft of the RH flap. While this is a naturally rigid location for a number of structural reasons, it is also near-inaccessible once the aircraft has had the interior floor skins installed. Placing an external receptacle there after-the-fact would require floor skin removal at a minimum.
The much more common location, and the one used on most receptacles you will see, is in the RH vertical sidewall, just aft of the baggage area rear bulkhead cover, roughly midway up the side. This is relatively convenient for both installation and usage. Its only drawback is that it requires temporary removal of some of the skin damping panel material. Some of the material will need to be reinstalled, so care is required during its removal. Then the correct vertical and horizontal bracing plus connecting angles, along with the skin doubler, must be primed and riveted in place. The skin-doubler hole is then punched, the mounting screw holes drilled, and the receptacle mounted along with its battery connection.
If this job is properly done, a few of the existing rivets are drilled out, and the holes re-used for the bracing and doubler. Additional needed holes are drilled using the same rivet spacing as was originally used. Once touch-up painting is done, the installation might as well be completely original (as it should be). The installation weighs well under two pounds. Assuming it is done using Beech parts, only a log entry is required; the IPC shows fleet-wide applicability on the 19/23/24/76/77. There are probably a fair number of these installations still available from salvage yards.