Jim Aonvashon:
I just purchased a 1966 Super Three A23-24 that has been sitting on the ramp of an airport in the Pacific Northwest for 5 years. I spent the last 3 days cleaning and lubing it. Finished the annual today, and am ready for the first fight. I have never worked with Beechcrafts; mostly “Bang your head and where’s the ladder” Cessnas. When I pulled up the carpets, there was plywood under them (floor boards or floorboards?). Is this a Beechcraft thing? Or is this something that was added later?
Editor:
Both the Bonanzas and the 19/23/24 line have high-strength thin plywood floorboards, to protect the underlying aluminum structure. With their usual “Beech is the best” or “Let’s build an aluminum tank” design philosophy, one the Beech design specs was something like a 115-pound woman wearing quarter-inch spike high-heel shoes. The floorboards had to keep the heels from damaging the aluminum below. A side benefit to this design is that it adds to the weight rating of the baggage area structure, and keeps unusual baggage area loads (like truck parts from a junkyard!) from damaging the aft aluminum flooring and support structure.
You can do a lot of damage to the floor structure if you work in the plane while the floorboards are out. Make sure you keep something under you to help spread the load. Otherwise the floor sheetmetal will become dished, and stress risers will develop in corners and around openings. That enables vibration to propagate cracks.
Original floorboard plywood specifications:
***
Floorboards P/N 169-530004-205, -211, -223, -565, -571 are manufactured from commercial fir plywood sheet, grade A-B, 3 ply, 0.187 thick (nominal 3/16″ thick). Then the floorboards are treated with a fire retardment to meet FAA requirements.
***