LOOKING BACK Getting Started: Part 3 of Ted Smith’s Memoir

For his book Stars and Commanders, Dave Duntz conducted years of research, including Ted Smith’s unpublished memoir. The memoir was published in chapter 7 of Duntz’s book, and will be presented here in three parts. This is the third and final installment. You can purchase Duntz’s book at www.starsandcommanders.com.

The fuselage structure was a series of frames, longerons, and clips with all metal covering ranging from .018 thickness in the aft section to .025 in the forward section.  The door for entry was 27 inches wide and the cabin floor was eighteen inches above ground level which was low enough to give relatively easy access to the cabin without the need for an auxiliary step.  The high wing design with the front spars at 35% permitted a level floor with no obstruction of spars running across the cabin floor.

The pilots’ compartment (cockpit) was roomy and comfortable facing an instrument panel that was carefully laid out from a human factor standpoint – electrical switches and fuel control valves were installed on an overhead panel in a natural sequence.  For start up the pilot started on the left-hand side of the panel and went from left to right for all primary systems including lighting, and on shutdown worked from right to left – again a natural human factor element sequence.  No looking all over the cockpit to find controls and switches for primary operational procedures.

The control for elevator and aileron on the prototype was designed with a push-pull tube of 1.875 inches in diameter through the instrument panel with the control wheel attached at the aft end of the tube and at the forward end the mechanism for elevator and aileron was installed.  Interconnect for the dual controls was by chain for aileron and a yoke behind the panel for elevator.

The control quadrant was more or less conventional for a twin engined aircraft.  Trim wheels connected to a cable system with 4-inch diameter aluminum wheels coming out each side of the quadrant, and on top of the quadrant for directional trim a similar wheel was installed.  Low on the center panel of the quadrant was the carburetor heat controls. In the days of the Aero Commander development, the engines all had float type carburetors which required heat to keep them from icing. As the years went by Bendix developed the pressure type carburetor, supposedly ice free, but experience showed that, although the carburetor might be ice free, the induction system was not and carburetor heat stayed with us for years to prevent induction system icing.

Empennage design was of all metal construction with vertical fin built as one unit but installed and attached integrally to the fuselage structure.  The horizontal stabilizer was built as one-unit tip to tip with welded up aluminum alloy tips approximately 6 inches long.  The horizontal stabilizer was designed and built with a 10-degree dihedral – the purpose being to keep the tips of the horizontal surface above the downwash of the wing to prevent buffeting, particularly at high angles of attack.  The entire empennage used a N.A.C.A. symmetrical airfoil, Section S, for the vertical fin, rudder, horizontal stabilizer and elevators.  Elevators, as well as rudder, were designed with both aerodynamic and mass balance:  the aerodynamic balance to reduce control forces, and the rudder and elevators were 100% mass balanced for dynamic requirements (flutter).

The aircraft was designed for a maximum Vd (max dive speed) of 300 miles per hour and a flutter speed of 350 M.P.H., all indicated airspeeds.

Structure of the empennage was simple rib and two spar construction with .012 corrugated aluminum alloy skin covering.  This permitted us to reduce substantially the number of ribs, yet provided greater strength in shear and torsion over a design which used many ribs with smooth skin covering.  Whereas the latter type of structure would show shear wrinkles under load, the structure with minimal number of ribs and corrugated skin covering would not and thus adding to the performance and structural integrity of the aircraft.

In most areas low profile brazier head rivets were used, with the exception of the wing which had flush rivets from the leading edge to the 35% spar.

Systems were laid out in coordination with structural layouts so that proper space and bracketry would be available for system components including control, hydraulics, instruments, electrical, landing gear, heat and vent, power plant, and all other systems pertinent to the operation of the aircraft.  All facets of the design must be done in coordination with each other.

As lofting of the aircraft progressed from the loft data, structural layouts were made and from these basic structural and mechanical layouts, detail drawings were generated.  In some cases, the layouts were converted to assembly and/or installation drawings.

From the drawings, as they were released, the tooling program was started with form blocks for hydro formed parts such as ribs and fuselage frames. This was in July 1946.[i]  Some of these were formed in house on the little hydro press that we had built in house using a welded-up channel frame and a four-inch long stroke hydraulic cylinder obtaining its pressure through the use of a hand operated aircraft hydraulic pump.  All formed parts had to have templates made in accordance with loft information and other details contained on the drawings.

The main wing spar caps were 24ST aluminum alloy extrusion.  The dies for all extrusions were built by Alcoa.  This company also furnished the extruded material for the empennage spar caps and stringers.  So, Alcoa was the first company to build special parts for the Aero Commander and also one of the pioneers in the program.

The main spars were bent each side of the fuselage to provide the sweep forward as well as the 4-degree dihedral angle.  This was accomplished with special form dies.  Four blocks were required:  two for the top cap and two for the bottom cap.  The bend was made cold on the 24ST material by carefully applying pressure from our little hydro press at a specified position on the cap and with one bend both the proper amount of dihedral and sweep forward of the cap was obtained.

Sheet stock and hardware in most cases was obtained from war surplus stock.

In the basic design of the Aero Commander, we stayed away from machined parts and castings wherever possible.  Main landing gear trusses were fabricated from extruded sections and plate material.  Gear trunnion fittings were made from plate stock and bushings for trunnion pins were machined out of oilite stock on the little South Bend lathe that we had purchased as necessary to meet the engineering drawing requirements, as were the nose gear attach fittings, bushings, and other small parts.  It is amazing what can be done on a small six-inch bench lathe.  In most cases all of the machine work was done by me.

The main landing gear trunnion fitting was a built-up section of ¼ inch aluminum plate stock, band sawed to shape, smoothed by hand filing, holes bored where necessary and oilite bushings pressed into place for the attach pins.

For the main gear we used surplus Vultee BT-13 struts.  We obtained drop test data from Vultee Aircraft Company, and as it turned out the drop test data and the strut matched the aircraft exactly.  The nose gear was one built by Firestone Tire and Rubber Company.  It was a trailing type of gear and the shock absorption was a series of rubber discs about four inches in diameter and stacked one on top of the other with a steel disc about .062 thick in between each rubber disc and the same diameter as the rubber disc.  The gear was very soft and absorbed shock extremely well.  To this day this type of gear is used on many light aircraft but predominately the air oil type of gear is used almost universally for most large aircraft.

The main gear was hinged about the center of its trunnion to permit retraction of the gear into the nacelle; no doors were provided to cover the hole in the bottom of the nacelle when the gear was retracted.  However, nose gear doors were designed to cover the nose wheel well opening when the gear was retracted.

All hydraulic cylinders were obtained from World War II surplus.  Another company from which we obtained most of our AN hardware items, (bolts, nuts, rivets, washers, and other items) was F & C Sales in Culver City.  Another little company called Wallace and Black furnished many small AN parts as well as specially made parts.  The owner, Joe, purchased 100 shares of stock and his shop was within a block of our operation.  Joe helped us tremendously during the building of the prototype.

The hydraulic system in the prototype was an electric driven hydraulic pump.  The system contained a pressure switch that was set at a low limit of 800 p.s.i. and a high limit of 1000 p.s.i.   When flaps or landing gear were operated, the hydraulic pump would come on the second pressure dropped to 800 p.s.i. and cut off when the pressure increased to 1000 p.s.i.

During the construction of the aircraft and before the first public showing, we had obtained from the C.A.A. most of the structural and systems approval. But, to obtain certification we still had lots of work to do:  Proof test of the structure of the power plant installation plus a flutter analysis. Problem was, at this stage, we were practically without finance.   We had concluded our stock sales.  Each of us had loaned small amounts of money to get the airplane to the showing stage.  Now we felt that by having a public showing of the aircraft, putting out press releases to the trade press and newspapers, the word would get around and perhaps additional monies could be attracted to complete certification and place the aircraft in production.  We estimated that it would take another $50,000.00 to complete certification and other $500,000.00 to place the airplane in production at the rate of eight per month.

We struggled on and completed the prototype early in April 1948.  All of our people were proud to have been a part of the project and I as an individual took great pride in the accomplishment.  We had hurdled obstacles that at times seemed insurmountable, especially from the financial end, but we had finally completed the prototype and were ready for public showing.

Some of the boys came in early the morning of the showing and polished the airplane to a mirror like appearance.  The only paint was at the leading edge of the cowls and a red stripe down the side of the aircraft.  The painting had been done prior to polishing and the completed aircraft was a thing of beauty.

We obtained good press coverage throughout the world and even through the local news media.  We had sent out invitations for the first showing, had arranged for a light buffet to be served along with soft drinks. Families of those who had worked on the project showed up. My family came down from the Bay Area, but in my heart, I was very sad because there was one person missing – my Dad, who just a few weeks prior to the completion of the aircraft had passed away.  He had been bedridden from shortly after the war started from a stroke but he did know and understand what I had accomplished at Douglas and he knew that I was working on an aircraft of my own design. But he did not live to see the completion of the prototype and to know that it would be successful.  He believed that I would gradually, with perseverance and faith, soon accomplish at least partially the fulfillment of my dream.  However, the realization that he was gone caused a great sadness in my heart.

In reminiscing a little and reviewing in my mind, this was a time of tremendous effort by over thirty people working against almost impossible obstacles.  Overcoming them with faith and perseverance caused us to continue regardless.  The worry over finances, including the drain on my own cash resources, which by this time, were being rapidly depleted to a point where I began to wonder if the right decision had been made in leaving Douglas. But inwardly, I knew that one day, if we continued, we would win.